LEAN is good, because it is designed around eliminating waste, and understanding profit. There are four principles of LEAN

1. Improve Quality
2. Eliminate the Seven Types of Waste
   1. Unnecessary movement of materials
   2. Excess inventory
   3. Inefficient Layout
   4. Waiting
   5. Over production
   6. Rework / reprocessing
   7. Defects
3. Reduce the time it takes to finish an Activity
4. Reduce total Costs

What’s interesting here is all four principles are based on the definition of an acceptable part. Here is where Common Sense must prevail:

Do you and your customer have a crystal clear definition of an acceptable part? How many times has a gate mark been both acceptable (because they needed the parts) or unacceptable (because you fell for the specification “no manufacturing / visible defects”)?

In molding there’s usually little need to ‘improve’ quality. However there’s a screaming need for a fixed, uncompromising, unchangeable definition for acceptable parts that is clearly defined and understood by you and your customer.

* *

SMED or fast changeovers come in two steps:

The first is purely mechanical. Is the new mold scheduled? Do you have all the accessory equipment and people available for the next run? Do you KNOW how to hook up the water and set the process conditions? Is the mold ready to run acceptable parts or is it out for maintenance and nobody told scheduling? Is the setup team/crane/forklift available when the job is ready for changeovers? This requires PLANNING by everyone. Not just an edict from a computer or a schedule.

The second in many instances conflicts with the ‘reduce total costs’ philosophy. The fastest way to begin running a new job is either to be able to use the same material as the previous run OR have a separate portable dryer that has pre-dried the material so you don’t have to wait. Do you have enough of these portable dryers available or do you need to buy more?

While there’s a lot to be said to comparing a mold changeover to the pit crews of NASCAR, if you don’t have useable material it doesn’t matter how quickly you changed the mold. The same is true if your setup team is troubleshooting another machine and ‘couldn’t get around to it’ because their first priority was to keep production running.

* *

Reducing the ‘time to do an activity’ and JIT are based on an interesting assumption: loading.

If your shop is under-loaded, idle equipment becomes an expense. There’s only so much you can do to fill up your capacity.

I’m embarrassed to say our capitalist system views people as an expense. We try to keep wages low when we should be looking at how much does each individual contribute to the profit (People Loading). Paying two people who can do the work of three or more at the same wage as a slacker explains why you lose your best people.

Training those who could contribute more is usually last on the list for available money, while ‘Lack of Operator’ is a shamefully common excuse for idle time. Cross train your people. Who says someone who is an operator can’t help hook up waterlines, or do the first few steps in troubleshooting? Spending a few thousand to train everyone in the principles of good molding, troubleshooting, mold changeovers, even driving a forklift; will pay back many times over even if only a two out of twenty apply it. New people create scrap. Retention of good people, periodic training of everyone (new and old), and rewards for the ‘players’ will keep your operation Lean and costs low.

JIT and SMED are based on a mystical assumption that if you reduce the changeover time to nothing (from the last good part to the production of goods parts for the next run) the unit cost of a ten part run is the same as the unit cost of making a million parts. PLEASE NOTE: I didn’t define SMED as only changing tools. This has to be a measure of the cost of idle time between two different saleable parts. When trying to cram this philosophy into a high volume industry like injection molding where a mold might be changed in fifteen minutes but a good part will be consistently produced after an hour of ‘dialing it in’, is false thinking. Once you understand how to change molds quickly; learn how to start them up equally fast.

The big ‘sales point’ to JIT is the lack of storage costs. Good thinking on the part of the customer; what about the molder? There are some easy to use Economic Order Quantity formulas available from any economics text book or the internet. What you quickly find is that while perhaps you shouldn’t make two runs per year for a customer when you ship weekly, you might make more profit is you made six or eight. What’s the cost of storage? If you have an international freight container in your parking lot and use it as a warehouse, what do you think the cost is per cubic foot?

* * * *

At the end of the day we’re all here to maximize profits with minimized expenses. While people with letters after their names expound on the individual components of LEAN, SMED, and JIT what you have to ultimately look at is a simply philosophy: “In the Big Picture, what gives the most profit?” Toyoda’s principles are neither academically technical nor complex. It isn’t about precision, it’s about consistency. It’s not about automation; it’s about properly using what is necessary whether it’s a robot or a person. More importantly, it’s about common sense.

ABOUT THE AUTHOR

Bill is a trainer in molding, a consultant and a writer. You can contact him at bill4012@hotmail.com

I was in the owner’s office that overlooked the production floor where all the machines were making parts.  His comment was “Look at that, a money machine!”  Interesting.  When we got around to discussing why I was there; he was complaining about his minimal profits although his machines were busy.  And there’s the problem: are you making money or just running your machines? Here are four simple (inexpensive) steps to make money:

#1 The first step the easy one – Don’t make parts, Make schedule.  Although you might fill the order, if the customer gets it late or you paid overtime to get it on time; you’re going to lose business because you’re an unreliable supplier who can’t properly schedule or contain your costs.

#2 Don’t accept variances find out why – I love student interns:  They work cheap, will do a job that no one else has the time for; their work output will be their Senior Project so you also get free consulting advice from a professor.

Have your student intern go though all your jobs.  Write up a list of the most recent cycle times that you based your part prices on and the actual cycle times (the pieces shipped for the last order divided by the total hours to fill the order)  This will give you the REAL cycle time.  On this same spreadsheet have them calculate the difference in hours.  In the next column have them calculate the poundage of material budgeted compared to the amount of material actually used.  Using what you believe to be your standard press rate and the materials cost, in the final column lay out if the job made or lost money compared to your expectation.

Now have your student intern create a Pareto Chart with the biggest losers ranked first down to the least losers and the back up to the big money makers.  If your Intern can do it, have him/her postulate the reasons behind the winners and losers.

What’s typically found in cycle times is that most people on the floor don’t think a second or two means anything.  Here’s where the law of Unintended Consequences will chew up your profits:

A. Longer cycles extend the run time and therefore lower your press rate – where you make all your profit.
B. Longer cycles steal future press time that could be sold to another job or customer.
Since materials consume the vast majority of the part’s cost, this component of the pricing should take special attention.
A. Does your scrap rate plus the contribution of the sprue and runner amount to less than the regrind allowance?  If it does, 1,000 pounds into the process should yield 1,000 pounds of product.
B. While $10/pound purging compound may seem expensive, how many pounds of material are you generating in cleaning the barrel and tossing out mixed material parts?  This is both machine time and material lost that you’ll never recover.
Yield rates affect both cycle times and material usage.
A. Speeding up a machine but making more scrap in the process has a negative effect.
B. Over inspecting - the operator every 20 minutes – the Inspector every hour – the final inspection before shipping tells you two things:
a. You are actually ‘inspecting quality in’ and therefore you’re more likely to reject parts.  You’re spending a lot of indirect labor on inspections with little return.
b. You probably don’t know what an acceptable (read: Shippable/salable) part is.

#3 Don’t make rejects.  I realize this is stating the obvious but when you ask an operator, an inspector and a customer to tell you what a good part is, you generally get multiple answers.

Face the facts – NOBODY makes parts to print.  There are too many dimensions on a part to comply with all of them; so we generally only look at the ‘critical’ ones.  But when the customer has a quality audit (just for the fun of it OR because he over-ordered) he’ll find some sniggly dimension or a visual surface that he’s never complained about before and reject the entire lot.

This comes from ignorance on the part of the customer and supplier.  All too often I’ve heard buyers whine ‘the part is OK, but you can do better’.  It’s interesting that this complaining doesn’t come with any financial incentives.  Look at your $1,000+ TV set or your new car with the eyes of an inspector not a purchaser – look for flow lines, dings, bad texturing, scratches, rippled paint jobs etc. – All the stuff your customer rejects your product for but something you couldn’t care less about because you bought the product.  Too many molders bid on jobs with the specification “Free of Manufacturing Defects”.  You’re kidding Right??  If you have these jobs, you’ve got an engraved invitation to a rejected lot anytime your customer feels like it.  Dummy.

MORAL – a good part does what it’s supposed to do (It functions per its intended use) and is acceptable to the customer who purchases the part at the retail level (cosmetic acceptance).  Get that definition clearly stated from your customer on what is acceptable (not perfect) – rejects will vanish.

Have your Intern give you a listing of rejects.  Have your engineers and quality people jump all over the customer for a solid definition of what they’re actually willing to pay for.

#4 DO SOMETHING DIFFERENT – With this wonderful data from your intern, focus in on the biggest losers and eliminate the causes, keeping in mind one solution that won’t kill you is to tell your customer to either change the requirements or take his molds and find someone else to bankrupt.

Don’t form a Kaizen or Lean committee who’ll study it to death.  I had a client once with a proprietary product (read: they defined all the specifications) who formed a Kaizen committee of 10 people who met for half a day twice a week for 6 weeks to see if they could reduce their scrap.  I found it funny because an engineer and an inspector could have come up with better recommendations in a couple hours of solid work.  However these two people probably wouldn’t have generated a 50 page report and an hour long management presentation (at what cost?).  I secretly hoped some brain-dead manager would have seen through all the fluff and feathers, but they didn’t.  The report was presented at a national convention and nothing ultimately was done.   Go figure. All the quality/manufacturing gurus tell us to solve the problem embedding the solution – nothing more.

I cannot emphasize this enough – DO SOMETHING, if whatever you’re doing now isn’t working, doing anything different has a better probability of success.  From your intern’s Pareto chart; work on the biggest losers first.  Redo the chart and again attack the losers until there aren’t any.

- Find the proper cycle time and material allocation for a job.  Hold your people accountable – money only comes from on-time shipments that get paid.  Late or poor quality shipments ultimately come out of everyone’s paycheck.  You can’t afford apologists or slackers.  It’s better to have people who are arrogantly proud of how well the place is run, then some PowerPoint-wonks giving lame excuses on why you’re bleeding to death financially.

- Look at your sales force.  These guys and gals are the classic Hunter/Gatherers.  Their definition of success is booking a job.  They’ll tell you it’s your job to make a profit on it (after their commissions are paid, thank you).  Unfortunately their commissions are based on percentages of sales and not percentage the best fit between the job and your expertise.  There’s no such thing as a general molder.  We all specialize.  A medical house couldn’t afford to quote automotive work.  If someone wants a precise gear, going to someone who make screwdriver handles and bicycle grips might not be a good choice.  Quote jobs based on what you do well.  Only quote jobs on things you’ve never done that have little impact if they are rejected but the upside of giving you the expertise to move into a different type of molding.

- Train your people.  Every molder will tell you hiring an inexperienced operator is always a high source of scrap.  However, asking them to spend money on training is almost blaspheming.  What do they expect? – standing near a machine will allow the operators to somehow absorb knowledge like cat litter soaking up a spill?! If you can pay for scrap and inefficiencies you can afford to eliminate these problems with training.

‘Nuf said.

* - * - * - * - * - * - *

You can read this article take it to heart and do something.  Who knows?  You might become more profitable.  Or, if your fiefdom depends on generating reports laced with Japanese words and esoteric presentation slides, you can bury it and hope no one else got a copy.  OR you can read it, smirk, and use the paper you printed it on to line the cat litter box of your corporate pest control beast.

You’re choice, in hard times like these; it’s only your future at stake.

ABOUT THE AUTHOR – Bill Tobin is a consultant and trainer who can help molders make more profit.  He is the owner of WJT Associates and can be contacted at bill4012@hotmail.com

Let’s give this a reality check – Your local gas station is raising prices almost on a daily basis. The phone company tells you they’re raising your rates. Do you call either of them up and tell them you “Won’t honor the price increase” but still demand their goods and services?  Nope.  If you do, then I won’t be able to call you in a couple weeks and you’ll soon be walking to wherever you go.

I show a picture in one of my seminars of a three year old little girl, holding the leash and walking a three year old German Shepard.  I ask the class “Who’s walking who?”  They invariably get it wrong – they tell me the dog is walking the girl.  Dog’s have been taught when their pack is composed of humans, they will never be the Alpha if they wish to live for any length of time.  The girl will always walk the dog.

As molders, when your customer tells you they won’t honor a righteous price increase they are really saying “I want you to lose money, so I can stay profitable”.  Dumb isn’t it?

Resin companies don’t single you out for a price increase. When they raise prices, everyone gets the increase at the same time.  Those who have in-house stocks of material may benefit in the short term but they cannot avoid the new price of material the next time they make a purchase.

This is one of the impolite components of JIT – you are always the victim of the marketplace.

Buyers say they won’t honor a price increase for five reasons (although the list is endless).

1. Because they think (automotive) “It’s a privilege to do business with us” they are so big, they do it because they can.  This is usually accompanied with the threat of ‘dozens of people like you who’ll do it 15% cheaper’ or ‘we’ll go offshore’ and blah, blah.

2. They conveniently forgot (ignored) your quote that said:  “The price is based on material being $X.XX per pound. Kilo, ounces-of-gold” etc.  OR you were silly enough simply to quote a part price leaving off the material cost.

3. They tell you they can only adjust their budgets twice a year.

4. They tell you it will take at least 120 days to adjust the system to reflect the new prices and cut the checks.

5. “KOST IS CING!!!!”

By the numbers let’s look at each one of these ‘reasons’:

#1 There is no ‘privilege’ to doing business with anybody.  Those who pay their bills in full are good customers; those who don’t are problem customers.  Recent history has shown us the degrees of ‘loyalty’ large customers have to their supplier base: So long as you do everything they want you’re considered loyal.  But when you finally object to losing money, they’ll look for someone else to.  If there a dozen local companies or offshore molders who could do it 15% cheaper you wouldn’t have been awarded the job in the first place.

#2 Forgetting or ignoring some clause in the contract is an interesting trick.  However it cannot go ignored.  Business is business

#3 -#5 Anybody who tells you they can’t adjust the system, process a change, etc. has conveniently forgotten they paid premium prices to you when the really needed parts, or paid the airfreight to bring in the part to keep their lines from shutting down.

This is simple School Yard Bullying.  So what do you do?

Most people, usually hang up the phone, whimper and ship the parts either at a minimal (read: unacceptable) profit or no profit at all.

What molders don’t realize is “Who’s Walking Who?”   If your customer doesn’t have the $.05 part you make, he can’t sell his $2,000 widget.  Who is in control of the situation?  You, not the customer.

I’ve been shouting to the void for years about a policy manual (you can download one for free in the FREE STUFF section of my website).  It addresses the concept of pricing changes.

I have one client whose system is so automated that when he gets a release to run more parts off an existing purchase order, or his quote finally becomes a PO: he contacts the customer and informs him of the current price of parts.  If the customer agrees (in writing) he runs the order.  If they don’t agree, he won’t run it.  They do this for every order.  It’s his ‘policy’ and he won’t be bullied otherwise.  He doesn’t tolerate threats.  Threaten to pull the job, he’ll tell you to come over this afternoon and pick your molds and parts, so long as you come complete with certified checks to cover everything you owe.

If you want to be a smarty-pants when your customer says he can’t (won’t) honor the price increase for three months, you can tell him you won’t (can’t) ship for three months.  While this is a great way to start a yelling match; it does put the issue directly on the table.

In reality it’s a privilege for your customers to do business with you and not the other way around.  You got the job because you can deliver a quality part, on time, at a reasonable cost.  While there’ll be a big deal about being the low bidder; they’ll pay anything to keep production going.  Occasionally you might remind your customers that YOU choose to do business with THEM.  You both have the right to cease to do business with each other if the relationship changes any time you want.

The ultimate solution is to stand firm on a fair price increase.  Don’t negotiate it.  You are passing through the costs of doing business and you can’t tell the people who sell you the Customer Specified resin you won’t accept their price increase.  If anything, your customer might want to call the resin supplier and mumble words about not longer being a ‘preferred resin supplier’.

As a business person you are entitled to make a profit.  If you want drama and stress, have teenage kids.  Tell your customers ahead of time how you’ll handle resin price increases.  When they happen, tell them you told them about it and what the new prices will be.

Buyers are exceptional actors.  While they’ll tell you they can’t do it, they can.  When they say they’ll pull the job because of price, they haven’t lined anybody up to take it over and with JIT firmly grafted to things like PPAP, once they place the job it is almost impossible to relocate it in a short period of time.

Counter the buyer’s arguments with your documented delivery performance record.  At the end of the day the buyer would rather have someone who consistently keeps his pipeline full than a low cost supplier who can’t deliver reliably.

* * * * * * *

You can read this, think you’re held hostage by your customers and go to bed crying.

Or you can ‘man up’ and not lose money anymore.  It will be a little tough not allowing the buyer to bully you anymore but it will soon be a whole lot easier to come to work in the morning.

Or you can just ignore this until your customers put you out of business.

Your choice, it’s only money.

Unfortunately the Gurus of Statistics were brilliant mathematicians but boring writers.  Very few of their disciples completely read their books to understand the lessons.  Soon the quality folks fell in love with the concept of CpKs, PPM defect rates, DOE’s etc. but failed to comprehend the consequences of the answers.  Most were satisfied with the Cliff Notes versions.  While the Gurus extolled the virtues of statistics they also heavily emphasized it was only a tool.  With the proper application it would vastly improve profits but with improper use, it would only increase overhead costs and degrade profits.

AN EXAMPLE
The concept of CpK is simple.  You look at a tolerance, and then compare the variation of the process.  This variation is then statistically analyzed to give you ‘all possible outcomes’ from the process.

Let’s look at a simple example:  Rolling a pair of dice.  The ‘tolerance’ of a pair of dice is fixed.  The lowest number you can roll is 2 and the highest is 12.  The most frequent number and the average of all the combinations is 7.  In this example, our specified Mean dimension is 7 with a tolerance of +/- 5. (On careful consideration you’ll notice this tolerance is quite tight.)  Now someone decides they require at least a CpK of 1.0 meaning all possible combinations will fit within the tolerance and be centered on the mean.  This is kind of fun to do on a spreadsheet AND it seems reasonable.  You’ll find the standard deviation of all of the combinations is 2.44949.  BUT when you do the three sigma calculations you find statistically the lower 3-sigma limit is -0.3447 and the upper 3-sigma statistical limit is 14.3447.  Oops!

If you rolled a conventional pair of dice in a casino and came up with a negative number or a number higher than twelve, large gentlemen would probably have an intense discussion with you before you were tossed into the parking lot. This is the fault of believing only statistical analysis and ignoring Common Sense.  Statistics don’t lie, but amateur statisticians frequently misunderstand and draw bad conclusions.

All too often I work with clients where someone in the Temple Of Documentation required a statistical proof of robustness in their mold qualification procedures.  The molders and manufacturers made multiple runs of thousands of parts and endless mold modifications only to come up with statistics similar to rolling dice.  After having spent considerable time and money on this silliness, the Designers, Quality Geeks, or Engineers actually approve this ‘non-robust’ process as ‘not statistically qualified but acceptable’. Isn’t this blaspheming against the Sacred ‘Qualification Procedure’?

Before agreeing to CpK’s and other requirements; let these procedures see the ‘light of day’:

If the designs are already to the SPI tolerancing standards two things should be apparent. (1) The part should function successfully at both ends of the tolerance and all combinations in between.  (2) If the designer wants a tighter tolerance than the SPI standards provide for, you will have to ‘Inspect Quality In’ using a 100% sorting process. What the designer is really telling you with a CpK tighter than 1.0 is he’s afraid of his own specified tolerance scheme and believes his product will fail unless you manage to be almost exactly on the Mean dimension. (3) What value, if any, is it to the customer to send a statistical analysis with every shipment?

If the SPI Fine tolerance says +/- .002 and the customer wants a CpK of 1.33 he’s asking you to hold a tolerance of +/-.001.  Meaning you’ll have ugly yield numbers.  “But”, my clients say “This is what the customer wants, and the customer is always right!”  My response is: ‘If the customer is always right he will gladly pay for it.  BUT if the customer’s purchasing agent demands lower pricing, you’re gonna have nasty problems to deal with.’

It’s kinda fun to listen to the Data Dogs expound on the virtues of precision, see the designers blindly follow this philosophy and then listen to the buyer pull his trump card to  this talk with his ‘Fast, Cheap and High Quality’ speech.  The buyer’s only goal is to fill his pipeline with useable parts of acceptable quality, in the volumes necessary, at a reasonable price.  Everything else is wastefully expensive fluff and feathers.

Do your homework and present your case to the customer’s buyer. Buyers/managers only speak one language – money.  Designers and quality people tend to be ignorant or at least not fluent in this language. At the end of the day it is money that plays and everything else gets ejected from the game.

There’s a lesson here:  Before you quote a job, look at what it will take to ‘qualify’ the parts you’ll be molding.  Get a firm, committed, written answer to these questions from the company’s buyer.

(1) Who is paying for all these qualification runs and the production reports?

(2) Although the customer asked for it, are the demands of the statistical calculations even practical? Or will it be an expensive exercise in multiple tooling corrections where you not only have to ‘hit the bull’s eye’ but have to consistently put the next million shots from your gun exactly into the bullet hole from the first shot?

Talk to the buyer before you talk to the Techno-Geeks. Send him the SPI standards and the costs to meet his requirements. Let him make the choice. If you have the data (even from another customer’s part of the same material) to back it up, you’d be amazed what the buyer can do to streamline your qualification process and improve your profits. Ultimately the customer always pays for the qualification - either up front, or many times over buried in the part price

Use statistics wisely, they are merely a tool to use to improve your own profits.  They never were Holy Writ.  .

It’s your choice.

Rejects come in two flavors:

Rejects from the customer – the problem.
If you’ve got reasonably good specifications and inspectors whose IQ is higher than a squirrel, rejects from the customer come from two sources.

First is that someone missed something gross and you shipped a production lot that was drastically different from previous shipments and didn’t have any hope of passing function or cosmetic requirements.  This is a righteous reject.  In this instance a witch hunt is appropriate for both the quality and production people too dumb not to know what a good part was.

The second cause of a customer reject is:  (1) Somebody pulled a quality audit and of the hundreds of dimensions on the specification they found one you didn’t comply with and therefore rejected it. Nobody ever bothered to see if the parts worked or would pass cosmetics.  The minute they found a dimensional discrepancy they shipped the whole lot back. (2) In the normal course of commercial manufacturing you shipped a lot of parts that were functional and cosmetically acceptable but the dimensions were slightly different.  Because you didn’t stay within a CpK of a zillion (+/- .001 mm) it was thought you lost control of the process and therefore there must be some unacceptable parts in the production lot and therefore “we’re rejecting them because their different” (3) Sales have slowed down and the customer’s inventory levels are too high.  They either reject them for any reason they can think of or no reason at all.

Rejects from the customer – the solution
You need a policy on how to handle customer rejects.  Go to wjtassociates.com  click on ‘free stuff’ then download the “Policy Manual”.  In essence it says when a reject happens here’s what you’ll do.:”
(1)    In order to be a valid reject a part must be shipped overnight express as an example of the entire lot with a description of what’s wrong.
(2)    Right or Wrong, all work on that part will halt for two weeks while you investigate the problem.
–If it’s your fault, after the Slaughter of the Usual Suspects, you need an All Hands Effort (24/7 if need be) to fix the problem and try to get replacement parts to your customer ASAP
– If it’s not your fault a stated policy of two weeks without shipments will cause your customer to go into a major pucker before rejecting anything.
(3) Know what quality is.  See below

Rejects from the production floor – The problem
This is usually a head scratcher.  Sometimes the mold goes crazy and it won’t make a good part.  Other times you’re just irritated at a low yield from this mold.  Regardless of what it is the solution is the same.

First, understand quality.  Second make sure your customer has the same definition of quality as you do.  When it doubt go to the industry standards.  Yes, there is a standard for cosmetics, and tolerancing, AND part finishing.  The Society of the Plastics Industry sells them.  Get a set for yourself and one for your customer.

“Parts free of defects” is not a quality standard; it’s an invitation to rejecting every part.  An inspector staring through a 5X magnifying lamp for 30 seconds at part the size of your thumb IS NOT IN ANY cosmetic standard.  Usually it’s 24 -36 inches under normal lighting conditions for 1 second per 2 square inches.  During that time the inspector must make a color match, and find all of the 17 cosmetic defects, AND know which won’t comply.   The last time you bought a car; did you whip out of magnifying lamp and stare at every square inch (interior and exterior) for a minimum of 30 seconds before you bought the car?  I don’t think so.

There are three components to the Universal Definition of Quality; it’s what your spouse thinks of you: (1) You work, for the function your serve.  (2) You are acceptably good looking, for the function in #1.  (3) With conditions #1 and #2 satisfied, size doesn’t matter.

Rejects from the production floor – The Solution
Non-scrap
Sixty percent of your in-house production rejects are usually from not knowing the definition of an acceptable part.

An acceptable part is one that the end use customer (the guy/gal buying the product your customer is selling) will pay what he/she believes is an acceptable price and will get the expected use from the product.  NOTE – While little Johnny’s bicycle helmet might be shiny when his mommy bought it from the store; she isn’t going to return it because it is scratched after it bounces off the sidewalk with or without Johnny’s head in it.

An unacceptable part is one the end use customer will DEMAND an immediate refund/replacement because it (1) doesn’t work (Function) or (2) the aesthetics look so poor it screams inferior workmanship of impending functional failure (Cosmetics).

When was the last time you bought a box of nails and measured each one?  If you did, you’ll find they are not particularly precise.  But you didn’t inspect them because all you did was get your hammer and what you wanted to nail together.  If the nails were reasonably straight and not horribly rusted AND the only reason they bent was because you’re not very good with a hammer, you didn’t care how long they were.  Moral – the end use customer doesn’t dimensionally inspect the products.

Yields – Molds don’t make scrap.  You do.
If your setups aren’t repeatable train your people.  Document your processes; do what works.  Figure out how to translate conditions between machines of different sizes OR run the mold in the same press every time.

Test your machines for consistency.  If a telescopic sight isn’t firmly screwed to the rifle, while you’ll always put the target in the crosshairs, but the site will only occasionally be aligned with the barrel. (Hint: the bullet ALWAYS goes where the barrel is pointed) Great equipment is useless if you don’t maintain it.

Maintain your molds – are vents/waterlines blocked?   Clean them.  Do the techs hook up the water the same way every time?  Train Them

Make a Pareto Chart of Scrap of the scrap from this mold.  This is a bar chart with the largest amount of scrap to lowest.  Analyze it using the 80/20 rule – 80% of your scrap comes from 20% of the possible causes — Is it cavity specific?  Fix the cavity.  Is it random?  Look at your process, something isn’t consistent.  Is it specific to some machine?  Fix the machine.

LOOK AT YOUR CHECKBOOK.
For a part with an 80% yield that represents $5,000 in annual sales with only a 5% profit margin, spending $1,000 to raise the margin to 10% is a waste of money.

Training your people can triple your profits.  Demanding your customer give you reasonable requirements and not tolerating silly rejects can double your profits.

“We’re making too many rejects” isn’t a factual statement; it’s emotional.   Figure out what’s acceptable and work on it.

* * * * *

You can read this and think “I’ll never settle of anything less than the quest for zero defects.”  Feel free to do that until you bankrupt your company by trying to ship the Crown Jewels but invoicing for Rock Salt.  Or, you can put this in the Do Not File file and continue to complain just to hear your lips flap.  OR you can do some real work and change things.  You’d be surprised how once you implement and embed change you’ll look back and be embarrassed at how poorly you ran your company. OR you can print this out and use it to line the litter box of the cat who you keep for in-plant pest control.

It’s only your career, you choose

Bill Tobin

Look at a molding operation as a cash generator. You sell marked up material, machine time and expertise converting it all into dollars per thousand pieces.  For the moment let’s not look at cost.  Suppose you have a purchase order for $5000 that translates into 25,000 parts.  Assume a 4 cavity tool and 20 second cycle.  With a little math that works out to $144 sales generated per production hour.  A simple analogy would be this is a taxi cab making $144/hour whether driving or idle.

If you included a setup charge of $200(?) you’ve allowed for about an hour and twenty minutes from the time you shut down the previous job to the time you’re producing acceptable parts on this new job.  This means if you don’t have acceptable new parts an hour and twenty minutes after you shut down the precious job, you are losing money.

That’s the theory.  Now let’s look at the Real World:

While probably not a complete list, here are the events in no particular order, that need to happen before you begin making money with the new mold:

1.    Unhook, blowout, and drain the water lines from the previous mold.
2.    Spray with preservative, do all appropriate paperwork for maintenance etc.
3.    Pull the mold from the press
4.    Store (?) knockout rods, hoses etc.
5.    Put the mold in storage.
6.    Drain (remove) the hopper containing the material for the previous job.
7.    Purge the machine’s injection unit.
8.    Hang the new mold in the press with the appropriate length knockout rods
9.    Hook up the cooling systems, power up the electrical system on the mold if necessary.
10.    Reset the machine’s settings – pressures, time, distances, speeds, and temperatures.
11.    Bring the mold up to temperature
12.    Hookup or fill the material hopper with the new material
13.    Dry the material per the specifications
14.    Fill the machine’s injection unit with new material
15.    Check the new material for proper temperature, adjust accordingly
16.    Have an adequate supply of packaging material at the press site
17.    Have the process, quality control, packaging, and secondary finishing documentation at the press.
18.    Clean off mold preservative from mold face.
19.    Start up the new mold.
20.    Adjust the settings until good parts are produced, at or faster than the quoted cycle.
21.    Get approval from Quality to begin production.
22.    Have an operator available when required.

Some of the steps must be done in sequence.  Some only must be achieved before actual production begins.  All of these steps are time, personnel and equipment/material dependent:

The setup team must do the setup.  You must have the people available. If they are pulled away to troubleshoot other machines, relieve operators during breaks etc. your setup stalls. If the setup happens during a shift change, there will be a further delay (unless somebody is paying overtime) when the new setup team has first checked production and then will resume the setup. All this delay time is billed off to the setup at $144/hr. Another personnel cost is having no operator available.  Equipment and material factors can be as simple as having the overhead crane unavailable to pull and hang the molds.  How much time did it take to bring the new material; boxes, skids, tape machines, labels etc to the press site?  Do you have all the paperwork at the press site?  How long was the wait time for QC to release the job to production?

The first step is to analyze the problem. Hire a ‘Joey’ or ‘Suzy’ – the infamous underpaid/overworked student intern.  Have them set up a spreadsheet using the items above.  Record each of the steps in terms of time – from the time one job was shut down, to the time the next job was in production.  Remember the Hawthorne Effect:  When you are observing people doing something, the very fact that you’re looking at them will change their behavior. To eliminate the ‘I’m watching you’ factor, record at least ten setups.

Put the data in a spreadsheet, do the calculation on how much the job should be generating per hour to give each component a cost per hour basis.  Remember the same machine might generate fifty dollars in sales per hour on one job and three times or even half that on the next job.

After a lot of keyboard thumping and spreadsheeting, have the computer merge all the data into one master spreadsheet.  Now sort the data and draw a Pareto Chart that orders the most expensive component to the least expensive. What you’ll see is usually an eye opener.

You’ll see two trends:  (1) Some jobs are ‘stinkers’ and have difficult setups and (2) some components are generically expensive. Have Joey or Suzy classify each step into the classic Operations Research categories:

MAN – most of the components in long setup times have to do with the availability of people.  Some shops only do changeovers on first shift.  Unless you can schedule all the runs to complete during the day your taxi cab is idling at our $144/hour overnight waiting for the setup team.  Scheduling operators, material handlers and inspectors for the job is just as important as hanging the mold.

METHOD – Train your people.  Most operators can do the first few steps of troubleshooting simply by comparing the required settings to the current settings on the machines. This keeps the setup team doing setups, and not troubleshooting.  Make sure the mold is ready to run with no blocked off cavities, dings from the previous run have been fixed, no wires are pinched etc. Having to pull the mold before you begin the run because maintenance wasn’t done is inexcusable. Before a new job is scheduled, pre-stage the materials.  Make sure getting the old mold put into storage, the new mold available, material, boxes, skids, and paperwork are all easily accomplished before you begin.  Make sure the inspector’s first priority is to be there to approve the parts when ready.

EQUIPMENT – a quick change mold system only shortens the ‘clamp up time’.  It is a waste of money if you spend time hooking up waterlines or going to the tool crib to make up new hoses.  If you spend the money to put manifolds on your mold there is only one ‘in’ and one ‘out’ to hook up on each mold half. Hookups can account for 20-30 minutes of setup time; different waterline hookup patterns also account for a lot of dimensional variation run to run.  Manifolds eliminate both problems.  Portable material hoppers with detachable mini machine hoppers allow you to pre-dry the material and in only a few minutes change materials.  Extra water and electrical hookups allow you to bring the mold up to temperature before you hang the mold.

The rule of PARETO analysis is to work on what costs the most first and ignore everything else. A practical goal is to cut that particular item’s impact in halve. When you’ve done your work properly on the costliest cause, redo the study.  If there’s something obvious in the ‘Stinkers’ fix it first, then look at the overall data. In many cases there is a spillover effect and something that was third or fourth place originally will now become first. Go work on that. When you get to where the elimination of the most expensive item costs more than the benefit you’ll receive; stop. It isn’t practical to continue.

With small run shops, setups comprise a significant portion of the overall run.  Here is where, if you can put it into the tooling cost, the quick changes systems make financial sense.  Other shops will tell you if the setup takes less than 5% of the run time, it doesn’t matter.  The answer to here is yes and no.  Yes – the portion of idle time can usually be buried in the part pricing.  No – this is leaving money on the table.  When you’ve lost several hours of potential money generating production time, you’ll never get it back.

There’s no such thing as an acceptable loss.

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For the Techno-Geeks and Gadget-Engineers this isn’t about new technology.  It’s about money.  Spend money so that you can maximize profits.  Technology constantly innovates. What is not practical now might be feasible in the future.  Keep informed on what can make your setups shorter.  There’s always something that can give you less idle time.

Your Choice

– Bill Tobin

I was having a conversation with a buyer on why a certain under performing supplier consistently got additional work. This supplier was neither bad nor good; it just wasn’t a fit for him and his customer.  I suggested there might be something under the table going on.

And then the fight started . . . . . . . . .

THE PROBLEM

Everyone is in business to make a profit.  Part of making a profit is having an edge.  A competitive edge has two components:

The first we all recognize:  being able to exploit whatever technology you use to its fullest extent.  In the molding business it’s building very efficient molds, and processing the plastic in such a way that you get the highest yields.

The second component to a competitive edge is marketing.  It doesn’t matter how good you are if you can’t sell what you do.  Being on the Preferred Vendor list is what every supplier strives for.  One way is to be the low bidder with excellent delivery performance.

Another way is to buy loyalty.  We call them ‘Commission Reps’.  Some shops don’t use Commission Reps but they do pay commissions.  In this case it goes to whoever can influence the decision to become the successful bidder.

While it is still a time honored way of doing business in the rest of the world I had thought these practices had pretty much died out in the USA; until the economy crashed.  When people are scrambling for business to simply keep the doors open, the time-honored practice of ‘gratuities’ comes back in full force.

While you may think this is ‘the way it is’; there is something your company can do about it whether you are a supplier or a customer.

When I first hired into the Automotive Industry many decades ago, I came in on the tail end of my employer cleaning up the practice of shameless corruption.  My employer wasn’t naïve enough to believe they could stop their suppliers tempting a ‘baby’ engineer like myself.  I was in my mid 20’s with the authority to direct several million dollars worth of business to whomever I thought was the right supplier.  They had four simple policies that were a condition of employment for those of us who directed business (and yes, it went all the way to the top of the organization):

The first policy had to do with ‘normal’ gratuities:  If you could eat, drink, smoke, or play with it in one day and worth less than $100; No problem. Don’t ask for it, don’t talk about it.

The second policy was: Gratuities of any material value you could accept with three conditions: (1)  lt had to sit on your desk for all to see for 24 hours - 3 business days - fully identified that it came from some supplier. (2)  Your manager had to be informed (if he/she got jealous, tough).  (3) At the appropriate time in the tax year you would be mailed a “Miscellaneous Income” tax form from whoever gave you the gift for you to declare as additional income for your income taxes.  If the suppliers ignored this policy, they were removed from the supplier list for three years regardless of how good they were.  For the suppliers, it was a simple write off as a cost of doing business.

The third policy was simple:  Any gratuity given privately (such as a Christmas Ham given in the parking lot) was a firing offense.  Period.  No exceptions.

The fourth policy was what scared everybody straight:  As a condition of employment you had to submit a copy of your final Income Tax forms to the company each year for those of us who directed business or spent out company’s money.  It would be kept in confidence.  It may or may not be chosen to be buggered by an outside forensic accountant.  You never knew if it was a random check or if they thought you’d been naughty.

Here was their logic:

No matter how you try to explain it, this ‘marketing cost-gratuity-sales expense’, is ultimately paid for by the customer.  If my employer is paying me, and a supplier is also paying me; the supplier is adding this additional cost to his products sold to my employer.  This means I am taking additional income from my own company (politely stated: stealing).

THE CONSEQUENCES OF GETTING CAUGHT:

Once caught, my employer filed suit for the lost money plus legal expenses and interest.  They would not negotiate restitution quietly nor sign non-disclosure agreements. This meant everything was public record.  Being public record, the company told everybody in a ‘position of trust’ who it was, how much was taken, how much they recovered, as well as the estimate of the embezzler’s out of pocket legal costs.  If a supplier was paying one guy to distribute it up the organization ladder to keep everything quiet, everyone got prosecuted.  If they quit, read the next paragraph.

When the lawsuits were over, they would inform the federal authorities about possible income tax evasion AND follow up on it until the people who took the graft got stomped by the Tax Nazis.  As the last step, they turned to the supplier: They would renegotiate the part prices (and look seriously at who approved them) to reflect future savings on all parts the supplier was producing if it was an isolated case. Or, as stated above, they’d cease to do business with them.

As an employee, if you got questioned on your ‘style of living’, there were no problems with the fact that some employees were rich because of inheritances, successes in the stock market, rich/working spouses, second jobs, etc.

If you didn’t like the job description that required showing your tax forms, you simply transferred out.  Nobody cared.

Once a year the purchasing department and the fraud specialists would put on a seminar on ‘how to steal’.  They’d tell us all the ways people had tried and failed along with what they did to them.  When a current investigation got someone, they’d tell everybody (a public hanging). Once this policy of ‘Public Hangings’ caught on, it was interesting to see the changes.  The first year was brutal, because many believed it was just more HR prattle.  Then they found out how much money the corporation was recovering and who got nailed. Other than the annual ‘seminars’ we rarely heard of anything by the third year.

Does this stop Christmas Gifts and the occasional ‘payment for services rendered’?  Not in the least!  But it has a profound effect on employees who think about taking them.  The fear wasn’t the Corporate Wrath brought down on the employee.  It was the tax people who would go back several years and assess back taxes, fines (big ones), and interest compounded for as many years as they audited on the taxes AND fines.

The B-schools tell us 5% of sales is the marketing budget.  This is tempting when you think of the millions of dollars of tooling and parts being purchased.  If your supplier doesn’t have to budget this expense, it’s a nice cost savings plan.

If you’re a supplier and this is becoming an irritating expense; write a polite note to your customers informing them of the new documentation requirements of name, tax ID number, address etc. and you’ll be sending the appropriate tax forms out to those requiring Finder’s Fees etc.  If you’re a customer, just tell your people you’ll be implementing a policy of ‘open financial disclosure’ with new employment agreements for specific people.  If nobody has a problem with it, it’s no problem.  But it’s kinda fun to watch the people who get nervous.

/ / / / / / / /  * * * * * * * / / / / / / /

I had companies tell me they have a ’strict no-gratuities’ policy.  This means even with a vendor visit the engineer pays for his own lunch.  While a lofty ideal it only promotes more creative ways to provide gratuities. (”want a lift ticket for your ski vacation?”  “tickets to the game?” “We can make a mortgage payment for you/pay off a credit card/pay for a couple of classes for your kid at college”)  Creativity abounds.

I’ve always believed in never doing anything I can’t afford to get caught at.  This doesn’t mean don’t do anything.  Just have a clear conscious saying what you did, when asked.

It’s your choice.

First, let’s get something clear: The word ‘manage’ means to exert a controlling influence.  However, the Customer seems to think Supplier Management means they can control their supplier base to do whatever they want.  In reality you have more luck trying to train a dozen cats to dance the polka.

Small businesses (suppliers) started up because they thought they could do it better than being lost in the bowels of big business.  They are more efficient because the money they spend doesn’t have the “mother may I?” mentality of proposals, PowerPoint presentations, and committees.  Things get done with a minimum of fuss and a focus on the product, not office politics.

The very nature of our tax system requires that from an accounting standpoint a small business ‘looks’ as if it is barely surviving.  Small closely held corporations aren’t required to have the accounting or reporting practices that must report to Wall Street and its stock holders.  Without experience in forensic accounting, looking at a small company’s financial reports is, at the very least, confusing.

When it comes to Supplier Management Practices many of the ‘games’ the customer plays on small businesses need only be personalized to see how foolish they are.  Here are some examples:

1. Financial Reporting - ‘send us your Profit and Loss statement with each shipment so we know you’re healthy’.  What if you’re employer asked you for your financial records before you got each paycheck twice a month?  Your response would be (1) you simply wouldn’t do it, or (2) you’d make something up because it was too much work.

2. Delayed Payments / Cost reductions - ‘It’s a privilege to do business with us.  We pay our invoices in N-60 (N-90 etc.)’.  Would you work for someone who held back your paycheck for more than two months?  Nope.  You’d quit and find another job. How long would you work for a company who hired you at a salary and two months later said they are cutting your pay by 15% and wanted more work from you?

3. Quality - ‘Send us proof of CpK (for free)’.  Would you work for a company who to keep it’s health insurance premiums low;  monitored what you ate, required you to go to a gym, not smoke or drink, and would fire you if you got a speeding ticket? And here you thought they hired you for what you could do on the job.  Dope.

4. Vender Visitation/performance reviews - Many companies do vendor audits looking at your plant and manufacturing practices.  Would you work for a company that came to your house to observe how you raised your children, what church you went to, asked you to describe your love life - all as a condition of employment?  Could you work for a company that filled your personnel file with a written report of every little mistake you made but didn’t allow you to refute the accuracy of the report?

If you think any of these above practices would engender loyalty in the Customer/Supplier relationship you are sadly mistaken.  But, when a customer does business with a supplier, it is valid to ask if the supplier is reliable and will continue to be so in the future.

Here’s the solution:

1. Financial Reporting - ask the supplier for permission for the customer to get (pay for) a monthly report from the supplier’s merchant banker.  This report will only state that whatever loans the bank has made to the supplier are being paid back on time and his credit is good.  Not the dollar amount or for what purpose.  If a company is financially healthy, its banker is more than happy to tell you.  Keep in mind credit reports or Dunn and Bradstreet ratings don’t give a good picture.  All of the Big Three have horrible credit ratings because they pay their suppliers late.

2. Delayed Payments/cost reductions - As far as the supplier is concerned you’re just another customer; no more, no less.  If he can’t make an acceptable profit from you, at some point in time he’ll tell you to take your business elsewhere. There is no ‘privilege’ in doing business with anyone.  You placed the job with this particular supplier because he was the low bidder.  If there was someone cheaper why didn’t you place the job elsewhere? Don’t agree to N-30 then pay Net 90.

3. Quality - Your only interest is a supply chain full of usable parts.  All the complexities of CpK, 6-Sigma etc usually end up in someone’s filing cabinet and nobody actually looks at it.  Proof - I’ve written computer programs that simply made up charts for a Supplier to send to his Customer at $100/chart.  All the parts worked, nobody cared.

4. Vendor Visits and Performance reviews - before you hop on a plane to visit your supplier ask yourself:  “If I see his plant and talk to managers; am I competent enough to understand the process and make an informed judgment?”  Smart suppliers won’t even let you on the production floor (”for insurance reasons”, “it’s proprietary”, “we’re not going to show you how we make your competition’s products”).  What they have to sell is expertise not a pretty plant.  How they make your product is none of your business.

More than 60% of negative comments on performance reviews are not due to the supplier.  Usually the customer hasn’t revised his specifications so that an acceptable part measures out to agree to the design.  Many Customer returns are really an exercise is having excess inventory because of bad forecasting.  What do you think would happen if the supplier gave annual performance reviews to all its customers stating the worst customer would be dropped?  While not a common practice, it’s beginning to happen.

You chose your supplier base because they have a history (verifiable) of on-time acceptable product shipments.  That’s all.  Everything else is wasted effort.

Supplier Management is a silly as saying you manage your spouse.  Those who think they can, usually end up divorced.  Doing business is like a marriage: each party has clear expectations of the other.  Trouble only arises when there isn’t agreement.  Yes, there will be the occasional ‘bump in the road’.  But if the relationship is based on trust and honesty it is fairly easy to work through the problem at hand.  Be honest with each other; make sure you both profit from the relationship, and be polite whether things go right or wrong.  Do this and you’ll have a long enduring relationship.

It’s simple.

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You can read this, agree with it and then bow and scrape as your supplier bullies you.  Keep in mind they aren’t paying you for financial reporting, the time wasted on vendor visits or the arguments of not complying to CpK but still shipping usable parts.

OR you can read this and take a stand.  If you don’t want problems learn to say “no” politely and firmly. The philosophy of Supplier Management is really a game of cat and mouse.  You’re the Mouse.  The cat stops playing when either it had killed the mouse, or the mouse fights back.  Think about it.

It’s your money.

All too often people quote “Please quote the design and build a class A mold, capable of producing x, xxx, xxx, xxx parts per the attached design with a CpK of 1.33” What have you really asked for? Did they even ask the right question? Or, is it like your 8 year old daughter answering your question with “Because”, thinking it’s a complete answer.

What’s a ‘Class A’ Mold?

Capable of producing x, xxx, xxx, xxx parts over the life of the tool or annually?

Can the parts even be made to your design? Who says so?

A CpK has cut all your tolerances in half. Can anybody make those parts?

Simply shot-gunning the above quote to five vendors (plus the one you picked offshore only because they took out an ad in a trade magazine or you received one of their bulk e-mails) will only result in six completely different quotes with different size and different technology molds. This give you NO information. Unfortunately what usually happens is someone picks the low bidder and you’re stuck with what you have.

First you need to know your annual volumes. If you don’t have that take what marketing calls a three year life span and divide by three. There are several economic formulas that will tell you how many operating cavities you’ll need to support this volume. If you have big parts, this may mean multiple tools. It may also come back and say you need 250 operating cavities. Unless your part is really simple you haven’t got a prayer building a mold with that many cavities that you can control.

Now you need to know what kind of a tool is best for your part: Two Plate, three plate, hot runner, insulated runner, valve gates, tab gates, sub gates or a combo tool using any of the runnerless technologies combined with conventional sprue/runner designs.

What’s the answer? Actually it’s simple: COMMUNICATION

If you don’t know (exactly) what kind of tool, what technology (no Injection Molding isn’t the only one out there), what kind of steel (Why steel in the first place?) and how many cavities are the best for you, hire someone who does. This person you hire must be able to do several things:

1. Not only recommend how to write the request for quote, but explain to you in simple language why it’s written that way.
2. He must be able to come up with tooling sources that have proven that are familiar with parts similar to what you’re looking to produce, and show you the proof – while hiring your friends might be nice in these economic times, you’re betting the future of your company on this part and friendship has nothing to do with it.
3. He must use specific and exacting tooling specifications. There’s no such thing as a ‘Class A’ tool. Some people use the SPI designations, but if you look at those they are very vague.
4. He must be able to prove to you your mold isn’t going to be a Maintenance Money Pit before you build it.
5. He must show you industry standards for tolerancing and show you that what you want is within those tolerances.

While this consultant may seem expensive by the hour, remember a good tool costs about the same as a house. Paying a few thousand to assure it will do what you want is a good investment.

Once you’ve chosen a tool shop capable of making your mold, you must have a weekly progress report assuring you it is on time and on schedule. All too many people will place a job for several hundred thousand dollars and then begin calling the tooling source two weeks before its delivery asking when it will be ready. They usually find out it won’t be ready on time.

If your only interest is in procuring parts, you should have purchased this tooling expertise from a molding house. However, they should have demonstrated expertise making parts in the volumes you want to the tolerances you need before you give them the work.

Once you’ve built the tool, not only try it out to see if it makes parts, but OPTIMIZE the cycle. You’ll need your designer, engineer, quality person and buyer present. Before everything is over, get a signed document on the definition of a good part. In the end you only want a pipeline full of functional, cosmetically acceptable parts. Since you’re not willing to pay for the Crown Jewels, don’t ask for them.

Things to avoid:

“We have velly hard workers and goode machines” If you tooling source’s website looks like it was written by an 11 year old, it probably was.

“We’re doing OK’ – instead of a progress report. Before you place the job have them show you the progress reporting form they use. If they don’t have one, what does that tell you?

Never pay more than 50% of the quoted amount before you get good parts. Conversely, never hold back money ‘just to keep them honest’ – who’s being dishonest here?

“You can process that dimension in” Maybe you can, but why should you? You’re purchasing a mold that supposedly will give you the widest possible process latitude, not a narrow one to get a dimension correct because the tool maker couldn’t.

Having a good tool made is like finding a marriage partner. If you go in blind, you get what you deserve. If you take the time to see how the relationship will work before you commit to it, your life will be easier.

* * * * *

You can read this, nod your head knowingly and place the job with ‘the low bidder’ with a shop whose major asset is its location where you can do some really nifty shopping. Congratulations you just purchased a very expensive boat anchor. Or you can read this and begin asking questions about the choice of a vendor. OR you can admit you’re not a tooling or molding expert and in the interest of your own company, hire someone on a short term basis who is. In the long run you’ll save money. OR your can use this to scare the rats in the executive offices and go back to sleep.

It’s your choice.

This is the designer/consultant’s Full Employment Act.  No requirements about taking it under a 100 meters of water, but the product would be exposed to temperature, humidity, rain, snow, dirt, spiders etc.  It just sat there receiving phone calls from the lottery’s computer and telling the sign one hundred feet off the ground what numbers to display.

The first consideration is whether this seal has to be permanent or temporary.  Permanent means you put it together and it stays together.  Temporary means either a one time (disposable) use or something you could open and close to repair the inner workings.  In the closed position it had a seal.  Being able to open it might allow repairs.  Because of the internal snazziness of certain components it was two parts that needed to be attached together. There are all sorts of ways to do make it hermetic:

MECHANICAL BONDING
Screws/bolts – this is a great way to make a hermetic seal (that mandates a gasket of some kind along with the appropriate retaining grooves and some heavy algebra calculating the crush on the gasket as the piece is put together.  But it is component and labor intensive.

Snap-fit/crush pins through a gasket.  All the design complexity of the Screws/bolts idea without the screws and bolts.  These can be designed as ‘one way’ meaning if you want to disassemble it you need to break it, or the snaps can be designed to push out of the way so that you can separate the two parts.

CHEMICAL BONDING
Adhesives/solvent welding – good but time intensive and with the concern that the bleed over might mess up the internal components unless the design facilitates someplace for the bleed-over to go. These must be jigged (clamped) in position until whatever you are using as an adhesive has ‘set’.

THERMAL BONDING
Ultra sonic/vibration welding.  This is an excellent technology to make hermetic seals.  However the imparted vibrational energy is not particularly friendly to printed circuit boards or their components.  Since this is a melting technology you also need a place for the bleed-over to go unless it isn’t a cosmetic concern.

Electro-magnetic bonding.  Here we have a ‘gasket’ made from the material but heavily loaded with ferrite.  We put it near and intense alternating magnetic field, the particles vibrate to the point of melting the gasket and the parent material and Viola!  Hermetic seal. Cool!  Very controllable, the darling of the medical device folks because it’s clean.  However just like the vibration welding techniques, it is not particularly friendly to electronics.

Hot plate welding.  This very simply asks you to make to ‘ribs’ on your sealing surface proud.  You then make (have someone make) a contoured heated plate.  Both halves are jigged together and separated only enough to allow the heated plate in.  The parts are then put in contact with the heated plate until the ribs are melted.  The plate is quickly removed and the parts are pushed together.  Your design needs to allow for the bleed-over to go somewhere (usually this is a designed in groove on either side of the ribs OR you just let it smoosh on the inside and outside.  The key here is also the limit you need in any thermal welding.  You need to have the machine designed not only to provide pressure to hold the pieces together but it must also be mounted with stops so that the melt pool isn’t pushed away.

In all thermal bonding techniques it is equally important to get a good melt pool AND keep the parts positioned long enough for the melt to cool.

NOTES:  Mechanical bonding is only as strong as what is holding it together. Under vibration or thermal softening many mechanical techniques fail.  Remember that plastic creeps, you’ll either need to install metal ultra-sonic insets and use some kind of locking screw to keep the screw from backing out or the tri-lobal screws where the plastic will creep back around the screw holding it in place.

Chemical/Thermal bonding is usually considered a one-way assembly technique. To test the quality of the weld, break the unit apart at the welded/glued interface.  An adhesion bond is defined as being able to equally pull the parent material from each of the two halves when it is broken.  This therefore makes the quality of the weld a direct function of cleanliness.  Greasy fingers will leave an ‘interface’ layer where your ultra-sonic/thermal melt pool won’t directly adhere plastic to plastic.  This microscopic seam line will destroy the hermetic nature of the seal.

What did my client end up doing?  Actually kinda funny:  He put the electronics in one half of the plastic part then covered it in Urethane potting compound.  Once it had set up, he then solvent welded the two parts together.  Not only was it waterproof, it could probably survive being hit by a meteor!  I couldn’t convince him either would do the job unless there was a hidden agenda somewhere.  I will concede it passed environmental exposure, water immersion and heat soaking with flying colors.

I had another client who was molding a little ‘rat fink’ load cell in GF Nylon coupled with a micro radio transmitter.  This little one inch cube was fixed to the hub of the tire for a long-haul trailer.  This gizmo would tell whoever read the radio signal, how fast the trailer was going, how long it stopped, acceleration and deceleration.  What fascinated me on this project wasn’t that it was Big Brother looking over the trucker’s driving style, it was how to put a plastic/electronic product on the hub of a truck tire and have it survive the abuse those things see.

In both cases what was important wasn’t the attachment technique.  It was whether the gizmo would survive its use environment for whatever the manufacturer considered an acceptable lifespan (defined in years for the billboard computer and thousands of miles for the truck thingy).  Strong doesn’t mean tough.  Strong means durable or (dare we say it?) Fitness for use.

End use testing is the ‘D’ in R&D that most designers find boring because they are usually not very good at designing real world testing and properly interpreting the (statistical) results.  If you’re in that boat; your friendly community college, university or the American Society of Quality Control can dig up a Geek who can help your design the test and then tell you in small simple words what the results gave you.

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This article, like all the other ones, is virtual.  You can go to the Engineers and tell them they need a few more line items in their budget to verify their designs (remember FEA is supposed to be based on worst case tests, not theoretical assumptions).  Or you can go to the middle managers and marketeers who’ll tell you it will ruin their profit picture and product recalls are why the company has a legal department.  (you disloyal, nay-saying dummy!) OR you can step up to the plate and do something. OR….. You can read it, nod your head knowingly and feed the printout to the squirrels outside as insulation for the cold winter and go back to sleep.

Your choice.