Times have changed.  Many companies have finally figured out ‘Kost is Cing” isn’t.  Off shore sourcing degraded quality standards, upset delivery schedules and too many parts were being air freighted in.  Now molds are being brought back into the country and sourced (as they should be) locally.  But the relocation program can easily turn into a mess!
I keep hearing the horror stories:  “We tried to bring the mold back into the country but the guy wants $XXX,XXX in Engineering Services Fees before he’ll release the tooling!”  Welcome to the real world!  Here’s what’s happening.

You’re pulling the job and the offshore molder is going to be losing profit he’d make if he kept it.  He’s across several time zones, international borders, and legal systems.  Here in the USA you only have to pay up all outstanding invoices and whatever charges you agreed to in your policy manual having to do with raw materials and such.  Once you’ve settled your account if you don’t get your mold, you go to court and things get nasty very quickly for your supplier.  If you try the same stunt with a Chinese molder, they’ll just laugh at you.  While you have recourse to go through the Chinese Court system, the game’s rigged for the home team.  You’re not the home team. Get it?

Scenario #1. Let’s say you do get the mold and you ship it to your best bud that you’ve not been allowing to quote because you sent everything across the pond.  Here’s your challenge:

Whose quality standards are we using?  If you expect the guy in the Windy City to produce the crown jewels from a mold that was lucky to make parts that even looked like what you’d specified; you’re in for a disappointment.

Expect any competent molder to take the mold as he would any other mold that just showed up on his dock.  In his view it’s nothing more than a pile of metal plates (maybe not even tool steel) until proven otherwise.

Expect to pay for an evaluation run.  This will show everyone what the mold is capable of producing, warts and all.

Expect a lengthy laundry list of repairs, replacements and refurbishments that will have to be done and paid for before this mold is put into production.  Keep in mind your buyer giggled with delight when the mold’s original cost was 1/3 the stateside cost.  The reason for this low cost was cheap labor and inexpensive (read different quality) materials.  In low labor markets they have no expectation of a mold lasting 1,000,000 cycles with its original components.  Because labor is so cheap, it’s more economical to continually rebuild components.  I’ve seen a few jobs that by the time the insourced mold was producing quality parts, the mold base was the only thing salvageable: all the inserts, mechanisms and pins were replaced.  Ouch! Spendy.

You might also brace yourself for the dreaded “There’s nothing salvageable in this tool” speech.  What you’re being told is that if the molder could pay his people $2/day it would be economical to hire an army of convicts to deflash every part and he’d be able to run the volumes you need.  But in the USA, it’s probably cheaper overall to simply build a new mold and get on with life.  Remember the buyer saying “I can by three molds in China for the price of one mold in the USA!”?  Now’s the time to cash in that boast.

SCENARIO #2
Regardless of whether you can directly produce acceptable parts from your ‘insourced’ mold, refurbish the mold, or replace it entirely; you’re faced with two problems.  How do I (1) track the repairs/refurbishment?  And (2) how do I requalify the parts/molds?

This is a big engineering commitment that neither the customer nor the molder can staff because the problem is an intense short term one.  Who are you going to find who’ll do this besides their normal responsibilities?  If you think the molder has tooling engineers loafing around, he doesn’t. He downsized his staff when you downsized on him.  If you think you can talk your people into working double duty (read 60-80 hour weeks) under the clause ‘any other duties management shall assign’ in your employment agreement; they’ll probably quit, or be divorced after the first month of this kind of panic.

What do you do?  Actually it’s simple.  This is what I do.  I’m experienced, don’t mind long hours, and short term (you don’t have to fire me, I just go home when the job is done). You hire me, or another consultant.  Tooling is rebuilt and reported to you on a weekly basis, qualifications are run and certified and you’re back in business as quickly as feasibly possible.  I’m not in love with traveling.  I extensively use the Internet for progress reporting (electronic spreadsheets complete with graphs), digital photographs to show the physical progress, and free video conferencing which is cheap. A one hour teleconference, is hundreds (sometimes thousands) of times cheaper than the time and billable hours for a road trip. Even a middle manager can figure that out!

Yup, it will cost you about what you pay your people IF you paid them for all the hours they’d work doing this themselves.  Or, you can do what you did with the Chinese mold-builder/molder: make one phone call, send off a check, go to sleep, and begin yelling for finished parts when the guy said he’d be done.  Oh Wait! You can’t do that! You’re already in production.  Now what?

+ + + + + + + +

You can read this and think it’s nothing less than Shameless Marketing on my part. You’re probably be right.  Or, you can read this and at least not get bushwhacked when a few dozen tools have to be relocated; not knowing the kind of commitment it will take to find new homes for all of them and fill the supply chain back up.  Or you can naively think your people will gladly jump to the task and ‘be happy in their work’ – you only have a few weeks of that silliness before burnout sets in and your people show up to work either grumpy, hungover or both.  OR you can just go back to sleep and wait for the dreaded ‘relocation memo’ to whack you on the nose.

I could use the work and you need to keep your people and your job.

Your choice.

Try these tips

- Start and finish the meeting on time. If there’s more to consider, plan the appropriate follow-up actions or schedule another meeting.  HINT ON PROMPTNESS Shut the door at the start of the meeting.  Lock the door and don’t answer the knocking if you want some fun.  Or if anyone (managers included) come in late, everyone stands up and applauds them for taking time out of their busy day to come to the meeting.

- At the close of the meeting, ask if participants are comfortable with the outcomes.  HINT ON OUTCOMES – business isn’t a democracy, but it also isn’t a dictatorship.  Make sure the assigned work is evenly distributed so that no one is overloaded and no slackers can point to someone else.

- Make sure all meeting participants know that you expect them to be on time and prepared to discuss their agenda items.  HINT ON DISCUSSIONS:  While a little brutal make a ground rule that anyone who comments off topic, isn’t prepared, or disrupts the meeting will be told to leave and must make up his/her assignment without further participation.

- Encourage everyone to speak up. Quieter people may have valuable contributions, but they may need some encouragement to share them.  HINTS ON PARTICIPATION: Everyone has something to contribute.  Make the ground rules clear that if someone sees a flaw in the plan should speak up, not criticizing but offering an alternative.  Ten people will have ten different points of view.  All of them are usually valid.

- Provide a detailed agenda for each meeting. It should include topics for and the purpose of discussion, as well as a discussion leader and time allotment for each topic. Distribute the agenda a couple of days before the meeting so that meeting participants have time to prepare.  HINTS ON MEETING AGENDAS – meetings are for problem solving, information exchange and consensus building.  Focus on the agenda.  If someone wants to preach point them to the local church.

- Assign someone to take notes in each meeting. That way, decisions and follow-up action items are documented and can be circulated to the meeting’s participants.  NOTES – there are computer programs that can record meetings and transcribe them into notes.  You don’t need a verbatim transcript.  Meetings are not a trial or deposition.  Highlight the bullet points, who is responsible for the actions and when they will deliver.  Three columns on a sheet of paper #1 Action Item, #2 Who’s going to handle it #3 the expected outcome (both action and completion dates).

- Determine which meetings are really necessary. If the objective of a meeting is to simply update others about ongoing projects, it might make more sense to send a memo or group e-mail, or to post the information on your company’s computer network. However, for in-depth discussions, meetings generally work best.  IMPORTANCE OF MEETINGS – While many people believe in weekly meetings and the importance of ‘Face Time’; meetings are expensive.  If you divide company profits by headcount you’ll quickly see each person at a meeting costs (or should be generating) $100+/hour.  A one hour meeting costs someone between $500 and $1000 worth of profit.  Think about the ROI and balance that against an e-mail before you schedule the meeting.

PRESENTATIONS
More and more, PowerPoint presentations are common in meetings.  Here are some hints:

-Graphics – Slides should be highlighting talking points.  Hard copy handouts are better to looking at data.  Use your slides to advance your meeting’s agenda. Don’t read the slide out loud.  This isn’t story time at nursery school.  The slide should either prompt your speech or be self explanatory.  Nothing else.

-Readability  - the rule of thumb for slides is that if the whole slide can’t be read in less than 5 seconds, you should use more slides.

-Data Overload – the slide should be in 24 point Font or larger.  Turning a spreadsheet into a slide will only allow the people next to the screen to read it.  If this kind of data is necessary, use a handout.  Small front is unreadable and irritating.

-Handouts.  Using slides as handouts only shows the presenter isn’t prepared. Handouts should be text, tables, photos and such as something to discuss.  Keep in mind, if you give someone a handout, they’ll read it and not pay attention to your slides.

-FORMAT – Your first slide to be a graphic ‘table of contents’ for the rest of your slides telling the audience what they are going to see later in the presentation.  Each presentation should have four parts: 1. Tell them what you are going to tell them.  2. Tell them.  3. Tell them what you told them.  4. Allow them to ask questions about what you told them.

-THEATER – a PowerPoint presentation is a kind of theatrical performance.
1. Rehearse what you are going to say in front of somebody.  Do it until they understand what you’re saying.  If they don’t understand, redo the slides.  Simple is better than confusing.  You should control the presentation not it controlling you.  Know what you are saying so well that you don’t even have to use the slides to prompt you.

2. People cannot take notes in the dark.  The only way you can see a slide with a dark background is in a completely blackened room and bright colored text.  If you ABSOLUTELY need a background color use a light one where black colored letters are easily readable.  If not, use a clear background and dim the room, don’t turn off all the lights.

3.  Use larger font for important headings and smaller fonts for subheadings.  Keep the font simple – Ariel, Times New Roman or Veranda.  Fancy fonts might look good on billboards or award diplomas but are impossible to read during a presentation.

4. Questions – questions during your presentation can quickly sidetrack the topic.  Hold off questions until the end of the presentation.  Allow 25% of your scheduled time for questions.

5. Grammar and spelling – PowerPoint has a spell checker, Use it.  Many managers will ask for a copy of your presentation (for their use in later meetings).  Each memo, report, and presentation is really a job performance review.  If your grammar looks like it was learned at the Prison Work Release program, that’s how you’ll be judged.

6. LAST SLIDE – nothing makes you look more like a rookie than at the end of the presentation everyone is staring at a black screen with ‘end of presentation’ in white letter staring at them.  You last slide should either solicit questions and comments.

Meetings / Presentations are taking on more and more of a theatrical flavor.  None of the rules are complex or hard to master but it does take a skill you probably didn’t learn in school.  Unfortunately more meetings/projects succeed on their theatrical content than they do on their substance.  Such is the Computer Age.

More bad ideas have been accepted and good ideas ignored because of the quality of the presentation.  Looking ill prepared or like an amateur trying to put on a presentation will cause your contribution to be ignored only a little slower than not presenting it at all.  Like everything else it is all about preparation and rehearsal.

======== =============== =============== ============

If you’d like to see how to make a mess out of your presentations check out this YouTube presentation
http://www.youtube.com/watch?v=XDRTFvQFJNo&feature=channel

This article is Virtual.  You can read this, take a little time to minimally master the skills and your meetings will go smoother and presentations be accepted with a higher percentage than before.  Or you can think by sheer force of personality you can get your ideas across and you’ll have your head handed to you by a rookie who can present better than you.  OR you can read this, think you know it all, use it to scare the vultures flying around the plant, and wonder why nobody listens to you.

The choice is yours, grasshopper.

Ideally customers want perfect parts at unreasonably low prices with the supplier maintaining a high level of finished goods inventory that the customer is not held liable to purchase.  But in the real world quality is only ‘sufficient’.  Unless there is a specific clause in the purchase order the molder keeps a minimum of authorized inventory because this is only a bet (not a guarantee) that the customer will purchase it.

The problem here is the conflict between a reasonable request, profit, and how to ‘service’ a customer.

Let’s look at some examples:  The molder has quoted parts at $/1000 pieces based on a pre-negotiated retained in-house finished goods inventory that is built up to some maximum level and shipments are made until it reaches some minimum that triggers a rebuild.

Scenario #1 – The BIG order: a huge order arrives at the customer.  He calls his supplier’s customer service and orders (for immediate shipment) more parts than are in the retained furnished goods inventory. He wants the parts ASAP and not a split shipment emptying the warehouse immediately and the balance shipped when the job can be scheduled into production.
The expectation:  The customer expects a Heaven and Earth move from the molder to juggle schedules, expedite production, and meet his requirements (all this at no increased in cost).
What happens: Unfortunately Customer Service usually complies.  The net result being a thoroughly scrambled production schedule, parts produced on an overtime basis with no profit to show for it.
What should happen: The entire retained inventory will be shipped at the negotiated pricing.  However the balance will be produced (if possible) and shipped at an expedited cost if it is truly needed ASAP or shipped at the original pricing when it comes out as a scheduled production run.  It’s the customer’s choice.

Scenario #2 The KanBan revision: The negotiated price was in $/1000 in boxes of 500 units/box.  The customer wants to implement a better KanBan program and wants 250 parts shipped twice a day.
The expectation: Since this all works out to a $/1000 deal anyway, there should be no increase in pricing.
What happens Usually there is no increase in the costing.
What should happen Each shipment requires paperwork.  It doesn’t matter if it is one part or a million; the administrative costs are the same to generate the shipper, the invoice as well as the record keeping for each shipment.  Also, the deal was $/1000 pieces not fractional $/1000 pieces.  The pricing was quoted at some volume with a packaging cost of 2 boxes per thousand.  He now wants (an should pay for) the packaging cost of 4 boxes per thousand as well as the one time ‘tear down’ repackaging costs for the warehoused inventory.  A request like this scrambles the lot shipping system for the molder.  In this light the cost should be renegotiated to accommodate both the split shipment mentality and the increased administrative costs.

Scenario #3  The ‘Obsolete’ part trick: An engineering change is processed, invalidating all the parts in the JIT warehouse inventory.
The expectation: Since the parts were never truly ordered, the customer isn’t liable to pay for them.  They should be scrapped and replaced.
What happens: Usually the request is honored with a little screaming and whining. If whining doesn’t work it is a common trick for the customer to pull a ‘quality audit’ and scrap everything on the grounds of poor quality.
What should happen: Somebody didn’t do their homework.  In the initial agreement this should have been anticipated so that if the standing unpurchased inventory is declared invalid because of a customer caused engineering change, the molder will be compensated for his loss.

Scenario #4  Busting your chops:
4.1 Customer service is called into the customer for a meeting to ‘review all the pricing’ in anticipation of renewing the next year’s master purchase orders.
4.2 Customer service is called into for a face-to-face meeting to explain the cost increases due to resin prices
4.3 Customer service is called into for a face-to-face meeting for an ‘annual performance review’ or to receive (have inflicted on them) a ‘cost reduction’ program.
The expectation: The customer expects Customer Service to drop everything, pack up a toothbrush etc. and hop on an airplane at a moment’s notice to attend a meeting and ‘explain their actions.
What happens: In most cases the expectation is not only met, but the customer service folks take the buyer and anyone else within hearing distance out to dinner!
What should happen.
4.1  There is NO REVIEW of pricing.  You were the low bidder those are your current (non-negotiable) prices. If you are going to be cross-quoted it will happen whether you show up or not.
4.2  Resin price increases are pass-through costs.  The pricing on materials is public data found in trade magazines or on the Internet.  Since the customer specified the material, if anybody is going to negotiate a new price it should be them, not you.
4.3  Performance reviews can be mailed.  If it’s poor you can’t explain their data any differently regardless of the truth.  Having a TASK or COST REDUCTION program shoved down your throat without the customer funding the productivity improvements is arrogant; showing poor manners and a bad upbringing on their part.

All of these actions are merely a rookie-sandbox-power-game to see if you’ll spend your money and time to ‘dance to his tune’.  Do you do these things to your local grocer, the owner of your favorite restaurant; the phone/utility company or the credit card companies?  If you did, you’d be less than politely asked to no longer to do business with them, and laughed out of their offices.

Customer service is a profession like anything else.  Its purpose on the supplier’s side of the equation is to be the interface between the customer and the suppliers, to ‘play’ according to a set of pre-agreed rules and make sure things go smoothly.  Anytime the customer changes the rules, he cannot selectively change one side of this equation without the consequence of having the other side change to balance it.

Customer Service is not in the business of Freebies.  Both the customer and supplier have to set a system in place that is flexible enough to adapt to the inevitable changes that are market driven.  If they don’t, it must be understood that everything has to be renegotiated on a case by case basis.

===========================

This article is virtual. You can read it and stop doing some very expensive money-losing favors asked by your customer.  Or you can read it and ‘soldier on’ continuing to be your customer’s lap dog.  OR you can send it up the food chain to management with a few notes penciled in the margins on how much each of these stunts is costing you and hope the Ivory Tower Troops will have a quiet chat with the customer’s director of purchasing.  If the quite chat doesn’t work, they might instruct Customer Service to say “NO!” like a parent would do to a petulant child and back them up when the customer complains.  OR you can read it, figure you can’t do anything about it, shred it and use the shavings to line the cages of the Office Gerbils (middle management).

Your choice.

We’ve all learned material types – Semi Crystalline and Amorphous (perhaps Liquid Crystal Polymers). What we missed is why we learned them: The crystalline family has a sharp melting point and processes well with a high compression screw. Amorphous materials have a wide melt point range and therefore do better with a low compression screw whose compression zone is much longer than the high compression screw. There is no such thing as a general purpose plastic. Yet, most machines use a general purpose screw which is usually a compromise between high and low compression designs – moderately acceptable for every material, ideal for none.

When buying a machine you need to look at what kind of materials you run. I had one client where 98% of his material inventory was polypropylene. Another had a silo out back with black ABS, and a third who could dedicate 5 of his 20+ machines to optically clear acrylic. Here is a perfect opportunity to use custom built screws for those particular machines because of the following advantages:

1. There is a more uniform melt injected into the cavity. Even with all the pressure sensors and black boxes regulating the fill speeds, there is an inherent level of scrap generated if the shot isn’t evenly molten (and most of the time is isn’t with GP Screws). Using a custom built screw significantly reduces scrap from this cause.
2. With an even melt, you can process the plastic at a lower temperature. Since plastic is a ‘heat-in-heat-out’ technology; the cooler the initial melt the less heat you need to pull out. This results in faster cycle times.

But even with all this; materials are tricky and need to be handled as though we were cooking a fine soufflé. With your soufflé too high a temperature and it is burned on the outside and raw in the inside. Too long a time in the oven and we are treated like Greek Gods by our efforts being rewarded with a burnt offering. Too little time in the oven leaves under cooked material. Too low a temperature and we get a result as dry as an Egyptian Mummy. The same holds true with Thermoplastics.

EXAMPLE: Many molders will not run medical grade non-thermally stabilized PVC. Yet others readily welcome jobs that use this material. What’s the difference?

The first group of molders are the General Purpose kind – They use general purpose machines, melt PVC with general purpose screws, and routinely burn the material releasing all kinds of nasty fumes as well as acidic vapor that eats their molds and machines. Hence PVC is avoided like the plague.

The vast majority of the second group use custom built screws specifically designed for PVC and pay a lot of attention to the size of the injection unit to the point of making odd (to the outside observer) combinations of injection units and clamps.

Clamp Size and Injection Capacity of molding machines were initially arrived at by market forces. The customers seemed to need these combinations and the machinery industry provided it. Over time, some machine companies became a little smarter. Besides the usual options of one clamp size and a few different sized injection units, they made the removal and installation of the entire injection unit easy enough so that when a molder was done running black 30%GF Nylon and his next material was water-clear SAN, he could change out the entire injection unit for a new one faster (and cheaper) than he could spending all day purging.

Filling the mold comes with a several caveats: The first is size. While the Common Knowledge Practice is the ideal shot should be between 20-80% of the injection capacity you must also attend to the concept of ‘shot inventory’. Shot Inventory is the entire volumetric capacity of the screw and barrel divided by the weight of the shot. If you have a 20 gram shot and the screw and barrel holds 200 grams of material you have a shot inventory of 10 (200/20=10). The implications here are if there is a very small shot inventory severely strains the repeatability of the machine to control the shot accurately. Conversely a high shot inventory the material is going through the compression and metering zones of the material so fast that the injected shot will have a relatively high percentage of un-semi melted pellets in it.

Shot inventory is only one concern. The more important concern is Residence Time. Here we take the shot inventory and divide it by the cycle time. If we have a shot inventory of 10 (as above) and a cycle time of 15 seconds; the residence time is 2:30. (10 shots @ 15 second each = 150 seconds divided by 60 seconds/minute = 2.5 minutes). For heat sensitive materials (vinyls, TPUs and some TPRs) you may see a high degree of degradation. This generates a definable percentage of scrap. But is you use a smaller screw/barrel combination where you have cut the inventory to 5; now the residence time is 1:07. With exposure to heat, the shot is molten but not degraded. Therefore your ‘degradation scrap’ percentage goes away. You have a higher yield, and without this degradation you can now regrind your runner system. This saves you time and material that quickly pay for the new injection unit.

What’s right? A little surfing through the internet and careful reading of the material spec sheets and data bases are capable of telling you the maximum allowable time under heat before your material degrades. It may take a little hands-on experimenting to generate your own data when it comes to heat induced color shifts because the organometallic dyes are extremely heat sensitive.

If you’re a General Purpose kind of guy, you look at thermally induced scrap (either the general scrap of color shift and bad melt quality or the slower cycle time cost for having to overheat to compensate for poor melt quality) as “part of the cost of doing business” because General Purpose designs cover all your applications. It’s like playing golf with only one club: While you can get through the course; your score will suffer.

“BUT WAIT!!” you may well say to my nay saying. “Those things cost a lot of money. Where’s the return?” Fortunately the folks who are the major manufacturer of custom built screws have heard your “but wait!!” argument shouted at them like a cranky baby. If you do a little surfing on the internet two of the major companies will give you an on-line calculator to use to see if this might help you. Of course that requires you to do a little work also.

+ + + + + + + + +

This article is virtual. While we all dream of the infamous ‘competitive edge’; usually we have to be hit over the head with it before we see it. Properly sized and designed screws will give you this kind of advantage over your competition. If you try it on one problem job you’ll be the Wunderkind of your company. Or, you can listen to some bean counter complain about the $10-15,000 you need to buy the new screw but won’t hear a peep when you put twice that amount into the scrap bin. Or you can put it in your “I told you so” file and watch your employer go bankrupt and show the article to the next guy you interview with. (P.S. – if you show your ‘I told you so’ at the interview, be prepared to tell them why you didn’t implement it)

Your Choice.

We’ve all learned material types – Semi Crystalline and Amorphous (perhaps Liquid Crystal Polymers). What we missed is why we learned them: The crystalline family has a sharp melting point and processes well with a high compression screw. Amorphous materials have a wide melt point range and therefore do better with a low compression screw whose compression zone is much longer than the high compression screw. There is no such thing as a general purpose plastic. Yet, most machines use a general purpose screw which is usually a compromise between high and low compression designs – moderately acceptable for every material, ideal for none.

When buying a machine you need to look at what kind of materials you run. I had one client where 98% of his material inventory was polypropylene. Another had a silo out back with black ABS, and a third who could dedicate 5 of his 20+ machines to optically clear acrylic. Here is a perfect opportunity to use custom built screws for those particular machines because of the following advantages:

1. There is a more uniform melt injected into the cavity. Even with all the pressure sensors and black boxes regulating the fill speeds, there is an inherent level of scrap generated if the shot isn’t evenly molten (and most of the time is isn’t with GP Screws). Using a custom built screw significantly reduces scrap from this cause.
2. With an even melt, you can process the plastic at a lower temperature. Since plastic is a ‘heat-in-heat-out’ technology; the cooler the initial melt the less heat you need to pull out. This results in faster cycle times.

But even with all this; materials are tricky and need to be handled as though we were cooking a fine soufflé. With your soufflé too high a temperature and it is burned on the outside and raw in the inside. Too long a time in the oven and we are treated like Greek Gods by our efforts being rewarded with a burnt offering. Too little time in the oven leaves under cooked material. Too low a temperature and we get a result as dry as an Egyptian Mummy. The same holds true with Thermoplastics.

EXAMPLE: Many molders will not run medical grade non-thermally stabilized PVC. Yet others readily welcome jobs that use this material. What’s the difference?

The first group of molders are the General Purpose kind – They use general purpose machines, melt PVC with general purpose screws, and routinely burn the material releasing all kinds of nasty fumes as well as acidic vapor that eats their molds and machines. Hence PVC is avoided like the plague.

The vast majority of the second group use custom built screws specifically designed for PVC and pay a lot of attention to the size of the injection unit to the point of making odd (to the outside observer) combinations of injection units and clamps.

Clamp Size and Injection Capacity of molding machines were initially arrived at by market forces. The customers seemed to need these combinations and the machinery industry provided it. Over time, some machine companies became a little smarter. Besides the usual options of one clamp size and a few different sized injection units, they made the removal and installation of the entire injection unit easy enough so that when a molder was done running black 30%GF Nylon and his next material was water-clear SAN, he could change out the entire injection unit for a new one faster (and cheaper) than he could spending all day purging.

Filling the mold comes with a several caveats: The first is size. While the Common Knowledge Practice is the ideal shot should be between 20-80% of the injection capacity you must also attend to the concept of ‘shot inventory’. Shot Inventory is the entire volumetric capacity of the screw and barrel divided by the weight of the shot. If you have a 20 gram shot and the screw and barrel holds 200 grams of material you have a shot inventory of 10 (200/20=10). The implications here are if there is a very small shot inventory severely strains the repeatability of the machine to control the shot accurately. Conversely a high shot inventory the material is going through the compression and metering zones of the material so fast that the injected shot will have a relatively high percentage of un-semi melted pellets in it.

Shot inventory is only one concern. The more important concern is Residence Time. Here we take the shot inventory and divide it by the cycle time. If we have a shot inventory of 10 (as above) and a cycle time of 15 seconds; the residence time is 2:30. (10 shots @ 15 second each = 150 seconds divided by 60 seconds/minute = 2.5 minutes). For heat sensitive materials (vinyls, TPUs and some TPRs) you may see a high degree of degradation. This generates a definable percentage of scrap. But is you use a smaller screw/barrel combination where you have cut the inventory to 5; now the residence time is 1:07. With exposure to heat, the shot is molten but not degraded. Therefore your ‘degradation scrap’ percentage goes away. You have a higher yield, and without this degradation you can now regrind your runner system. This saves you time and material that quickly pay for the new injection unit.

What’s right? A little surfing through the internet and careful reading of the material spec sheets and data bases are capable of telling you the maximum allowable time under heat before your material degrades. It may take a little hands-on experimenting to generate your own data when it comes to heat induced color shifts because the organometallic dyes are extremely heat sensitive.

If you’re a General Purpose kind of guy, you look at thermally induced scrap (either the general scrap of color shift and bad melt quality or the slower cycle time cost for having to overheat to compensate for poor melt quality) as “part of the cost of doing business” because General Purpose designs cover all your applications. It’s like playing golf with only one club: While you can get through the course; your score will suffer.

“BUT WAIT!!” you may well say to my nay saying. “Those things cost a lot of money. Where’s the return?” Fortunately the folks who are the major manufacturer of custom built screws have heard your “but wait!!” argument shouted at them like a cranky baby. If you do a little surfing on the internet two of the major companies will give you an on-line calculator to use to see if this might help you. Of course that requires you to do a little work also.

+ + + + + + + + +

This article is virtual. While we all dream of the infamous ‘competitive edge’; usually we have to be hit over the head with it before we see it. Properly sized and designed screws will give you this kind of advantage over your competition. If you try it on one problem job you’ll be the Wunderkind of your company. Or, you can listen to some bean counter complain about the $10-15,000 you need to buy the new screw but won’t hear a peep when you put twice that amount into the scrap bin. Or you can put it in your “I told you so” file and watch your employer go bankrupt and show the article to the next guy you interview with. (P.S. – if you show your ‘I told you so’ at the interview, be prepared to tell them why you didn’t implement it)

Your Choice.