Tribal Knowledge

TRIBAL KNOWLEDGE
I’d like to publish a book gleaned from the experience of everyone – if you will, Tribal Knowledge.  It is amazing to me that there are people who think their ‘tricks’ are something they thought of and are their own ‘personal’ competitive edge. Actually most tricks get rediscovered over and over again so there’s no sin in making them public. It is also amazing how many people (especially off shore) get into the business with no knowledge whatsoever and just fumble along until they discover or someone shows them a more profitable way of doing things. To that end this is a ‘call for papers’

THE FORMAT

  1. It could be only a few paragraphs or one or two pages per topic.
  2. It should not be a PhD thesis nor should it come with complex mathematical formulas. I will not accept any contribution that requires a Graduate degree to understand it. However if you have a formula that can be easily solved (square root etc), those would be OK.
  3. Your submission should be in Microsoft Word or similar editable format.
  4. If you’d like to put your name and company on it, feel free to do so. You’ll get credit for writing it; however you may be one of several contributors on the topic.
  5. It must be readable and practical. E-mail your ‘paper’ to me (bill4012@hotmail.com).
  6. It should be formatted in What the Rule of Thumb is, Why does it work, and How does it work.
  7. When the book is published, you’ll get a complimentary e-copy, and credit for your contribution.
  8. This is a wide open field generally covering the topics of estimating costs of tooling and parts. Here is only a partial list of topics. If you have more to add, feel free to do so.

SOME SAMPLE TOPICS (feel free to add more)

PARTS

  1. What are the Rules of Thumb to estimate cycle time? (I don’t want the thermodynamic argument in Kilocalories and heat transfer equations).
  2. What are the Rules of Thumb to estimate cycle time depending on semi-crystalline or amorphous material?
  3. How do you estimate (what is the equation) for the cost of a part (cost NOT sale price)? – yield, setup time, purging, auto v. semi-auto, percent regrind etc.
  4. When recommending wall stock to a customer what is the Rule of Thumb to estimate the max part thickness based on the type of filler and the % filler?

MOLD / MACHINE INTERFACE

  1. How do you estimate the required clamp pressure? (3-5 Tons/square in surface area is a function of melt index – what rules do you use?)
  2. How do you size a mold to a machine by both percentage clamp and shot capacity?
  3. Assuming the press came with a sprue picker / robot AND the part was to run fully automatic – what would determine the choice of using the robot compared over simply letting the pars fall into a chute?

MOLDS

  1. What are the Rules of Thumb to estimate the ideal number of cavities based on an annual requirement?
  2. What are the Rules of Thumb to estimate the size of runners in a conventional mold?
  3. What is the ‘generic’ cost of a slide/side action?
  4. When do you choose a hydraulic cylinder over a mechanical slide?
  5. What are the Rules of Thumb to size a vent? (melt index v. vent depth)
  6. What are the Rules of Thumb for the ‘ideal’ size of a waterline?
  7. How close should a waterline be to the cavity for even cooling?
  8. When/why should you choose a monolithic mold over interchangeable cavities (i.e. MUD systems).
  9. What are the Rules of Thumb for how long should an ejector stroke be?
  10. What is the Rule of Thumb for max flow length or number of gates on a part?
  11. How do you estimate the cost of a mold (cost NOT sale price)?
  12. How do you specify the shrinkage of a part to the mold designer?
  13. Valve gate, hot tips and three plate molds can all accomplish the same function. What determines the choice assuming the secondary equipment is available? (Percentage increase of the overall mold cost – how much compared to what savings? Shortening overall cycle time – how much? Etc.)
  14. Of all the steels that can be used for mold cavities, What are the Rules of Thumb for which type of steel should be used compared to the volume of parts run?
  15. Of all the steels that can be used for mold cavities, What are the Rules of Thumb for which type of steel should be used compared to (A) material melt temperature (B) what kind of fillers, (C) what concentration (%) of fillers – to minimize ‘washout’ of the cavity?

PROCESSING
What are the Rules of thumb for mold positions?

  1. Slow open
  2. Fast Open
  3. Full open
  4. Ejection
  5. Fast close
  6. Slow close
  7. Clamp up.

What are the rules of thumb for screw position/speed during the overall cycle?

  1. Fully returned -= decompression
  2. Screw off when returned
  3. Cushion
  4. Gate freeze off
  5. RPM speed for return and the time it takes
  6. Decompression time

What are the Rules of Thumb of cycle time?

  1. Fill
  2. Pack/hold
  3. Cool
  4. Screw return
  5. Decompression
  6. Ejection
  7. Mold open / closed
  8. Robot

What are the rules of thumb of drying material if you don’t have the tech sheet?

  1. How long to dry
  2. What temperature range for hydrophilic v. hydrophobic materials

How do you know a machine is . . .. . . “Qualified” “Robust” etc.?

One response so far

One Response to “Tribal Knowledge”

  1. Greg Beachon 11 Sep 2013 at 8:34 am

    Please let me know when the Tribal Knowledge book is published.

    Thank you.

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