80 Questions Moldmakers Should Ask Themselves … and Their ...
80 Questions Moldmakers Should Ask Themselves … and Their ...
As a consultant, I continually see mold and molding issues that could easily have been avoided. The most common problem has little to do with cutting steel. The problem is failing to consider, obtain and verify all the pertinent information up front—prior to the mold’s construction.
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It’s the responsibility of the moldmaker to ensure the mold will produce dimensionally, functionally, and aesthetically acceptable parts for the life of the program. There is no way to achieve that goal without first determining what the dimensions, function, aesthetics, and lifespan requirements are from the customer.
Most clients are not well versed in our industry, but all too often think they are experts. Still, they prefer to work with knowledgeable vendors—someone who is looking out for their best interest. It is the moldmaker’s responsibility to educate the customer, which also serves to protect the moldmaker. For example, no matter how insistent a customer may be, the moldmaker should never agree to build a seven-cavity hot-runner family mold for parts of various sizes and wall thicknesses in a high-shrink semi-crystalline material.
Don’t laugh. This is a real example, and the project is 11 months late and will soon be converted into four molds. The expensive hot-runner system is now a boat anchor. If that wasn’t bad enough, the moldmaker agreed to amortize the mold into the piece price, with no down payment. Ultimately, if the molder can’t produce acceptable parts, the finger is going to get pointed at the moldmaker.
This tooling checklist is focused on communicating all the pertinent information about the mold from and to the customer.With all this in mind, I compiled a list of questions that should be asked both internally and to the customer to help avoid any delays or oversights that could affect getting paid for the current mold, as well as any future tooling orders. I am not going to expand on why each question should be asked. If you are an experienced moldmaker, you already know why. None of the questions below are about the details of the mold design, such as the type of interlocks, plate thicknesses, eyebolt holes, etc. The list is focused on communicating all the pertinent information from and to the customer.
If the molder can’t produce acceptable parts, the finger is going to get pointed at the moldmaker.
Initial Inquiry Questions
1. How did you hear about us?
2. What is the end use of the product (medical, automotive, consumer, etc.)?
3. Are there any mating parts?
4. Do you need any part-design assistance?
5. What are the expected annual production quantities?
6. What is the expected lifespan of the product?
7. Do you have a CAD file of the part? If so, what is the file format?
8. Do you have or need a 3D-printed or machined prototype?
9. Do you have a 2D dimensioned drawing of the part?
10. What is the material type?
11. Will the parts be made in more than one type of material or more than one color?
12. Do you have any mold-design specifications that need to be adhered to?
13. Can we get your molder involved in future discussions?
14. Is the number of cavities desired based on the mold cost, part cost, or production requirements?
15. If the mold is to be a MUD or other quick-change insert type, is a specific frame size required? If yes, what is the frame size or number?
16. Do you know if you want a cold runner, hot bushing, hot runner, valve gate, etc.?
17. Are there any interchangeability requirements, such as various versions of the part or engravings?
18. Are there any inserts that will be overmolded?
19. Are there any secondary operations that might affect the mold design?
20. What are the surface finish requirements for the cavity?
21. What are the surface finish requirements for the core?
22. How many samples will you need initially?
23. Are any inspection or testing criteria required for the parts?
24, Are there any mold qualification requirements?
25. Is there anything else we should know?
26. How many other moldmakers are quoting this project?
27. Are any of these moldmakers offshore?
28. When are you expecting to place the order for the mold?
29. How critical is the delivery date?
30. If you gave the potential client a ballpark mold cost, what was their reaction?
Internal Review of the Supplied 3D Model
31. Did the model translate well?
32. Should the part design be modified to reduce the mold cost or increase its longevity?
33. Can the model be modified in-house?
34. Are any actions required (cams, lifters, two-stage ejection, unscrewing, etc.)?
35. Are there any holes or features requiring shutoffs?
36. Does the part have uniform wall thickness?
37. Is additional coring needed?
38. Is there sufficient draft to prevent sticking or scuffing in the cavity?
39. Is there sufficient draft to prevent sticking or scuffing on the core?
40. Are there any undercuts?
41. Are there radii on both internal and external corners?
42. Should any radii be removed to eliminate cavity impression in both halves of the mold?
43. Are there any ejection concerns?
44. Are there any gating concerns?
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45. Are there any filling concerns?
46. Should a flow analysis be considered?
47. Are there any cooling concerns?
48. Should high-conductivity materials, or conformal cooling be considered?
Internal Review of the Supplied 2D Drawing
49. Does the 2D drawing have everything defined? Everything includes
a. Dimensions,
b. Tolerances,
c. GD&T requirements (straightness, flatness, concentricity, etc.),
d. Surface finish or texture,
e. Notes.
50. What is the date and revision level of the drawing?
51. Are the critical dimensions identified and toleranced?
52. Are there any dimensions or tolerances that are not obtainable for tooling or molding?
53. Has the material type and grade been specified?
54. Does the material contain any abrasive fillers, such as glass?
55. Does the material contain any flame retardants or other additives?
56. Do any of the notes refer to documents that were not provided?
57. Should a prototype tool be considered?
The more steps we take up front to minimize risks, through the collaboration of the concerned parties, the more competitive and profitable we will be.
Part Design Review with Customer—Prior to Mold Design
(In addition to any concerns or questions from above.)
58. What is the controlling document—a 3D model or a 2D drawing?
59. Are you familiar with the inherent issues of family molds?
60. Are runner shutoffs required?
61. Is the intended gate location acceptable?
62. Can a gate recess be added?
63. Can ejector-pin bosses be added on deep ribs?
64. Are samples and 2D drawings of the mating parts available?
65. Are alternate material types or grades acceptable?
66. Are you familiar with anisotropic shrinkage?
67. Who is specifying the shrinkage factor?
68. Who is supplying the material and colorant?
69. Are the intended molding machine’s specifications available?
70. Is the molder planning on using a robot or picker?
71. Is it acceptable if the engraving is raised on the part?
72. Is a recycle symbol, date clock, revision symbol, or cycle counter desirable?
73. Do you have artwork for any engraving?
74. Are the font type and size specified?
Mold-Design Review with Customer
(In addition to any concerns or questions from above.)
75. Is the cavity number location, size, and depth acceptable?
76. Are the ejector pin locations acceptable?
77. Are the witness lines from any actions acceptable?
78. Should some areas be left steel safe and adjusted after sampling?
79. Should any spare parts be made?
Molding Considerations
If you think molding issues have no effect on the part or mold design, think again. For example, sink and knit lines will affect the gate location. Splay and jetting will affect the gate type, size and location. Flash will affect shutoff considerations, steel types and heat treatment. Sink, warpage, and material type will affect both the part and mold design. Burn marks and shorts will affect the vent types and locations. Color values will affect the part’s wall thickness and mold’s surface finish.
80. What are the limitations on each of the following?
• Color (L, a, b, Delta E, gloss),
• Gate vestige,
• Sink,
• Warp,
• Knit or flow lines,
• Flash,
• Shorts,
• Splay,
• Burn marks,
• Black specks,
• Grease or dirt,
• Other.
Our business is full of risks. The more steps we take up front to minimize these risks through the collaboration of the concerned parties, the more competitive and profitable we will be.
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Rookie questions on plastics injection or blow mold work???
I am not opposed to buying or fabbing some basic equipment for this odd job. I think the biggest question here is do I really need to go all out and machine a nice Al mold for this part? I guess if I do this in sections that bolt together, it could work but seems like a LOT of work for low qty stuff. Seems there should be a faster/easier way? Thanks for your help. Probably zero experience in plastics anyway.....But I will try to answer what I can. Jeez, a POT shape, 24" diameter, 24" tall, closed off bottom. Maybe about .020" wall thickness. Problem is I would be designing on what I want, not on what industry standards are!!! What exactly do you really need to answer the questions???? Do you really need to know what it is, does, what industry, etc? I have already determined having it made is not going to work. I have also indicated I am WILLING to buy REAL equipment to do it. I suppose this is where people say "so ur gunna buy that $400k injection machine for this???" No, but I will buy that $500 one used that is old and needs fixed. As mentioned above, there isn't much information. But I will take a shot at it.
If it is low volume, and plastic was your first idea, could you make it out of fiberglass? There are a whole range of different strength capabilities. I made some plaster of paris molds to make some fiberglass bowls, and some force induction grill inserts for a newer GTO. It took some time to get it right, but it was dirt cheap to do.
I have a couple odd parts of low qty I wanted to mold. sort of a pot shape but big. Seems there should be a faster/easier way?
Have you considered 3D printing? It would require a fairly large machine, but if you want a quote, let me know. I have a friend very close by that can handle it.
If it must be injection molded, I finally found a shop that I was happy with. They are in the northeast, but they do good quality work, they were on time with delivery, and very reasonable. In fact, they were half the price of some of the other quotes that we received.
I have also indicated I am WILLING to buy REAL equipment to do it. I suppose this is where people say "so ur gunna buy that $400k injection machine for this???" No, but I will buy that $500 one used that is old and needs fixed.
I don't use this word often, but "What???"
Cut 24" off the end of food grade plastic barrels. You're not getting a moulding press for $500, anywhere. Even "old and needs fixed" cost my previous company $20,000, and then it leaked 400L of hydraulic oil on the floor overnight (which alone costs more than $500). And then it needed the nitrogen accumulators recharged. And then the 200hp motor re-wound.
Mould work is not cheap. Should not be cheap. Find another method.
BTW there are companies that will run moulds so you don't actually have to move production in-house. Where are you? By the sounds of it, "UT" means University of Toronto. OK, this part must be custom made as the special features are what make it needed for me. It must be molded from plastic. I need roughly a couple hundred right now but I could need more and have a life cycle of only a few yrs. Glass would never make financial sense.
For the literals, I was only kidding about the $500 machine. I realize it will cost more but I also seem to think I can do this without some of the fancy high volume goodies. Maybe I am wrong.
I am trying to think up ways around this sitch.... For a relatively thin wall, what Charlie says makes sense. Look into rotary.
At this point, I wouldn't bother with moulding it myself. That's a decision to be made once you have a customer base and are determining the cost/benefit analysis of sticking with a vendor or moving production under your roof. Quantities of a few hundred do not warrant injection moulding.
You can make fibreglass moulds cheaply (heated wire & builder's foam/insulation). Expect much trial and error.
Make from plastic tube and weld the end/bottom + required features on? LOL, ya'all are gunna shoot me but the rotary idea has given me something to think about. Basically the ideal component would be a woven basket made of plastic!!! Randomly perforated is actually required. I said injection because I don't know what process I need yet but I know blow molding is for thin, high volume stuff and I have seen it done. Problem is I don't think I can get the structure I need from the wall thickness of blow mold.
Some of this will require some testing. I can apply engineering data all day long but function testing is will tell me a LOT.
I then had the idea for recycled filament run around my designed drum to sort of lace up what I need. I know this all seems ridiculous but......
I was thinking either the filament could run at the right soft state temp to bond to itself as it is laced, or run it through a liquid product just before lacing to get it to glue up.
In either case, I think with the right process and a little basic automation, they should run out pretty quick almost requiring no cooling?
This is ALL just a total brain fart so excuse me if this is not thought through. Just thought of it 5min ago. Well that helps. I have a couple different areas to explore! I honestly did not get a chance to see all the nuts and bolts of rotomolding but IIRC, you basically randomly rotating the part until the plastic is cool enough and by that time, it should have applied a very uniform layer on the ID of your mold? Adjust thickness by just adding more plastic in the mold?
Suppose I want to be dense and explore this filament lacing thing a bit, where might I find recycled HDPE and such in course filament spools? All I can seem to find is fine filament for 3D printing. I would want say 1/8" and probably lots of it. Not even sure how much plastic costs. I know the nylon we machine aint cheap! Hoping the recycled industry looks better.
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