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Basic steps to mold design review

May 31, 2001

4 Min Read
Basic steps to mold design review

Reviewing the design of a mold is often a lengthy and complex process, and at times important elements can be overlooked amidst the morass of detail. Attempting to streamline this process, Cedric Carlton, senior research associate with $39 billion consumer product firm Procter & Gamble (Cincinnati, OH), created a mold design review form (shown here), which he says has cut mold review time in half for the 100-plus tools P&G sources globally every year. The content is based on Carlton's experience in the company's mold design review meetings, attended by mold designers, part designers, and others involved in the project. 

Serving as an organizational guideline for these meetings, the form, says Carlton, provides a structured approach to covering fundamental aspects of the mold and enables changes to be tracked in the meeting. It's also useful prior to the meeting for raising discussion issues, and after the meeting as a followup tool. 

To contact Cedric Carlton at P&G, call (513) 626-3609 or e-mail [email protected]. 

FUNDAMENTAL APPROACH TO REVIEWING AN INJECTION MOLD DESIGN



Part__________________________________ 

Date__________________________________ 

Moldbuilder (Company)__________________________________ 

Mold designer/representative__________________________________ 

Part drawing number__________________________________ 

Mold drawing number__________________________________ 

1. OVERVIEW


In this step, the reviewer gets a basic idea of the type of mold to be built. 

A) Tonnage required
Surface area _______ x # cavities _____ x 3.5 tons/sq in =_______ (plus 10 percent for stack molds) =
___________________________________________________________________ 

B) Estimated mold weight 

L_______ x W_______ x H________ x .283 lb/cu in = _______________________ 

C) Cavitation _______________________________________________________ 

D) Mold construction (e.g., three plate, stripper, two-stage ejection)____________ 

E) Maximum daylight required for the mold________________________________ 

F) Tiebar distance___________________________________________________ 

G) Robot access (side or top)___________________________________________ 

2. PARTING LINE(S)


Starting point to consider for every other aspect of the part (injection, ejection, part appearance, and so forth). 

A) Shape____________________________________________________________ 

B) Location__________________________________________________________ 

C) Quantity__________________________________________________________ 

D) Parting sequence___________________________________________________ 

E) Parting method (e.g., spring, latch lock, nothing special)_____________________ 

3. INJECTION


After determining how the part is oriented in the mold, look at how the plastic is getting into the mold. 

A) Type (hot or cold runner)_____________________________________________ 

B) Gate location (in relation to part geometry)_______________________________ 

C) Sprue (length, sprue pull geometry)_____________________________________ 

D) Runner (shape, size, balancing)_________________________________________ 

E) Gate (type, size)____________________________________________________ 

4. VENTING


Make sure steps are taken to get rid of air in the mold. 

A) Location__________________________________________________________ 

B) Adequate for flow?__________________________________________________ 

5. COOLING


Now that the plastic is in the mold, verify that the cooling methods are adequate. 

A) Preferred values for (D)istance (from part to centerline of cooling) and (P)itch (centerline to centerline distance between each waterline, d = diameter of waterline) 

Preferred D = 1.5 x d______ =__________________ Actual D =_________________ 

Preferred P = 3 x d_______ = __________________ Actual P =_________________ 

B) Cores (e.g., none, conduction, baffle)________________________ 

C) Turbulent flow? (preferred)________________________ 

D) Coolant layout checked for optimum efficiency?________________________ 

E) Ins and outs labeled?_____________________________ 

6. EJECTION


Once the plastic in the mold has cooled sufficiently, consider how the part is removed from the mold. 

A) Type (e.g., stripper plate, unscrewing, air assist) _____________________ 

B) Will part be there to eject? _____________________ 

C) Number of ejection stages _____________________ 

D) Pushing (preferred) or pulling? _____________________ 

E) Ejector pin bearing surfaces (surface contact between pins and mold) checked? If ejector pin diameter is greater.gif.125 inch, then bearing surface should be two times the diameter; any smaller-diameter pin should have a minimum .5-inch bearing surface. 

F) Optimum method for surface contact with the part (e.g., stripper plate, pins, or combination)________________________________________________________ 

G) Are ejector plates bottoming out in ejector housing? (not desirable)___________ 

H) Are there clearance feet at the bottom of the ejector plate?_______________ 

I) Is there sufficient guided ejection?_____________________ 

J) Is there anything impeding the part from falling out of the mold?____________ 

K) Material's mechanical properties appropriate for what it needs to accomplish?_____________ 

7. CLOSING


The part is out of the mold and it's time to close the mold to start the process over again. 

A) Sequence_______________________________________ 

B) Potential of closing impeded?_________________________________________ 

C) Ejector system return method_________________________________________ 

D) Mold alignment checked?_____________________________________________ 

8. HANDLEABILITY


Understand how easy it is to handle change-out of components. 

A) Wear areas checked?________________________________________________ 

B) Is there access to interchangeable areas?________________________________ 

C) Eyebolt installed for mold transports?__________________________________ 

9. SAFETY


Does the mold have all necessary safety precautions for fabrication and part processor? 

A) Mold protection provided? (open and closing, timing of slides)________________ 

B) Disassembly instructions and safeguards provided?________________________ 

C) Are there sufficient clamping slots to secure molds to platens?______________ 

D) Eyebolts installed for maneuvering mold in press?_________________________ 

E) Mold maintenance procedures included?__________________________________ 

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