Plastic Mold Approval Checklist

[stick1]

I would like to have a comprehensive set of parameters that I am prompted to review when I receive a mold layout drawing for an injection molded part. Does anyone have a checklist or approval form they use upon review of the supplier's submitted drawings of the mold layout? Or can anyone supply any suggestions as to what they look for when approving the mold layout? Some things that come to mind are: Gate locations, injector pin locations, no. of cavities (economics included), location of raised characters or symbols, etc.

 

[mjh368]

HMMMnot sure where you are going with this. you will need more than a check sheet to approve a mold. but a good way to "learn" about the mold is look at is the way the designer did:
1.part design
2. number of cavities *required machince-shot size, tonage
3. type of mold
2 plate-hot runner, cold runner,
3 plate-hot runner, cold
4.placement of cavities.
5.type of gate-
6. temperature control system-surface, cores
7.ejection-pins, stripper rings
8. Vents- PL, inserts, ejector pins,
9. mold materials-base, inserts, cores
10. anticipated shrink-part design, gating, processing conditions.

Thats a good start.
Thanks gastrow

 

[stick1]

Thanks mjh368. You have some good suggestions.

For context, when my company orders a plastic molded part from a supplier, we typically request an overview of the mold drawings. The idea is to look for the things that may affect our part functionally, cosmetically, or economically.
I don't pretend to understand the intricacies of mold design and development, and wouldn't begin to be able to tell the supplier how best to construct his mold.
Therefore I am interested in knowing if others have a similar method of operation, and how they approach it.

 

[MikeHalloran]

Reviewing the mold drawings is mostly a waste of your time, thought not as much as taking possession of the actual mold and sending it to another molder.

The performance of any given mold is determined more by external factors, like skill, process control and machinery condition, than it is to details of mold design.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Water passages, undercuts and draft angles, type of polymer and subsequent impact on mould material selection, flow path to section thickness, mould cooling at corners, vents, change in section thickness, excess metal left on mould to allow correction of dimension by removal of metal after off mould samples are measured.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Alexpsq]

in fact,every mold factory have approval check list!I hink
As you,the most important is:try to shorten the cycle time (cooling layout)and mold size,the mold quality(hardeness,no sharpe,no impaction between mold components)!
you can also give a expexted cycle time to the mold factory for a reference!

Wish this can help for you!

 

[toolman801]

While only being a Tooling Engineer for the last 14 year and a tool maker for 18 years before that, I have only seen a design checklist produced by the mold molder only 3 times for what you are really looking for. Most times the party that purchases the mold has a design checklist to go over during the Priliminary Design Review. The one I have used for the last 8 years is 6 pages long. The design review checklist Is not the only thing you need. You also need a Mold Specifications Document that tells all your mold builders how you expect your mold to be built.

You need to verify that the mold will fit your press, are the lifting holes right size for the weight of mold, are the KO locations correct and so on.

I would not have a mold built without having a design review done before steel is ordered.

 

[ToolEng1]

I agree with toolman. But I must say that these design check lists are put together by people who have a lot of experience and should be used a guide only. Every part is different and this may require new specifications to be written.

I have been a tooling engineer and processing engineer for the past 15 years and I have learnt the most important things to look for are cooling circuits, gates and runners, position of ejector pins, press size, shot weight, clamp force required etc etc...

Toolmakers will always put in the least amount of cooling as possible as this creates less work. I always make sure if possible to have 4 x separate circuits per half of the tool. This enables the process engineer to set variable temp across the tool in the event of distortion on the moulded part. Gate design can normally be taken from material data sheets but always start small. If at all possible try get a MoldFlow done and send this onto the toolmaker, make sure the steel selection is of high quality steel i.e P20 or H13 tool steel. Deep ribs/bosses over the 15mm mark should be fitted with split inserts, this helps with polishing and venting. Thin blade sections should be inserted using berrilium copper or equivalent.

The list can go on but if you follow the simple points above you can't go wrong