General approach to the plastics selection for molding

[sinus45]

Hello everybody!
I'm new to the plastics design and I have maybe strange question.
We have made a consumer electronic device design for customer and made molds and parts out of ABS plastic. It's so happens that some parts are bend after assembly and create about 0.5 mm gap in undesirable place(they actually should create some tension, but not that big, plastic cooling also deforms parts a bit). My idea would be to try few different materials like ABS with 30-40% glass fiber, SEBS, PC_ABS. I would like to see which materials for manufacturer is easier to acquire and mold few pieces out of those materials. It should show me how the color will change and if all assembly will work well together.
Is it weird idea and I should simulate everything in CAD including deformations or it sort of normal practice to explore different materials on factory? the project budget is quite low...

 

[btrueblood]

- "I should simulate everything in CAD including deformations " Yes, as much as you can. See if you can duplicate the problem you are getting with the ABS parts.

I would assume that the cost of a short run of parts would be multiplied if you wanted multiple materials. Each material change will result in a fair amount of wastage, because the injection barrel must be purged (emptied) of the prior material before running the next one. Also, good mold designers will design parts and molds for a specific material; the mold you have may not work well at all for some other material type. Lastly, ABS is probably one of the cheapest materials, and easiest to mold, relative to the others on your list (with the exception of SEBS maybe, but why would you want something softer?).

 

[MBaroni]

It is always a good idea to test out different materials, but do remember that each manufacturer will have materials that they work with more often and in greater volumes.

This means that on part of those materials they will be able to:
[ul]
[li]Get a better bulk material price thanks to high volumes of purchase[/li]
[li]Have a more extensive knowledge of the ins and outs of processing that material, generally resulting in better quality and/or shorter cycle times[/li]
[li]Have material "lying around", including regrind from scrap parts, that can be used without long lead times for procurement[/li]
[/ul]

All of this can translate to time and cost savings for the end client, so in general it is a good idea to have a talk with potential manufacturer, explain the scope and requirement of your item and let them make proposal of good materials. This is particularly true where there is no regulatory burden or thigh specification to conform to.

As a side note, also consider adding ribs or other reinforcing features to prevent warping.

 

[MikeHalloran]

Did you ignore what your molder said in response to your first RFQ? That's how you get bad parts.

One way to get good parts:
Kill your Supply Chain Manager.
Develop a cooperative relationship with a small number of suppliers.



Mike Halloran
Corinth, NY, USA