Nylon vs. ABS

[rc0213]

We have a product design, dimensionally the same, but made from two different materials. One design is made of Nylon, Zytel 801. The other design is made of ABS/PC. We modified the Nylon diameter to fix an issue, and it worked. We don't know the difference in Nylon and ABS/PC to know what the ratio is to increase the ABS/PC version to have the same result as the Nylon.

So, for example, let's say the Nylon diameter increased 25% to fix an issue. And, we have to fix the same issue for the ABS/PC. So, what is the modified diameter of the ABS/PC to have similar results as the Nylon, Zytel 801? I have attached a presentation of the issue. I appreciate any help.

 

[MikeHalloran]

You have to analyze the snap-fit of the part into the hole.
By hand, you could call it a short cantilever beam with a fixed deflection (the snap-fit), and see how the resulting elongation of the beam compares with the resin's properties. Nylon will take a lot more abuse than ABS.

You may need to buy a new mold and use a different geometry for each resin. ... or heat the parts during the snap-fit. ... or both.

It's unusual to get two parts of substantially different resins from the same mold, both successfully.



Mike Halloran
Pembroke Pines, FL, USA

 

[Paulkuklych]

How did you increase the diameter on the nylon part ? Did you change the mould or machine the part?

Did you run both materials thru the one mould to see the difference shrinkage? That will give a relationship.



Paul Kuklych

http://www.improve-your-injection-molding.com

 

[MikeHalloran]

Could you be more specific about how you're using the word 'fail' in this context?

I assumed that the nylon part survived both steps of assembly, but the ABS/PC part fractured after its prongs were first bent in by assembly into the hole, then bent back out by insertion of the mating part.

... but there are other ways in which a part could fail to meet your expectations, which are not as clear as one might wish.


Mike Halloran
Pembroke Pines, FL, USA

 

[rc0213]

Thanks for replying, everyone.

Paul, we increased the inside diameter on the Nylon version. And, we machined the part for the prototype, and it worked. So, then, we went to change the mold, with success. I believe we are using the same mold. But, being of different material, after this change on the ABS/PC, I would think there would be two different molds since the ABS/PC would have a different diameter change. Or, maybe we need to change the design of the prongs.

Mike, what I mean by 'fail', is that the prongs broke during the assembly. The prongs have to secure the mating part from pulling back out. The purpose of this part is to slide into a hole of a vehicle, and another part slides inside this part. This is why, when they changed the inside diameter of the Nylon it worked, because it relieved the pressure of the part sliding into this part.