Nylon 66 Molding Process - It is normal to have voids when molding nylon?

[quality1]

Hello Plastic Molding Experts,

Our company just received a small batch of materials that were molded using Nylon 66 materials. We found voids on 10 samples crossed sectioned. The voids vary in size, but all are right in the middle of the part. It is normal to have voids when molding nylon? if no, is there a specification we can look at (ASTM) to put a criteria in place for our molder? Yes, they're overseas.

Thank you!

 

[Golfman25]

Voids are more function of part design than material. Is the void in a thick area of the part?

 

[Miner]

No, voids in nylon are not normal.

See The Troubleshooter, Part 20: Warping and voids in nylon for some ideas.

 

[SJ Anand]

Hello..
Voids are mostly due the DESIGN.There is nothing to do with the material.

 

[world quality]

Here are two guide lines you might use to help in detecting and controling plastics.

Good standard plastic and design not material.

 

[quality1]

Yes, it is cylinder shape. Dia is 3mm, length is 5mm.

 

[quality1]

Hello SJ & Golfman25, can you elaborate on why it is more of a design issue then the material? THis is a cylinder 3mm dia X 5mm length.

Thanks

 

[Golfman25]

Voids are a function of lack of pressure in the mold cavity. Design problems with thick to think part sections, gate locations, etc. exacerbate these pressure problems. Might I suggest you locate a book entitled "On the Road with Bob Hatch," published by Injection molding mag. Page 133 provides excellent guidance on voids in a thick cylindrical part. Short story is you may need to enlarge the sprue and runner diameters to improve cavity pressures. Good luck.

 

[bazzle - 2012]

Voids are a function of lack of pressure in the mold cavity. Short story is you may need to enlarge the sprue and runner diameters to improve cavity pressures. Good luck.

Same in my experience as well.
Nearly always had to adj sprue.

Bazzle

 

[roverman]

This is all assuming the overseas moulder is competent and has set the machine corectly.

You need to establish this before making tool mods. You can take metal off but you can't put it back!