View Full Version : Need Help! EPS foam deffective? Hotwire issues.... Help!

05-21-2009, 02:55 PM
I've cut EPS blocks from a variety of national manufacturers and distributers. Lately, however, there seems to be an inconsistency in the size and density of the beads (or pellets) expanded within the foam. This is more noticable once a section of the block has been cut with a hotwire, as the smaller tighter beads leave a fairly flat surface, while the larger beads seem to burn back quicker leaving craters and holes. The 1lb low density foam is pretty full or large beads, so it doesn't change much, but the 3lb higher density EPS comes out with rough beat up surfaces that resemble acne scarring, if you will.

This defective foam seems to be showing up more and more often lately, from different manufacturers. I'm having a hard time explaining to these other companies what exactly the problem is and why I am wanting an exchange of products.

Has anyone else had this problem or know what to suggest to the EPS manufacturers? I use the foam forms as molds for precast. Although I usually coat the foam with blockfiller, sand and repeat, and then coat with styro-spray or styro-poxy, the surface is usually fairly flat and smooth right off the cut table. I can't imagine that we should just get used to more prep work, more sanding, more Spackle and more precious time down the drain just because the EPS blocks are so inconsistent. There has to be a way around this! Years ago when I first started foam cutting, I remember every block of foam was pristine from cut to cut, and now it seems like quality EPS is lost in the past. What happened?

06-24-2009, 02:07 PM
Sounds like recycled foam to me. We purposely buy recycled foam (because it's cheap) to use as foam cores for composite layups. Every part we cut comes out slightly different and every part acts differently under vacuum (density variations). Maybe the foam suppliers are slipping in more and more recycled foam rather than making pristine new stuff.

06-24-2009, 03:14 PM
I am not sure, but I think they are using more and more recycled materials.
I have not much experience, on the foam quality.
Any way I use only virgin foam blocks and have very good cutting quality.