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Trying to remember how to make foamcore building and having an issue: I run into these 'lumps' on the foamcore that are very difficult to cut, they's like higher density styrene that my carpet knife had a tough time cutting thru smoothly, so they leave uneven edges and even tears in the paper. I'm uysing super cheap foamcoare, is this an issue wiuth that type, the mix doesn;t get smoothed out as well? Anyone else have this?

Never seen foamcore with lumps... sorry

Are you sure they are lumps? Often while cutting foam core a blade that is not super sharp, and held at a good angle, will not cut the foam but push it forward into a "lump" like structure that becomes a hard knot. My solution to this is to make multiple, shallower cuts with the blade at a shallow angle. This requires a good straight edge held in place through all the cuts, but results in cleaner edges.

Make sure you use a new blade. Fat blades like carpet cutters will cause friction & make lumps. I advise using a scalpel. I use a Swann Morten with 10A blades. If cutting lots, you will have to change your blade on a regular basis.

Yeah, that's what it looks like. It felt like there were lumps in it, but apparently unless your blade is a virgin this happens. Thanks for the data guys.It seems that cuttiung styrofoam just clogs the blad eup at some microscopic level. WOuld washing it in acetone help?

I am not sure acetone would help. You can resharpen a blade if you know what you're doing and have the right tools. Search youtube I'm sure someone has a video. My opinion, cheaper to just buy new blades. I cut my foamcore with a stanley 99e, and just rotate/change blades often. Is this the same as your "carpet" cutter?

On another note, what do you have going? Do we get to see/hear about it? I love terrain work!

When I can cut straight enough to build it and not look laughable.

I have an ambitious plan for a first time building: I want to make a 6x6x9 3 floor building that looks like it cracked very roughly in half and the smaller half fell over, broke into a few pieces and now lays alongside the standing half.

Foamcore blunts blades pretty quickly. Sometimes you only get 10-15 cuts before this happens. The combo of the paper/card and the foam is what does it. The paper is an edge-killer.

I switched over to sintra board a while back. You still need a knife to cut it (it's a foamed pvc board, so it CANNOT be lasercut) but superglue doesn't melt it and you can safely rattlecan paint it without it being eaten.

I found a perfect solution to joining two walls at a perfect 90d angle, sharing it in case someone hasn't seen it.

I'm using the method where you cut the the foamcore at a distance from the edge equal to it's own thickness but do not but the outer paper, they glue it together. Seems like a simple and sturdy means.

Here's the video at the time he starts to talk about the method i settled on, hope it helps someone.

https://youtu.be/S_nyV1C0cYM?t=316

I'm still measuring carefully, cutting carefully and finding that one and is narrower than the other by just enough to screw me. Gggrrrrrrrrrrr.....

We've all been there! Hang in there. Love your idea, hope it comes out!

@Chromedog: Sintra BOard is new to me. Maybe give it a try. The edges of foamcore and melting is an issue.

Could I recommend using a box cutter with one of the snappable extending blades? I use those for making buildings out of nice, thick foamcore. And yeah eventually after a while its gets dull and you'll feel the material tear as you cut. But give the blade a snap to get a new sharp point and it goes through again like butter.

Besides that it is possible you've had a janky batch? I've never had it myself but it's always a possibility the extruded foam they used wasn't properly mixed.

edwardmyst wrote:
We've all been there! Hang in there. Love your idea, hope it comes out!

@Chromedog: Sintra BOard is new to me. Maybe give it a try. The edges of foamcore and melting is an issue.

Google "PVC foamboard". I have a supplier a short drive away, but I live in an "industrial" town (we have chem manufacturing as well as plastics and foams - and some steel products).
It's also available under other names. The one I use is "Palight" ("Sintra" is what I've heard my US friends call it).
Comes in a variety of thicknesses (I use 2mm and 3mm locally), some of them even come precoloured (Palight only comes in white locally, but other pvc boards come in green, black, yellow, orange, red as well).
Two 8'x4' sheets cost me $80AUD.
1 sheet of "foamcore" 1/8th the size costs me $12.

Just be warned, you have next to NO time to reposition when you glue it with superglue. It will pretty much grab INSTANTLY.
It's not as rigid as mdf, but it is lighter.
It's a bit more resilient than foamcore.

You know about the dressmaking pins trick for foamcore building, right? (use pins to hold corners together while the glue sets).

I got bit by the build a building bug to be honest when I picked up this at a dollar store.

118770072_3876951635654524_8294288963753387353_o by matt swain, on Flickr

I looked at that pentagonal shape next to the half circle and said "That makes a good window on a building in 40k."

Yes mine will be point up.