Let's talk Kerfs (curving your foam)

[atahoekid]

It seems the best and most common foams to use is what is known as XPS or EPS (same stuff different names) (Extruded PolyStyrene). It's the solid panels of foam sold as home insulation. Either pink from Owen Corning or blue from DOW? I think there's green stuff too but I don't know who manufactures it. The white beaded stuff is not very strong. The extruded stuff is better for our needs.

[KCStudly]

I think I have also fallen victim to using XPS and EPS interchangeably, but have also read that EPS is often incorrectly called out.

Some sources say that EPS = Expanded Polystyrene (the white bead stuff) and XPS = Extruded Polystyrene (the construction board that we all are so enamored with).

Not sure which is definitive.

[SteveW]

build up the shape with solid foam. Attack it with saws and rasps and other medieval tools and then glass the whole thing.

This makes the most sense to me for something like this. Sculpt it rather than shape it.

[GPW]

Great place for thick blocks of easily shaped beaded foam ... messy , but easy ...

[ARKPAT]

I wonder about reshaping a router bit ( 1/8" straight gouge ) to the shape of the "V" notch you need. You would need a bench grinder and "Drimble - type" tool with cutting wheel ( to cut a groove down each side for product removal relief of the bit ). Just an idea



Pat

P.S. I enjoy Foamies .... I pull a steel sided one I'm watching the foamies ..... to make a larger box on my frame

[GPW]

Somebody must make a bit like that already huh ? ... so many available ...

[Junkboy999]

I think you need to look for V Grooved bits. Usually used for bid letter engraving ( sign making ) and design work.

http://www.toolstoday.com/p-5183-solid- ... -bits.aspx

[Vindi_andy]

junkboy, was reading a build thread talking about kerfs and this exact thought hit me. Instead of using a saw blade use a v shaped router bit someone must make one.

[Bogo]

You mean like these: http://www.amanatool.com/bits-fv/45705.html They have a 60 degree one. I know I've seen 30 degree ones in the past. OK, 30 degree here: http://www.amanatool.com/cncroutingdetails/45771-signmaking-engraving-bits.html Other places also have them. The grove depth may not be enough for your needs.

Here is an even narrower one: http://www.toolstoday.com/p-5891-carving-liner-solid-carbide-router-bit.aspx


I always figured it was a no brainer to use a router for cutting kerfs.

BTW: I googled on "v-groove router bits" and the above links came up near the top.

[mgb4tim]

Just thinking outside the box.. but if you cut the kerfs as in the original example, then turn 90 degrees and cut again, could you create a bowl?

[KCStudly]

I think it would take at least a decahedron cluster (i.e. three sets of cuts, 60 deg apart), similar to geodesic domes.

[GPW]

Maybe a square bowl ?? ... perhaps usable as a front end for a trailer ???

We really need to investigate this kerfing’ business more . With Heat bending on a small scale being problematic for the home builder , the kerfing' process becomes even more important than ever if we want to build something other than angular boxes ... hot wire seems the least messy way to go ...

[KCStudly]

My previous comment about the triangles having 60 deg corners was bugging me, so I looked into domes a little further. Turns out that in order to form loft the triangles are not symmetrical.

Reference Dome Calculator

Now I am thinking that the way to do it would be to make a hot wire cutter that has the pattern of one section of the dome, then repeat that as a plunge cut over and over to cover a broader area.

[KCStudly]

Hmm. Still doesn't work. A wedge shaped section would need to be removed from each cluster. Maybe do a cluster of clusters (like a flower bud with one in the center and additional clusters around each perimeter chord of the center cluster. Form and glue the seams.

Sounds like more time and work to make nice than other methods.

[GPW]

How about radial wedge cuts , made from a center point ? Then concentric wedge cuts from the same point ?