Thread: Looking for a smart bugger

Originally Posted by Snap 4T

That's a lot of stop/start for the machine,
Even thou someone does you a favour by not charging you, his/her time to draw, program and set up
water or wire cutter time alone costs a lot more than US$100
Turret (metal) or router (wood) is probably the cheapest way to go if you want to go thru cnc way,
sandwich the foam between 2 sheets to keep it steady and put it through the machine,
Or get a drilling template made up and you can drill them out in your spare time.

Never said I don't want to pay for time or the job getting done. What I'm not interested in is not + $100 USD for freight to get the bits here. Drilling template is an option but wont be as nice a finish as the CNC.

I would be looking at either a laser cut service (don't know of any in NZ at the moment) or a heated but very thin core cutter that moves through on a press so it's a vertical cut. A card template with the holes cut in it in the right places would act as the guide. You could even print it out on paper, glue it to a thin piece of plastic or ply and cut the guide out that way. Once you have the guide set up stick it to the foam and press away. The high density foam is not cheap in the thickness you are needing for this, and it doesn't really freeze well enough even at -4 to make rotary cutters an option for my experience. Maybe if you had liquid nitrogen on hand, but in the freezer won't do cold enough to last for the length of time you'd need to drill out that many holes.

It isn't that hard to make a cutter tip to do this, you do need the stiff ni-chrome wire or the stiffer ribbon to fashion the cutter out of and this can be a little pesky to come by. Once you have the wire, bend up a two-row coil on the bottom with two legs going up to where you need to connect the power to make it hot. When the cutter goes through, you find a balance point in rate of push through the foam where you are getting a good melted cut without cooling the cutter too much and not melting to much. Once the cutter is withdrawn you need a little punch of some sort to push the offcut out. Then onto the next hole pretty quick so the cutter head doesn't get too hot... Control of the cutter heat is a factor of resistance, commercial setups have a resistor on a control knob that does this.

I've made up a heated wire cutter for this sort of foam and the pelican case type foam to cut out tool profiles and the like, it's hand guided so not that straight but apart from the up and down and the size of the hot wire (this is under tension to keep it straight so the fine stuff is OK) the concepts are the same.

Hi @nzfubz
I don't have access to the workshop anymore but I'm happy to model up whatever you need. I think 3D printed would be better than foam but this company would be able to watercut it for you.
https://www.laserstream.co.nz/home
Here's a Pic of what a single layer printed one would look like.