[neeboy]

I need help with milling tool selection.

I have access to a Kuka robotic arm, and I have successfully programmed it as a CNC Router. I have cut several, simple pocket designs, and now I'm ramping up to a human-sized bust. The plan was to glue up several sheets of Home Depot pink insulation foam into a block using wood glue. I did that and tried cutting a roughing toolpath, but after cutting, I had nasty residue all over the end of the ballnose bit I used, and it was very hard to get off. I know it's from the glue, it is very pale brown in color and I have cut lots of foam on several machines w/o the glue and had no buildup whatsoever.

My initial thoughts are to switch to white Elmer's glue or turn up the rotary speed of my cutting tool. Spray adhesive for foam does not dry very well, it remains sticky even after 24 hours, so i don't plan on going that route. Anyone have any other thoughts on adhesives that dry solid/hard enough for machining w/o buildup?

My other problem is that the 8" long, 1/2" diameter carbide ballnose bit I used in my Hitachi M12VC router is apparently too much for the router to handle; after 20 minutes of cutting a roughing toolpath on the pink foam with a pass depth of about 1.25", the metal housing of the router itself was just absolutely insanely hot, and I'm honestly surprised there was no evidence (visual or smell) of anything burning. My router also has speed settings from 1 to 6, and I could not run it faster than about 1.5 before the sound got to be very disconcerting and I think the bit may have been ready to start physically bending the router's shaft.

I am seriously considering buying this spindle:
http://ugracnc.com/CNC-SPINDLES/GMT-...kW-220V-R.html

Anyone else using Ugra's stuff? They seem to have good feedback on their services/products. Would a spindle with these specs be able to handle my monster bits?

I have all the programming done in SprutCAM; it's very slick and I am very anxious to resolve these material/cutting bit issues. Thanks in advance for any informed replies!

[awerby]

It's great that you've got your robot arm working. What are you using to control it - Mach3, LinuxCNC or something else? I think all that type of glue is going to have a problem curing quickly between sheets of foam. Have you tried a polyurethane glue, like Gorilla Glue? You need to dampen both surfaces with water before applying it, then it foams up. Have you tried getting foam in big blocks, so you don't have to build them up from sheet material?

It's not surprising that your little Hitachi router's having trouble running that tool. A tool that long will probably give any spindle a problem, but at least foam isn't going to break it. If it was me using it, I'd set up some sort of enclosure around that arm, and hide behind it before turning the thing on - one electronic glitch and it could easily kill a person.

Ugra sells Chinese spindles, but supposedly they check them for quality and stand behind them better than most Ebay sellers; they get pretty good reviews here, although I haven't dealt with them personally. You'll need a VFD to run that spindle, and the Chinese ones aren't too good. I've had good luck with the Hitachi VFDs, though. If you don't have 3-phase electricity, you'll need a VFD that can convert single-phase to 3-phase, and you'll have to overrate it accordingly.

[inov8r]

Have you thought of pouring your own two part foam into a solid block? Also we need some vids of this thing working! It sounds very cool.

[Jason_Scott]

Wood glue will soften with heat. You might try a polyurethane glue just remember to wet your surfaces. Another option would be urea resin glue like Dap Weldwood but it pretty much sucks to work with. If you want to stick with regular type glues try tightbond extend. It has one of the best heat resistance of any wood glue.