How much horsepower can I safely use?

Running different bits and materials through the G-Wizard Feeds and Speeds calculator, trying to learn good settings and program new bits into MeshCam. G-Wizard keeps listing my HP in Red numbers, which I assume means it thinks I’m using too much.

Currently it’s at 0.0393. The HP Limit of the Nomad is 0.07, according to G-Wizard. Is .0393 actually too high? What HP should I be aiming for?

Also, anybody have any experience cutting Precision Board Plus High Density Urethane Foam? Pretty sure it’s about the same stuff as Renshape 460. Any thoughts on feeds and speeds for the Nomad?


I’ll leave the HP discussion details to others who have G-wizard, but if it helps, remember that horsepower and watts are both measures of energy with a simple conversion: 1HP = 745.699872 watts.

Since the Nomad has a 50w spindle, that’s 0.0670511045 horsepower, so all that is adding up well so far, as to why it’s warning you at .04HP, it’s probably got to do with duty cycling or something.

Regarding the material, I can vouch that the board is likely to NOT be quite the same as RenShape, because it’s a foam rather than a filled composite. Renshape is a polyurethane based composite, but it’s blending a soft mineral filler similar to gypsum powder in, if I remember correctly. This means that it produces chips instead of lots of dust, which is what you get off of foams.

I’ve cut polyurethane foams, and my word of precaution is wear your respiratory protection when cleaning out the machine. The particles won’t dissolve or dislodge easily once they find their way into you, and as a result will be with you pretty much forever. Consider yourself warned :smile:

With that said, polyurethane foams machine quite easily, and is easily hand-sanded and such afterwards. You can then impregnate them with acrylic or polyurethane if you want to further strengthen your parts, as otherwise they’ll be a bit fragile if they’re small or have thin walls. For feeds and speeds I’d say you could go quite fast—shoot for a target chip-load of .005" in G-wizard at 1:1 diameter/depth passes for roughing, maximum traverse speed probably 55 or 60ipm? I’ve gotten that in the foam I have, but it is a different density/different brand. You may want to shop around online as you can order by the board-foot from companies such as General Plastics and probably will get a better price-per-board-foot, you just will have to cut it to size from whatever sheet-size you order it in.