View Full Version : How do we figure spindle specs for woodworking?

05-27-2008, 06:40 PM
Greetings fellow wood enthusiasts!
From the beginning, what does a newbie need to know to figure out how big a spindle motor is needed for routing/cutting/milling wood on a decent gantry CNC?

For examples sake, let's use numbers from a theoretical machine setup this way-

Gantry Size: 8' by 4' cutting area on an overhead gantry style CNC machine.

Gantry Speed: 2800 ipm free travel speed.

Feedrate: ? (Depends on the cutting bit, the number of flutes, rpm, and... anything else?)

Material: 3/4" hard plywood

Spindle Motor: 6 Hp, 21.1 lb/in. torque, 17,800 rpm w/VFD, fan cooled, 230v 60 Hz 1 phase, 230v dynamic brake, rotation = CCW, vertical nose down working position, ER 32 collet to hold bits. ~$9,800 USD, total weight of spindle unit with tool is approximately 51 lbs.

Is this overkill, underkill, or what do we need to know to figure out how to size a spindle for woodworking? I understand that a lot of factors are involved. What are the factors or considerations we newbies need to know when designing a woodworking gantry CNC system?

Thanks for all the brainpower on loan guys, CNCZone members are great!
"Persuing the elusive 'max rapids rate = max feedrate' formula."

05-27-2008, 08:42 PM
You need to decide what you want to cut and how fast you want to cut it. Including depth of cut and tool type and size. That should tell you what kind of spindle you need. Unfortunately, I don't have any magic formulas that tell you what you need. I'd guess that for 3/4" plywood, that spindle would be good for about 500ipm, maybe more with sharp 1/2" bits. If you want to cut at 1000ipm or more, then I'd go bigger.