So, I finally am running my first full job with my upgraded X Carve. I am cutting out a custom letter “K” for my friend’s wedding out of 3/4" Birch plywood. I am running this VERY conservatively (15 IPM and a step down of .05" - yeah, kinda embarassing) but I am still getting a hell of a lot of chatter using a brand new 1/4" Bosch Solid Carbide 2-Flute Downcut Spiral router bit. I have tuned and calibrated the machine so slop has been eliminated as much as I can so I am fairly certain that my woes are due to my Spindle speed.
Now, I have hooked the Arduino to the power supply but I cannot figure out how to change the Spindle speed. So, the questions that I have are as follows:
- What is the default Spindle speed when just flipping the switch out of the power supply?
- How do I change the spindle speed and can I do so while running a job in Universal G Code Sender?
- Any other suggestions about how I can optimize my next cuts to get them cleaner and hopefully faster?
I think you’ll find that with the stock spindle, a .050 cut with a 1/4" diameter bit is still slightly too deep, especially through plywood. That stuff is hard on bits. Even at full speed (12,000 RPM), the 300W DC unit loses torque very quickly when it engages the material. It’s just not a terribly powerful motor, and trying to drag a 1/4" bit around is that much harder on it. I’m going to also guess - and please correct me if I’m wrong - that you probably have at least an inch of the bit protruding from the spindle. That will cause “runout”, which is the amount of deflection of the end of the bit off-center when the spindle is rotating. A 1/4" bit is actually a pretty significant amount of rotating mass for the stock spindle, and will tend to run out a lot more than a smaller diameter bit. The protruding length contributes a lot to this as well - the longer the bit, the more the runout will be amplified.
Just as a suggestion, try taking a much shallower cut, like .010 or .015. That’ll take a lot of the load off the motor and help to reduce torque loss. Yeah, it means the cut will take 5x longer, but you have to work with the tools you have. 
I don’t believe you can alter the spindle or feed speeds in UGS once the job has started. You can, however, change the spindle RPM in your gcode file by opening it in Notepad or another text editor, and locating the command near the top that looks similar to:
S12000 M3
The SXXXXX means Spindle, X RPM, and M3 is the gcode command to start the spindle running. If you’re flipping the switch manually, you’re going to be at 12K RPM regardless of what that command reads. You have to use the automatic start/stop function to gain control over the speed.
Hope that’s at least a little helpful. Try changing the parameters I mentioned, and maybe knock the spindle RPM down to 8 or 9000 to help reduce the chance of runout. Just remember that slower speeds will reduce the amount of overall available torque, so you may need to reduce cut depth/feed speed even further to compensate.
Well, I will be getting a new spindle in the near future. I thought that it had a little more umph than this. I got the control feature working but as you said, I can’t get it to go any faster…just slower. I guess that I’ll just decrease my cut depth. Thanks for the insight and the help
