Backlash Compensation

[john dakinParticipant @johndakin59277]

I have read a few articles on cnc backlash compensation for a hobby cnc mill, I've got a basic understanding on how to calculate for it, but I have an additional backlash problem in my z axis, the spindle chuck is moving up and down about 0.0050, do I just add that value to the ball screw back lash

[john dakinParticipant @johndakin59277]

[Martin ConnellyParticipant @martinconnelly55370]

If you have a vertical mill then gravity will have an effect on the Z axis. You may not need backlash compensation. If you have a spring set it so that the spindle is pushed down so that together with gravity it acts as a backlash eliminator. Having the spring opposing gravity as is usual in a drill will result in variable backlash so backlash compensation may need to be variable. The forces on the Z axis may in some positions push it down, in others they may balance and at the other end of travel they may push it up.

If you are using a knee for the Z axis movement then gravity is usually acting as a backlash eliminator so no problems with backlash are the most likely outcome.

Is it possible that the chuck movement of 0.005" is due to loose bearings? If so this should be sorted out as loose bearings are not good for milling in general.

Martin

[John HaineParticipant @johnhaine32865]

As Martin says, you shouldn't have play in the spindle so not a good idea trying to compensate for it.

Are you asking about setting up the BC in Mach3? If so beware that though it works it doesn't cope well with large values of backlash such as with a normal lathe screw. I have it working with ballscrews on my little Novamill but the backlash is ~0.02 mm from memory.

[john dakinParticipant @johndakin59277]

Looks like I need a new spindle then because the one in the machine seems unserviceable as its one of those sealed spindles on the Chinese machine with a drive cable attached Tonsen TS3040

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