# Z-Axis Binding



## papermaker (Jun 3, 2013)

I received the CNC conversion kit from CNC Fusion this afternoon and went about putting everything together. The only snag is the Z- axis binds at the top of the column. You can see where the screw is binding on the block that holds the ball nut.
I've read a post somewhere that somebody had the same problem. Has anyone experienced the same problem with this kit and what did you do to correct the problem.


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## papermaker (Jun 3, 2013)

Here is a picture of the area that is binding


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## Richard King (Jun 7, 2013)

Can you loosen the top bearing bracket and let it move to the right.  The bracket not shown that holds the top end of the screw in place?  Can you take a picture of that and the complete machine?  Can't you call the company you bought the kit from and get the answer from them?


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## DMS (Jun 7, 2013)

I'd recommend taking your time, and walking through step by step, to see what is binding and why... seems obvious I know. Depending on how the ball-nut is mounted, it may be a simple matter of shimming the bottom edge of the mount to rotate that mount a bit, to provide clearance. Though, given that it only binds at the top, the top, the screw may not be parallel with the z axis; do you have a dial indicator, or a dial test indicator?

One thing you can try is to drop the head all the way to the bottom, then take a dial indicator (if you don't have one, Harbor Freight sells a servicable model for between $10 and $20 depending on the coupons you have), and measure the distance between the z-axis dovetail, and the ball screw (measure with the point in the "valley" of the screw). This should be as close as you can make it (definitely within 0.001"). If it's not, adjust the top/bottom brackets to get it there. If that is straight, check the distance from the face of the column, to the screw using the same method. You should be close there too. 

If that all looks good, you can check the bearings by rotating the ball-screw 1/4 turn, then doing the same test. If you don't get the same results, then you have runout in the bearings. If it's real bad, then call the mfg and see about a replacement.

If all that seems straight, then I would check the alignment of the ball-nut mount. As I said above, if this is the issue, just shimming the bottom may be all you need.


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## papermaker (Jun 8, 2013)

The top bracket where the stepper motor is mounted was what was causing the problem. The mounting holes were "off" by a few thousandths of an inch. I ended up slotting the holes toward the left. Not normally a problem if you had a milling machine but trying to get real accurate results on a drill press was a challenge! I'm not complaining about CNCFusions workmanship because I can imagine that there is probably quite a bit of variation in the quality of the machines from China.


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