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Improving CNC Setup: Home Switches, Table Mounting / Leveling





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Published on Apr 26, 2012

In this video, I try improving my Zen Toolworks CNC setup to improve accuracy and ease of use. The main things accomplished in this video are...

Mounting the wood table using bolts through counterbored holes:
This was necessary because I was previously using C-clamps to mount the table which only allowed me to used half the X-axis travel. The first attempt at mounting failed because I forgot that the bolts will hit the edge of the CNC machine. This is because there is almost no room between the CNC table and the frame. In the second attempt, I move the holes as close as possible to the center. I still lose almost 1 inch of travel but I still have over 12 inches of maximum travel. The X and Y travel of the Zen Toolworks 12x12 CNC machine is actually greater than 13 inches.

Installing home switches on the X and Y axes:
I used normally-closed lever switches that I found in some junk bins. They are surprisingly accurate. They were toggling consistently down to the individual step which is less than 0.001" on my CNC machine. However, one of them turned out to not work properly and I had to replace it after I had mounted it. The super glue held the switches in place very securely. I had to destroy the one I replaced in order to get it off.

Leveling the wooden (MDF) CNC table:
I needed to do this for PCB milling because the piece of MDF I am using is warped. I wrote a small g-code program to mill the surface of the table flat. I used a 1/8" end mill to mill the table. It is very small for the task, but I am limited by the chuck and the spindle speed. I ended up milling 0.025" deep at speeds between 7 and 8 in/min (I changed the feed rate occasionally during milling). The milling process took about 6.5 hours. It took an extra hour because I had a weird problem were the CNC machine lost track of the position. It is possible that the computer did something that stalled the signals going to the motor control board.

Other minor things that were accomplished was oiling up the lead screws and other hardware, tweaking the machine to reduce some squeaking noise when operating, raising the spindle slightly, tweaking the LinuxCNC configuration to my liking, and modifying my motor control board to tie the parallel port signals for the home switches to ground instead of leaving them floating.


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