Hello, I have a problem that is almost driving me crazy, I have a openbuilds 1500*1000 belt driven machine that I bought used. It has 2 nema 32 for X axis, 1 nema 27 for Y and one nema 27 for Z. I usually cut mdf and soft wood so I think the motors will cover me as long as I have patience . Only the breakout board was missing from the cnc, so I bought a usb 5 axis for mach3, the one shown in the photo. For the motors it has 4 tb 6600 5a drivers, a 24 volt 20a power supply for the drivers and a 12 volt 10a power supply for the board. Before connecting the electronics I did some maintenance, changed some bearings and screws as well as some eccentric nuts. I connected the electronics and started to calibrate the machine, unfortunately so far I have not achieved anything. The cuts have no precision.straight lines, pockets, circles from design to cutting have differences from 0.75 to 2 mm. these differences are the same no matter how many times I run the program, at least the machine is consistent in this . So I looked again for a mechanical error, I didn't find anything, o checked all the wire connections everything is ok ,I tried the backslash, nothing changed, I tried different acceleration and velocities for the motors, as I also tried all the options that the drivers give me for microstepping, the machine insists on doing its thing. I've tried and tested almost all the options and settings that Mach3 gives me, the problem persists, maybe I'm missing something about it and I'm asking for your help, has anyone faced something like this and found a solution successfully?I will also upload some photos with different cuts and I will write the differences I have in the dimensions. I design in rhino kai aspire, I have exported code from both programs but I haven't seen any difference. I apologize for the long post but I tried to write all the steps I have done so far. if the thread is in the wrong topic, I would ask the administrators to move it to the right one thanks.
In the first photo, a 40*40mm square that was engraved with a 2mm end mill, where the yellow arrow points, you can see where the cut starts and ends, actual dimensions w40*h39.5mm. The horizontal lines indicated by the red arrow are relative to the center line 0.75 mm to the left. I didn't measure the center line if it's in the middle, but I'm pretty sure it's wrong. In the second photo is the best circle cut so far and I think you can clearly see that it is not a circle
oh yes I did it several times I took measurements with a ruler, caliper and even a micrometer, every time I calibrate an axis I take at least 5 measurements to be sure. The problem is with the two axes I mentioned above, Z works fine, it is also the only axis that does not have a belt. Is this the solution? should I put leadscrews on all axles instead of a belt? I know that with a belt I will never have great accuracy, but a tolerance of 0.1-0.2 mm is fine for my work.
I use a fishing spring balance to pull the belts to the same tension. I use 12kg. This makes sure that they all stretch the same amount. After adjusting tension, do the calibration again, do the calibration over the longest distance, caliper and micrometer are too short. A quality metal yardstick should do it, and watch out for parallax error. Use the micrometer to measure the diameter of the cutting flutes on the bits, they are never exactly the saem size as the label. Put the measured diameter into the CAM software.
