https://wiki.artscienceblr.org/wiki/index.php?title=Dhruva/CNC&feed=atom&action=historyDhruva/CNC - Revision history2024-03-29T02:08:55ZRevision history for this page on the wikiMediaWiki 1.22.6https://wiki.artscienceblr.org/wiki/index.php?title=Dhruva/CNC&diff=3594&oldid=prevDhruva.GS: Created page with "The CNC machine wasn’t working so I was asked to fix it. The problem was that the x and the y axes moved well, but the z axis made a horrible grinding sound. Suspecting t..."2018-08-06T05:28:59Z<p>Created page with "The CNC machine wasn’t working so I was asked to fix it. The problem was that the x and the y axes moved well, but the z axis made a horrible grinding sound. Suspecting t..."</p>
<p><b>New page</b></p><div>The CNC machine wasn’t working so I was asked to fix it. <br />
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The problem was that the x and the y axes moved well, but the z axis made a horrible grinding sound.<br />
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Suspecting the Z axis stepper driver (which was a DRV8825), I switched the drivers for the Z and Y axes, switching the two Vrefs as well. <br />
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Now, the Z axis motor worked fine, but the Y axis made the horrible sound.<br />
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So It was the driver. We ordered a new one.<br />
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When the new driver arrived, another problem presented itself; The CNC would not drill very deep, and would sort of drag around the drawing it was making leaving drilled lines along its travel path.<br />
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I suspected the microstepping here, so I switched from 1/16th step (the previous configuration) to full step. <br />
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Now, it could drill properly, but the dimensional accuracy was off. If I wanted to drill 1 cm, it would do 1.2 instead. I don’t know why this happened but I fixed it by altering the GRBL (CNC firmware) settings.<br />
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You can do this on Universal Gcode Sender (Ugs platform) by typing <br />
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>> $$<br />
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in the commands window.<br />
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You will get a long list of settings numbered $0, $1 and so on. <br />
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The problem seemed to be with the steps/mm. ugs told the printer to do 10 mm, but it did more. Therefore decreasing the steps/mm should resolve this difference.<br />
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To find the steps/mm you need I simply found the ratio between the expected and actual movement, and multiplied by the current steps/mm (200).<br />
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(1/1.2)*200 = 166.666<br />
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so I set the steps/mm of the Z axis to 167 and all was good. The command used was <br />
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>> $102 = 167<br />
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Finally, I found that the X and Y axes were also a bit skewed: an expected movement of 1 cm instead yielded 2.5 centimetres, so I altered the x and y steps/mm accordingly to about 80 steps/mm. <br />
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After this, the CNC was perfectly operational. <br />
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Future plans include attaching a vacuum cleaner to suck up dust, and adjusting the microstepping to 1/32 to make the motor movements more silent. This would also involve multiplying the steps/mm to account for the changes.</div>Dhruva.GS