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General Mach Discussion / Set Steps Per Unit function not accurate
« on: July 10, 2014, 02:58:24 PM »
I have been trying to calibrate using the Set Steps Per Unit tool in settings. I have been using something similar to ( http://www.amazon.com/iGaging-Absolute-Digital-Stainless-Accuracy/dp/B00KWCUZ4W/ref=sr_1_5?ie=UTF8&qid=1405017153&sr=8-5&keywords=digital+movement+slider ), except mine has 10 inches of movement. So I set it up so I can check within .001 accuracy axis movements. So the problem is, no matter how many times I calibrate and put in the suggested steps per unit I will be off when I try a different length of movement.
For example, I will choose X axis, tell it to move 6 inches, and input how for it moved, lets say, 6.008. Then accept the adjusted the steps per unit. Now I can Go To Zero and it will keep that 6 inches correct, but if I now choose to move it 10 inches, it will be off by a good margin, 10.036. So I adjust the steps for 10 inches, accept, then check 6 inches and it will now be off. Its like no matter what I do, the movement will not be correct if I choose a different length to calibrate.
I have tried lowering velocity, acceleration, but nothing seems to help. I have tried to compensate with Backlash function, but it doesn't seem to do anything at all. I have gone around and tightened everything I can on it and everything is tight and sturdy. I am using a table made by http://industrialcnc.com/routers/routers.php . It must be an older model because I cant see the exact one I am using but its most similar to the Apprentice 404 model.
I am not sure what to do here, its very frustrating because the table is mostly used to make circles in Baltic birch with a center hole. And while circles are not horrible, its still not reliable or accurate. These circles are used in a printing press so it has to be somewhat accurate, +0, -.020 tolerance. But the circles will differ by as much .050 and that in turn makes the center hole off also. I usually use a 30"x30" board, so I really only need to make it accurate over that length but I cant seem to get this dialed in. Any suggestions would be helpful.
-Tim
For example, I will choose X axis, tell it to move 6 inches, and input how for it moved, lets say, 6.008. Then accept the adjusted the steps per unit. Now I can Go To Zero and it will keep that 6 inches correct, but if I now choose to move it 10 inches, it will be off by a good margin, 10.036. So I adjust the steps for 10 inches, accept, then check 6 inches and it will now be off. Its like no matter what I do, the movement will not be correct if I choose a different length to calibrate.
I have tried lowering velocity, acceleration, but nothing seems to help. I have tried to compensate with Backlash function, but it doesn't seem to do anything at all. I have gone around and tightened everything I can on it and everything is tight and sturdy. I am using a table made by http://industrialcnc.com/routers/routers.php . It must be an older model because I cant see the exact one I am using but its most similar to the Apprentice 404 model.
I am not sure what to do here, its very frustrating because the table is mostly used to make circles in Baltic birch with a center hole. And while circles are not horrible, its still not reliable or accurate. These circles are used in a printing press so it has to be somewhat accurate, +0, -.020 tolerance. But the circles will differ by as much .050 and that in turn makes the center hole off also. I usually use a 30"x30" board, so I really only need to make it accurate over that length but I cant seem to get this dialed in. Any suggestions would be helpful.
-Tim