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tuning motor issue
« on: January 26, 2009, 10:33:50 PM »

I am running a 3 axis hobbycnc product with mach3. 2 of the motors I can tune very easy and moving it fractions of an inch is flawless.

When I go to tune my table Y axis stepper no matter what I do I get missed steps at start and at fraction of an inch turns motors sound like they are arcing. I turn the accel and velocity up and it sounds a lot better but missed steps get a lot worse.

When I do get the motors to stop losing steps it is so slow and sounds like its running quarter speed.

I have read just about every post here and did the corrections I found including the step pulse and direction but couldnt find much more that helps.

Any other suggestions?



Offline jimpinder

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Re: tuning motor issue
« Reply #1 on: January 27, 2009, 03:23:03 AM »
Louis - what you need to do is find out where the problem is.

I will assume you have your steps per inch/millimeter properly set, your acceleration is reasonable etc. I assume that both your X and Y motors are set to the same settings as each other.

What you need to do is check the X axis motor and make sure it is all working correctly. If it is, then, without altering any settings on Mach 3, change the four drive wires on the motors - i.e. run the Y axis motor from the X axis wires (nothing else needs to be changed). Turn to Mach 3 and jog the X axis, the Y axis should move. Put commands in the MDI line for the X axis, the Y axis should follow exactly.

If the Y motor does not operate correctly, then the fault is a mechanical one with the Y motor, or the slide etc of your mill. Check it for smooth operation, and make sure th gibs are not too tight.

If the Y motor works correctly, then connect the X axis motor to the Y driver wires, and check that (using the Y jog and controls) - see if that works. If it doesn't, the the fault is in Mach3 or the driver.

If you can, change the wires from the LPT1 socket to the drivers - X for Y again, and try running the axis. If the fault is on the same motor, then it is your driver, if the fault has changed, then the fault is in Mach, probably with the settings. (If you cannot physically change the wires, the reassign the wires on the Config/Ports and Pins page, this will have the same effect).

I do not know the Hobbycnc product, and how much choice you have about wiring it. If it is all prewired, then you cannot do much else. If it is not prewired, then you can use different pin outs to drive the axis, to check all the pins.

I can't go much further at the minute until you post some results.

Not me driving the engine - I'm better looking.
Re: tuning motor issue
« Reply #2 on: January 27, 2009, 07:06:51 PM »
Hello and thanks for the advice.

I will try your suggestions but I noticed you mentioned the other 2 motors should be tuned approx the same? They are not but run very well. I was assuming the weight gravity and friction could make a difference but all three axis seemed to have the same amount of spin. Basically all the motors should be close to the same tune?

I will go thru the test you suggest and report back tomorrow.

Thanks for your help

« Last Edit: January 27, 2009, 09:26:06 PM by louisc »
Re: tuning motor issue
« Reply #3 on: January 29, 2009, 01:00:37 AM »

First thing I tried was changing the ports and pins and reversing the x and y axis. Now it all works and all motors are tuned the same.

How can this be?