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Author Topic: Trouble with the Z axis  (Read 2218 times)

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Trouble with the Z axis
« on: August 05, 2014, 01:29:21 PM »
Hello all!

Running into an odd little problem.  We are using a Maxnc-10 machine, converted controller using a Gecko G540 board and Mach 3 software.  It seems that during a machine run, every time the Z axis makes a move, the Z axis moves up .0250.  When it is supposed to descend, it doesn't.  So the spindle is effectively rising up above the engraving area by .0250 every time there is a break between speed change but is not returning to the engraving area for the next move.  It just continues to move up and not down.

Does anyone know what is causing this and how it can be corrected?

Appreciate any help!

Jeff
Re: Trouble with the Z axis
« Reply #1 on: August 07, 2014, 03:19:08 PM »
Have been playing with this problem for a couple of days now.  I tried several different things.  I retightened the set screws in the coupler on the stepper motor shaft.  At first it seemed to work.  For about the first 10 minutes of the test run, the Z axis drive rod turned on descending moves where it wasn't before.  Then it only occasionally dropped the Z on descending moves.  I am wondering if there is an issue with the stepper itself.

I am using a Sure Step 276 oz-in 2.8 amp 1.1 ohms 1.8 degree/step motor.  Does anyone know if there are issues with this particular motor?  The X and Y axes seem to be operating just fine (although the motors are getting pretty hot).  I need to check the resistor to make sure the current limitation is the correct value setting in Gecko for motors.  I am pretty sure it is.

I will take any and all suggestions into account.  I am running out of ideas and I know there is an answer and a solution for everything.  For all I know the motor on my Z axis might just be faulty.

any guesses?

Offline Hood

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Re: Trouble with the Z axis
« Reply #2 on: August 10, 2014, 02:41:15 PM »
Can you jog the Z in both directions? If not check your Direction wire is properly secured and making good contact. Also check you have the correct port and pin number entered for it in Ports and Pins.
Hood
Re: Trouble with the Z axis
« Reply #3 on: August 11, 2014, 11:49:17 AM »
That is the mystifying thing.  We are able to jog the Z in both directions with no issues.  It is just that sometimes after a speed change move (G-code line runs at 10% of full speed when resetting into the engraving area) the Z descends for a short time and then it just stops.  So you end up with a Z that keeps ascending and moving farther and farther off of the engraving area.

It is getting a little frustrating.

I think I am going to move the other Gecko controller box over to see if the problem mis mechanical or in the coding somewhere.

Offline Hood

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Re: Trouble with the Z axis
« Reply #4 on: August 11, 2014, 11:56:28 AM »
Do the DROs show the position the axis is at or do they show where it is meant to be?


Hood
Re: Trouble with the Z axis
« Reply #5 on: August 11, 2014, 03:32:30 PM »
Yes, they do.  In fact, every piece of G-code in Mach3 is being fed through, even if the Z axis commands are not following the programming.

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Re: Trouble with the Z axis
« Reply #6 on: August 12, 2014, 04:27:18 AM »
Ok if the DROs correspond to the position it should be at, then it is almost certainly not a Mach issue and most likely a hardware/wiring issue.
Try reducing the acceleration and velocity by 50% for the Z to see if it helps, if it does then increase until the problem appears again then back off a bit.
The other thing to check is the step pulse active state is correct for the drives you are using and might be worthwhile increasing the pulsewidth and dir prechange to something like 10 to see if that helps.

Hood