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Author Topic: Losing Z Height in Mid Operation  (Read 2273 times)

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Losing Z Height in Mid Operation
« on: October 25, 2013, 08:54:48 AM »
I bought my CNC router with Mach 3 configured with a USB connection instead of a Serial.  Recently I started dropping Z height in Mid Operation.  Checking bearings, slop in the screw, connections, and anything else I could think of is good.  I'm running in a metric configuration, and when I calibrate it sets at 355 "steps per". Operation starts out good, but after several minutes Z height will drop 5 or 6 mm. The manufacture suggested changing the Steps Per to 160.  At that configuration, things seem to be working better, but when I do a profile cut, the depth only reaches 55% of where it should go.  Anybody think that having it with a USB setup might be my problem or is there any other advice?

Offline Hood

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Re: Losing Z Height in Mid Operation
« Reply #1 on: October 25, 2013, 09:33:13 AM »
You can not chop and change steps per unit, they are a fixed value and determined by the hardware you have connected, ie 1.8 degree stepper, what microstepping the drives are, what pitch screw etc.
You may be losing steps, if I understand it is cutting deeper? That could be due to the axis being tight and thus if doing an upward move it loses steps and doesnt rise to where it is meant to. Mach just assumes it is there so on the next move down it will cut deeper.

What USB board do you have?

Hood
Re: Losing Z Height in Mid Operation
« Reply #2 on: October 25, 2013, 09:43:27 AM »
I tighten the nut on the screw a couple of turns to take the slop out, which was about 2 mm, but I didn't see any change.  Maybe I should loosen it to see if that helps.  I don't know what USB board, it was installed by the factory.  It is a Chinese machine.  I did insist they configure it as a USB connection, because I don't have a serial port on my laptop computer.  Thinking it might be my laptop, I tried running it from a Desktop, but it didn't change anything.
Re: Losing Z Height in Mid Operation
« Reply #3 on: November 02, 2013, 05:39:06 PM »
I have a small American made router and have had the same problem it would lose the steps when the code asked it to raise the Z rapidly with the G0 code. So I changed all the G0 to G1 and a feed rate less than full speed and it works fine. I had this unit for several years and did not have or notice a problem till I started doing some 3d relief stuff moving the Z axis a lot and fast.
No expert by any means still learning hope this will help.
Bill.....
Re: Losing Z Height in Mid Operation
« Reply #4 on: November 02, 2013, 05:57:23 PM »
I finally solved my problem by replacing the Stepper Motor.  Gary
Re: Losing Z Height in Mid Operation
« Reply #5 on: November 02, 2013, 07:50:13 PM »
did you replace it with a larger one?
Re: Losing Z Height in Mid Operation
« Reply #6 on: November 02, 2013, 09:27:49 PM »
No, I replaced with the same size.  I tried to get one with more torque, but it would fit.