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Author Topic: Z zero (plane) moves upwards with every Z dir movement  (Read 3434 times)

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Z zero (plane) moves upwards with every Z dir movement
« on: April 03, 2018, 06:19:56 AM »
Hello,
I'm new here., but I've been using Mach3 for some time now.

I have a problem.
I had a G-code, a 3D finishing, that worked great on Thursday, it was a 66k line long code.
Then I had another project, that run great yesterday, but that was only a roughing code.
And then today I wanted to run the finishing code, but the Z level kept going upwards. After 10 mins, I was 2 centimeters (almost an inch) over Z0, while Mach thought that I'm at Z-4.
I've had some problems like this, but those were solved, when I set the pulse lenghts to 4-4. That problem was that whole movements were missed. Now it's just steps, that are missing.
They are missing at even half acc, half vel and even at max pulse lenghts, and only on the Z axis.

I've been watching it, and every time is moves downwards and then up again at the same position, the axis of the stepper motor doesn't stop at the same place, but somewhere else with some degrees or steps.
I didn't have these problems with grbl, that was just unstable af.


Here is the program. : https://drive.google.com/open?id=1EponAlFKEk5OM6yDW5QlYinTkRcUPz0h
Nagyolás is roughing
Simítás is finishing
Tetejesikba is just a "pocket"
Could you run the "simítás" file on your router without any workpiece inserted to check it?

I use a 3 axis router with tb6600 drivers and a mach3 breakout board with an lpt connector, and the drivers get 36Volts.
The steppers are nema23 sized "56mm" type ones, as eBay regards to them, with 200 steps/rev. And I use no microstepping.

Could you hep me with my problem?

Offline rcaffin

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #1 on: April 07, 2018, 06:03:48 AM »
Have you checked the grub screws on all couplings between motor and leadscrew? Mark with feltnib pen.

Cheers
Roger
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #2 on: April 07, 2018, 06:33:16 AM »
Yes, I checked it, it is not mechanical problem.
I tried writing a code that makes the axes, on by one, go from (x, y, z) 0to 50 and back about a hundred times, and there was no mistake or off millimeters at all, like 0.002-3 mm accurate after the program, measured with clock type device, I don't know what it's name is, it looks like a clock and has a pin pointing out one end.

Tried making smaller motions than the machine can (4mm pitch, 200steps/360 degree), and it was accurate if I did it a lot of times and then went back to zero.

I now tried micro stepping the z axis and now the finishing program runs in the air. It is to test whether the micro stepping solved the problem. I don't understand why could that help. It I hope that it will.


Also, with Sherline option enabled, the mistakes were far smaller, than without it. I tried that before the microstepping, that's why I know it.

Offline ger21

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #3 on: April 07, 2018, 06:46:59 AM »
Reduce your Z axis acceleration by 50%.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #4 on: April 07, 2018, 07:34:35 AM »
Why do you think that'll help?

Offline ger21

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #5 on: April 07, 2018, 07:36:24 AM »
Because you're likely losing steps from trying to move faster than the motor is capable of.
And it's helped many others in the past.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #6 on: April 07, 2018, 08:12:58 AM »
I don't know. I used 300(mm/s/s) acc before on grbl, now I use 200, but I set it back to 150 for now. But I think the micro stepping solved it.
What I wanted to say was the fact that it could handle 300 on grbl before.
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #7 on: April 07, 2018, 08:14:08 AM »
Anyways, thanks for your help :)

If the problem isn't solved after these, I'll write here again.

Offline ger21

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Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #8 on: April 07, 2018, 08:48:54 AM »
grbl likely puts out a better pulse stream than the parallel port, which could allow higher velocity and acceleration.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Z zero (plane) moves upwards with every Z dir movement
« Reply #9 on: April 07, 2018, 09:18:42 AM »
That's possible. Shame it was so unstable that after 5-10 minutes it froze up ally the time. It was very easy to use for a beginner.
Luckily it was very cheap to switch to mach3 from grbl. It only cost me about $10.