help with z axis driver config

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help with z axis driver config

Postby netdude » Wed Feb 07, 2018 4:20 pm

Built plasma table using uccnc, uc300eth-5lpt setup. The x and y settings I figured out and are working perfectly in inches. But I cannot get z axis to be anywhere close to actual travel distance requested.

The driver was originally set to 1/4 microstepping. In UCCNC I had steps per unit set to 564 and velocity 1000 to start which is what my x/y are. x/y are belt driven and z is lead screw directly connected to motor. This moved the z ok speed wise, not particularly fast but ok.

Problem is it thinks z travel is about 1/20th of what it actually travels. If I go to config > z axis and calibrate then tinker with it to get close it wants steps to be about 18000. When i set this high, the z goes to fast and motor stalls. I have tried changing micro stepper settings to 1/8, 1/16, 1/2A, 1/2B, and 1 and re-calibrate but no combo seems to work.

Any suggestions on how to fix this would be appreciated.

IMG_0329.JPG
z axis

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driver options

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uccnc z axis settings
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Re: help with z axis driver config

Postby netdude » Wed Feb 07, 2018 5:23 pm

I found info on screw here: https://www.roton.com/family/acme-right ... s-7059486/

Looks to be 0.083 (in./rev.), so needs to turn 12 turns for one inch.

Thanks for the help.
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Re: help with z axis driver config

Postby netdude » Wed Feb 07, 2018 9:11 pm

Very Interesting. Have not heard that before. What speed do you recommend the Z should be able to travel in inches per min? I think Nema 23 can go about 2000 rpm, which is approx 33 revolutions per second. If I need 12 revolutions per inch, I can travel 3 inches per second or 180 IPM. That seems pretty fast to me. When I get the right settings in my testing it is extremely fast IMO. Just not accurate for movement.

This is the Z axis with floating head I purchased and am using: https://www.ebay.com/itm/Z-AXIS-SLIDE-C ... Swc-tY5tMq

Appreciate all the input.
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Re: help with z axis driver config

Postby cncdrive » Wed Feb 07, 2018 10:10 pm

The "steps per" value of the axis sets how many step pulses makes the axis to run one unit travel distance, in your case one inch.
From what you wrote as I understand that you direct driving a screw which makes and inch from 12 turns.
You wrote you set the stepper drive to 1/4 microsteps so it makes one revolution from 200*4=800 steps.
To make one inch travel the motor needs to make 12 turns and each turn takes 800 steps which means that it needs 12*800 = 9600 steps per inch, so your steps per value should be 9600 if the pitch is precisely 12 turns per inch. If not then it will still be around that value, but fine adjustment may be required.
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Re: help with z axis driver config

Postby netdude » Thu Feb 08, 2018 2:58 pm

Thanks for all the help. I ended up using 9600 spi, 1/4 ms and it moved correct distance. I had to mess with vel and accel. Anything above 60 velocity would stall the motor, so I settled on that and 40 velocity.
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Re: help with z axis driver config

Postby netdude » Thu Feb 08, 2018 5:44 pm

Now that I have my machine up and running and can cut parts, i'm going to make my own Z axis. I have a screw already and checked it last night and pretty sure it is 2tpi so I'll play with that. I'd have to take apart the existing one and figure out the replacement screw for it. I may do that after I get new machine running.

Can I ask why you need it so fast for plasma? Is it to make fast adjustments with THC when running on thin materials? I haven't hooked up my ohmic thc yet, making the mount for it now. I've been cutting 14 ga steel at 140 ipm just fine for small parts so height isn't changing much within a few inches. I want to be able to cut 18 ga and 22 ga sheet metal for various things. Let me know.
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