help with z axis driver config

This Section is for users to discuss hardware

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

IMG_0330.JPG
driver options

IMG_0331.JPG
uccnc z axis settings
netdude
 
Posts: 10
Joined: Fri Feb 02, 2018 12:19 am

Re: help with z axis driver config

Postby Vmax549 » Wed Feb 07, 2018 5:21 pm

What is teh pitch of teh feed screw ?

If you calibrate it to get teh distance correct THEN use a resonable Vel/Accel settings it will work. IF teh Vel or Accel values are too high it WILL stall the motor.

I would start with 1/8 micro steps and work from there.

(;-) TP
Vmax549
 
Posts: 1312
Joined: Sun Nov 22, 2015 3:25 am
Location: USA

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.
netdude
 
Posts: 10
Joined: Fri Feb 02, 2018 12:19 am

Re: help with z axis driver config

Postby Vmax549 » Wed Feb 07, 2018 5:39 pm

OK that thread pitch is going to cause problems. For a Plasma table you need a thread pitch no higher than 5TPI a double start 2TPI is best. With a 12TPI screew you will not be able to get teh speed/acell high enough before teh stepper stalls.

Just a thought(;-) TP
Vmax549
 
Posts: 1312
Joined: Sun Nov 22, 2015 3:25 am
Location: USA

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.
netdude
 
Posts: 10
Joined: Fri Feb 02, 2018 12:19 am

Re: help with z axis driver config

Postby Vmax549 » Wed Feb 07, 2018 9:58 pm

Get it setup where it works then TEST teh settings and make sure it does not stall teh motor.

200 X 8 X 12 = 19200 steps per inch

start at Vel = 200 Acell = 20 and test from there

(;-) TP
Vmax549
 
Posts: 1312
Joined: Sun Nov 22, 2015 3:25 am
Location: USA

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.
cncdrive
Site Admin
 
Posts: 2263
Joined: Tue Aug 12, 2014 11:17 pm

Re: help with z axis driver config

Postby Vmax549 » Thu Feb 08, 2018 2:09 am

My settings were for 1/8 microstepping that is what I use here. And I use a 5tpi screw.

(;-) TP
Vmax549
 
Posts: 1312
Joined: Sun Nov 22, 2015 3:25 am
Location: USA

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.
netdude
 
Posts: 10
Joined: Fri Feb 02, 2018 12:19 am

Re: help with z axis driver config

Postby Vmax549 » Thu Feb 08, 2018 3:56 pm

If you want to get the Vel up you will have to decrease the thread pitch of the screw. 5tpi max 2tpi perfect. Steppers can only spin so fast before they stall out. Teh idea solution is to move Z 1 inch per motor revolution.

Just a thought, (;-)TP
Vmax549
 
Posts: 1312
Joined: Sun Nov 22, 2015 3:25 am
Location: USA

Next

Return to Hardware

Who is online

Users browsing this forum: No registered users and 3 guests

cron