[highwaymancnc]

Hello All,

I have had a problem which I cannot resolve. My Z axis stalls mostly when
pulling the router up which is the heaviest load. I have a 270inoz motor on it
with an 5/8-11 threaded rod and an 12 to 39 gears and it still stalls. It has
the same reaction with or without the gearing which I just added to help
eliminate this problem. No help with the gears.

Any suggestions please.

[davidmb]

does it stall at all speeds?

has it being running ok up to present or has it always been like this?

with the z axis leadscrew removed, does the z axis move freely by hand without binding.

what type of motor and driver are you using ( full step / half /quarter / microstepping ) what voltage are you driving with ( psu ) if it is a chopping driver.

[highwaymancnc]

After all the quick replies made me stop and take a breath. Before saying anything else thanks to all.

Update: I have re-done z axis trucks and checked and refined every aspect of the design. No binding at all.

Running: Hobby-CNC EZ-Board with a 36 Volt 10AMP Power Supply

X & Y Axis are running Nema 34- 660 in-oz motors
x has 5/8-13 rod Y has belt and pulley ( belt testing going on)
Driver set to 1/8 step

Z-axis Nema 23 270 in-oz 5/8-11 threaded rod
Driver set to full step

Z-Axis Total weight: 20 Lbs Max Router Included

Using EMC2 for the software side so have also set speed and acceleration

I have had some success and was able to make signs and replacement parts in the past except for this z axis issue which has over time destroyed a lot of material.
I was just running again and it stalled enough to lose almost 1/2 an inch. Was running Z-axis at 27 in/min on the top of the stroke it lost the 1/2 inch.

Maybe I'm trying to go to fast but it does nor occur every cycle up nor does it occur at the beginning of the stroke where most of the load is exerted and down.

[davidmb]

as daft as it sounds, there may not be enough inertial load on the stepper motor, if you can try adding a flywheel of some description, I had a similar issue with my z axis originally, ( 0.98Nm Pacsci motor, M12 leadscrew ). I used a 1.5" length of 1 1/4" diameter steel mounted onto the end of the short z axis leadscrew. I can now get 1200mm/min without problems, I have included a photo that shows the small flywheel.

[mike_Kilroy]

good info. need to tell us some more about WHERE & WHEN the stepper motor stalls; sounds from your description like it is NOT during the accel when it first starts lifting up out of cut - if it stalled there it would indicate too fast an accel for the load and inertia. If it stalls AFTER the accel is done, then it would indicate your speed is too fast for the load. so which is it?

Obvious thing to try is to reduce the speed if stall is during constant high speed running, or reduce the accel if stall is during the accel period.

[andypugh]

X & Y Axis are running Nema 34- 660 in-oz motors
x has 5/8-13 rod Y has belt and pulley ( belt testing going on)
Driver set to 1/8 step

Z-axis Nema 23 270 in-oz 5/8-11 threaded rod
Driver set to full step

Try setting the Z axis to microstep too.

However, I think that the speed is probably just too high.

Try fiddling about in the Test Axis tab of Stepconf and experiment with speeds and accels (probably in a dummy new config so as not to mess up the existing)

I suspect you can probably afford rather more accel and rather less speed.

[highwaymancnc]

Yes the problem is at the top of the stroke after speed has been achieved. I have run step conf so many times I have about 50 or more configs.

I have had this problem a long time and this xmas I trashed 2 gifts one of which was attempted 7 times. A little frustrating No. I have run them as slow as 4 hours per piece to 1 1/2 hrs per piece same result


Good news! went out and got some pucks. Put one on Z and it runs at 48 in/min. Going add one to my X axis and ramp up the speed there too. My belt driven already does 72 in/min.

Thanks again for the help. Who thought a $1.50 fixed the problem.

[davidmb]

glad you got sorted,

depending on what type of drive electronics you are using you may find at higher speeds on the x-axis ( longer screw so maybe a reasonable amount of radial inertial load ) there may be a pronounced notch in the torque curve due to mid-band resonance ( I found this at Christmas after a 3.5 hour run on 1 part ), there are some examples of 'ratlers' or dampers that may help with this on this site, you need to do a search.

It seems that the best way of avoiding this is with a more expensive drive such as Gecko's that do active resonance damping but at a price. I'm currently running on a v.cheap Chinese 3 axis driver with half step resolution.

[mike_Kilroy]

not enough info as davidmb said in his post.

FYI, what is the issue? not enough torque? too fast an accel? too high a load inertia?

FYI, go to:
http://kollmorgen.com/website/com/en...tioneering.php

and put your data into this motioneering program and see for yourself why your stepper motor is stalling.... sticking the little data I have from your post into it, I see you would need only 10 oz-in of torque to lift a 30# router so your motor should be plenty big enough. you are probably exceeding the stepper motor's capability to accel fast enough for the load inertia it sees. Or you are going too fast for the stepper motor?

I would reduce accel ramp by a factor of 50 and see if it then works as a starting point.

Gotta give us more info to help diagnose this. How heavy is the router you are picking up? 30#? WHAT ELSE is lifted for a total weight? how fast is your programmed accel rate? what is your commaned max speed? what kind of friction is there? bearings? turcite?

[ger21]

The threaded rod is probably the biggest culprit. It's probably only 30% efficient at best, so most of your torque is wasted.

Gearing is making it worse, because the motor has to spin much faster, where it has much less torque.

If you're using Mach3, try setting the velocity to 25 and the accel to 2 or 3.