when motors reverse, they stall then slowly pick up speed. HELP!

[steelman]

Hi guys, I'm a newbee. Bought a taig cnc from Deepgroove a few years back with xylotex 4 axis board and never could get the motors stepping right and finally gave up and didn't touch it till now. I'm going to try again hopefully with help from the forum so I can use this thing. I have 280 oz, 1.8 deg. 2.7amp motors with a 24 volt 8 amp power supply. I have tried every kernel on Mach 3 but was never able to get them to run right. I have checked the voltage settings on all the axis's and they are set at 3.3 volts no motor attached. The power supply has 24 volts and doesn't drop when the motors turn. The motors will get up to speed and be very smooth if you keep going the same direction but if you  reverse directions, the motors stall and slowly get up to speed. If you keep going the same direction its great but if reversed, same thing again. I'm lost. It seems like some kind of pulse thing but I just don"t know. The z axis  doesnt do this. Only the y and z. Any help is appreciated.  Thanks, Steelman

[Tweakie.CNC]

Hi Vincent,

Welcome to the forum.

There are quite a few Taig owners and Xylotex board owners here - someone will know the answer to this one.

I suggest you set the kernel to 25kHz initially, it is seldom necessary to go higher. The problem could be that the X and Y Axis Acceleration is set too low and the Velocity is set too high in motor tuning. You could perhaps go through the motor tuning procedure again.

Tweakie.

[RICH]

I think a higher voltage along with lower amp setting for each motor would cure the problem. Try a 2 amp setting for each motor as total amps should not exceed total available. You need to deliver higher
voltage  as the stepper rpm increases  preferably the 24 volts available.

RICH

[steelman]

Hi Rich and Tweakie. Thanks for answering. I tried the things you said but no help.Right now I'm set at 25000,50 & 5. When I push left or right arrows, it gets to speed in one direction and runs very fast and smooth as long as I go that same direction whether I stop 1 time or ten times with no hesitation on x or y axis. But if I reverse direction, it winds down to a stop and slowly comes back up to speed. If I keep going that direction no problems at all until I reverse again then the same thing again. I'm still at a loss.

[RICH]

Post your xml file and also the manual for the xylotex board.
RICH

[Tweakie.CNC]

Vincent,

Try increasing your acceleration from 5 to 16 and save the settings then try again and see what happens.

Tweakie.

[stirling]

good documentation of your system appears to be hard to find, but from some posts over on the zone I'm getting the feeling that the 24V PS is too low. It appears the xylotex board can handle up to 35V but of course without proper motor and machine specs it's impossible to work out your "ideal" voltage. Certainly it appears that the later systems from deepgroove use a Gecko G540 with a 48V supply with apparently the same motors - Hmmmmm. seems to me it's not what's correct but what's available is the main design criteria here.

Any info/label on the motors?

Ian

[ERP]

I think this is the motors he uses http://www.kelinginc.net/KL23H276-28-4B.pdf, by my calculation the optimal voltage for them is 60V.
Having said that I would expect all your losing from running them at 24 would be torque, you'd end up with ~120oz/inch of holding torque, which should be more than enough for the X/Y of a Taig though you may have to dial the speed down a bit.

What you're describing sounds more like what I would expect with a low acceleration in Mach, any chance you could post a video of it somewhere so we can see what it's doing. DO the DRO's reflect the slowing down and speeding up or do they immediately start moving in the other direction?
If you run simple Gcode like

G1 X5 F10
X2
X5
X2

Where does your axis end up?

I have his later Gecko based system which work very well for me, the wiring is clean, only thing I wish he did is use a real EStop button and run an additional connector to the outside of the case for limit switches.

[ERP]

Actually I see you stated you have 280oz inch steppers, that one is 270oz inch's so that may not be the stepper he was providing when he used Xylotec boards.
Also checking my theory, all the reduced voltage would do is reduce the maximum speed, not the torque.

[steelman]

Wow, I'm impressed. Thanks every one of you for taking the time to answer.. I tried the 16 acc. but same thing. I ran a small g code program and it worked until it made a different direction then the stall thing and then up to speed again even tho it was running at about 7 imp. The power supply is 28 volts and steady. I think the amps are around 8. The motors say Deepgroove 3.3 v,2.8 amp, 1.8 deg. , 280 oz. I will have to learn how to video with my Iphone to post a picture of what its doing. I am set at 25000,50, and 8. It runs very smooth and fast if you leave it in the direction it was running in last. No stalls or anything. If you go the opposite direction, stalls down and then starts back up to speed and will run all day in that direction with no stalls after stopping no matter how many stops and starts until reversed, then same old. I'm not trying to keep saying the same thing over and over, I just dont know how else to explain whats happening. I'm beginning to think I may have a computer problem. I noticed that when I click on something its slow to react. Maybe thats whats going on. Thanks again guys. Its appreciated.  Vincent