Y Axis Bind and Loosing Steps

[ranchak]

I'm having trouble with my Y axis loosing steps. I have narrowed it down to a mechanical error (I swapped motors and cards). I am using Mach3 with a Hillbilly Bob. My X axis setting is:

Velocity 50"/min

Acceleration 10"/min

The Y axis will not run this fast(?) without loosing steps. I have found that it seems that the velocity not the acceleration is where the motor will bind. My Y Axis settings are:

Velocity 15"/min

Acceleration 15-100"/min

At these settings I am not seeing much binding or slippage. This all started without any adjustments to the machine. Also I have yet to run this machine after conversion to Mach3. It appears that there may be excessive stiction, I have tried to clean and oil the Y axis and ballscrew, this seemed to help, but only slightly. What should I look at next? Also what speeds and feeds can I run at? Thanks, Ron

[HimyKabibble]

Originally Posted by ranchak I'm having trouble with my Y axis loosing steps. I have narrowed it down to a mechanical error (I swapped motors and cards). I am using Mach3 with a Hillbilly Bob. My X axis setting is: Velocity 50"/min Acceleration 10"/min The Y axis will not run this fast(?) without loosing steps. I have found that it seems that the velocity not the acceleration is where the motor will bind. My Y Axis settings are: Velocity 15"/min Acceleration 15-100"/min At these settings I am not seeing much binding or slippage. This all started without any adjustments to the machine. Also I have yet to run this machine after conversion to Mach3. It appears that there may be excessive stiction, I have tried to clean and oil the Y axis and ballscrew, this seemed to help, but only slightly. What should I look at next? Also what speeds and feeds can I run at? Thanks, Ron

You sure you don't just have the gibs set too tight? It doesn't take much. The way I set mine is to set then tight-ish, then measure the backlash. I loosen them until the backlash is minimized. You should still be able to feel a *very* slightly movement (maybe a thou) if you push on the end of the table. I once read the manual for a VMC, I think a Haas, and they had a spec for how much movement there should be at the end of the table when setting the gibs.

Also, of course, lots of good way oil on the ways helps.

Regards,
Ray L.

[ranchak]

HimyKabibble, all of this problem started without adjusting anything on the machine. I did remove the gib and clean out some crud that was in the area. I did install the gib loose and I still had binding. I continued to tighten the gib and run the table back and forth to "settle" the gib. I still have binding. I hate to think this but I wonder if something in the ball nut is binding. Maybe a piece of gunk or a worn ball?

[ranchak]

I found that my problem is something to do with velocity vs. acceleration. If I use the intial settings of 30:1 I have no problem. I am running at 75:1 at the moment, but as soon as I increase the acceleration I run into problems.

[machintek]

Please remember that stepping motors suffer from age and heat. The strength of the magnets decay. Then you lose the ability for the motor to accelerate as well as cut.
Any drag on the motor will cause it to stall or lose steps. These are open loop systems so the control puts out pulses but cannot verify if the axis achieved position. This is why machines switched to closed loop (position feedback) when it became cost effective.

George