Viper 200's...Having trouble on 2 axes

[TomL21]

I've been working on a Mach3 retrofit of a YCM-40 Mill. I'm using the NEMA 42 servos that were on the machine with 500 line differential encoders. As the title says I've implanted 3 Viper200's. Mach talks to them through a SmoothStepper and CNC4PC bob. Powered by a Keling 7220 (72V/20A) power supply. I've got the X axis running great, 200 ipm rapids, no issues. The Y and Z are a different story. I can't seem to get them running right. I've tried swapping cables, motors, power supply with the X axis and the problem seems to follow the Y ans Z Vipers. Larry was good enough to send me new 40 pin chips for these too drives, updating them to version 2.7.

When trying to move the Y axis the red fault led on the drive immediately starts blinking very fast, the motor groans, and looks like it wants to go but doesn't. If I try a "high speed" move, 25ipm or more, the drive instantly trips and shuts down the motor output. I've tried bringing the PID loop way down low, and also going real high, neither seems to change it much, but softer does seem to run a little better.

The Z axis is a little different. It seems to be ok going down, but on the way up I get massive overshoot, like 1/4 inch. And it oscillates 2 or 3 times before settling in. Only on a rapid positive move though.

Anybody have any ideas, suggestions, seem similar problems that could help me out?

Any and all help is greatly appreciated. Attached are the parameters I had worked up to in all three drives. When I first reached these numbers I didn't see these issues, I had the Y axis moving back and forth at 120ipm, same in the Z. I ran one small part (about 1/2 hour run time) and these symptoms came up.

Thank you in advance for any help.

TOM

[keithmech]

Tom there are 2 pots on the board for setting current limit and trip.
In the manual it recommends setting them at 50% or turn them half way out
for testing.Fine tune them once all is working.Page 20 in the online manual.
http://www.larkencnc.com/dloads/viper-manual.pdf

[TomL21]

Yea...When I started they were about half way up. Now they are both turned up as far as they will go. I turned them to both extremes to be sure they were indeed set to the max. If i turn them to the min the drive will trip just holding position.

[Larken]

Can you jog the Y axis slowly, or can you not move it at all. Are you sure the drive is holding ?. If you get a fast flashing light right away, you could have a noisy encoder adding a burst of pulses. What resolution are the encoders ?
Test that the drive is holding solid in both directions when you twist the shaft by hand.
Did you try swapping drives ?


On your Z axis, adjust the Balance command to help it lift the load (see manual).
Maybe the Z axis doesn't have enough PS Voltage on the way up to move as fast with the extra load. Try slowing your rapid.

Increase the Range setting to 200 while testing so it doesn't limit the current. When the range is exceeded, it limits the PWM by 50%

[TomL21]

The X axis drives runs the Y axis perfectly fine, with the Y axis drive connected to the X axis I get the same issue. I've been concentrating on the Y first. It is holding in both directions, I can trip it out by rotating the handle, but I can do the same on the X. Slowly it has a hard time starting to move, but after a second or so it takes off like it should, nice quiet and smooth, and comes to a stop fine. I've also swapped wires. The issue definitely follows the drive.

I will try the range setting and also play with the balance setting on the Z.

Thank for the help, I'll post back with results.

[Larken]

Sounds like the drive has a problem. If you send it back I can fix it.
Thats one of my older drives though and can't take the power of the newer Viper200's. It you want to trade it in I can do that.

Larry

[TomL21]

I'd be interested in that. I'm sending you an email now.

[TomL21]

I tried upping the Range setting on the Y axis, up to 200. That is the r value right?

Still acts the same.

TOM

[TomL21]

After working out a trade, I've got two new Viper 200's in the machine. Mounted them up, plugged them in, did a quick tune starting with known good values from my other drive, and they're now running awesome. 200 ipm rapids not overshoot, looks good. Now to get a bigger power supply to get more out of it!

Thanks Larry!

TOM