New DMM Servo install

[Raceman17]

It almost seems like that. I can feel the the slight vibrations in the screws after it homes and you can watch the absolute position value change in the motor monitors in the DMM software. The position value goes all the way up to 1.5 million or so and them the driver is trying to keep it on position
The variance is only 1-3 numbers off once it hits its position. Is there anyway to give some more positional error allowance in any of the settings?

[Raceman17]

I disconnected each of the drives to single out which one was faulting and ran each drive from acorn with only one axis homing at a time. X and y axis would home with no faults. As soon as I tried z axis it faulted. Then i ran x and y together and homed and no faults on those two axis by itself. Then I ran all three and and got random faults again. But most were on the z axis. So then I decided to put a bottle Jack under the spindle housing and give the z axis support after it homed. Guess what! No faults on any of the axis! So I ran the test without the bottle jack supporting and sure enough another fault! If the bottle Jack is under the z axis for support it wont fault. So I'm guessing the z axis is too heavy for the 1.8kw motor. The weight its supporting right now has the motor only. No pulleys or power drawer yet. I'm gonna wait and see what DMM says but my guess is I'm gonna have to add some counter balance to the z axis....
Just for another test I removed the spindle motor and homed without the extra 80lbs for the motor...no faults without the motor. I added the motor back and sure enough it faulted out. So most definitely the fault is caused by the z axis weight and the motor no being able to hold the position. I was also able to correctly calculate the z axis weight as it sits on the machine. I have a pressure force gauge used for taking pressure/force measurements when building fireworks/rockets (another side hobby...) but anyways with the pressure force gauge cylinder diameter of 1.69" and a pressure reading of 400 psi on the gauge I come to a weight of 896 pounds. Quit heavy..

[Nigelo]

If you back off the Z axis by ~ 0.050" immediately after homing, as you stated earlier in the thread, does it still fault? If it does, backing off appears to be a red herring. Conversely, if faulting out disappears could you not edit the hom file to provide an amount of backing off automatically?

Just my 0.02

[martyscncgarage]

Does the machine have a counter weight on Z?
If not either figure a way to add one or belt reduction...
So there were no problems on X/Y it's Z....
Marty

[Raceman17]

I'm gonna a few more trials on moving the axis off the switches to see if its for definite a change in direction that helps keep it from tripping. The machine doesnt have a counterweight. But the whole colum is empty so it would be easy to fab up some chain and rollers to put the weight down the center of the colum. I'm gonna wait and see what DMM says. I hate doing bandaid fixes if not necessary.

[martyscncgarage]

I'm gonna a few more trials on moving the axis off the switches to see if its for definite a change in direction that helps keep it from tripping. The machine doesnt have a counterweight. But the whole colum is empty so it would be easy to fab up some chain and rollers to put the weight down the center of the colum. I'm gonna wait and see what DMM says. I hate doing bandaid fixes if not necessary.

I had a Bridgeport Torque Cut 22. It too had no counter balance. But large DC Brush servo, but had much finer ball screws. Do you know what size DC servo was on the Z and what encoder count it might have?

The lack of counter weight along with that coarse ball screw would make sense as to why the servo is struggling. Unless you really need crazy rapid speeds, maybe belt reduction would make sense?
Counter weight would definitely help.

[Raceman17]

I do not know the encoder info on them. Here is the specs for the servos that were on it. The rated torque of the 1.8kw servo on it now is 11.5 nm so it doesnt even need what I had on there before. Its peak torque covers it but if the servo is constantly sitting over the rated torque wouldn't it fault out?

[Raceman17]

DMM suggested I turn up the gain parameters tonsee if it would hold better. I'll try that before I go to the counterweight. On a different topic. Can someone explain to me how to hook the Brake output up from the dyn4. I really want to get away from having acorn control the brake since it would be possible for the drives to be not powered on (say after clearing a fault) and forgetting to turn them back on and then having acorn command a move. It doesnt look pretty when the head of this machine falls from no brake control. Here is the documentation from the manual. It just doesnt make sense to me. I read it as pin 19 sends out a signal and you connect that to a relay that controls the brake but I'm not sure that's what it says.

[martyscncgarage]

Try and cut your slow jog for Z to 25ipm and see if it makes any difference.
Are you looking at PEAK torque or continuous holding torque ratings?

[martyscncgarage]

DMM suggested I turn up the gain parameters tonsee if it would hold better. I'll try that before I go to the counterweight. On a different topic. Can someone explain to me how to hook the Brake output up from the dyn4. I really want to get away from having acorn control the brake since it would be possible for the drives to be not powered on (say after clearing a fault) and forgetting to turn them back on and then having acorn command a move. It doesnt look pretty when the head of this machine falls from no brake control. Here is the documentation from the manual. It just doesnt make sense to me. I read it as pin 19 sends out a signal and you connect that to a relay that controls the brake but I'm not sure that's what it says.

The way its supposed to work
With no power to the servo motor brake, the motor rotor should be LOCKED
You wire an external 24VDC power supply, run it through the Axis3BrakeRelease (Z axis) output assigned on Acorn.
The brake is not energized (released) until a move is commanded from Acorn, whether you jog it or home it.
If you hit Estop the output is opened locking the Z axis brake. If Acorn sees a fault, it opens the Axis3BrakeRelease output, locking the Z axis brake.
IF the control is powered down, the brake is de-energized and locks the rotor
It is the correct way to control a brake.