Hello Guest it is April 15, 2021, 07:06:01 PM

Author Topic: Help! Please! this Chaos has to stop!  (Read 19554 times)

0 Members and 1 Guest are viewing this topic.

Re: Help! Please! this Chaos has to stop!
« Reply #20 on: December 05, 2006, 11:01:01 PM »
Hi,
This is not a video of the machine freezing up while contouring, it's of me manual jogging the machine in the Z axis.  I just finished a program and was bringing the machine over for me to change tools, and I moved it up in the Z and it locked up. This is not the same as when it locks up while contouring, this one made a whole lot more noise and sounds like it binding or under some sort of load, while contouring it doesn't.

Notice when I take the camera over to the computer to show the feeds and I have it at 240% is because in the program my default feed rate was 50 ipm but I wanted to run it how I feel it should run and not baby it because it screws up, besides that's why I am making the video in the first place.  ;)     I forgot that half way through the program that there is a feed rate so it slowed down so I just cranked the override to 240% to run it how I want.  I don't normally do that I usually have the feed I want in the program and might adjust 10-20%.

I will make another video to catch it messing up while contouring, figure when I want it to mess up it wont :P

This is the link to the video:

http://s117.photobucket.com/albums/o50/greg_boo/?action=view&current=LockupintheZaxis.flv

Thanks
Greg
"Ideas have consequence" Ravi Zaccharias

Offline chad

*
  • *
  •  361 361
  • When the going gets weird, the weird turn pro.
    • View Profile
Re: Help! Please! this Chaos has to stop!
« Reply #21 on: December 06, 2006, 03:59:47 AM »
A couple of things. First usually you want to start out high in the g code and then slow down the feed, not crank it up. The override will try to makes things faster than your motor tuning.

Second your acceleration and velocity sounds too fast back them down 25% and try that for a while.
also just for fun in the step and dir pulse width try setting it to 5ms.

It sounds to me like you are just trying to run things right on the edge. These are steppers not servos, steppers loose power the faster they go.


Chad

 
« Last Edit: December 06, 2006, 04:03:01 AM by chad »
Re: Help! Please! this Chaos has to stop!
« Reply #22 on: December 06, 2006, 06:29:09 AM »
Hi, The video say's it all. The sound is the stepper not keeping up with the amount of steps being sent from Mach. If you go to Motor tuning and select the drive, Let's say Z and decrease the Accel value then click on save settings. This will allow the pulses to ramp up from a slow start to the feed rate you set.

I did notice that during the quick ramp up to speed there is a low resonance vibration that occurred before losing steps. If you have the driver with microstepping there is a small adjustment screw on the back of the Gecko driver

ADJUST: This trimpot adjusts the motor for the smoothest possible low-speed operation. Set the motor speed to
about 1/4 revolution per second, then turn the trimpot until a distinct null is noted in the motor’s vibration. This will
result in the most even microstep placement for a given motor and power supply voltage.

Failing all the above, Your power supply Voltage is too low for your needs. I would suggest upgrading the power supply to a higher Voltage.

If you eventually decide to do this we are all here to help.


Kind Regards
John
Re: Help! Please! this Chaos has to stop!
« Reply #23 on: December 06, 2006, 06:32:13 AM »
Hi, The video say's it all. The sound is the stepper not keeping up with the amount of steps being sent from Mach. If you go to Motor tuning and select the drive, Let's say Z and decrease the Accel value then click on save settings. This will allow the pulses to ramp up from a slow start to the feed rate you set.

I did notice that during the quick ramp up to speed there is a low resonance vibration that occurred before losing steps. If you have the driver with microstepping there is a small adjustment screw on the back of the Gecko driver

ADJUST: This trimpot adjusts the motor for the smoothest possible low-speed operation. Set the motor speed to
about 1/4 revolution per second, then turn the trimpot until a distinct null is noted in the motor’s vibration. This will
result in the most even microstep placement for a given motor and power supply voltage.

Failing all the above, Your power supply Voltage is too low for your needs. I would suggest upgrading the power supply to a higher Voltage.

If you eventually decide to do this we are all here to help.


Kind Regards
John
Re: Help! Please! this Chaos has to stop!
« Reply #24 on: December 07, 2006, 01:10:47 PM »
After looking at the video, I feel you could have a second problem. Yes, it is possible that the steppers are running too fast, but it is also likely that the drive screw is binding with the drive nut. It is interesting that it binds mostly in the direction of easiest motion, down (The motor is being assisted by the weight of the carriage assembly). This can come from misalignment if either the screw and/or the nut. Make absolutely sure that there is no binding. Turn off the power and turn the screw by hand and make sure that it turns freely the entire length of the screw, especially near the limits of travel.
If the screw is out of alignment, it will bind, or Get noticeably harder to turn, near the limits of travel. You may want to take some of the weight off the carriage to make it easier to feel.

If the nut is binding, it may happen near the screw center where shaft whipping can come into play. To test the nut for alignment (it may bind anywhere on the screw), loosen the nut, in its mount) so that it can freely follow the screw, and run your up/down test. You may notice that the jamming has stopped. If this is the case, you will need to make sure it stays aligned when you tighten it down again.

It is surprising how critical these adjustments are for smooth operation. I would first Align the screw at both ends several times to make sure it runs true with the nut, then make sure the nut is straight. Then do it one more time. The Z axis us usually more forgiving than X and Y.

If the unit has been in service a long time, the nut can be filled with debris (especially cutting plastic). If this is the case, the screw will be hard to turn anywhere on the shaft. Cleaning the nut threads will fix it.

Thanks.
Bill

Offline DAlgie

*
  •  314 314
    • View Profile
    • Algie Composite Aircraft
Re: Help! Please! this Chaos has to stop!
« Reply #25 on: December 07, 2006, 04:42:58 PM »
I read all the posts in here and not once did I see the voltage mentioned you are running. Amps is one thing, but voltage is what a stepper needs. Measure what voltage is actually at the Geckos, I'm betting it's under 30V. You really need over 50V if you want any real speed, and your machine has sticky ways and does not have ballscrews. The buzzing sound is the steppers stalling for sure.
Re: Help! Please! this Chaos has to stop!
« Reply #26 on: December 08, 2006, 07:42:29 PM »
Hi,
I have been busy so I didn't have time to post earlier, thanks for the help. 

I when the power is off I can move all three leadscrews by hand.

The way the machine is designed is the stepper motor is connected to the lead screw with a coupling that has a plastic piece that is sandwiched between two aluminum pieces they have key shape in it. They are fastend with set screws to the lead screw, then there is a bearing that fits into a aluminum piece that has four screws holding it in place. Travelling on the lead screw is the antivibration nut it is mounted in aluminum plate that has three screws holding that in. Then the leadscrew ends with  another bearing held in another aluminum block and has a threaded end with a lock nut on it.

That was a description of the X axis it is my length of the table, the Y axis is the same but the Z is a bit different it has no thread on the end or lock nut it just has a stop.

The other thing is that the voltage on my stepper drivers are all the same at 35.2v so what does that mean? What is the max feed that I should run machine at?

Thanks,
Greg
"Ideas have consequence" Ravi Zaccharias

Offline Chip

*
  • *
  •  2,055 2,055
  • Gainesville Florida USA
    • View Profile
Re: Help! Please! this Chaos has to stop!
« Reply #27 on: December 08, 2006, 10:00:07 PM »
Hi, Greg

Would you Post the G-code that goes with the video, ether your velocity, acceleration are set to high or some kind of binding is occurring.

Thanks, Chip
Re: Help! Please! this Chaos has to stop!
« Reply #28 on: December 08, 2006, 11:44:52 PM »
Hi,
I wasn't running a program I was just manually jogging the machine up and down in the Z. 
I got some good advice about acceleration and velocity and it seems to be working. I will run some more programs and see what happens.  I was told that the machine could handle what I was trying to run it at so I backed it off a bit and we will see if that helps the problem.
Thanks,
Greg
"Ideas have consequence" Ravi Zaccharias

Offline Chip

*
  • *
  •  2,055 2,055
  • Gainesville Florida USA
    • View Profile
Re: Help! Please! this Chaos has to stop!
« Reply #29 on: December 09, 2006, 10:57:34 AM »
Hi, Greg

You stated the Z axis screw i sent supported at one end, is it whipping around at times, this would cause extra drag.

Its probably just to high Vel., Accl. though.

Just a Thought, Chip