I have a three axis wood router that is displaying some very strange behavior. After tuning the motors I can jog both X and Y at 6000 mm/min with no problem. I can jog them either one at a time or at the same time, no problem. If I issue the following command in the MDI screen: G01 X500 F6000 then the X axis moves 500 mm at 6000 mm/min. If I issue the following command: G01 Y500 F5000 then the Y axis moves 500 mm at 6000 mm/min. When I issue the following command: G01 X500 Y500 F6000, then the motors make loud grinding sounds and stall before they finish the move (I would say the don't even properly start the move before they start to sound like hell.)

The only way I am able to get a program to run at all is to set the feed rate close to 2000 mm/min. To much more or less causes the motors to miss counts and/or stall. The motors still sound pretty funky doing this, but the part comes out right.

You have the velocity set too high for the motors/drives you are running.  When the machine makes a diagonal move the actual motor speed has to be a lot higher than the commanded rate to create the  commanded feedrate.

As a test lower your motor vel setting in config by half then retest. If that works keep bumping UP the vel until you find the sweetspot.

Just a thought, (;-)TP

You have the velocity set too high for the motors/drives you are running.  When the machine makes a diagonal move the actual motor speed has to be a lot higher than the commanded rate to create the  commanded feedrate.

Terry, when making a diagonal XY move, the two axis are actually moving slower than if they were moving in a straight line along the axis.




I see this problem come up every now and then, but have never seen an answer on why it occurs. My thought is that it's PC related. Open the task manager and check the CPU usage when doing your diagonal move and see if it goes to 100%.

yep you are correct. I was remembering that Art had said there was a situation that caused Mach to exceed the max vel on a combined move. I'll have to do some rerearch now(;-)

(;-) TP

BUT....irrelevant of what the controller does or does not do,..... let me broaden this somewhat by saying "SYSTEM" , it just dosen't make sense to try to run a machine at some speed where it is not reliable. If it turns out that reliability is found at only 40 % of max ,so it is that one should run the machine at. If not happy then change what is necessary to accomplish the requirements.  


RICH

BUT....irrelevant of what the controller does or does not do,..... let me broaden this somewhat by saying "SYSTEM" , it just dosen't make sense to try to run a machine at some speed where it is not reliable. If it turns out that reliability is found at only 40 % of max ,so it is that one should run the machine at. If not happy then change what is necessary to accomplish the requirements. 


RICH

I could live with a lower cutting speed, but even slower speeds around 1000 mm/min are causing a problem. The only feedrates that really seem to "work" (the motors still make pretty weird sounds like they are fighting themselves,) for these coordinated moves are between 1500 and 2500. Anything else stalls the motors. All cuts are being made in free air right now in case you were wondering.

Quote from: BR549 on September 16, 2011, 07:18:23 PM

You have the velocity set too high for the motors/drives you are running.  When the machine makes a diagonal move the actual motor speed has to be a lot higher than the commanded rate to create the  commanded feedrate.

Terry, when making a diagonal XY move, the two axis are actually moving slower than if they were moving in a straight line along the axis.




I see this problem come up every now and then, but have never seen an answer on why it occurs. My thought is that it's PC related. Open the task manager and check the CPU usage when doing your diagonal move and see if it goes to 100%.

Will try when I get a chance, thanks. Any ideas on what to do if the CPU usage is high? Someone suggested to me that windows XP had some sort of issue with parallel ports that sounds similar to what you are describing, so maybe a switch to a different OS is in order.

It's not XP, XP works fine.

What it sounds like to me is resonance. What kind of drives do you have?

You might want to read through this thread about making dampers to remove resonance.
http://www.cnczone.com/forums/stepper_motors_drives/32284-my_take_stepper_damper.html

Here's what they did for my machine.
http://www.youtube.com/watch?v=UJjivsVwSsQ

Are your motors steppers or servos?
If steppers:
Power supply voltage and amp ratiing?
Drive info and amp setting?
Motor info and how wired?

RICH

Are your motors steppers or servos?
If steppers:
Power supply voltage and amp ratiing?
Drive info and amp setting?
Motor info and how wired?

RICH

I am using Stepper motors.

40 V, 10 A Power supply.
Using the MondoStep drive from Probotix, http://www.probotix.com/index.php?view=product&path=15&product_id=129.
Peak current output is set to 2.8 amps.
I am using these motors http://www.probotix.com/index.php?view=product&path=14&product_id=152
They are wired in series.