Stepper Motor Question

[Rob37]

Hello

I have built a Hobby CNC router and I am using Keling 382 oz-in steppers for the 3 axis. The lead screws are 1/2 inch 10 tpi ACME. The power supply is a 24 v 16.7 amp and the driver board that I am using is a TB6560. I am using Mach3 for the software driver.

Jogging the motors in all axis they run very smoothly with no problems but every now and then I get a stall out while running. (you know the sound the wild harmonic buzz and the motor stops for a split second) I'm new to the hobby cnc scene and also new to the motor tuning scenario in Mach3. Below is the way that I currently have the steppers setup in Mach3 and any and all advice would be greatly appreciated as I am very new to the tweaking of this program.

Steps per inch set at 4000

Velocity set at 50

Acceleration is set at 25

Stop pulse is 4

Dir pulse is 4

TB6560 board is set to full amperage and 1/2 step on the dip switch settings

Thanks For your Help
Rob37

[vger]

Rob,

You are probably hitting mid-band resonance on the motor(s) / screws. If you think of the magnetic field in the motor as a spring and the mass of the rotor/screw as hanging on that spring, there is a natural resonance. Once a certain step rate is reached this resonance can interact with the step action and cause the motor to stall.

Make sure your motors are firmly mounted. Using just long screws or rods/stanoffs will make matters worse. Mount them like you are trying to ensure they cannot twist on their mount at all.

If you are wanting more speed out of it, you might consider using a different pitch screw. Check out some 5 start acme....

Steve

[ger21]

If you can put a damper on it, you might get more speed. However, you may be reaching the limit of the motor/drive/screw combination.

On my Z axis, I use a Xylotex, 24V and 1/2-10 acme. Best I can get reliably is 55ipm with an accel of 5

X and Y have 1/2-8 2 start, and dampers on the motors, and I get 150ipm on X and 190ipm on Y, with accel at 10.

Damper info here.
http://www.cnczone.com/forums/steppe...tml#post256639

[Rob37]

Oh Man!! maybe my acceleration is set way to high I've got mine set at 20 on all three axis! Wow! what a newbie I am. I'll try droppng my acceleration by 1/2 and see what happens.

Rob37

[Drools]

Do you find the stall happens more when the computer has been running for a while? Either running making projects or just sitting there idling then starting a project?

[Rob37]

Hey Drools

When it is air cutting not all the time but sometimes it actually misses steps or stalls so when it finishes the cut it is off by the missed steps. I did drop the acceleration to 10 and got it to run the cut patten 2 times consecutive finishing at the zero each time. I am new to this cnc stuff so I am testing the unit without the router attached trying to tune it a little better before cutting on wood. I did find that I have to sometimes restart the Mach3 program before the motors will run smoothly.

Rob

[sneakwerks]

Originally Posted by Rob37 Hello I have built a Hobby CNC router and I am using Keling 382 oz-in steppers for the 3 axis. The lead screws are 1/2 inch 10 tpi ACME. The power supply is a 24 v 16.7 amp and the driver board that I am using is a TB6560. I am using Mach3 for the software driver. Jogging the motors in all axis they run very smoothly with no problems but every now and then I get a stall out while running. (you know the sound the wild harmonic buzz and the motor stops for a split second) I'm new to the hobby cnc scene and also new to the motor tuning scenario in Mach3. Below is the way that I currently have the steppers setup in Mach3 and any and all advice would be greatly appreciated as I am very new to the tweaking of this program. Steps per inch set at 4000 Velocity set at 50 Acceleration is set at 25 Stop pulse is 4 Dir pulse is 4 TB6560 board is set to full amperage and 1/2 step on the dip switch settings Thanks For your Help Rob37

I'm using different settings but similar equipment and am having the same problem. I noticed that one of my axis was very loose so I adjusted the jib and tried it with the handwheel and it moved very easily. I reconnected the stepper and now it has the problem more often. I'm using 280oz. steppers so I'm at a loss here.

[James Newton]

When you improve the mechanical bits and the motor stalls /more/ often, it almost always is the result of resonance issues. Mechanical dampers, or a better driver (gecko or linistepper) are the solution.

[Drools]

Of course mechanical issues aside, one of the Mach3 optimization steps say to make sure the OS install is set to "Standard PC" instead of "ACPI Multiprocessor PC". This is a huge change in the way the PC functions, it is a change at the HAL layer. This will directly relate to hardware communication. I'm still in test mode and on the fence as to how much the change helped but if Mach3 says to do it this way then it has to be for a reason.
BTW: it is not easy to change the computer type after the OS is installed. I did a complete reinstall just to be sure.

[James Newton]

Originally Posted by Drools Of course mechanical issues aside, one of the Mach3 optimization steps say to make sure the OS install is set to "Standard PC" instead of "ACPI Multiprocessor PC". This is a huge change in the way the PC functions, it is a change at the HAL layer. This will directly relate to hardware communication. I'm still in test mode and on the fence as to how much the change helped but if Mach3 says to do it this way then it has to be for a reason. BTW: it is not easy to change the computer type after the OS is installed. I did a complete reinstall just to be sure.

Yike... Almost makes ya wanna keep an old DOS machine around and run TURBOCNC. ;o)

[Drools]

Well, I'm not sure how many people actually have their PC set to "Standard PC" or even know how to check. The only reason I changed my setup is because I was unable to set my vel/accel to anything over 50/10 without getting the occasional stall. However I did notice if I left the PC running for several hours idling then I would for sure get a stall. I decided to add a feeble attempt at resonance dampening which did not help. After that I decided to look for any Mach3 optimization articles.
Anyway after reinstalling the OS to “Standard PC” my stalling has disappeared at 70/20 vel/accel but I have yet to run much at the new settings. I have cut a lot of PCBs but they hardly can get to a vel of 40.
Steppers: 280oz/3amp Tormach.
Drivers: avrstmd.com 1/10 microstepping.
Screws: ½-10 single start.
Power Supply: 40VDC unregulated.
Frame: 80/20
Style: Moving Gantry X30, Y20 inches.

[Mariss Freimanis]

Rob37,

Listen carefully to the motor. Mid-band resonance is indicated as cause for stalling if the motor makes a warbling sound just before stalling. "Just before" can be as short as half a second or as long as 10 seconds.

Mariss