[CNCwoodMan]

Hello,

New to the forum and could really appreciate the help. I know that DIY CNC is painful unless you 100% know your machine, which I honestly am still getting to know everything about it.

Here is my problem:

I notice that one of the motors on the X-Axis does a real bad jerking movement mid J0 command while cutting a 1 inch circle (pocket). I have slowed down feeds and speeds in Mach 3 manually overriding it but does not seem to be root cause. As well, to confirm it also does the same action whether or not it is air cutting or has load on it. I have changed depths within Fusion 360 thinking it was related to either hogging too much but no luck.

Here is link to video of problem (Jumps at 17 sec and 26 sec): https://drive.google.com/open?id=0B4...VZMT01Sc1BmOVE
Here is picture of G-Code: https://drive.google.com/open?id=0B4...05EdlhPOXhZSzg

Thanks for any help in advance!!!

[louieatienza]

sounds like stalling.... info on stepper size and torque rating? Drive? PSU? You could try lowering acceleration., see if that helps. But just from looking at the video seems to me a loss of torque because you're direct driving that pulley.

[CNCwoodMan]

sounds like stalling.... info on stepper size and torque rating? Drive? PSU? You could try lowering acceleration., see if that helps. But just from looking at the video seems to me a loss of torque because you're direct driving that pulley.

Thanks, couple questions on your questions (Sorry, still working on getting to know machine.)

Stepper size - Are you asking for what I have programmed in Mach 3?
Torque rating - Of the x-axis motors I am using from manufacturer?
Drive - Not sure what you mean here
PSU - Will check and post back.

You mentioned stalling, wouldn't the motor sound like its topping out then continue without a jerking motion? I experience stalling on my other CNC, which was my first build, when i try to move to fast on the axis. Does not seem to be the same motion/movement I am seeing here.

Interesting that you say loss of torque because looking at the video it was clearer that I am not hopping or skipping a tooth on pulley which I though could cause this as well. Do you mean that the motors are not capable of moving the gantry and causing a loss of torque?

[ger21]

Stalling can take many forms, and it's definitely stalling.

By size, he means the torque rating of the motor.
The model number of the motors is fine.
The drive is what controls or runs the stepper.

[CNCwoodMan]

Stalling can take many forms, and it's definitely stalling.

By size, he means the torque rating of the motor.
The model number of the motors is fine.
The drive is what controls or runs the stepper.

OK, Thanks!

Motor - Open Builds - LDO - 57STH56 - 2804A


PSU -



Drive - Probotix PBX - RF - PROBOTIX PBX-RF RF Isolated CNC Breakout Board

[CNCwoodMan]

FYI, tried lowering acceleration to the lowest it can go and it still happened. Seemed to be less frequent but I stopped the air cut after a couple jumps.

[louieatienza]

When you hear that high pitched whine of the stepper, and it doesn't turn, that means the stepper has stalled out. Either the torque needed to move the axis is far greater than the available torque, or the stepper is having resonance issues. While it's possible that there may be resonance due to some compliance in the belt, I think it's more a matter of not having enough torque available.

See, that pinion acts somewhat like a gear multiplier; or in other words, it spreads the motor torque out over a greater distance - exactly pi times the pitch diameter of the pulley. This in turn forces you to use a high step multiplier to gain back some "resolution" and smoothness. But this creates another dilemma where the torque decreases at each microstep. And also, while the controller can command a move to the drive, the stepper may not necessarily turn because it has to reach the next microstep that has enough torque to overcome the weight and friction of the particular axis. So that possibly could explain some of the "jumping" witnessed.

In ye olden days, the hobby stepper drives were not as sophisticated as today's, and we'd add either a weighted disk, or home-made "rattler" damper, or purchase a viscous damper, to alleviate resonance in the stepper. This would require a rear shaft, which your steppers do not have. Today's drives have electronic damping. Again, I don't think this is a resonance issue. Those steppers are only rated to 175oz-in stall torque, and they're at a mechanical disadvantage direct-driving that pulley. Easily.

The way I see it, you have three choices. The most expensive is probably the easiest - source NEMA23 planetary gearheads with a reduction ratio of 7:1 to 10:1. You can get them for under $100 each, and you can just bolt your steppers to them and the gearheads to where your steppers are now. You'll have to modify the pinions to fit the new shafts or purchase new pinions.

The second choice would be to make your own belt reduction setup. I think this would be rather difficult compared to the first option, but it would be cheaper as the cost would be sweat equity.

The final option, which I'm not the keenest on, is find the strongest NEMA23 steppers you can (I believe that's 570oz-in) and pair them with the smallest pinions that will fit the shaft. This is not ideal as you'll still have the resolution issue, and if there was a resonance issue, it may be worse with the larger stepper.

[ger21]

The "Drives" are the four Probotix Sidestep boards, in your power supply pic. These use the same A3977 chip as my Xylotex drives, which are very susceptible to resonance.

You need to make sure that the current is set correctly, using the VREF and onboard pot.
Also, make sure you have them set to 1/8 microstepping.

Those chips should have heatsinks on them, to prevent overheating, which can cause issues.

More info here. SideStep - PROBOTIX :: wiki
You set the current by powering the drive, with NO motor connected, and adjust the trim pots while measuring the voltage between the VREF test points, as shown on the page in the link.

[X07gavrp]

Louie is correct it's stalling mine would do exactly the same thing if velocity and acceleration where set wrong mach3 has a setting to configure this automatically also your step size setting on your drives might be wrong setting for the project your Machining maybe try 1600steps if calibrating the velocity and acceleration doesn't work. Good luck

Sent from my Le X820 using Tapatalk

[CNCwoodMan]

The "Drives" are the four Probotix Sidestep boards, in your power supply pic. These use the same A3977 chip as my Xylotex drives, which are very susceptible to resonance.

You need to make sure that the current is set correctly, using the VREF and onboard pot.
Also, make sure you have them set to 1/8 microstepping.

Those chips should have heatsinks on them, to prevent overheating, which can cause issues.

More info here. SideStep - PROBOTIX :: wiki
You set the current by powering the drive, with NO motor connected, and adjust the trim pots while measuring the voltage between the VREF test points, as shown on the page in the link.

Thank you for the link! The drive boards were set to 1/4 microstepping and the voltages were all out of wack. Seems as though it must of been troubleshot before me and not working as expected. I purchased this machine through a buddy and we walked through a couple "simple" test cuts prior to taking delivery. I will be purchasing heatsinks for the chips, they are always a good idea. For now, I am not going over 2.4V (1.5A) as that document listed it will need heatsinks.

After reviewing what you said and the information you sent, I think I finally got it honed in without the motor's stalling :banana: The test cuts that were stalling before were no longer stalling after adjustments and calibrating Mach 3 with proper steps/velocity/acceleration.

HERE COMES THE PART WHERE I ALMOST BODY SLAMMED THE MACHINE OUT OF PURE FRUSTRATION....

Attachment 364012

Seems as though when I was tightening the nut on the disconnect for the Z-Axis the screwdriver slipped off and hit one of the motor wires on the connection breaking the solder (at the time I did not notice). I did notice, however, that my Z-Axis had horrible chatter and would barely respond to any jog requests. Literally after opening up my control box (after celebrating that everything was fixed) I lift the cover and BOOM...Sparks shoot out almost singes my face and I immediately hit the EStop to cut power. FML!!! Looks like I will be getting another drive board:boxing::drowning::violin:

[CNCwoodMan]

Louie is correct it's stalling mine would do exactly the same thing if velocity and acceleration where set wrong mach3 has a setting to configure this automatically also your step size setting on your drives might be wrong setting for the project your Machining maybe try 1600steps if calibrating the velocity and acceleration doesn't work. Good luck

Sent from my Le X820 using Tapatalk

Seems the step size on the board was wrong, thanks!

[CNCwoodMan]

When you hear that high pitched whine of the stepper, and it doesn't turn, that means the stepper has stalled out. Either the torque needed to move the axis is far greater than the available torque, or the stepper is having resonance issues. While it's possible that there may be resonance due to some compliance in the belt, I think it's more a matter of not having enough torque available.

See, that pinion acts somewhat like a gear multiplier; or in other words, it spreads the motor torque out over a greater distance - exactly pi times the pitch diameter of the pulley. This in turn forces you to use a high step multiplier to gain back some "resolution" and smoothness. But this creates another dilemma where the torque decreases at each microstep. And also, while the controller can command a move to the drive, the stepper may not necessarily turn because it has to reach the next microstep that has enough torque to overcome the weight and friction of the particular axis. So that possibly could explain some of the "jumping" witnessed.

In ye olden days, the hobby stepper drives were not as sophisticated as today's, and we'd add either a weighted disk, or home-made "rattler" damper, or purchase a viscous damper, to alleviate resonance in the stepper. This would require a rear shaft, which your steppers do not have. Today's drives have electronic damping. Again, I don't think this is a resonance issue. Those steppers are only rated to 175oz-in stall torque, and they're at a mechanical disadvantage direct-driving that pulley. Easily.

The way I see it, you have three choices. The most expensive is probably the easiest - source NEMA23 planetary gearheads with a reduction ratio of 7:1 to 10:1. You can get them for under $100 each, and you can just bolt your steppers to them and the gearheads to where your steppers are now. You'll have to modify the pinions to fit the new shafts or purchase new pinions.

The second choice would be to make your own belt reduction setup. I think this would be rather difficult compared to the first option, but it would be cheaper as the cost would be sweat equity.

The final option, which I'm not the keenest on, is find the strongest NEMA23 steppers you can (I believe that's 570oz-in) and pair them with the smallest pinions that will fit the shaft. This is not ideal as you'll still have the resolution issue, and if there was a resonance issue, it may be worse with the larger stepper.

Appreciate all the info! That was really helpful in understand the RCA of the issues. However, seems as though I have now created another problem for myself as you can see in the other post!!!!

[CNCwoodMan]

The "Drives" are the four Probotix Sidestep boards, in your power supply pic. These use the same A3977 chip as my Xylotex drives, which are very susceptible to resonance.

You need to make sure that the current is set correctly, using the VREF and onboard pot.
Also, make sure you have them set to 1/8 microstepping.

Those chips should have heatsinks on them, to prevent overheating, which can cause issues.

More info here. SideStep - PROBOTIX :: wiki
You set the current by powering the drive, with NO motor connected, and adjust the trim pots while measuring the voltage between the VREF test points, as shown on the page in the link.

Ger21 - I did have a question for you. How did you determine that the driver boards need to be at 1/8 microstep?

[ger21]

The higher the microstepping, the smoother they'll run, and reduce the chance of resonance. Generally, all microstepping drives have the best balance of power/smoothness at 8-10 microsteps (1/8-1/10).

And these drives are VERY intolerant of miswiring, or shorts in the motor wires. Do not do anything with the wires while the drives are powered.

[CNCwoodMan]

The higher the microstepping, the smoother they'll run, and reduce the chance of resonance. Generally, all microstepping drives have the best balance of power/smoothness at 8-10 microsteps (1/8-1/10).

And these drives are VERY intolerant of miswiring, or shorts in the motor wires. Do not do anything with the wires while the drives are powered.

Appreciate the info, lesson learned!!!

I have literally been working on this thing all day long and the one time I slip and not turn it off...BOOM. Thanks, and I will update the thread if I can find out where to buy another board of the same. As of right now it is proving hard to find it from probotix.

[ger21]

Something like this will give better performance.
High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin

[CNCwoodMan]

Something like this will give better performance.
High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin

Would it be hard to migrate all four of these boards to those? They do not seem to be as "plug and play" as these ones are. By the way, super hard to find online...

[louieatienza]

Something like this will give better performance.
High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin

Looks like a re-branded Leadshine DM-542... AmericanMotionTech is now selling the DM-542E for $39.95 each, a pretty good bargain.

Leadshine DM542E stepper motor drive / controller

[ger21]

The boards you have are obsolete, and not made any more.
If you replace the Probotix breakout board with something else, changing over will be pretty simple.

[CNCwoodMan]

The boards you have are obsolete, and not made any more.
If you replace the Probotix breakout board with something else, changing over will be pretty simple.

Ok, do you guys have any suggestions on breakout boards?

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