hi all

getting some really weird action :confused:

in testing the debounce values further, i found that if the z car gets too close to the x-rails and near the x motors, the EStop is triggering. this is intermittent and doesn't always happen along both xrails. in one instant, it reversed my z motor! thank goodness it was only 1 inch and no harm done. at first i thought i might have typed Z-1.0, but i double checked and it was Z1.0.

In full disclosure, I am running Mach3 on a laptop while waiting for my lcd touchscreen. Ferrite rings are also on their way. Beside switching to desktop and adding ferrite rings, anything else i should be checking for? (i also will be trying some of the other suggestions from earlier.)

Another BUG, a big one, moving in the positive direction for all axes. I've noticed after having the system on for awhile the following occurs:

1) I can only jog in the negative direction. jogging any axis in the positive direction will only produce motor hums and no movement (Mach3 DRO are increasing.). If there is movement, motors are miss stepping for sure. Motors are ungeared and are tuned to basic specs from Gear Speed Step Frequency excel.

2) If there's movement in the positive direction, jogging in the x will torque the gantry as if only one x motor is turning or the two x motors are turning opposite (if even possible)

The way I've debugged this problem thus far is to shut off the motors and drives. Wait a few minutes. Turn them back on. Open and run the first few lines of the road runner Gcode sample. Back to "normal".

Any thoughts or pointers will be much appreciated as always!

T

Tuan,

Lower you velocity on motor tuning window in Mach, check if you have good ground/earth everywhere. check the grounding thread http://www.mechmate.com/forums/showthread.php?t=4

RGDS
Irfan

Tuan, did you ever switch those motors, or are you still on the 6.8mh inductance units? Are your geckos still running very warm?

When the system is running, is it easy or difficult to cause a motor stall if you (carefully!) push back against the gantry while it's moving? It should be scary difficult to stop the gantry; ideally the springs will let the pinions go before the motors stall. If this isn't the case, you aren't getting enough power from your motors.

Earlier in this thread, the discussions about the motor power calculations were based on using a 3-1 gear-down, but you appear to have direct drive at the moment, so I suspect you have insufficient torque.

Slowing your velocity, and particularly your accelerations settings may make the gantry move, but it will still be very prone to problems once you start cutting - think
about the kind of force a hand-held router can throw back at you.

So, your first problem to solve is: get your electronics and motors running without excessive heating. This may involve switching out the motors, decreasing the amperage, and/or increasing the voltage. Switching the motors is the best.

Your second problem to solve is getting enough mechanical advantage: switch the motors to some with gearboxes, or add belt drive transmissions. Either solution is fine.

The fastest way home is an expensive set of OM geared motors. Next best is 8 wire motors plus building transmissions.

Irfran, thanks for the link. I will reread the thread to make sure I'm running my ground proper.

Brad, I did switch motor. I'm using these with Bipolar Parallel wiring. The geckos are not warm at all. These 201x has DIP switch to set their current output. I set them at 5.8. Should I go higher?

I haven't tested pushing against the gantry while it's moving. That does sound scary. Can you explain a bit more by what you mean "...ideally the springs will let the pinions go before the motors stall."

There is current no gearing and there isn't $$$ in the budget for expensive OM. I was hoping to get the machine to acceptable working order and cut transmissions with it.

As for torque and motor tuning, in one experiment, I pushed the motor velocity to 600 in/min and acceleration to 8/in/sec/sec. The gantry was moving smoothly and fast. It was like music to my ears :D However, this also fell ill to the BUG I described in my last post.

Ah, Tuan, that's good news so far. I'll focus elsewhere then.

The springs that hold the pull the motor mount plates to hold the pinions in the rack are designed as a failsafe mechanism - they will let the pinion slip out of the rack in extreme conditions like the gantry or toolhead crashing into an immovable object.

However, given that you've already gotten strong motion and you're on a reasonable motor, that takes us back to why it's shutting down, and then working again after a rest period. That still feels like heat to me, and not noise.

Here's two other thoughts: When the system is in it's failure mode and will only
jog in a negative direction, can you move the gantry or Y car by hand? If yes, then something is funny in the power stage - you aren't getting holding torque from the Geckos/Motors. If no, then the issue is in the control stage - either the computer or the BOB is getting unhappy.

How is the BOB being powered? Is it possible that the power supply to the BOB is unstable when warm? In particular, is there a voltage regulator that is running warm?

In Bipolar Parallel, you should potentially be able to push higher amperage through those motors. You could also try switching to Bipolar half-coil.

Hi Brad

I tested the spring action you described by running the gantry at very slow speed against the stop blocks. The pinions slipped.

I tested for heat like this:
I isolated the motors for each axis and tested a thousand lines of code for each. Geckos 201x Standby is turned OFF so full current is always flowing to the motors. Motors were tuned to run at 600 in/sec an 8 in/sec/sec. I also changed to Dir/Step pulse setting in Motor Tuning to 5 microsecond. Per axis, I ran the code twice. The motors are warmer than normal after the first run. But the second run did not show any symptoms of the BUG. This led me to believe it is not heat. I should mention that the gcode for each axis is specific only to that axis. For example, the X axis gcode was:

F300
G1 X0
X1
X2.56
X67.32
......

I then loaded roadrunner into Mach3. The problem came back at the 6th and 7th line. On the 6th line, the Z did not travel to 0.2. On the 7th line, the X and Y did not move. From here on, the X and Y moved just fine. The Z continued to be a problem. I had moved the spindle to 2 inches above the bed, and then zeroed it out before starting the program. By the time the gcode is done, the spindle is touching the bed. Yikes!

As for holding torque, it's present when the system is in failure mode. BOB is power by a 5VDC from the power supply. No heat present any where BOB or power supply after the exercise I just described above.

After all this, I have two questions:

1) Is is possible that there's a loss of signal and/or power through the length of the cables? They are 16awg. The longest run to the Z is 25 feet.

2) I read somewhere in a post related to the PMDX that the Geckos should be grounded to the box through their neutral power line. Can anyone shed some light on grounding the Geckos if that's required?

I'm running out of ideas and running low on patience as I've been trouble shooting this for the past 2-3 weeks. Help?!?!?! :eek:

Tuan, I havn't looked at your full history....
Have you tried other PC's and another printer cable?

Gerald, I tried two different pcs. We have a few different ones at the shop. I suppose I could try again with a newer pc and cable.

I have some questions.

Have you tried to run the motors half coil?

What kind of wire are you using? Can you give us the numbers off the wire?

Measure the resistance of the run of the wire with an ohm meter. Tell us this resistance value.

I would also shorten the hookups and make them as short as you can so as little wire as possible is sticking out of the shielding. Both ends. Also make sure only one end of the sheild wire is grounded.

This may not help, but I would also twist the motor wires so they are not laying patallel to each other.

Show us more pictures of your setup.

Also I would like to see a closupe or the color code of your set resistor on your gecko. If you relied on someone to give you the correct OHM resistor they may have given you the wrong one.

What power supply are you running for the motors? Voltage?

You need to turn the Gecko 'standby' on. Leaving 'standby' off can only be used when the motor's current is 2A or less. You'll eventually get excessive heating unless the stepper drivers are allowed to automatically reduce current.

Isolating electrical noise can be very hard. I would first try disconnecting the spindle and then doing air cuts. If the machine works properly with the spindle off, then further attention must be paid to the spindle and its wiring. If the machine still has problems with the spindle off, then something needs to be changed in the basic wiring of the control box, but, at least you would have an idea where to start.

Mike & Mike & Team Mechmate

Motor has 8 wires. I tried unipolar (half coil?). No difference. I'm usine 16 AWG cables from here. They are shielded.

I have a digital mutlimeter. I was able to measure voltage and saw -58V and 58V at the motors. Negative and positive direction I assume. How do measure resistance? Do I measure the same way with the dial on the meter turn to ohm? I tried that and all readins were 0. Not sure what that means.

I did shorten all control signal hookups. From and to BOB. From to Geckos to motors. As for the grounding of the cable shielding, I haven't done this yet. Do I ground the shielding to the same point as earth ground?

I will try twisting wires. Pictures of set to come soon.

Power supply is a Keling 6520. 65V 20A.

Geckos Standby are turned back on.

Lastly, I've been trouble shooting this whole time with the spindle off.

Thanks again everyone for the suggestions. Just have to keep trying I suppose....:)

So neither end of your cable shielding is grounded?

Hi Tuan, just getting back to this after some time traveling. Back in posts #59 / #60,
I was asking if you had strong motor torque _while the system is exhibiting the problem_. You indicated that you ran the machine against the stops slowly and the pinions disengaged. Did you manage to do this in the direction that the machine won't go?

What I'm after here, is trying to assess if the motor strength is dropping during the time the system is failing; you could also try turning the system on, trying to manually push the gantry in both directions (shouldn't be possible), and then trying again after the issue shows up. If it becomes possible to push it, we're looking at a power stage problem; if not, likely a control stage problem.

Another thing to try is to measure the control signals at the Geckos. You should be
able to clearly see two solid voltage levels on the direction pin (relative to ground), depending on which way you jog. And if you jog several times, you should be able
to observe the step pin stopping in either the on or off state after each jog - you can again see the voltage levels. The question is whether these change in behavior when the system is working correctly vs incorrectly. Choose the Gecko for one of your problem motors, of course.

Are you able to turn stepper axle easily by hand, when there is no power to them? I had problems with some steppers with miss aligned rotor, it too wanted sometimes to go in one way and not the other and would heat fast, if you cant turn it easily it must be the same problem. I solved mine with dr.Hammer knock to the axle from the back of motor, that set the rotor to right position and motor gained in torque and speed.

Hi Tuan

It's no fun when things don't work as they should, but persistence pays off in the end.

From my reading of your thread grounding does not seem to be in place on your machine yet, so that is where I would invest my time first.
Several grounding strategies are discussed on the forum however my information is that grounding the cable shields at the machine is the typical way grounding is done in an industrial setting.
The machine itself will also need to be grounded, eg Y car to Gantry to Table Base to Earth.

Reducing complexity of the system to the bare minimum while still displaying the unwanted behaviour is really important.

1. As you have indicated you do not operate the spindle (but you have not said if the VFD is still turned on, so actually disconnect this until the issue is resolved)
2. In Mach3 turn off the resume and feedhold buttons in ports and pins, input signals.
3. Do not use any wireless devices to jog, only use the keyboard
4. Turn off or reduce micro stepping on the stepper drivers to a minimum.
5. Ensure the steps per values in Mach are correct for the stepping values you have selected using Gerald's gear speed calculator spreadsheet.
6. Actually check that the system you are using is capable of pulsing reliably enough using the application called drivertest.exe in the root directory of the Mach3 install.
7. Your Power Supply seems good from what I have read, but you might also consider disconnecting any steppers that are behaving well, as this will ensure power is not in short supply to the steppers that are problematic.

Regards
Ross

Some new development.

The slaved X motors started making really loud grinding noise like the bearings are broken. Lets add insult to injury. I thought. :mad:

After regaining my composure, I decided to decommission the entire line. I disconnected the power to the Gecko for this motor. Connections to the PMDX are also cut (pin 8 and 9). Something clicked! :eek:

Power supply current output is 15A at 56V. My Geckos had always been set to draw more than 4 amps up until this point. Simple math of 4 x 4 = 16 lead me to think the Geckos were over drawing current from the power supply. With the slaved X motor still down, I set all the Geckos to draw 3A. Voila!!!

I ran the roadrunner gcode program at the different feedrate of 15, 60, 100, 150, 300. I also isolated the axes and ran each independently. I also ran combination of 2 axes: XY, YYZ, & XZ before running all three axes at the same time. The spindle returned to correct referenced (0,0,0) at the end of the program everything single time :D

I am reluctant to rewire the slaved X as I am not 100% confident the bug is power. I have a job that needs to be out by the end of May, if this configuration continues to work, I'd rather keep it working before bringing the slave X back online.

Will the gantry get of out square with only one X? I am keeping the the slaved X engaged but not powered.

Again, thank you everyone for your advice and suggestions. Keeps me trucking on. :)

Don't know if it will work so well without both X-motors driving. Long long time ago in the world of Gecko I had a Gecko stop working on my one x-motor and the gantry was WOBBLY...or must I say shaking like a man in need of a stiff drink.

I'm surprised that the gantry moved cleanly with only one X motor. I expect that if you attempt a heavy cut close to the inactive motor, you may have some issues with accuracy. Why not try adding the additional motor at the lower amperage settings?

Another thing to try would be to swap motors to see if the one motor is bad.

However, given that you have a 15 A supply, and you had peak currents set for
over 23 A (you said 5.8 x 4, right?) I think you're on the right track. As mentioned above, you may want to try going to half-coil wiring instead of the parallel. This would match up nicely with your supply. Note that we often have systems with power supplies smaller than the total calculated draw, since all motors drawing at peak doesn't happen. But given a draw of 2.9 * 4 = 11.6a at idle, it's not hard to see that you might go over the top. You won't have that problem at 3A, and I'd bet, not at 4.4A either (half-coil).

I think you've probably solved your own problem here, now you just need to test it!

Got into the shop and did some more testing.

I can say with 99% certainty the former slaved X Gecko was the culprit for all my troubles. Any motor I hook up to it will make that clicking noise (grinding as I described in #69). I also tried to run this same Gecko from different pins, other than 8&9. Same problem.

Can anyone shed some light on how a bad Gecko would put the whole system into failure?

Also, turned on VFD and spindle and everything is smooth thus far. Ran the spindle at 6000, 8300, and 11250 rpm with no noise problem.

By the way Brad, is half coil the same thing as unipolar? I ran unipolar and the motors got really really hot.

Tuan, half coil is not the same as unipolar; you would need a different driver to run unipolar (6 wires from each motor, not four). However, it's electrically very similar to unipolar; in both cases, you only energize half of each coil at a time. Unipolar does this by switching from one half to the other half; Bipolar half-coil does it by using one half, but reversing the current through it. In both cases, you would need to keep the amperage down below the 4.4A specification on the motor to prevent excessive heating; so that is probably why the motors ran hot.

Since you've indicated that your gantry runs with just one motor, I would say that it has been doing that all along; the clicking motor was effectively not being driven electrically, just dragged along by the good one. Not surprising that it wasn't 100% repeatable. There's a good chance that your early overheating made that one Gecko unhappy. The clicking is consistent with either thermal or current limiting circuitry kicking in too soon, or with a blown driver MOSFET. In any case, Geckodrive should be able to help you.

Looks like you're in the home stretch now.

I did not think you can wire Geckos up Unipolar?

Isn't half coil where you use half the windings that you have hooked up for Parallel. For Example Blue/Red and Brown/Black. Or Yellow/Green and Orange/White. So you only use 4 of the 8 wires and tape off the other 4 so they do not short.

This way you are only using half the motors coils.

Here is a guide of different wiring configs:

http://img231.imageshack.us/img231/5...rvsbipolar.jpg

Hi Tuan

Well done, sometimes the amount of disassembly and reassembly to solve a problem can be intimidating - but you did it none the less.

I'm with Kobus on the gantry. I have ran both sides of my gantry with one motor only engaged and the wobble Kobos mentions is evident.
The slaved motor is not only winding up and down the rack it is also locking into a position on the rack when not moving.
This is very different from passively sitting there.

Effectively the locked motor becomes a pivot point for the gantry for any movement induced from the other axis's or any inertial movement from a change in direction or acceleration from the X axis itself.
Accuracy would be compromised and it would show up as an arc line from wherever the cutter position is with its center on the locked (or functioning) X motor.

Regards
Ross

Hello everyone

First off, thank you everyone for your help! I am happy to report she is live.

I hope this is the last time I'll be talking about my control woes. It turned out that in, addition to the bad Z gecko, the real error was the power supply to the BOB. :o All this time I did not once suspect the trouble was coming from the BOB because there was motion. After contacting tech support at PMDX, I learned 2 things:

1) I wired the regulated +5VDC into the BOB improperly. I should've taken notes and pictures from the kitchen table project so that I could have some reference after putting everything inside the box.

2) The reason why I had intermittent positive motion was that the BOB drew power from the computer.

It's quite embarrassing to learned it's been my carelessness all this time. However, I thought I would write it up as a lesson for future builders. On a positive note, I'm more confident with trouble shooting now :) The lesson is, like Ross said: sometimes starting over from SCRATCH is a good idea.

On an even more positive note, I'm still high on joy and excitement after a first successful run, from CAM to cut!!!

Doh! I was on that trail back when I was asking if the BOB power supply was getting warm. It probably was, but it was inside the computer so none of us saw it! We'll remember to ask the question the next time somebody is having problems, so thanks for sharing the resolution with us.

Very glad to hear you are up and running, hope you have lots of fun and profit with your MM!

Congratulations Tuan

My guess is you are going to appreciate your machine just that little bit more now after such a rocky start.
When I bought my toroidal power supply, it had additional taps for 5 volt and 12 volt so that was what I used as power to the BOB.

Probably a wise lesson for other builders to distrust the PC power supply, not so much as it is a PC power supply but because of the great variability in their build quality.
$10 - $200 last time I looked. I'm sure you could weld with the $200 PSU but not with the $10 one !!

Your test run looks quite artistic, It looks very much like some of the sixties graphics.
Pump out the work and show us a few pics to keep us interested.
If you can match Kobus for speed and variability of your projects, you achieve instant legend status :)

Regards
Ross