Do I have a bad motor, or something else?

[chipster]

My friend Don (RoutnAbout) was over looking at my SB this weekend and in additon to so many things I learned from him (Thank you again Don!), he pointed out what seems to be an issue with one of my X motors.

When my controler is active, I am able to move one side of my X by hand, but not the other side (normal). It takes a small bit of pressure to move it, but not a lot. We removed the motor and found that it does respond to keyboard commands.

I have a PRT (5' x 8') with the G4 controller.

My X motors are PK299-01AA (1.8 degree/step). One interesting thing about these two motors is that they have different code (lot numbers??) on each of them. Does this matter?

So my questions are, could a motor that responds to keyboard commands still be defective? Could something else (controller issue?) allow the x to be moved? This problem may be leading to cutting issues that we observed.

If I have a bad motor, where is the best place to buy them?

Thanks in advance!

[rb99]

You can do a little trouble shooting...as it could also be wiring or the driver card.

Switch the wires on the x motors and see if the other one becomes dead...

RIB

[don]

Chip has a PRT that is 8' on the X and 60 on the Y.
He also has upgraded to the 4G board (don't remember what version of software)
When turning the control box on, all of the motors bump like they should.
You also can feel the Xdrive motor (on the Y0) side while turning on the control box and can feel it bump also.
Then grab the Carrage on the Y0 side and it holds its location.
With in a short period of time,10-15 seconds this motor won't hold the carrage in place.
By switching the X wires on the motor gave the same results.


There also were times when you could use the keypad to move the carrage around but would not move. But digital read out would move. ( with all the motors hooked to the control box )

My guess it is his drive motor.
Is there a better way to confirm this?

[richards]

Which Gecko stepper drivers do you have? The G203 model is red, the G202 model is black. The G202 has a jumper inside to disable auto-current reduction. The red G203 does not have that option; it automatically goes into auto-current reduction.

If auto-current reduction is turned on, you may be able to turn a motor by hand when it is stopped. Again, depending on the stepper driver, auto-current reduction limits the current to be between 20% and 50% of normal. Lower current, when the motor is not running, means lower heat buildup.

Also, check the current limiting resistor on each Gecko stepper driver. The higher the resistance, the more current. If all motors are the same model, all four resistors should also be the same value. Check the third color band (multiplier band) to verify that someone did not make a 10X error, which is easy to do.

You can drop the motors down, away from the rack, then verify that each motor spins correctly when commanded.

In three years of torture testing a lot of motors and a lot of Gecko stepper drivers, I've never had either a motor fail or a stepper motor fail. There have been times when I had a loose connection or a faulty power supply that made the motor appear to fail, but a little checking showed where the error really was. (I did have the wrong resistor on one motor which severely limited the current going to the motor.)

[don]

Mike,
Thanks for the response.
I think his drivers are the black G202
When I was there, I attempted to pull the Gecko drive from the board. But it was pulling really hard. I even tried using a large flat screw driver to pry. I pulled while prying, but the mother board started to flex a little. I stopped as I didn't want to damage his board or machine.
Is there a tool to remove the driver from the board?
I'm also approx 180-200 mile from him. So I won't be able to check it myself.

[gundog]

I had a similar problem and mine ended up being the control board. On mine at start up all motors would lock up but then later my x-1 motor would drop out. Sometimes at start up I would not have the x-1 lock up. I also had problems with my z axis not maintaining zero and losing height.

It took me a long time to figure out what the problem was. I first thought my material was moving I then thought the pinion to rack was getting sloppy so I tried many things to fix this stuff before I figured out I was losing one of the motors. Now every time before I start cutting I grab the YZ car and check for slop in any of the motors before cutting.

One of the things they told me to try was to open the side of my control box and lay the control box on its side. My control box was a PC tower type. I was told they get hot and when the tower is standing the heat transfers from one driver to the next. My machine was not fixed by this and actually had the problem even at start up sometimes. I did do this to the new box just to be on the safe side. I also added an extra fan to blow across the controllers. I don’t want any more problems.

The new control box seems to have fixed my issue but I have not used my machine enough since the new box to be absolutely sure.

My machine is a 1 1/2 year old PRS standard. My controlers are red that is a question they asked me.

Mike

[richards]

Heat may very well be the problem. The G202/G203 is meant to be used with a heatsink if used with motors pulling more than 2A. The Pk299-01 motor pulls 1.4A if wired bipolar series and 2A if wired unipolor (half-coil) As far as I know, all motors were wired bipolar series (black/green, red/blue). The problem with that wiring arrangement is that the Pk299-01AA motors have over 50mH inductance, hardly the ideal for a stepper driver that works best with an Inductance level of < 10mH.

Back to the heat problem. The G202 stepper drivers are built to take up to 7A of current with proper heat sinking and up to 2A with no heat sinking; however, that is with the jumper set to the auto-current reduction mode, which is NOT the default setting for the Shopbot.

I would immediately mount the Gecko stepper drivers on a piece of 3/8" thick aluminum that is mounted on standoffs so that air can freely move all around the stepper drivers and the heatsink. If there is still a heat problem, I would mount a fan to circulate the air inside the control box so that the Gecko stepper drivers and the heatsink stay well within tolerance.

The Gecko stepper drivers have a built-in sensor that shuts off the stepper drivers if they get too hot. They are reset by removing power from the stepper drivers completely and then re-applying power.

Mounting the Gecko stepper drivers without heatsink may have seemed reasonable, but in practice, it hasn't worked that well. Too many users have had the same problem. A $15 piece of aluminum will cure that heat problem.

[chipster]

I checked this morning and the drivers are red (G203). They do have a black surface on one side Don, which I'm sure made you think that.

I've been crazy busy since the weekend, and I haven't had a chance to call SB yet, but I will today. If I just spent all that cash for the controller and now I need to modify it with a heat sink, that indicates some design changes are necessary, and it also means I'm not going to be a happy camper!

[chipster]

I contacted Shop Bot, and received the customary top-notch customer service. Frank suggested that I look at all of my Wagos to see if there was a wire causing the problem. This was after we talked about why it would not be the controler.

After doing as Frank suggested. I found that the problem persisted.

I then looked at the rack / pinion interface and low and behold, despite my previous review of this, the pinion was slipping on the shaft while under power. I had looked at this before with the motor off, and becasue the pinion is tight on the shaft, I could not detect movement by turning it by hand. However, with the motor torque, it became obvious.

So the good news is the problem is solved. The bad news is I need to go back to school to know how to properly install a gear!

Thank you to all who helped! Don, you have a PM on Vectric where I eat even more humble pie!

[ted]

A bit more follow-up on this one.

Glad we were able to help get at Chip's problem.

On the potential overheating issue with gecko drivers (202/203): We have had an occasional situation where a gecko drive has overheated. This has usually been in a situation where the control box was inside a cabinet or in a situation with limited air circulation so that there was a lot of heat build up. The symptom of a heat failure on a driver is that it totally shuts down. The motor will freely spin, and is not at all responsible to signals to move. When the control box is turned off, allowed to cool a bit, and is then turned back on. The driver will reset and fully recover. These were not Chip's symptoms, but it could have been an issue.

As Mike suggests above, one of the design considerations for our Version 4g board was to be able to use the drives without a heat sink so that we could create a convenient drop-in replacement board, and so that we could continue to use the control box layout that we had in production at the time (discussed in an early column here: http://www.shopbottools.com/teds_report.htm#My%20First%20Post).

Gecko's published recommendations are that the 202 drivers get heatsinks over 6Amps and that the 203 drivers get heatsinks over 3Amps. We run at lower than these currents (2A or less depending on motors). After testing and discussions with Gecko, we decided that our mounting system was practical as well as convenient. In practice, the heat problems that have occurred have usually been with the older 202 geckos. They have a highly variable threshold for thermal shutdown and some will trigger at pretty low temps. Better air circulation (or occasionally swapping out drives) solves the problem. The 203s seem considerably more stable.

I might mention the availability of a neat new open-loop driver from Oriental Motor. It's in a nice, easily mounted and heat-sunk package. It has several smoothing and vibration suppression functions. It's microstepping ratios can be configured and has a range of current settings. We've put it through a lot of testing and it seems very robust. [We've also been impressed with the durability of the Oriental Motor alphaStep drives over the last 5 years -- they seem bullet-proof.] We have not had a chance to get info on these drives up on the web site yet, but we have started shipping them drives in a new control box on PRSstandard tools (info on the website soon; unfortunately a price increase has come with the control box).

Ted Hall, ShopBot Tools

[don]

Thanks to everyone that Jumped in and helped.
And a Thanks to Ted for shedding more light.

I'm glad to see that your up and running Chip.

Since Chips 4G board was the first one that I've seen and was able to use the keyboard with, I have a couple questions.

The Stepper motors were very warm. Is this normal? how warm or hot do they get?

If the Carrage was pushed by hand while the control box on, will it ruin the Gecko Drive, like it does on the original board with the PRT?
If so, do these Drives pull off the board? or do you need a special tool to pull these off? or send the whole board back for repair?

Again thanks to everyone that helped.

Don