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Author Topic: Z "Home" bug causing me problems  (Read 4353 times)

NoiseReduction

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Re: Z "Home" bug causing me problems
« Reply #15 on: February 21, 2013, 12:10:43 AM »
You still need a properly-functioning endstop. The Z endstop in particular is crucial.

To see if there's an issue with that endstop, you can move the axis up and switch Z endstop with another one. Put one finger on that endstop and the other on the reset button (to prevent the head from crashing if the enstop fails) and tell it to home the Z axis. Press the endstop that is wired to Z and see if it stops. Normal behavior is for it to back off a few mm from the endstop, and then go back toward it more slowly, so you'll want to tap the enstop twice.

OK I'll try and move the axis manually. Thanks!

Despite all the suggestions, I maintain my opinion that the endstops seems perfectly fine - because I switched them last night and the problem remained on the Z axis (only when switching motor and driver board, the problem was transfered to X, which points to it being an Azteeg firmware issue, and not something associated with hardware)...

NoiseReduction

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Re: Z "Home" bug causing me problems
« Reply #16 on: February 24, 2013, 02:48:00 AM »
Yeah, now even X and Y are not responding well in repetier. Sometimes it works, but sometimes I get "X commands waiting" in the host, and it stays there for a while.

It's possible my X3 might just be completely screwed. I have no other explanation for it. Maybe I should try an X1

whosawhatsis

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Re: Z "Home" bug causing me problems
« Reply #17 on: February 24, 2013, 03:53:35 AM »
I've seen that happen before, and I'm not entirely sure what caused it, but unplugging it (power and USB) and leaving long enough for all the capacitors to throughly discharge and all of the semiconductors to thoroughly cool cleared up the problem.

NoiseReduction

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Re: Z "Home" bug causing me problems
« Reply #18 on: February 24, 2013, 05:32:01 AM »
I've seen that happen before, and I'm not entirely sure what caused it, but unplugging it (power and USB) and leaving long enough for all the capacitors to throughly discharge and all of the semiconductors to thoroughly cool cleared up the problem.

Interesting. It's been like that, for the last couple of days

jit

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Re: Z "Home" bug causing me problems
« Reply #19 on: February 24, 2013, 05:49:44 AM »
I've seen that happen before, and I'm not entirely sure what caused it, but unplugging it (power and USB) and leaving long enough for all the capacitors to throughly discharge and all of the semiconductors to thoroughly cool cleared up the problem.

I too have observed weird behavior that disappeared after doing this.  (And if it only happens once, you'll never be sure what was going on...)

At this point, it couldn't hurt to try swapping everything you can think of.  Swapping out the Azteeg is not something you can try in the next five minutes, but how about these things, one at a time:

- try a different USB cable

- try a different computer (with a fresh install of the controller software), or at least try a different USB port on the computer

- try a different power supply for the Arduino electronics (in other words, move the Azteeg jumper that selects 12V vs. USB power)

And presumably you already checked the actual voltage from the 12V power supply, and don't have an undervoltage.
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NoiseReduction

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Re: Z "Home" bug causing me problems
« Reply #20 on: February 24, 2013, 06:47:18 AM »
I've seen that happen before, and I'm not entirely sure what caused it, but unplugging it (power and USB) and leaving long enough for all the capacitors to throughly discharge and all of the semiconductors to thoroughly cool cleared up the problem.

I too have observed weird behavior that disappeared after doing this.  (And if it only happens once, you'll never be sure what was going on...)

At this point, it couldn't hurt to try swapping everything you can think of.  Swapping out the Azteeg is not something you can try in the next five minutes, but how about these things, one at a time:

- try a different USB cable

- try a different computer (with a fresh install of the controller software), or at least try a different USB port on the computer

- try a different power supply for the Arduino electronics (in other words, move the Azteeg jumper that selects 12V vs. USB power)

And presumably you already checked the actual voltage from the 12V power supply, and don't have an undervoltage.

That's true, should have tried the PC too. I'll do that, thanks.

The arduino came powered by USB. I switched it to input and re-flashed the firmware. No change in behavior. Thanks for that reminder tho, I wanted it always powered by input.
Already bought a new USB cable, no noticeable change.
Measured 12.20 V at the power supply.

NoiseReduction

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Re: Z "Home" bug causing me problems
« Reply #21 on: February 24, 2013, 08:10:07 AM »
Found the problem.    ;D

Replaced the stepper driver board from Z with the one in Ext 2 and now both stepper motors are cooperating.
I left Ext 2 slot empty, I only have 1 extruder anyway.

jit, you smartly suggested switching the driver boards - and I think that showed the problem was the board, so I don't know why I didn't think of this before  ::)
« Last Edit: February 24, 2013, 08:50:07 AM by NoiseReduction »

Tyson

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Re: Z "Home" bug causing me problems
« Reply #22 on: February 25, 2013, 05:27:56 PM »

I also had a bad stepper board, in this case it was my "X".   I also swapped with the 2nd extruder driver since mine is a single to get the system going.   My failure behavior was periodic no response.   It was working, stopped working so I swapped driver board and it worked.  Swapped back to check, and the bad stepper board was working again briefly but stopped soon after.  Swapped back to the extra and it has been fine ever since.


jit

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Re: Z "Home" bug causing me problems
« Reply #23 on: February 25, 2013, 07:15:23 PM »
The driver boards that came with the Azteeg X1 and X3 can fail.  That's why the wiki warns about never applying 12V power to the Azteeg when it's got any driver boards on it that don't have motors wired up to them  --  this can damage the driver.  (Not a new problem;  this style of driver board predates the Azteeg line and the Bukobots.)

And this is probably one of the reasons why Roy at Panucatt is making the 1.1 version Azteeg.  It comes with improved driver boards that are described as "more robust" (although the warning about applying voltage without motors wired in still applies).
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NoiseReduction

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Re: Z "Home" bug causing me problems
« Reply #24 on: February 25, 2013, 07:30:01 PM »
The driver boards that came with the Azteeg X1 and X3 can fail.  That's why the wiki warns about never applying 12V power to the Azteeg when it's got any driver boards on it that don't have motors wired up to them  --  this can damage the driver.  (Not a new problem;  this style of driver board predates the Azteeg line and the Bukobots.)

And this is probably one of the reasons why Roy at Panucatt is making the 1.1 version Azteeg.  It comes with improved driver boards that are described as "more robust" (although the warning about applying voltage without motors wired in still applies).

Interesting! Also, scary  :o

jit

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Re: Z "Home" bug causing me problems
« Reply #25 on: February 25, 2013, 10:02:30 PM »
I think driver board failures on Bukobots are fairly rare (much less than 1% so far I think;  the Deezmaker guys have a better idea about this I'm sure).

These boards are not hard to find.  They are known as pololu boards and various places now make them  --  they are open source hardware.  They typically range from US$10 to $14 apiece.

For a long time they were based on the Allegro A4988 driver chip, but now new ones based on the TI DRV8825 are coming out.  These can handle higher voltages and higher currents, and can provide finer steps.  You can still destroy them if you fail to follow directions.

In some cases the new ones can be used as drop-in replacements for the old ones.  See documentation about this (for example http://www.pololu.com/catalog/product/2133, but note that Roy's design may be a bit different).  Not sure how compatibility works with the older Azteeg boards.

Basically, remember the warning about powering up with no motors.  And, take care if you use voltages much higher than 12V, or if you use bigger stepper motors, or if you increase the feed rates, as these things can increase power dissipation on the driver.  Air flow over the drivers will keep them cooler, and sometimes heatsinks might be needed.  But a standard off-the-shelf Bukobot with the recommended settings probably won't have problems with this.
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Tyson

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Re: Z "Home" bug causing me problems
« Reply #26 on: February 26, 2013, 03:51:19 AM »

Is there a reference for the concern about powering up without a motor attached?
(More than just the warning on the Panucatt datasheet)

I would like to understand more.

whosawhatsis

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Re: Z "Home" bug causing me problems
« Reply #27 on: February 27, 2013, 10:27:54 PM »
The boards are usually fine if you power them without a motor attached. The real problem occurs if you plug or unplug a motor while the board is energized. I suppose a short circuit on the unconnected motor header is a risk that could fry the chip, though.

The DRV8825 chips are a bit more robust and better-designed in general, but connecting and disconnecting motors while they are energized is still a bad idea. Roy's DRV8825 drivers are compatible as drop-in replacements for the old ones, except that the default jumper setting gives you twice the microstepping ratio. Pololu's own DRV8825 drivers initially had some incompatibility, which is why their first revision is now on clearance. Their second revision behaves the same way that the Panucatt version does.

NoiseReduction

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Re: Z "Home" bug causing me problems
« Reply #28 on: February 28, 2013, 12:43:40 AM »
The boards are usually fine if you power them without a motor attached. The real problem occurs if you plug or unplug a motor while the board is energized. I suppose a short circuit on the unconnected motor header is a risk that could fry the chip, though.

The DRV8825 chips are a bit more robust and better-designed in general, but connecting and disconnecting motors while they are energized is still a bad idea. Roy's DRV8825 drivers are compatible as drop-in replacements for the old ones, except that the default jumper setting gives you twice the microstepping ratio. Pololu's own DRV8825 drivers initially had some incompatibility, which is why their first revision is now on clearance. Their second revision behaves the same way that the Panucatt version does.

That's fascinating - thanks whosa!

Once we adjust to realizing it's an arduino board, that in any other situation of retail product sale would be enclosed to avoid tampering with connections, it all makes sense. Now I'm just not sure if my driver board came messed up, or if I did it at some point while troubleshooting the Z axis issue  :-X

Nevertheless, I'm very happy that my bukobot is working and printing like a champ! (except last night, when I accidentally turned off the USB hub the printer was plugged to, halting the print job :P). Mental note: I wish there was a way for both the firmware and host software to recognize a USB disconnection, pausing the print, lifting the hot end (if possible) to allow cleanup of extruded plastic during pause, and then, once reconnected, allowing for a "resume job". One can dream...
« Last Edit: February 28, 2013, 12:46:49 AM by NoiseReduction »

whosawhatsis

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Re: Z "Home" bug causing me problems
« Reply #29 on: January 20, 2014, 04:05:15 AM »
Finally found the Z home bug. You can get a copy of the firmware with the just the bugfix here:
https://github.com/whosawhatsis/Marlin/tree/Bukobot_config

If you're feeling a bit more adventurous, you can instead install this updated branch (shipping on new Bukobots as of the beginning of the new year). This will require a bit of rewiring, but it now includes the bugfix as well as some updated features, and on a Bukobot v2, the motor connectors should now all be facing the same direction (smooth side on top). Note that as part of this update, we have switched to considering "Extruder 1" to be the RIGHT extruder (the one that comes with single-extruder models, and the one that is at the corner of the platform when homed). To use this you'll either have to flip your extruder motor connectors to keep your current extruder order or switch the heater, thermistor and motor wires for the two extruders (recommended). The updated Marlin can be downloaded here:
https://github.com/whosawhatsis/Marlin/tree/Bukobot_update

 

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