Stepper extruder looses torque

When I power up my mendel and open the reprap host software, the X, Y, and extruder stepper motors lock up, as they should. The holding torque is adequate on these steppers. When I press "extrude" in the host software, the extruder stepper steps the correct distance, but with very little power (and a bunch of buzz/beeping, which I understand to be normal without a separate stepper driver). The extruder stepper twitches and misses steps, and can be stopped completely with little force.

I played with the potentiometer and couldn't gain enough torque to extrude consistently, then restarted the machine (remember full holding torque on startup?) well, I blew the A3949 chip doh.. I replaced the chip (waiting for parts sucks!) and returned the pot to where it came set to. The problem exists still.

I'll try tomorrow to transplant one of the axis stepper boards to drive the extruder, and report back my findings.

I'm using the following:

Windows7
RepRap java host
The latest FiveD_GCode and Extruder firmware
Techzone electronics
Lin Engineering NEMA17
Motor No.: 4118S-15-13
rated current/phase 0.5Amps
resistance/phase 15Ω


Any suggestions?

I tacked on an image of the blown chip, don't do what I did kids!

Thanks,
Braden

... you loose torque when the clock speed is to fast or when you activate the 'reduce output energy' pin (don't know what's with the A3949) ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I could be wrong, but I think I had a similar problem until I put heat sinks on those A3949 chips. I think they tend to overheat which causes the motor to be twitchy and miss steps. Maybe that's why it blew up too. Also, do you have Extruder0_ExtrusionPWM set to -1 in the host software preferences? I think that needs to be set to -1 in order for the on board pot to work.

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Tony Buser http://tonybuser.com * http://reprap.org/wiki/User:Tbuser#Projects

VDX, I'm not sure which pin is the "reduce output energy"

gr0k, Extruder0_ExtrusionPWM is set to -1, the A3949 chips get warm to the touch after being powered up for a while, but not hot.


Thanks for the help so far

Braden

Hi Braden,

... i've checked - the A3949 don't have a power reducing mode as most other stepper drivers, only SLEEP, but then he's really down ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

question:


Extruder0_ExtrusionPWM -1 does not show up in my host software. (most recent release) which release(s) is it in and is it not needed anymore?

I just downloaded the latest release reprap-mendel-20100719 and I still see that option...

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Tony Buser http://tonybuser.com * http://reprap.org/wiki/User:Tbuser#Projects

15 ohms seems pretty high for an extruder stepper, not sure you'll get enough torque even when your driver is working properly

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Wooden Mendel
Teacup Firmware

at the risk of hijacking the thread, screenshot showing the option doesn't appear for me.

That is really strange, here's what I see using reprap-mendel-20100719. Maybe try starting a new preferences file?

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Tony Buser http://tonybuser.com * http://reprap.org/wiki/User:Tbuser#Projects

i'lll have to dig in further. I've replaced all the files a couple of times, still no clear answer. If anyone else has the issue i'd love to hear a solution (although my trim pot does adjust the voltage going to the extruder stepper)

Braden Kear-
here is something that I tried today that seems to work pretty well- in the stepping sequence code of the extruder I commented out the even number steps and left the odd numbers (so the ones that have pwm>>1 + pwm>>3 are active)

this allowed me to get a more consistent strength from the stepper motor and kept the heat coming out of the h-bridges to a more manageable level. no more thermal shutdown type problems while maintaining some strength.

Same exact problem here,,,, bummer... ready to go but zero extruder torque... I am using gen3 makerbot electronics converted and the 07/02 build... everything is perfect besides the torque issue....
ANY help at all will be welcomed!
Dan

Ok I am a pinhead.... what is your extrude speed at? bet that's the problem.....mine was wayyyyy to high.

lunchtrayrider Wrote:
-------------------------------------------------------
I commented out the even number
steps and left the odd numbers (so the ones that
have pwm>>1 + pwm>>3 are active)



Where in the code will I find this? I've looked through quickly and I'll dig some more, but guidance would be appreciated.


Thanks,
Braden

in the extruder sketch in the arduino editor under the tab extruder.class i believe near the bottom.

it is similar to the code that is posted in the wiki

[www.reprap.org]

Well I've tried everything I can think of.

I installed a stepper driver board in place of the extruder board's on board driver.
I ran the reprap host in linux (I like the additional options in the linux version).
I changed the extrude speed between 10 and 9999.
I adjusted the driver boards pot up and down.
I swapped the stepper motor out.
I uploaded the latest firmware to both boards, with the only modification to un-comment the use thermistor line.

The extruder still jitters and moves very slowly, and also gets very hot if left idle and locked up...
Hot enough that it melted the PLA of the extruder and stripped the drive gear's ID

Thanks for the help everyone.

Edited 1 time(s). Last edit at 08/22/2010 09:47PM by Braden Kear.

OK, got this sorted out in the IRC, reflowing a couple solder joints, and configuring the firmware, I can extrude just fine now.

now (after reprap host locking up often) I'm trying to use replicatorG and having problems with maxhines.xml.. uggg.

I added the reprap element to in machines.xml in the replicatorG folder, but replicatorG dosen't list reprap in the menu. what am I doing wrong?

here's the machines.xml file

You need to put it in the right place, see this thread: [forums.reprap.org]

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[www.hydraraptor.blogspot.com]

thanks nophead, I'll try that when I get home tonight

machines.xml in the other directory worked!

In replicatorG I made a skeinforge profile for Mendel-PLA, and attempted a print, but it tried to move the Z screws way too quickly, and skipped all but a couple steps. The skeinforge box that is in repG dosen't list Z mm/s in the speed menu . I opened skeinforge standalone, slowed Z down quite a bit, and generated G-code. In replicatorG I opened the G-code and attempted a print, this time the axes acted correctly, but the extruder didnt even try to step. I have the latest mainboard firmware, provided by replicatorG, and V2.2 extruder firmware modified for a seperate stepper board (at work and cant find the name of the author). ReplicatorG gave me some m code errors, and wont extrude in the control panel screen either.

Sorry for the lack of specifics, I'll update anything I'm missing when I get home.


Thanks,
Braden

[00:55:33] Error: Unknown M code: M113
[00:55:33] Error: Unknown M code: M140
[00:55:33] Error: Unknown M code: M141
[00:55:33] Error: Unknown M code: M142
[00:55:33] Error: Unknown M code: M113


I'm looking through the G Code reference page now. The firmware on the extruder is Rick Pollack's patched firmware.

These look OK, I don't have a fancy bed or chamber yet, I think I can ignore these:

M140: Bed Temperature (Fast)
M141: Chamber Temperature (Fast)
M142: Holding Pressure

I'm worried about this one, as I do have a stepper extruder:

M113: Set Extruder PWM
Example: M113
Set the PWM for the currently-selected extruder.

Edit:

The G Code generated by ReplicatorG uses M101 to turn the extruder on and no error is generated, the command has no effect on the machine.


reading more.....

Edited 1 time(s). Last edit at 08/25/2010 05:13AM by Braden Kear.

I think my issue is that I have step / dir from the extruder stepper board wired to SDA/SCL still, and should have them on D9 / D10 of the extruder board.

I'll try this out when I get home later, but I still wonder why Skeinforge used M113 in it's G Code, is there an option somewhere I missed?

Hi

I understand Skeinforge uses some M functions internally even if your firmware does not need them.
You can play with replace.csv in the Skeinforge alterations directory to change the final output in the G code.

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Regards

Ian

Thanks Ian, I'll try that.

In the meantime, I was able to slow the Z feedrate in ReplicatorG's outputted G Code by lowering the max rate in the machines.xml to 75 for now.

Since I fixed one problem, another has arrived! the extruder stepper motor gets HOT! hot enough to melt the PLA of the extruder block.

Changing the position of the stepper board's pot has no effect on the heat of the motor.. hmm...

I'm not sure exactly what fixed it, but the motor runs correctly now!

I pushed another nozzle out of the barrier though will rebuild tomorrow

Now I just need to figure out how to use the skeinforge plugin to find and replace M108 S### with M108 R###

Replacing M108 S### with M108 R###

S (tab) R in replace.csv should do it. Will change all S to R.
For specifics you can I believe put M108(space)S (tab) M108(space)R

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Regards

Ian

Braden Kear Wrote:
> Now I just need to figure out how to use the
> skeinforge plugin to find and replace M108 S###
> with M108 R###

I still haven't tried it yet, but take a look at this rpmify skeinforge plugin: [groups.google.com]

Edited 1 time(s). Last edit at 08/28/2010 06:40PM by gr0k.

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Tony Buser http://tonybuser.com * http://reprap.org/wiki/User:Tbuser#Projects