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Extruder G Code hack for more torque

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Posted · Extruder G Code hack for more torque

I have one of the original UM2 printers - 6-7 years old.  Several of these printers, like mine, had/have issues with the extruder skipping when the torque threshold is exceeded.  I seem to remember there was a g code hack to set the torque limits higher. 

 

I think it's just cut and paste to modify the code, but I've never done it, so baby instructions please.  Is there a "way too high" value?  How about a plugin that will make this change so I don't have to remember.

 

I typically print at .2mm height, .4mm dia, and 40mm/sec.  I think that's 3.2 mm3/sec.  For faberdashery PLA I set the temp at 240C.  The extruder will skip some at lower temps - usually at the worst location.

 

This leads to another question - how fast should I expect?  I know the answer is "it depends," but this rate seems low for objects where the final quality isn't critical.

 

Thanks

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Posted · Extruder G Code hack for more torque

I don't recommend it but you can mess with the current.  Generally higher current means higher torque but not if the stepper driver gets too hot in which case higher current then means lower torque.

 

So M907 sets the current for all the axes.  This is the default, sets E axis (extruder) to 1250ma.

M907 E1250

 

So you can (for example) up it to 1300 ma with M907 E1300.  Or lower it to 900ma with M907 E900.  You can insert this in the gcode wherever you want the current to change.  The current will be remembered at the new level until you power off the machine.  If you want to save it more permanently add M500 which saves this setting to longer term memory on your printer.

 

But why do you want to up the torque?  It's skipping a lot - well have you changed the teflon part in the last few years?  You should be changing the teflon part every 500 hours or so - check your printing hours in the menu system on the printer.  As that teflon gets old the extruder has to work harder and harder until it starts skipping.

 

Or maybe you are just printing too fast for your extruder.

 

Or you could upgrade to the "plus" to make yours a UM2+ printer.

 

Or you could do the meduza upgrade (I sell a $19 kit but only if you are in USA).  The meduza upgrade and also the "plus" upgrade increase the feeder torque by 2X and it's a great upgrade.  The "plus" upgrade costs around $400 USD but you get some other nice bonuses.

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Posted · Extruder G Code hack for more torque

Why does everything have to be so hard . . .

 

In the pic you see a recently failed print.  The lower levels were nearly perfect.  There is a section with a skip below the t on the build plate.  When the print got to the upper layers, the ones with more retractions for nozzle jumps, there are way, way more extruder skips to the point where I terminated the print.  When I discovered the skips I slowed the speed to 50%, so it was at 1.6 mm3/sec.  I did have the "retraction prime extra amount" set at 3mm3 to compensate for the blob that oozes from the nozzle during a retraction move.  If I can make the temp about 220C, that blob more or less goes away.  I will retry with the value set to 0.

 

I have not replaced the teflon part in a long time and have used a 1/8" dia drill bit to reshape the hole.

 

I've been printing for 6 years now, m/l.  At this point, it still feels like every print is an experiment.

 

Here's hoping you have plenty of TP.  If not, I can box up some corn cobs from Iowa to send your way.

 

IMG_4979.thumb.JPG.54d51a45f1a48682a05df52b34e9b71e.JPG

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Posted · Extruder G Code hack for more torque

Definitely replace the ptfe part.  I'm sure you've done more than 500 hours in the last 6 years or so.  People who use their printers every day replace them typically every 3 months.  Drilling it out while under pressure (while in the head) and very carefully, is a good way to extend the life long enough while waiting for your shipment to arrive.

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Posted · Extruder G Code hack for more torque

After changing the "retraction prime extra amount" to 0, the next print turned out perfect.  I did have to set the flow to around 2.5mm3/sec and the temp to 240C, but it worked.

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Posted · Extruder G Code hack for more torque

You have massive underextrusion in the photo.

 

Yeah it's the flow, not the extra prime.  Well you shouldn't be doing extra prime - I suppose that could cause the extruder to skip a bit.  I just tested an original UM2 with original feeder (but new bowden and new teflon) and it was able to do 10 mm^3/sec with no underextrusion.  It could do 16 mm^3/sec with slight underextrusion (about 10% - very thin cracks between infill lines).

 

Change the ptfe.  It will change your life, lol.  Oh wait - I think you just ordered one from my store.  I think you will be pleased.

 

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Posted · Extruder G Code hack for more torque

Thanks for the help. 

 

Right now I am printing the 3 parts for the extruder upgrade.  I changed the setting "optimize walls," (or something like that,) to on.  It eliminated a lingering question I have always had, "why does Cura jump to a circle and print one wall section, then retract and jump to another circle and print one wall section, then jump to the outside wall and print one section, etc, etc."  After turning that on, it will print all sections of a wall, then go to another location and print those walls.  This saves a lot of retraction/jump moves and seems to make it all run better.

 

I also turned combing to "all" vs "none."  With these changes I get awesome results and can print way faster.

 

I still don't understand combing.

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Posted · Extruder G Code hack for more torque

On a side note, I work in the maintenance dept for a major food manufacturer.  They trust me with their multi-million dollar cereal packaging equipment, some of which is extremely technical.  I am frustrated by the help features offered by the manufacturer.  The description of the functions were written by the engineers who designed and programmed the machines - they totally understand how it works.  I wish they hired a farmer to write the descriptions - dumb it down a little.

 

I wish the folks who write the Cura help descriptions did the same thing.  Maybe add a pic to describe what a feature does.

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