Braddocks' Grinding UM2 Extruder Thread

[braddock 1]

This is a failed print... due to the all too frequent blocked nozzle. About 7 hours in to a 9 hour print, woke up this morning to the UM2 printing in thin air with nothing extruding, about 5mm above the last under extruded layer. The filament was also worn down at the feeder so the grip wheel was no longer touching it.

It's getting to the point where I'm reluctant to print anything that will take more than a few hours.

I was printing this as one piece, flat bottomed, unlike the grey render you see here. I used mesh maker supports, and it was working well, until, for no apparent reason the nozzle decided to block.

I'm curious to see how experienced users would print this. I'd be happy to share my file if anyone is interested, but I don't want it uploaded on youimagine, or thingiverse.

 

 

[ian 32]

id love to give this one a good braddock if i may.

my email is: ian.spring@gmail.com

Just out of curiosity... have you completley cleaned out your nozzle when hot (240) with a syringe.. really got in their... and then tried a different filament.. I have some blue pla from ultimaker and that for some reason is really not good... but then i also have some gold pla from them and that is printing amazingly.... :-)

if i was you.. clean your extruder fully. and nozzle... change filament... then print slow to start-- maybe 50 with a high temp of 230... that should get you started.. after about an hour when you see your model is printing well... drop the temp down to 220 and leave the fans on 50 percent for the night... should work.. well... works for me anyway :-)

Ian :-)

 

[braddock 1]

Cool, I'll send you a file via hightail.

Each time I start a print, I heat the nozzle to 260 and poke a brass wire bristle up there. I also print my first layers very slowly.

I see you use glue on your bed... quite a lot? I even avoid this as surely the glue must get in the nozzle?

I only have filament from Ultimaker, but might invest in some colorfabb.

Have you adjusted your feeder pressure at all from factory?

 

 

id love to give this one a good braddock if i may.

my email is: ian.spring@gmail.com

Just out of curiosity... have you completley cleaned out your nozzle when hot (240) with a syringe.. really got in their... and then tried a different filament.. I have some blue pla from ultimaker and that for some reason is really not good... but then i also have some gold pla from them and that is printing amazingly.... :smile:

if i was you.. clean your extruder fully. and nozzle... change filament... then print slow to start-- maybe 50 with a high temp of 230... that should get you started.. after about an hour when you see your model is printing well... drop the temp down to 220 and leave the fans on 50 percent for the night... should work.. well... works for me anyway :smile:

Ian :smile:

 

[ian 32]

to be honest the gluestick doesnt go into the nozzle..

also i upped the flow to 103 percent to get a really nice constant flow at 220 temp :-)

Ian :-)

 

Cool, I'll send you a file via hightail.

Each time I start a print, I heat the nozzle to 260 and poke a brass wire bristle up there. I also print my first layers very slowly.

I see you use glue on your bed... quite a lot? I even avoid this as surely the glue must get in the nozzle?

I only have filament from Ultimaker, but might invest in some colorfabb.

Have you adjusted your feeder pressure at all from factory?

 

 

[braddock 1]

I've just had another fail, same reason, but this time I saw what happened, the feeder wheel actually wore through the filament... possibly due to too many retractions?

I've slowed down the retraction speed, and distance, will see if that helps.

 

[illuminarti 18]

Braddock - the part you are printing doesn't look like it would have that many retractions really - it's mostly perimeter, and then I imagine it jumps around to do some of the extra upskin/downskin infills. What speed and layer height are you printing at? Talking of head speed independent of layer height doesn't really say anything about how hard the extruder is working.

All the prints I have done lately have had a ton of retractions - lots of islands of print on each layer due to either the underlying geometry, or lots of added meshmixer supports. One of those average one retraction every 0.8 seconds for 48 hours. And I'm retracting 5.5mm at 35mm/s. And I haven't had the slightest problem with it.

Once the extrusion stops, then there's a risk that the extruder gear will wear a hole in the filament; if the filament stops moving, and the gear keeps turning, something has to give. And then once it's worn the filament it can't grip it any more, so it becomes a chicken-and-egg thing. Theoretically, the extruder current should be set so that it slips and clicks back, rather than abrading. So, three thoughts: 1) is the fan on the back of your print head (still) running all the time; 2) did you tighten/change the tension on the spring in the extruder; and 3) does the bowden tube on the hot end go all the way down to the white part where the filament enters the head, and stay there all the time, or does it pull out any - e.g., during retractions.

 

[gr5 2,167]

1) is the fan on the back of your print head (still) running all the time;

 

@braddock - I had the same thought as illuminarti - make sure this rear fan comes on the instant you power on the UM2 (even before the lights). It should always be on. If not you can get upper head clogs.

My extruder won't grind the filament no matter what I do. This is because the amount of current sent to the extruder stepper is low enough so that it just doesn't have the power. I think your tension is either too high or too low. My tension is set so that the white square on the extruder is near the top - basically at the top. This is how it arrived and I haven't messed with it.

Or maybe your knurled bolt on the extruder is a bit clogged up with material at this point?

If you do an experiment, and heat up the head to 210, and then go into advanced and extrude filament "manually" (meaning using the "move filament" menu option). If you crank it out fast, does the extruder stepper move forward slowly and then skip/click/jump back suddenly quite a bit? It should slip back a lot - something like 1/3 turn. It should never let the filament slip - instead the whole motor should slip backwards suddenly.

 

[illuminarti 18]

Regarding glue on the bed - at first I definitely had issues with glue clogging the head, and I suspect that's what has affected some others too. What I do now is to apply the glue fairly lightly, and then spread it around with a wet paper towel, rubbing the lumps of glue until they are fully dissolved. The solution will dry quickly as the bed heats, leaving a uniform, barely noticeable film of glue that the first layer sticks to perfectly, and still leaves a mirror finish on the bottom of the print.

 

[ian 32]

i know im still learning the tricks of the um2... but i just add a quick dash of glue all around my needed working area.. then leave it for 5 minutes to try a little and then start printing.. my first layers are not totally crushed aginst the glass. so there is about a third of a mm for the filament to flow out and onto the glass. works for me :-)

Ian :-)

 

[braddock 1]

thanks guys.

My rear fan is always on, and I've not touched the feeder tension at all, it's how it was set from factory. There is also the possibility that the ultimaker filaments aren't the greatest quality?

I had the cura retraction settings on:

Minimum travel (mm) 0

combing: off

Minimal extrusion before retracting (mm) 0

So, regardless of how the model looks, it was retracting a lot as it printed the furry sides of the model.

 

 

[braddock 1]

guys, does this tension setting look right? I was using the orange PLA here, using blue now, but getting the same results.

 

 

[Nicolinux 288]

My extruder settings look exactly like yours.

 

[illuminarti 18]

Braddock - I'd be inclined to set the minimal travel distance to 1mm, so that it doesn't retract when moving between lines of infill, for instance. But otherwise everything looks good.

Even so, I'm still surprised that there would be much retraction on the print. The outside texture of the shape should print as several single continuous loops, so the only retraction should be when adding extra thickening infill on the inside of that. Are you printing it hollow, or does it have a grid infil?

 

[braddock 1]

Thanks, no I don't usually print with any fill.

I also print a shell thickness of 1.2 The retraction seems to happen because instead of just printing the perimeter by drawing the outline as you'd expect, it does one or two passes like that, but then does short strokes across the width of the 1.2mm shell... not sure if that makes sense. I'll attach a video, retractions set to 10 mm / second here.

 

 

 

Braddock - I'd be inclined to set the minimal travel distance to 1mm, so that it doesn't retract when moving between lines of infill, for instance. But otherwise everything looks good.

Even so, I'm still surprised that there would be much retraction on the print. The outside texture of the shape should print as several single continuous loops, so the only retraction should be when adding extra thickening infill on the inside of that. Are you printing it hollow, or does it have a grid infil?

 

[illuminarti 18]

Ah, ok... I guess if the surface detail is fine enough, it can leave gaps between the outer loop and the inner ones (where the inner loop won't fit into the bump out of the detail), so I guess it's filling those.

What distance do you have for retraction? I use 5.5mm.

I'd try increasing the retraction speed up to 35mm/s... that means the hot filament will spend less time heating further up the hot end assembly, and might improve reliability. Plus it will make your prints go a lot faster, and mean that the head spends a lot less time stationary, retracting and de-retracting, and remelting/blobbing on your print while it does.

Plus, a faster retraction may be more effective as it gives the plastic less time to flow away from/around the withdrawing filament.

 

[braddock 1]

I've only set the slower retraction speed in an attempt to stop it striping / flattening the filament. Prior to this, I had it set at 35mm / second.

There has to be a reason why my filament strips so often, yet you're able to print thousands of retractions at good speed with no incident?

What brand of filament do you use?

 

Ah, ok... I guess if the surface detail is fine enough, it can leave gaps between the outer loop and the inner ones (where the inner loop won't fit into the bump out of the detail), so I guess it's filling those.

What distance do you have for retraction? I use 5.5mm.

I'd try increasing the retraction speed up to 35mm/s... that means the hot filament will spend less time heating further up the hot end assembly, and might improve reliability. Plus it will make your prints go a lot faster, and mean that the head spends a lot less time stationary, retracting and de-retracting, and remelting/blobbing on your print while it does.

Plus, a faster retraction may be more effective as it gives the plastic less time to flow away from/around the withdrawing filament.

 

[aaronalai 2]

Sorry for the potentially noob question, but how do you change the retraction speed? I see Min travel, combing, and min extrusion before retracting, is there another set of options somewhere?

 

[illuminarti 18]

Several of my tougher prints have been done with Faberdashery, but I used Ultimaker filament on the Joint Stars print, that is pretty retraction intensive. The eiffel tower that I'm still working on is using my own brand filament, and that has handled the even more insane number of retractions just fine, as well.

Perhaps the difference in your print is that you're using three shells, not two as I do. Generally, all my prints have two perimeters, and then added infill on the insides of that for extra thickness. From the video, it looks like a lot of your infill is incredibly short 'dots' of printing to fill in the gaps within the perimeters. Perhaps that is grinding the filament because it is retracting over exactly the same spot each time?

I don't know if that's specific to the size of the surface detail that you're printing, or due to an effect of printing three shells rather than two... but it might be interesting to try with just two shells (I find them still plenty strong enough). Also, another test might be to set the minimal extrusion parameter to 0.02mm, rather than zero, so that it won't retract for all of those tiny fill-in dots inside the perimeters.

 

[illuminarti 18]

Sorry for the potentially noob question, but how do you change the retraction speed? I see Min travel, combing, and min extrusion before retracting, is there another set of options somewhere?

 

On a UM2, the speed and distance of retraction are set directly on the printer. 'Ultigcode' just includes pairs of G10 and G11 commands that tell the printer to retract and de-retract, respectively, and the printer uses its set speed and distance to do so.

On a UM1, the firmware doesn't know about G10 and G11, so the retractions are explictly coded into the gcode as filament-only moves. Therefore, when configured for a UM1, Cura gives additional speed and distance options in the user interface.

 

[braddock 1]

illuminarti I printed the front face piece last night, I used different retraction settings, hence a bit of stringing in the mouth, and the last blob ruined the nose, but other than that, it came out ok.

If anyone is interested in printing this small part, let me know, I'll send it to you.

 

 

[braddock 1]

So, with a 0.4mm Nozzle, does a shell thickness of 0.8 = 2 shells?

Several of my tougher prints have been done with Faberdashery, but I used Ultimaker filament on the Joint Stars print, that is pretty retraction intensive. The eiffel tower that I'm still working on is using my own brand filament, and that has handled the even more insane number of retractions just fine, as well.

Perhaps the difference in your print is that you're using three shells, not two as I do. Generally, all my prints have two perimeters, and then added infill on the insides of that for extra thickness. From the video, it looks like a lot of your infill is incredibly short 'dots' of printing to fill in the gaps within the perimeters. Perhaps that is grinding the filament because it is retracting over exactly the same spot each time?

I don't know if that's specific to the size of the surface detail that you're printing, or due to an effect of printing three shells rather than two... but it might be interesting to try with just two shells (I find them still plenty strong enough). Also, another test might be to set the minimal extrusion parameter to 0.02mm, rather than zero, so that it won't retract for all of those tiny fill-in dots inside the perimeters.

[illuminarti 18]

Yes - shell thickness of 0.8 will give you two loops around the outside of the shape. When I say 'added infill' on the inside, I mean the thing Cura does automatically to thicken up the walls where ever there are slopes - I set the Infill percentage to zero, and the top/bottom thickness to at least 6 times the layer height.

 

[braddock 1]

you mean the "infill overlap (%)"? Do i need to set this if my Fill Density (%) is at 0?

 

[gr5 2,167]

I hate that this thread has been taken over. But anyway: @braddock - I think you need to tighten your extruder just a tiny bit. Rotate the screw head until the white part moves down and then back off a tiny bit. I think yours is so loose that sometimes it slips which grinds slightly and if you have too much retraction it gets worse until it takes a bite out of the filament.

[illuminarti says: The conversation was subsequently moved into its own thread.]

 

[braddock 1]

Thanks gr5 - Yes, sorry for taking over the thread with a trouble shooting issue... will post more pics soon!

Cheers for the help guys.

 

 

I hate that this thread has been taken over. But anyway: @braddock - I think you need to tighten your extruder just a tiny bit. Rotate the screw head until the white part moves down and then back off a tiny bit. I think yours is so loose that sometimes it slips which grinds slightly and if you have too much retraction it gets worse until it takes a bite out of the filament.

[illuminarti says: The conversation was subsequently moved into its own thread.]