Retraction and Extrusion problems.

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Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Sun-12-Jun

HELP!! My Printrbot Simple Metal hates me! It prints beautifully when I'm printing parts that don't require a lot of retractions. Calibrated to a T, everything comes out to perfect measurements, etc. No bet adhesion problems either, I'm using Buildtak with a heated bed (for PLA) and it works really well.

My problem: Whenever a part requires lots of retractions or short burst of prints between retractions, things come out like junk! It feels to me from looking at it while it's printing, that it either retracts too early, or isn't primed right when starting printing after a retraction. For example, i'm printing the attached fan holder. Where the screw holes are, it only prints about half the circles before jumping away to the next hole and dragging a bit of ooze along the way. That would seem to indicate it's not extruding enough, but when it starts printing again, it's missing a bit of plastic, as if it didn't start extruding fast enough.

DSCF6262__1__preview_featured.jpg


Kind of hard to describe. Another example is the attached carrier. The base prints beautifully and is really solid (aside from the mess it makes with the screw holes). When it gets to printing the "pillars", it needs to retract, extrude, retract, extrude very quickly. The missing plastic makes the pillars just disintegrate either while printing, or when touching them once printed.

Screen Shot 2016-06-19 at 1.09.20 PM.png


Any idea
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Retraction and Extrusion problems.

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Re: Retraction and Extrusion problems.

Postby Mooselake » 2016-Jun-Sun-16-Jun

What kind of hot end are you using (ceramic ubis, metal ubis, something else)? What are your retraction settings; speed, distance, and acceleration?

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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Sun-16-Jun

Sorry, Kirk, should have specified. E3DV6 (not Lite). 1.75PLA, Retraction speed is 40mm/s, distance is 1mm (E3D recommends 0.5-1mm IIRC), acceleration... ??? Can't find this setting in Cura... Or would that be somewhere in the M501 output?
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Re: Retraction and Extrusion problems.

Postby RetireeJay » 2016-Jun-Sun-19-Jun

Yes, the acceleration setting is in the M500 series, i.e. stored in EEPROM.

Overall, it looks like you are fairly significantly under-extruding. Check your Extruder calibration (steps per mm); if you find it needs changing, put the correct value in EEPROM. Check your actual filament diameter with a digital caliper if possible (take the average, it's probably a bit oval); if you find it's not exactly 1.75, put the correct value into Cura (or Slic3r, etc). Check that you have not over-ridden the default trace width, i.e. normally you specify "0" and let the slicer (Cura, Slic3r) decide how wide to make the trace based on your actual nozzle diameter (also a setting in your slicer). All of these settings and calibrations have been discussed at length in this forum, so if you aren't sure how to do it, use Search.

Here are my settings for acceleration and jerk. In my slicer, the "retract speed" is set to 500, although it's actually limited to 30 by the EEPROM settings.
Code: Select all
echo:Maximum feedrates (mm/s):
M203 X125.00 Y125.00 Z5.00 E30.00

echo:Maximum Acceleration (mm/s2):
M201 X400 Y400 Z30 E10000  //originally X & Y were 4000

echo:Acceleration: S=acceleration, T=retract acceleration
M204 S4000.00 T4000.00

echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s),  Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)
M205 S0.00 T0.00 B20000 X5.00 Z0.40 E5.00  //originally X was 20
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Sun-20-Jun

Thanks Jay, I'll check all that tomorrow night, I've gotten too frustrated tonight and need a break!!!!
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Tue-11-Jun

Oh boy! First print in progress after changing my acceleration and jerk settings. WHAT A DIFFERENCE!!! For the first time, I don't fear finding the printer in the next room because it shakes so much. Details appear to come out beautifully. Update to come when I get to the tricky parts!
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Wed-16-Jun

Looky looky what I printy!!!

Still have a few problems with screw holes on the first layer (seems to be more and adhesion problem) but overall, the acceleration and jerk settings have helped tremendously...

Jay, may I ask what your retraction settings are with your current setup?

1.jpg


2.jpg
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Re: Retraction and Extrusion problems.

Postby RetireeJay » 2016-Jun-Wed-17-Jun

Just based on what others have said when using E3D or metal Ubis, I'm limiting my retraction to 0.5mm or less. Different plastics have different tendencies to ooze, so you just have to experiment and use what works for you with your plastic, your hot end, and your fan setup.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Wed-20-Jun

Thanks Jay, that's what I have been using. More experimentation I guess!
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Re: Retraction and Extrusion problems.

Postby Mooselake » 2016-Jun-Thu-14-Jun

Experimenting is the best part!

First layer holes are usually small due to first layer "smoosh". Actually they're always small, has to do with slicers not understanding that holes are actually round and not polygons. stl files don't have a true circle since they're made up of triangles, and the only slicer I've used that recognized polygon holes and converted them to arcs was slic3r - and they removed the conversion since it was buggy.

Marlin supports G2/G3 arcs, although Tim has said they are still converted into larger than stepsize segments internally (implementing arcs properly means that they're polygons with stepsize lines). I haven't looked recently to see if/how smoothieware (Hi Arthur) does them. The new cheap Monoprice 3D printer uses an ARM based controller board, there's absolutely no information available on the firmware, which will definitely have the resources to do arcs (and lots of other things). OT, but It has built-in wireless (reportedly you need to flash the latest firmware from the boards manufacturer) and a color LCD, not to shabby for $200. I'd buy one for the kid if a thingybot wasn't imminent.

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Re: Retraction and Extrusion problems.

Postby RetireeJay » 2016-Jun-Thu-14-Jun

Speaking of holes, I made an interesting discovery the other day. A single small object with a single small-diameter hole (3mm or so) in fact created a smaller hole than a somewhat larger object with four identically-designed holes! I think beyond the previously-discussed points of the geometry of polygons vs circles, the phenomenon of "die swell", the tendency of materials to shrink in length as they cool (thus decreasing the diameter, wanting to shorten arcs) there is ALSO some "squish" of the previous partially-cooled layer that varies depending on how long the previous layer has had to cool before the next layer is laid down upon it. No wonder that the makers of the $100 000 and up industrial machines - machines whose models "never warp" and "never have problems with bed adhesion" - still say that if you want a precise hole in a printed part, then print it very slightly under diameter and drill it out to the desired diameter.

We can experiment, and with enough patience and enough material we can in fact print a hole that is an exact fit - but that's only valid for that particular part (with that particular spool of material, with that particular hot end and nozzle, when the moon is full and your favorite sports team won their last game.)
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Thu-14-Jun

Interesting thoughts guys. My biggest problem with holes is not that they are small, it's mainly that only half of them gets printed. Like the printer moves away before it's done, or extrudes "nothing" for the first part of the hole. This is mostly a problem on first layers, which requires constant monitoring to make sure the head doesn't catch any blob. After that, everything is awesome for the remaining layers... :-/
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Re: Retraction and Extrusion problems.

Postby Mooselake » 2016-Jun-Thu-14-Jun

Do you use a skirt, and maybe prime the extruder in your startup gcode, to get things moving properly? The other thing that comes to mind is retract/detract (or whatever you call the recovery) imbalance. Slic3r has a config option to add a bit when recovering after a retract, but it shouldn't be necessary.

Watch when the holes get printed. Is it before anything else, or does it do the perimeters first? If the holes are first then you definitely want to do some priming (raise the carriage in a convenient spot, called a dump zone, and extrude 10mm or so). Somewhere here are some examples, including my startup code, that'll get you going.

Kirk
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Thu-14-Jun

Yep, I do use a skirt, 8 full spins around the model before it starts printing. I can see the same effect when it starts printing the skirt, it takes a few mm (5, 10?) before the plastic comes out (even though I prime the extruder in my gcodes with a 15mm extrude before I start printing). Once it's done with the skirt, it starts the perimeters, which the holes are part of from what I can see. Then it fills in the first layer. I had a video on facebook which I can't seem to find the original anymore. I have a part finishing printing in an hour, I'm starting another one after, I'll make a quick video as I can't really describe it properly!
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Thu-15-Jun

Edit, found the video. Low quality but I think it shows the issue pretty clearly at the end...

https://youtu.be/SuMZa0YM-YU
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Re: Retraction and Extrusion problems.

Postby RetireeJay » 2016-Jun-Thu-15-Jun

What that brief video shows is circles that look incomplete because the plastic is not sticking well enough to the bed. So what should be a circle looks like a capital letter G, for example. There are dozens and dozens of posts about improving bed adhesion - but the first place to check is your vertical clearance between the nozzle and the bed.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
User avatar
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Re: Retraction and Extrusion problems.

Postby Mooselake » 2016-Jun-Thu-16-Jun

Beat me to it; getting the ham radio camper ("Hamper") ready for amateur radio field day. Found a great way to attach the camo mast to the hamper so I can push it up without help, got it up 44 feet without help or extra support (hint, fits nicely inside 2" sch 40 PVC, which fits nicely inside 2 1/4" exhaust clamps), plus a not so great way to disassemble it (don't hold the mast sections so they stop at the top of the pipe while pulling them off the next to bottom piece, seems they want to fall over without any support, Best to learn that without an audience...

I'd second RJ; looks like there's a little blob at the start of the hole in the lower right, then as the head moves to the outside it drags part of the hole perimeter with it.

Besides improving stick (drop the head a bit with the Z offset, try 0.05 or even 0.1 mm drops, add some of the all timey favorite glue stick) you can also increase the number of perimeters so you get more area to hold on to the bed.

Kirk
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Thu-21-Jun

I'm already at +/- 0.05 between dragging on the bed or not... microsteps it is I guess! I will try the gluestick option too... I thought Buildtak was the be-all-end-all-solution!
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Upgraded to heated bed + XY extension from Matrix Precision
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Re: Retraction and Extrusion problems.

Postby RetireeJay » 2016-Jun-Fri-08-Jun

You can lay down a small sample first layer only and then measure its thickness. It definitely needs to be less than your nozzle diameter, and probably in the ballpark of half the diameter or even a little less.

Another thing is cleanliness. Surface condition is a key determinant in all kinds of adhesion. Maybe BuildTak is great, but if it's not clean it's not going to work. Use Isopropyl alcohol to clean your surface.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
User avatar
RetireeJay
My next printer is...
 
Posts: 4915
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Re: Retraction and Extrusion problems.

Postby ChinookTx » 2016-Jun-Fri-13-Jun

Yep, I keep a spray bottle of isopropyl alcohol and clean the bed before each print.

I have enabled 9 point auto-leveling in the firmware today, it seems to make a bit of a difference but still not perfect. I'll get there! ;-)
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Upgraded to heated bed + XY extension from Matrix Precision
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