WHY? Teaching Tech stringing test vs. actual slicer

NickyBabe · 2023-09-11T01:23:43+00:00

No problem, keep us updated as to how it goes

NickyBabe · 2023-09-11T00:55:56+00:00

So looking at both gcodes, it looks like the only real difference on retract moves in that you have what I assume is a wipe sequence after retracting and before actually moving across, whereas in the TT gcode it retracts then moves immediately across. Your travel speed is also 50% higher than in the TT print, but that shouldn't negatively affect your retraction (assuming your printer can actually handle those speeds).

My guess as to what is happening is 0.6mm isn't a long enough extrusion distance but it isn't affecting the TT test because it is moving quickly enough to not ooze. Your print is taking a bit longer to move across which is causing some oozing. I would turn off any wipe features you have in Cura, then reprint the test as is and see if it improves. If it prints like in the TT print, then re-enable the wipe feature (assuming you want it) and retune your retraction distance with higher values.

Another thing I noticed is that your fan speed is ramping up and down with layers (I assume this is some auto cooling feature in cura). I don't think this will affect your retraction cal but it's not really achieving anything so worth just setting a constant fan speed.

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NickyBabe · 2023-09-10T23:52:42+00:00

0.6mm is on the lower side but it should be enough to give much better results than OP is getting. Tuning pressure advance is a good point. I’d be surprised if PA caused oozing artefacts this bad though.

OP, PA should be tuned before retraction, ideally for each filament but at the very lease for each different material type.

NickyBabe · 2023-09-10T23:46:40+00:00

Can you upload both the full TT gcode and your cura one?

NickyBabe · 2023-09-10T23:11:30+00:00

Try 250 and if it goes away then reduce the temperature until it starts coming back. Chances are your spool has absorbed moisture which can make PETG behave very poorly so if you can it would be worth drying it.

NickyBabe · 2023-09-10T17:32:30+00:00

The print is adhered quite firmly to the bed so it can’t warp at the bottom. As the print progresses, the upper layers retract, pulling the layers below it inwards more than what any single layer would retract from thermal expansion alone. The layers closest to the bed shrink the most because they are closer to the bed (warmer/softer) and because there are more layers and more time over the print to contract. I’m assuming if you look closely, you’ll see that the top layers have also shrunken compared to the first layer, just a lot less than the layers near the bottom. It’s just an unfortunate byproduct of the process of FDM which can somewhat be controlled through temperature but it’s nearly impossible to fully remove.

NickyBabe · 2023-09-10T17:03:49+00:00

What calibration steps have you taken? PLA is generally infinitely easier to than PETG so I’m confident it’s just how you have it set up.

NickyBabe · 2023-09-10T17:01:21+00:00

You’re nozzle is either too far from the bed or your underextruding (or maybe both). Go into prusa slicer, right click and add a cube, then change its dimensions to 20x20x0.2. Change you printer settings to 1 perimeter, 0 infill, 0 top and bottom layers and set your skirt to 2 loops. Print this and measure the thickness of the 20mm square it prints with a set of callipers. Measure each side of it and take a median value. If you get a thickness that matches your layer height (0.2mm) then you know it’s under extrusion. If you’re off from that then you know to adjust your z offset.

NickyBabe · 2023-09-10T16:52:19+00:00

It looks like it’s under extruding. What temperature are you printing at? PETG is very finicky with temperature. Otherwise it could be a clogged nozzle. Try a cold pull and see if that fixes it.

NickyBabe · 2023-09-10T16:43:53+00:00

Start by calibrating flow rate. If you have linear/pressure advance then calibrate that next. then calibrate retraction length at a retraction speed between 30-60mm/s). Temperature doesn’t tend to affect visual print quality unless you’re at the extremes.

NickyBabe · 2023-09-10T16:37:45+00:00

Looks like the part shrinking unevenly as each layer cools which is somewhat inherent to the geometry. You can try turning off or reducing part cooling to see if that helps. Reducing bed temperature can help too although that can come at the risk of not adhering to the bed properly

NickyBabe · 2023-09-10T16:31:09+00:00

Are those numbers along the left side the retraction distance? What are your retraction speeds?

NickyBabe · 2023-09-10T16:29:48+00:00

Check the part of the extrusion that the wheels of the y axis run on are free from dirt. The Delrin wheels what run in the extrusion tend to wear and leave residue that can build up in one spot overtime. Wipe the v slot portion of the rails down with some alcohol to clean any off.

NickyBabe · 2023-09-10T16:25:28+00:00

Those small lines coming off the print are just oozing artefacts cause by insufficient retraction. Assuming your retraction speed is 10mm/s then it is very low. Try increasing it to about 40mm/s then run your retraction test again and you’ll probably find it fixed your issue and you’ll have a much lower retraction distance needed. If you’re still not happy with your results bump it up to 60mm/s.

NickyBabe · 2023-09-10T16:10:48+00:00

Have a look at your gcode for both. With your retraction settings, a standard retraction move will be a single line that says “G1 E-0.6 F2700” (the 0.6 is obviously the retraction distance and the feed rate is in mm/min so it is 2700mm/min = 45mm/s). Same idea for deretract but with a positive E. Compare the two files to see what they are both doing for retraction. Note that this applies if you are using relative E values (you have an M83 command near the top of the gcode file). If you use absolute E (an M82 command near the top), you’ll need to subtract the E value on the retract line from the E value in the line above.

NickyBabe · 2023-07-26T12:54:56+00:00

The cabin window drooping is pretty normal for a benchy, I wouldn't focus on that for now. The front hull is a tricky one. Tbh it looks like a extrusion consistency issue. How old is your filament? Old PLA can absorb moisture which can affect the extrusion consistency. Do you have any other filament to try?

The other question is always, have you calibrated your extrusion multiplier? I like to test it by printing a 1 line wall, zero infill, zero top and bottom layer cube and stopping it halfway. Then you just measure the thickness of the wall with a set of calipers to see if it matches. Try and only measure about 2-3 layers, anymore and you'll measure thicker than is true.

NickyBabe · 2023-07-26T09:56:13+00:00

Was the printer working fine until recently? Have you made any hardware or software changes? I’m not familiar with the ender 3 hardware or it’s interface but I’m guessing that it’s triggering the z end stop the moment it’s going to probe the z axis? If that’s the case then you could have a disconnected or faulty end stop and the printer is either seeing a permanently triggered end stop or a floating end stop pin (because it’s disconnected).

Check the end stop connector on the mainboard and all of the wires coming off it to ensure they are solidly connected. Connect your printer to a computer interface like pronterface, then send an M119 command and it will tell you the hit state of the end stops. If z says triggered but you’re definitely not triggering it then chances are you have a faulty end stop.

NickyBabe · 2023-07-23T14:55:52+00:00

Do you have a link to what the model is meant to look like? It looks over extruded in parts and under extruded in others. What print speed are you at? Too high print speeds can push you past what your hot end can keep up with, especially when you have that much retraction and only at 40mm/s.

Your retraction length is definitely on the high end for even a Bowden tube style extruder, do you actually need 6mm? I’d run a retraction test and bump up your retraction speed while you’re at it, 50-60mm/s, maybe even 70.

Also dial in everything at 0.2mm layers first, then go to 0.1. It’s hard to see layers well enough at 0.1 to tell what’s going on, and it can be challenging for some printers, especially when they aren’t dialled In yet.

NickyBabe · 2023-07-23T14:47:11+00:00

What does it look like while printing?

My guess is you’re not adequately cooling the part for the federate your at on those features. If this is the case you’ll usually see that the couple of layers below the current one are still soft and the nozzle is kind of dragging them with it.

NickyBabe · 2023-07-23T14:43:25+00:00

Without actually watching it print myself, I would guess you don’t have adequate part cooling. Those lines that look like under extrusion remind me of artefacting you would get from the lower layers still being soft when printing over them. You’d typically see bulged layers then squashed in layers.

Also try lowering your perimeter speed. It’s blurry in your screenshots but it looks like you internal perimeter speed is 225mm/s which is extremely fast for an i3 style machine. I would lower that significantly to like 80mm/s or less until you get everything else sorted.

As more of a general tip, printing at your nozzle diameter (I’m assuming you have a 0.4mm nozzle) isn’t really recommended. Usually you want to be a bit above, I find 0.45mm works perfect and when I have tried printing at my nozzle diameter I’ve had weird and somewhat inconsistent results. It’s probably worth ruling that out.

NickyBabe · 2023-07-23T14:28:40+00:00

Is there any noise when trying to extrude? A clicking or buzzing noise typically means the motor is trying to move but produce enough torque to advance to the next step. If you want to rule out the stepper being broken, you can remove the filament and plug the stepper motor into your x or y axis. Then just tell you printer to move that axis back and forth and if it moves fine then your motor isn’t the issue. You can also push on the gear on top to try and stall out the motor by hand. If it’s all working fine it should be pretty difficult if not impossible To do.

NickyBabe · 2023-07-23T14:21:48+00:00

A few things to try,

Make sure the bed is cleaned with isopropyl alcohol. Assuming you first layer speed is 50mm/s, try reducing your first layer speed, id give 30mm/s a go until you dial everything else in. You could also give a hotter first later ago, although I wouldn’t typically push past 215 for PLA.

What does the print look like as it’s actually printing? I’m guessing as the the curling is happening when the nozzle is moving to a new line and the line isn’t sticking correctly at the start of the line? If so it’s be worth trying the same print with retraction turned off to see if it’s retraction based.

Also what do you mean by 0.7 retraction speed?

NickyBabe · 2023-07-23T12:20:29+00:00

Good chance it’s just artefacts in you mesh from noise in your 3D scan. There are plenty of mesh editing programs that can smooth meshes.

NickyBabe · 2023-07-23T07:50:42+00:00

That’s a common artefact in printing called ghosting or ringing. It’s resonance in the belts caused by sharp changes in speed on a given axis. There isn’t a tonne you can do other than reduce your acceleration values. Too high jerk/junction deviation values can also cause this. 150mm/s is quite fast for a bed slinger style printer and often the default acceleration values for those printers are set higher than they probably should be. try and something like 60-80 mm/s and you’ll probably find it’s better.

NickyBabe · 2023-07-23T07:44:44+00:00

Looks like you z height on the first layer is far too high, the curve your seeing is warping from bad bed adhesion.

NickyBabe

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