nozzle hitting print
I kept hearing a dragging noise and I believe it's the nozzle dragging against cooled plastic. You can see it in the video when the print head moves forward and back and you can hear it as well. You can see the print literally getting pushed a bit as well.
I switched filaments and I was trying to do an EM calibration with petg. This is the built in orca flow rate. Everything looks great until it starts to print internal solid infill on layer 4. The settings are pretty close to the default for petg but it appears that the infill doesn't lay down all the way and then the nozzle starts knocking off chunks of semi hardened plastic 🤷♂️. I've turned on zhop on when retracting but that doesn't seemed to help much.
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Is the printer enclosed?
it is, but the video is PLA with the top and door off and the EM patches were PETG also with the top and door off.
The video with hitting the print could be overextrusion
The EM patches I have no idea
It looks like the top right one is fine?
Yeah the picture was taken before the top right one was done on that layer. I switched to using Ellis' em cube and setting it up as described. I can consistently reproduce the first layer of infill not completely printing and then the second layer of infill goes to hell. Here's a video
This first infill layer in the video was actually pretty good but it still didn't matter come that second infill layer
Can you try the same again where you drastically reduce the infill speed?
My printer is not really well calibrated and balanced, but I print nowhere near that infill speed
Maybe 20% of that
These are my very conservative settings for ABS
So my original settings were 120mm/s for outer wall and pretty much 200mm/s for everything else. I've printed ABS really well with these setting, but I took your advice and slowed it down to half that for the sparse and solid infill. I think I missed a setting and the whole second solid layer printed at 200mm/s still but still comes out looking great. Videos incoming. Slowing it down did have an effect, it took till the third layer before it failed this time 😔.
Second layer going down well at 200mm/s
First layer of infill went down well, this is the second, slowed down to 100mm/s. It still missed some extrusion in the far right corner if you watch closely.
Third layer of infill was garbage. I let it run a little longer and it literally looks like it completely stopped extruding anything.
Here's where it looks like it completely stops extruding. This should be a solid layer.
Just for fun I switched back to ABS and printed the exact same cube with all the same settings, just changing the filament to my settings for ABS. Here's after the last layer of infill, the first layer of internal bridging going down. Much cleaner.
And here is a much higher layer but you can clearly see when the layer is done, the line made in the layer as the nozzle drags across it
Here's a picture of the end cube printed at 200mm/s in ABS. The top is pretty slick to the touch.
I really think youre printing waaaaay too fast. Im not saying you can never print 200 mm/s again, but try PLA and PETG at like 50 mm/s max, and see if it improves it
And in your last photos I would still say youre overextruding
I hear what you are saying and I'm not saying your wrong. Take what I'm about to say and help me understand where I might be thinking about it wrong myself.
The default speed in prusa for normal printing on a vcore, for infill is 160mm/s, and for HF its 230mm/s. The default in OrcaSlicer is 200mm/s. I also ran max volumetric flow tests on the ABS filament and my conservative flow rate for that filament is 24mm^3/s. Given a 0.4mm nozzle and a 0.2mm line height, that's a max speed of 300mm/s conservative. I'm doing 2/3rds that speed.
For the ABS print you see above that "looks" over extruded, according to Ellis' guide "The best method I have found is purely visual/tactile." for tuning EM. This top is slick to the touch. Dragging a fingernail across it, it feels smooth. One angle is harsh and yeah it looks over extruded, but it looks slick in the other direction and it is smooth to the touch. I just took a nozzle cleaning needle and pushed it point first across the top, across the grain of the layer lines and it glides across the top like's it's been sanded.
And if the ABS is overextruded and doesn't fail with the same issue the PETG is does, then overextrusion isn't the reason the PETG is failing. And none of this explains why the nozzle is contacting the print surface.
Okay things that I know can make nozzle hit print surface:
- Overextrusion
- Thermal expansion of bed
- Thermal expansion of nozzle
- Gantry bending down from bimetal effect
If youre not printing in an enclosure, the bimetal effect should be minimal
The thermal expansion of nozzle and bed can be tested by just preheating for a while
And Im not saying youre wrong in that your printer SHOULD be able to print at those speeds, but I still think you should test if there is a speed that can consistently make a nice print
The reason I keep saying overextrusion, is that my own EM tests I did a few days ago, ended up with a too large EM by visual and touch inspection
I started with a 0.94, and have been steadily decrementing it to around 0.87 before finally no nozzle lines on the print
And the surface still looks great
I cant say Im any expert on the subject, and hopefully someone comes in here and corrects me
The print speeds can be explained by differences in filament. My own ABS is recommended with a max print speed of 50mm/s (I know this also depends on nozzle size and layer height and stuff)
A volumetric flow test does not test retraction, fast moves and acceleration, etc
And if youre happy with your EM, you can do z-hop while retracting to make sure the moves doesnt hit the previous layer
I appreciate the response. I gotta say though that 0.87 sounds super low to me but if it works I guess it works. For the PETG that is failing, I'm literally doing em patches to figure out what em to use and I can't get those to print to even know if I'm in the right ballpark. And as far as zhop is concerned, hat's the crazy thing. I have zhop turned on now.
Yeah I had to google if others had to go that low, and I checked my extrusion steps, but apparently is not uncommon
Check if theres a filament override for z-hop that you havent noticed
I slowed it way down. Down to 50mm/s and I'm still getting the same failure with petg
Obviously I have no idea whats wrong, but Im curious
Have you tightened the couplers from the motor to the lead screws?
Also it maybe important that the coupler is a specific orientation to the motor pin?
And if youre not sure if its a measurement error with the z axis move commands, try a larger distance and see if the error is the same
Like first go 50mm, then 50mm more
And if the error is still 0.1-0.4mm, maybe its a measurement error
I cant think of anything that would explain why the lead screws random rotates MORE than expected
Except a loose connection?
Thanks for the thought work. I'll definitely double check some of this tomorrow. I'm pretty sure I tightened them but it wouldn't hurt to verify. I might also pick up a real dial indicator gauge and rule out any human error from my measurements.
And if possible, check the travel distance on each of the lead screws separately, if its one of the motors, it cant possibly be all of them
So I tightened the couplers, oiled the lead screws, etc. Thought about what you said about it not being all the z motors the same and decided I'd home, z tilt, send it to z = 395, then z tilt again, rinse and repeat. Thinking I'd see one get way off but that never seemed to be the case. I heated the bed and started all over and still nothing weird. But I noticed that the PETG settings had the fan off for the first 3 layers and my big failures are happening at layer 4. Printed a cube and saw the failure at layer 4, changed the fan to not come on till layer 5 and changed nothing else. It printed all the way to layer 6 before the failure. Why would the fan coming on make the extruder stop extruding?
Layer 4 failure
Layer 6 failure
I just tried manually turning up the fan 20 percent at a time and hitting the extrude button in klipper. It's fine up until 80% and then it slows down a lot. At 100% it barely moves and I can hear the extruder grinding slightly (hard to hear over 100% fan though).
I finally got all the way through a single cube. I had to set the fan speed to min 20% and max 60%. The outside edges don't look great so I'm going to try pushing the max up to 70% and maybe setting the min back to the default of 40%. At least I can get through EM calibration now hopefully. I can still see the nozzle dragging through the top surface a bit, but I thought that was related to this failure and it doesn't seem like they are related. I guess I need to play with my zhop settings more.
Is it the stock 4028 fan from the kit?
Solution
Because I had to set it to 10% min, 30% max for my PETG prints
I later replaced it with a 24V 4020 fan, that I could connect directly to my toolboard, since I didnt need the full cooling the 4028 provides anyway
Yeah it's the 4028 from the kit but I'm also running the beta 2 toolhead upgrade if that makes a difference.
I think my cooling ducts are a lot different.
Hmm I dont have the new toolhead, but are you using the UHF sock?
The sock on mine is a lot further down
normally the uhf comes with 2 socks, a regular one and a long one for UHF
Yes, and it looks like hes using the short one
Interesting. I didn't realize they were different lengths. I thought it was just a spare 🤔. I'll have to play with that
I got some EM cubes printing. Between the fan speeds and the sock change I think my original failure is fixed. It wasn't due to the nozzle dragging, though it is doing that still. But I can print PETG now which is a huge improvement. Thanks!
Glad you got it fixed, and thank god it wasnt some problem with the z motors or z screws