Extrusion slows and stops at a predictable point
Still tinkering with my extruder. Ever since my third print, Nefertiti, failed to produce a head I've had extrusion failures at predictable points. A nozzle change resulted in a slightly drunk Benchie but even that failed at the tip of the stack. At around the 30% point of producing the Benchie extrusion slows, then stops, and the feed mechanism just keeps clicking and the filament doesn't move.
Removing the filament reveals a little mushroom head where it appears the tip was impacted from a blockage. Tightening the long spring tensioned screw does not help the feeding. I've read that this could be do to heat creep softening the filament where it feeds, but even lowering the PLA temp to 200C produces the same problem at the same place.
Has anyone had this problem before?
RE: Extrusion slows and stops at a predictable point
Any chance the extruder motor is getting very hot?
RE: Extrusion slows and stops at a predictable point
Any chance the extruder motor is getting very hot?
Not according to the temperature sensor. It stays at exactly where I set it, at either the default 215 or the lowered 200. What bothers me the most is that it previously produced a perfect SD card provided vase; it's beautiful and amazing.
I'm going to verify the PINDA probe height when I get home. I wonder if it's too low and creating nozzle backpressure.
RE: Extrusion slows and stops at a predictable point
Maybe it's the filament sensor: https://www.reddit.com/r/3Dprinting/comments/9d79i5/my_printer_simply_refuses_to_extrude_anymore_and/
Will adjust PINDA first.
RE: Extrusion slows and stops at a predictable point
I mean the stepper motor, not the heater block.
RE: Extrusion slows and stops at a predictable point
I don't know how I'd know for certain without a temperature reading. I've not touched it to see how it feels but have no reason to believe it's the motor. How hot is too hot? Why would it only overheat now after successful prints? Solutions? etc.
The motor seems to work fine as evidenced by its attempts to feed and the impaction at the filament tip. It will also fail to extrude manually after extrusion failure requiring removal and clipping. Initial manual extrusion works fine, but not once the gears start slipping.
RE: Extrusion slows and stops at a predictable point
If the motor overheats (>50°C), it'll still work and turn fine, however, it'll also heat up the extruder gears and that'll soften the filament between the gears to the point it starts slipping. This typically happens when the springs on the extruder door are tightened too much - the motor has to work harder and heats up quicker. You can check how hot the motor is by holding a hand on it.
There can be other reasons, including the heat creep through the heat break, when for example the cooling by the side fan is not enough, when printing PLA in an enclosure or when a print has many retracts, but that usually happens with very low melting filaments only. Or there can be debris in the filament path, PTFE shavings being the worst.
The way you describe it, always failing after a certain time, points to the motor overheating as the most likely one.
RE: Extrusion slows and stops at a predictable point
Without a photo to go by - wild guesses as to why a print is failing will probably not get a solution.
With the stock sample files, the extruder isn't being stressed enough to cause filament deformation at the BondTech gears, which is what a hot motor can cause. While possible, it probably isn't that reason in your case.
Post up an image - use drag and drop and be sure to select Link to: Media File is the lower right of the post screen.
If you have calipers and the end of the filament you've pulled is 2.2 mm... you may be fighting the infamous Prusa Custom Heat Break issue.
RE: Extrusion slows and stops at a predictable point
Heat break induced jamming ... filament looks like this when unloaded.
RE: Extrusion slows and stops at a predictable point
Posted by: Vojtěch
If the motor overheats (>50°C), it'll still work and turn fine, however, it'll also heat up the extruder gears and that'll soften the filament between the gears to the point it starts slipping. This typically happens when the springs on the extruder door are tightened too much - the motor has to work harder and heats up quicker. You can check how hot the motor is by holding a hand on it.
There can be other reasons, including the heat creep through the heat break, when for example the cooling by the side fan is not enough, when printing PLA in an enclosure or when a print has many retracts, but that usually happens with very low melting filaments only. Or there can be debris in the filament path, PTFE shavings being the worst.
The way you describe it, always failing after a certain time, points to the motor overheating as the most likely one.
Thanks. So things I’ll try will be adjusting the PINDA and loosening, not tightening, the extruder door spring. >50C should be pretty obvious to the touch. There’s no enclosure, yet, but I’ll likely only use one with a more sensitive material. I’ve only used PLA so far, and a single wobbly Benchy did print after replacing the nozzle. What helped during other attempts was to uncoil the filament so it didn’t have to pull the spool.
Posted by: Tim
Without a photo to go by - wild guesses as to why a print is failing will probably not get a solution.
With the stock sample files, the extruder isn't being stressed enough to cause filament deformation at the BondTech gears, which is what a hot motor can cause. While possible, it probably isn't that reason in your case.
Post up an image - use drag and drop and be sure to select Link to: Media File is the lower right of the post screen.
If you have calipers and the end of the filament you've pulled is 2.2 mm... you may be fighting the infamous Prusa Custom Heat Break issue.
Thanks. I keep clipping and discarding the dreaded head. The deformation is more symmetrical than your images and should be under 2mm. Now I’m curious as to why some prints worked. The printer is only a couple months old. One would think an infamous issue would have been resolved by now.
RE: Extrusion slows and stops at a predictable point
Parts with lots of retractions - a lot of spikes, turrets, towers, or many segments where the printer is moving around a lot - will exacerbate the heat break issue. And you'll see the part fail at almost the same place on multiple print attempts.
Parts with a single perimeter, like a jewelry box, or a box with a lot of infill, will never show the issue.
By the way, my extruder routinely gets to 50c and has never caused a problem. Most PLA filament doesn't begin to soften until 65c. The gear-melts-PLA problem is common for enclosed printers, not common for open printers.
RE: Extrusion slows and stops at a predictable point
Readjusting the PINDA probe led to my best first layer test yet. Benchie started out perfect but soon afterward plastic started to leak and eventually stopped. I've printed successfully before but can't even finish the files on the pre-loaded SD card.
I've spent a lot of time and money on this and would like it to do the basics. It's been a couple days since I sent an email to [email protected] and don't even know if they received the message. It's not worth it at this point.
RE: Extrusion slows and stops at a predictable point
Tried using quiet mode, printing at 190, and both; the heat and jamming gets worse. I have some PETG arriving tomorrow. If that doesn't print well I'm hesitant to buy the MMU but Prusa won't sell a complete E-Axis assembly, which I would use for testing.
RE: Extrusion slows and stops at a predictable point
Printing colder (190) will make the extruder motor hotter. Try printing at 225 or 230 as the other extreme.
RE: Extrusion slows and stops at a predictable point
Looking at this blog entry again, section 3 is exactly how my first Benchy turned out. However, the extrusion assembly pictured is not the one I have on my printer.
RE: Extrusion slows and stops at a predictable point
Looking at this blog entry again, section 3 is exactly how my first Benchy turned out. However, the extrusion assembly pictured is not the one I have on my printer.
I'm lost here. What section 3 of what blog entry?
RE: Extrusion slows and stops at a predictable point
Looking at this blog entry again, section 3 is exactly how my first Benchy turned out. However, the extrusion assembly pictured is not the one I have on my printer.
I'm lost here. What section 3 of what blog entry?
Sorry, this will help: https://blog.prusaprinters.org/does-your-freshly-assembled-original-prusa-i3-mk3-print-as-the-best-it-can/
RE: Extrusion slows and stops at a predictable point
Looking at this blog entry again, section 3 is exactly how my first Benchy turned out. However, the extrusion assembly pictured is not the one I have on my printer.
The pictured extruder is from a Mk3. If it's not the same, then you probably have an Mk3S. The issues and the steps to rectify them are, however the same with the Mk3S. Based on forum posts, it seems the Mk3S design is somewhat more prone to extrusion issues than Mk3 was.
RE: Extrusion slows and stops at a predictable point
Looking at this blog entry again, section 3 is exactly how my first Benchy turned out. However, the extrusion assembly pictured is not the one I have on my printer.
The pictured extruder is from a Mk3. If it's not the same, then you probably have an Mk3S. The issues and the steps to rectify them are, however the same with the Mk3S. Based on forum posts, it seems the Mk3S design is somewhat more prone to extrusion issues than Mk3 was.
Yes, thank you, I have the S. I'll run a PETG test when the filament arrives Saturday. The Amazon recommended white had good reviews and perhaps the best price.
Still working on it every day and will crack it open again today using tips from the blog.