Print Failure Late in Print
I am trying to print some large ABS parts. I have read many threads on printing ABS parts on this site as well as other sites and have attempted to address all the issues described in those threads. My parts are thin-walled but nearly the full dimensions of the printer. They all start out sticking and building just fine. Somewhere around 100 mm up (say after 5 hours of printing) things start to look underextruded and starts getting gaps in the walls. These appear to get more numerous as printing continues. And finally, the Mk3 detects lack of filament movement and prompts me for a filament change.
Some details (don't know what's relevant)
Some other observations:
Re: Print Failure Late in Print
Admission.... I don't d ABS...
is 50C a good tempeature for ABS, I seem to recall Prusa's print farm runs in a room at about 30C ambient, no drafts...
abstract thought... if you use the change filament option mid print (Before you get to this issue,), do you get a stay of execution? does it print longer?
you have ruled out Filament tangle... but identified that the bondtech filament drive mechanism has ground away the filament,
if filament can get into the extruder then it must be having problems getting out of the extruder...
causes for this include
Nozzle blockage, some folk use a sponge wiper to prevent dust ingress... some folk get particles in cheap filament
low temperature extruder (But this should trigger a thermal runaway error)
Out of spec filament (Oversize) causing a Jam in the PTFE / heatbreak tubes
maybe you can investigate these whilst awaiting a more knowledgeable ABS expert.
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Print Failure Late in ABS Print
Thank you Joan for responding. I've been trying different things since your suggestion... and since each test runs for 5+ hours before issues begin cropping up, it's taken a while. I've tried to isolate the issue or at least get more evidence. As far as temperature, I thought Prusa was making their parts with PETG now and 30C would make sense for that material.
It's my understanding (from many other threads) that because of ABS's CTE (coefficient of thermal expansion) and the differential between the extrude temperature of 250C+ and the bed temperature of 100C and the room temperature 23C is the main cause of warping, splitting and delamination.
So far from my tests:
1) The gold colored material of the last photo was really bad. Although it could be just bad or cheap material, I've also read an article saying the dyes added can weaken a material. And the gold having what amounts to particles to glitter makes it even worse. I should have rationalized this before the material purchase. That hind-sight is far better than fore-sight. Note in small pieces < 100mm diameter < 100 mm tall, the gold works just flawlessly.
2) Taller height is worse, but only above about 80 mm. It seems being closer to the bed and its 110C either relieves stresses due to a smaller temperature differential or because it keeps the ABS more pliable.
3) Bigger print diameter is worse. The previous gold one was splitting badly at the top even on the smallest piece. In white, the smallest piece is about flawless. The middle one got its first minor delamination about 100 mm up. The largest piece (so far) started minor delaminations at about 80mm, but had several major splits starting around 120mm.
Anyway my qualitative belief is if I can get the box temperature closer to the bed temperature, it would eliminate the stress cracking. In practice I do seem to get taller in the print. Unfortunately, at some point the extruder starts chewing the filament and finally the Mk3 detects no movement in the filament and thus tries to get me to replace the filament. This is not an option... opening the box causes the part to turn into a Frito.
Getting high-end ABS may be the only solution, but I need to exhaust all other variables first. My reasons for this are:
1) Obviously cost. When using potentially hundreds of kilos of ABS, halving the cost is quite significant.
2) I am concerned about what has been added to recipe of these "for 3d printer" ABS. These additives that make it easier to print may also reduce the desirable properties of ABS. ABS is a great structural plastic with years of experience in major structural pieces.
3) I don't want to switch to one of the other plastics because of the great Acetone post processing ability - Vapor smoothing and bonding.
Re: Print Failure Late in ABS Print
It's my understanding (from many other threads) that because of ABS's CTE (coefficient of thermal expansion) and the differential between the extrude temperature of 250C+ and the bed temperature of 100C and the room temperature 23C is the main cause of warping, splitting and delamination.
This is basically right. The only thing I would add is that the reason for 100C as the bed temperature is that it's warm enough for the ABS to soften enough to relieve some of the internal stresses, sort of like annealing glass. Expensive commercial FDM printers that print in ABS will heat the build chamber to around 100C, but a chamber this warm causes other problems for hobby level printers (as you're discovering).
So far from my tests:
1) The gold colored material of the last photo was really bad. Although it could be just bad or cheap material, I've also read an article saying the dyes added can weaken a material. And the gold having what amounts to particles to glitter makes it even worse. I should have rationalized this before the material purchase. That hind-sight is far better than fore-sight. Note in small pieces < 100mm diameter < 100 mm tall, the gold works just flawlessly.
2) Taller height is worse, but only above about 80 mm. It seems being closer to the bed and its 110C either relieves stresses due to a smaller temperature differential or because it keeps the ABS more pliable.
3) Bigger print diameter is worse. The previous gold one was splitting badly at the top even on the smallest piece. In white, the smallest piece is about flawless. The middle one got its first minor delamination about 100 mm up. The largest piece (so far) started minor delaminations at about 80mm, but had several major splits starting around 120mm.
Anyway my qualitative belief is if I can get the box temperature closer to the bed temperature, it would eliminate the stress cracking. In practice I do seem to get taller in the print. Unfortunately, at some point the extruder starts chewing the filament and finally the Mk3 detects no movement in the filament and thus tries to get me to replace the filament. This is not an option... opening the box causes the part to turn into a Frito.
What's almost certainly happening is that your enclosure is getting warm enough to soften the ABS to the point where the plastic can't be gripped hard enough by the gears.
What you really want is for the print to be inside the build chamber but the bondtech gears outside the chamber where they can grip cold filament. Unfortumately that's not really possible with the Prusa design: you either need a Bowden, or a design where the build plate moves vertically and the extruder stays at the top of the chamber.
Getting high-end ABS may be the only solution, but I need to exhaust all other variables first. My reasons for this are:
1) Obviously cost. When using potentially hundreds of kilos of ABS, halving the cost is quite significant.
2) I am concerned about what has been added to recipe of these "for 3d printer" ABS. These additives that make it easier to print may also reduce the desirable properties of ABS. ABS is a great structural plastic with years of experience in major structural pieces.
3) I don't want to switch to one of the other plastics because of the great Acetone post processing ability - Vapor smoothing and bonding.
Three things I would try:
First, you can try using one of the filaments sold as "ABS+". These generally extrude at a higher temperature, are a little stronger, and don't warp quite as much.
Second, try printing with a wider line width. This smooshes each layer down more and improves the layer bonding. I've gone as high as 0.6mm with a 0.4mm nozzle using ABS and I've had very good results, at the cost of some printing detail. The downside is that overhangs and bridges won't be as clean.
Third, try redesigning your parts. Printing large parts in ABS is always going to be a challenge. Cutting them up and printing multiple smaller pieces will definitely give better results. The other thing you can sometimes do is design the pieces with some scalloping (if that's acceptable from a design perspective). The inside corners on the scalloping give the plastic a way to shrink and relieve stress without tearing the whole piece apart.