Printable View
Hello,
I'm having an issue while printing, hopefully you can see it on this video :
https://www.youtube.com/watch?v=MIov9xAa5Es
This happens on "complex prints", it prints pretty fine on simple objects (like a cube).
I don't think it is over extrusion, i spent quite a long time calibrating this, and it is only on SOME edges...
I'm out of ideas, can anyone help me ?
Thanks a lot !
Which slicing software did you use?
Hello,
I'm using slic3r, with Geeetech repeiter host.
Which version of Slic3r? There's a bug in version 1.2.9 that can cause over extrusion, try 1.1.7 to see if that gives better results.Quote:
Originally Posted by awanegenebayo
Actually i was on an old version of slic3r when recording this video ( i think it was 1.1.7), i then upgraded to 1.2.9 and had the exact same issue...
Looks to me like you're trying to add new layers on top of material that isn't firm enough.
Is this PLA filament? If so, adding print cooling airflow would help.
Yes it is PLA.
What do you mean exactly by "print cooling airflow"? I already have the fan always on
If you don't know what print cooling airflow is, you probably don't have any. This isn't the fan that is typically mounted on to the hot end to cool off a heatsink. Print cooling airflow usually involves a separate fan (or small blower) with a duct or shroud that provides a stream of ambient airflow onto the print right below the hot end nozzle.
PLA can be problematic in that it retains heat for quite a while, remaining fairly soft for a long time. The video isn't the greatest, but it seems to show the print shifting underneath the nozzle. This is a classic sign of trying to print fresh material onto layers that are still soft. Print quality almost always suffers when that is happening. On overhangs (like on your print), the overhang will tend to curl upwards. 90-degree corners tend to end up rounder than they should be.
PLA print thermal management can involve a number of factors. You don't want to print PLA on a bed any warmer than necessary. You don't want the nozzle temperature any higher than it has to be. You can set up a minimum layer time in the slicer which can help, at least to an extent. You can print multiple copies or multiple designs at a time. As I mentioned, adding or increasing the amount of airflow specific to cooling off the printed material will usually provide the most significant way to minimize issues with residual heat in the extruded PLA. This blower-based cooler is specific to my MakerFarm i3v printer, but it'll give you an idea what I'm talking about - http://www.thingiverse.com/thing:461014
awanegenebayo,
I have struggled with this EXACT problem for a year. What causes this, as far as I can tell, is very aggressive overhangs. It happens to me on every overhang where a significant portion of the flesh filament (PLA) is extruded over the air and it has very little to bond to. I tried everything, including cooling to no avail. I was finally able to overcome most (but not all) of the issue by significantly increasing my extrusion temperature. I was printing at 193 and had terrible overhangs just like yours. After a few experiments I found that 210 and even 215 work much better. I tried to go higher (220) but started experiencing jams.
What temps are you printing at? Please try bumping up your temp and let me know how it works for you!!
Thanks a lot for your answers !
I'm having two opposite adivces here haha !
I'm currently printing at 180 for the extruder and 85 for the bed. I think the bed may be a little hotter than necessary, i'll try printing something at 75.
I will also try to significantly increase the extrusion temperature, just to see what's going on, but it seems completely at the opposite of what printbus what saying, that is layers don't have time to cool down before the next layer is made. I'll try anyway, PLA is cheap :)
If i can't get any improvements, i'll consider buying a fan and printing a cooling airflow piece.
Thanks again for the help !
PS : For the record, this is what most if my prints look like :
Attachment 9334Attachment 9335
Quote:
Originally Posted by awanegenebayo
Yes, I see that :) Printbus is very knowledgeable on the subject of 3d printing. He has helped me with many problems. I do not mean to contradict his advice at all. I'm just trying to point out my personal experience.
I use a 5" desk fan to cool my prints. With that much cooling (admittedly, it is overkill) they tend to pop off the heated glass about 20 minutes into printing. So when cooling I usually need to use blue painters tape as my surface. In any event, I have only seen a small improvement on my overhangs with cooling. The benefit really came when I increased print temps.
As far as bed temp, I am now running at 63 degrees. I find that when I use a higher bed temp my longer/flatter PLA parts tend to warp/curl up off the bed at the corners.
Final note: All printers and environments are different, My 63 will not be the same effective temperature as your 63. You will need to observe the results and make adjustments as needed, one way or the other.
This is the result of printing at 210 and 75:
Attachment 9336Attachment 9337
Il looks better, but still not what i reach for ^^
I'll tune the temperatures and check if it's any beter !
It could be that we're both right. Depending on how the 180 correlates to an actual temperature, I agree that could be too low to be providing good adhesion to the layer below. On my printer, I don't think I can get good results with any of the PLA I have being printed that low. But I'll stand by my suggestion that your best prints will result from printing on layers that have fully hardened.Quote:
Originally Posted by hernejj
It could be that a desk fan doesn't provide a focused enough airflow for the small area it is needed. My first experimenting with airflow involved a can of compressed air. I was only printing a small extruder gear at the time, and was having issues getting a result that meshed smoothly with the large gear. I eventually realized the teeth were squishing around quite a bit as the nozzle moved. I ended up following nozzle around with the tube from the can of air, cooling off the print as it was printing the gear teeth. Not a full blast of air - just a light touch on the can trigger. Awanegenebayo, that could be another method to try as an experiment.
Back to add that there's another trick that I sometimes apply on overhangs. I try to be in the area when I know a print is getting to a tricky overhang, and have a metal blade like a putty knife handy. If I see a soft edge or the unsupported edge starting to curl up, I'll quickly and gently rest the metal blade on the curl to flatten it; touching the extruded filament with the cool metal pulls heat out of the filament and hardens it flat. Sure, this can be tricky depending how quickly the nozzle returns to that same area of the print, and too much pressure with the blade can compress the soft material that leads to other problems. But I figure it's worth a shot if I'm likely to have to scrap the print anyway.
I'm ready to do this even though I'm usually using my print cooler blower. Print coolers typically blow in air from one side. That means not all sides of the print will get the same cooling. Due to heat from the hot end, the part of a print downwind from the hot end can end up with less cooling effect. Edges that are in-line with the airflow direction get more airflow exposure than edges that are perpendicular to it.
Thank you very much for your help everyone!I managed to achieve some pretty good prints mostly by reducing print speed on small objects. I think you were right printbus, thanks a lot.I think i will still install a cooling fan, to see if i get better results. I'll keep you updated if you want.I stumbled upon another problem lately : when printing small objects, the extruder tends to clog, it did twice in a row yesterday printing a small figurine with a lot of support material. I think i may be printing support material too fast, what do you think?
Hard to say. You haven't shared your support settings. We don't know what you have for a hot end. We don't know what you have for an extruder scheme. We don't have a link to a specific product page where we could figure out what you have there for a printer.Quote:
Originally Posted by awanegenebayo
For me, extrusion stopping has typically been from being too aggressive with retraction settings. I have a hobbed bolt extruder scheme, and aggressive retraction can cause the same area of filament to roll back and forth on the knife edges of the hobbed bolt, simply causing the filament to be carved away...