Inconsistent Filament Extrusion

#1
Hello,

We have spent a good bit of time leveling the bed, and we feel that we have gotten it to a point where we are comfortable with it. However, during our recent prints, we have had issues with the filament not flowing at a consistent rate. At some points it will come out slower, almost in a dashed line/dribble on the first layer, then on the other half of the first layer it will be perfectly fine. It seems to change randomly, not much of a pattern as far as location.

When it does work well on the first layer, our extruder jams up almost every single time after a few layers. It looks as though the head of the extruder makes contact with the previous layer and jams itself up. We have tried multiple set-ups with different extrusion multipliers, temperatures, speeds, layer thicknesses, etc. etc. and we keep running into this issue.

We are currently printing with 1.75mm Hatchbox PLA on the Gcreate Maxx 1.5+.

Any assistance anyone can provide would be greatly appreciated!

Anthony
 

AlexD

New Member
#2
Since you have already played with the temps etc. I would look to see if the nozzle is blocked, you could try a 'Cold Pull' to try and see if it improves the situation.
 
#3
Alex,

What is a "Cold Pull"? Sorry, we are new to this..... I have to be honest we are pretty frustrated with how this has been going so far. We have had two degreed mechanical engineers working on this for about 3 weeks since we got this printer and we have had one successful print, it is EXTREMELY FRUSTRATING!

Attached are some photos of our most recent failed print. If you, or anybody else has any suggestions, PLEASE HELP!
 

AlexD

New Member
#5
Ok so the print skirt looks pretty even all the way around so we can assume the bed is quite level, I would still put my money on a blockage. Does the stepper motor start to skip when the filament stops extruding? Can you see that the filament is no longer being driven into the hotend? Is the filament being burred by the driving gear?

A Cold pull is done preferably with ABS, but still works well with PLA.

- Heat the extruder to temp (Maybe 210?).
- Extrude a decent amount of filament
- Then turn the hotend off. Wait for it to cool till about 80, then pull the filament, usually works best if you grab it with a pair of pliers.

This should pull all the PLA in the chamber and nozzle, along with any foreign nasties out. I usually do this 2 or 3 times, it helps to pull with a different colour filament so you can tell when all of the previous has been removed.

This might no remedy your problems but i think this is the easiest solution to try first.

I have not heard of the filament brand you are using so can't comment.

Make sure the extruder gear isn't clogged full of shredded filament and that the lever is applying a decent amount of pressure.

Make sure the filament is not dusty or dirty, some people make it feed through a sponge or similar before it enters the extruder.

I used to get terrible clogging with my E3D V6 Hotend, many people suggested using Rapeseed Oil to Season the internals, just dip the filament in before feeding it into the extruder. I do mine once a week although it could probably be done a lot less.

There is a good facebook group that has a lot more traffic than the forums, its called gMax 3D PrinterUsers, i have posted a link on there to try and get you some more help, or you could pop on over and put up your pictures & problem etc.

Thanks

Alex
 
#6
Hello!

Just my two cents... I've seen stuff like that happen myself, and generally it had to do with the filament. Do you happen to have another roll of filament you can try? What temperature are you extruding at?

Something else I have done is raise the Z axis up about 30mm or so using the control panel, then push down on the tension clip (the clip you push down when you load filament) and manually feed filament through the nozzle by pushing it through. There will likely be some resistance, but it should be fairly smooth flowing.

Does the stepper motor seem to 'skip' when trying to feed it at any point in time? If so, it could be a blockage, it could be a temperature issue, or it could be the drive gear on the stepper may not be quite where it should be. If the latter, you can loosen the set screw for the drive gear/pulley on the stepper for that extruder and push it back or pull it forward a bit so it gets a better grip on the filament.

I have not used that filament either... but it could be that it is also not a consistent thickness, causing the stepper to sputter when trying to pull it through.

Lot of things to check... but soon you'll become a master at it! :)
 
#7
We don't currently have another filament in house, but I just went online and ordered 3 rolls of Colorfabb so hopefully that does the trick!

We haven't noticed the motors skipping at this point. We have tried a lot of different temperatures, but our best results have come with a 200 first layer and 208 after that. I have manually fed filament through quite a few times when it was clogged badly enough that purge would not work. I will double-check the drive gear, I am not certain on that one but it is a very good point.

In regards to Alex's post, while we don't see the s tepper motor start to skip, we do notice the filament no longer being driven when it gets clogged/jammed. It is not a serious blockage in the hot end I don't think, because I can purge and start a new part, I have a different part running right now actually that (fingers crossed) seems to be doing well. This part has a smaller footprint, and these parts seem to run better. While we have had clogs on these parts, the parts we have had the most trouble with are the ones with larger footprints where the extruder travels a lot, something happens where it rubs or I don't know what, but you can see PLA on the extruder itself and it gets quite jammed up.

I may try the rapeseed oil yet. Haven't seen that suggestion anywhere else yet, but it does seem like a pretty good idea!

Also, while we did just order the colorfabb, does anyone possibly have a list of suggested filaments to try? It seems we may try quite a few of these before we determine which ones work best for our uses. Thanks!
 
#8
UPDATE: 2 hours in, print failed. Extruder jammed/clogged. Printer was still trying to print but hovering 10-15mm over the model with no filament being extruded.
 

AlexD

New Member
#9
I know how frustrating this can be! I had it for weeks when i first put my E3D V6 hotend on. With the E3D sometimes the filament heats and swells before it enters the heatbreak, this means that it is then too thick to enter the heatbreak, causing the jam, the only way to get it to feed again is to remove the filament, cut the tip and feed it back in. This happens a lot if the retraction setting (how much the extruder turns back in between printing moves, to prevent oozing) is too big. Although i have never heard of this problem with the J Head hotend.

Colorfabb consistently blocks on my E3D Hotend, but prints perfectly with the J Head (It must be me doing something wrong).

At the moment i am using E3D filament, it is very cheap (£12.50 / spool) and prints perectly.


Alex
 
#10
Hi ANovak,
This is almost certainly a clogged extruder as you guys have already mentioned. The risk you take when purchasing cheap filament. There are several methods you can use to unclog the extruder. And many more found with a google search of "how to unclog an extruder" .

The cold pull, AlexD was referring to, is removing the filament when the extruder is 80-150 degrees. This will extract more material, and hopefully the clog, than removing the filament with the extruder up to operation temperatures. This is also a handy trick when changing materials.

With the no filament in the extruder, and with the extruder up to operation temperature. Use a small strand of wire to probe up the extruder. Be careful not to burn your self. With the clogged material now loosened up a bit, it is more likely to come out when more material is pushed through by hand.

Hope this helps. Keep us posted.

Kyle
 
#11
Hi guys!

So I don't think it was really a clog, because the printer would run perfectly for anywhere from 30 min to 2 hours and would just jam up during the print. I THINK it may have been debris on the filament, because I used a little bit of oil and ran the filament through a sponge like Alex suggested and it made a HUGE difference. Before we were building up some debris on the roller bearing, but it is staying perfectly clean now.

That allowed us to at least complete the 3 and a half hour print we were trying to run. Didn't come out as perfectly as we would like, but it finished and the geometry was correct.

One thing I did notice however is that the temperature was fluctuating quite a bit. We have it set to print at 208, but it was going all the way down to 204 and up to 211 at times. Any idea what might be causing those fluctuations? Maybe I'm wrong, but that seems pretty significant to me...

Thanks for your help guys, it has made a huge difference so far.
 

AlexD

New Member
#12
Debris can float around in the melt zone and only cause a blockage when it moves to a certain position. Glad to hear you are getting it sorted, eventually you will be able to print perfectly.

Regarding the temp fluctuation, is the fan pointing onto the hotend, or just below it?
 
#13
It looks like it is directly on the hot end to me, here are a few pics.

Also, please let me know if you think that what you can see of this 1st layer looks good, I think it is coming out well but I'm still new to this so opinions are appreciated!
 

AlexD

New Member
#14
Ok well the way to test whether it is the fan or not would be to turn it off for a little while whilst printing. It the temp stops fluctuating then your might just want to try pointing the fab shroud just under the exttuder. First layer looks good to me, maybe a little bit close to the bed...? Try playing with the Z Babystepping if you think it is.