skipping extruder!

Sometimes I've had to disassemble the bowden at the extruder end to remove this bulb in order to remove the filament, fortunately this happens more often on my Mendel than Fisher, but its never a problem during printing, just the consequence of melted filament being fed through a nozzle that is (has to be) larger than the filament diameter.


The picture of higher up the filament looks like gouging from the extruder, this should be expected when your nozzle is obstructed.

Wouldn't recommend cleaning out your nozzle with a 0.4mm drill its probably the best way to get a broken drlil stuck in your nozzle or turn your 0.4mm nozzle into a 0.5mm nozzle, if you have to clean it this way get a larger drill bit and clean out from the back and maybe use a hot pin to clean out the nozzle itself.

I find the best way of cleaning it is to heat the filament up to 200C, extrude a little and cut it off then cool to 100C and retract the filament, since Ive adopted this practice on my Fisher I've found it a lot easier to do filament changes, but since you already tried this it probably wont help.

Problem is, few on the fisher forum will be using your exact nozzle (unless they have a second printer), the 'double bulb' one of your pictures shows is curious but could just be a characteristic of your hot end or extraction method.

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
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Jelle - By saying "you can_not_not_get a 'bulb'" do you mean that you CAN get a bulb?

I learned a lot today from this problem. I loosened the idler and looked at the hobbed bolt and the teeth were caked with filament (not too much any where else, which was good). I removed the hobbed bolt and thoroughly cleaned it with a toothpick and put everything back together and heated the hot end up. I ran 100mm through the hot end and it came out straight (as it should) and didn't curl up on itself as it did before! Success!!

I printed a couple of small test pieces and they turned out great. There used to be a kind of buzzing/crackling noise before when it was printing and I thought it was from the fan. I think it was maybe from the filament grinding through the extruder (?).

I went ahead and printed a couple of more items and the buzzing/crackling returned - mostly when laying down the initial layers (which I noticed had a streak here or there where the hot end dragged across it). The noise lessened or went away when doing the 20 to 30 % fill I usually use on objects. I thought about why this was happening, when it didn't happen when I first started printing things. A couple of things came to mind - layer height and bed leveling.

When I first started printing, the layer height was .12 to .2 mm for better quality. However, I started creating test pieces and such that didn't need to have a high quality appearance so I upped the layer height to .28mm to cut down on the printing time. Add to this change the "acceptable" level of my bed that I had been using and I think that's where my clogged extruder came from. I believe my bed was too close to the hot end and at lower layer heights of .12mm there was less filament to get backed up from the hot end being too close to the glass. When I went to .28mm layer heights there was nowhere for the increased PLA to go other than backing up from the nozzle being too close to the glass. The extruder constantly trying to push .28mm of layer height out ended up grinding away and clogging the hobbed bolt as well. Added to that was the increased printing speed I was using under these conditions and it really was too much for the hotend to handle.

I realize now how important a level bed is. I should have realized earlier when some of the pieces were a bit hard to remove from the bed because of the first layers being squished into the glass. Now I know better.

Okay, I finally removed the retraction completely and starter to use the web interface, the result was great, with no skipping! But now I have another problem! The retraction made the prints look nicer, but most importantly, I could lift Z so I wouldn't damage the print! So what retraction settings are you guys using that actually works?
I will also try the "avoid crossing parameters" function to se if that helps. Now it sometimes "scratches" off the first layer because I can't lift Z!

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psneddon
Jelle - By saying "you can_not_not_get a 'bulb'" do you mean that you CAN get a bulb?

yes you always get one, it is the seal that gives you the pressure that makes the plastic come out of the nozzle. What I cannot explain is the double bulb though, perhaps it was an artefact from pulling it out?

Yes. That's what I thought as well. It looks like it may have been one bigger bulb (or pill-like piece) that stretched in the middle when pulling it out. I'm glad I was able to get it working again without any serious issues (yet).

I bought some taulman filament just in case and when searching for a thin wire to run through the hot end I came across some beading wire (.35mm). Do you think that would work?

One other thing about my printer. I went the route of buying a few pieces at a time and building it over the course of a few months. The hobbed bolt I purchased was one of the last pieces I purchased and according to the description it was made with a tap, so the grooves are cut (tapped) at an angle. I was wondering if this would contribute to unnecessary twisting of the filament when being fed through the extruder. I may buy another conventional hobbed bolt just in case. Just a thought.

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kellef
Okay, I finally removed the retraction completely and starter to use the web interface, the result was great, with no skipping! But now I have another problem! The retraction made the prints look nicer, but most importantly, I could lift Z so I wouldn't damage the print! So what retraction settings are you guys using that actually works?
I will also try the "avoid crossing parameters" function to se if that helps. Now it sometimes "scratches" off the first layer because I can't lift Z!

I don't know what you mean by "can't lift Z" ?? If your scratching the first layer you probably don't have the bed levelled properly - see my previous comments. I was using 4.5mm for a retraction setting and I reduced it to to 3.8mm just in case since my recent bout with a jammed extruder. Seems to work fine either way.

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psneddon

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kellef
Okay, I finally removed the retraction completely and starter to use the web interface, the result was great, with no skipping! But now I have another problem! The retraction made the prints look nicer, but most importantly, I could lift Z so I wouldn't damage the print! So what retraction settings are you guys using that actually works?
I will also try the "avoid crossing parameters" function to se if that helps. Now it sometimes "scratches" off the first layer because I can't lift Z!

I don't know what you mean by "can't lift Z" ?? If your scratching the first layer you probably don't have the bed levelled properly - see my previous comments. I was using 4.5mm for a retraction setting and I reduced it to to 3.8mm just in case since my recent bout with a jammed extruder. Seems to work fine either way.

nah the bed isnt the problem, im talking about lift z when retraction is triggered. so when it travels, it lifts the nozzle a little bit..? or am i wrong here? just completed a print anyways, without retraction... oh my thats gonna need some serious cleaning! gotta try out some more retraction settings! i tried 1mm up to 3 mm retraction, with speed from 20 up to 40... it always made the nozzle clog and extruder started skipping. without retractioin there was barely no skipping, but i just cant get rid of it completely! i guess i just have to try more settings! =)

Usually a Z-lift on retraction leaves a little upright stump of plastic at the exit point. Next layer the nozzle can run into it, leading to visible knock-on effects if the retract happened on the perimeter. If you need the lift then there are some other things misaligned/configured.

Yeah, have you calibrated extruder steps/mm yet?

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Theolodian
Yeah, have you calibrated extruder steps/mm yet?

I have! I got it to something like 137.32..... Did this before the new Sd image was avaliable for download! Now i'm running it at 137!
Ive ben thinking about replacing the bed with a glass one! Om mayby just 3m sticker a glass one on top of the current one and add a buildtak! But the bed shouldnt be that uneven i think? im not sure what the root to all my problems are, this is my first printer so i'm really new at this!

try increasing print temperature i am printing 220-230 depending on the filament brand

I hope it helped

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upsch2000
try increasing print temperature i am printing 220-230 depending on the filament brand

I hope it helped

I removed the fan duct, and I'm now printing the first layer at 215 and the rest at 210! Haven't tried to go up even higher and put it back yet, since I'm facing some other problems right now I'm dealing with!
But I think my thermistor is a little off, it shows 26-28 when the hotend is turned off, and I guess it's about 20 degrees in my room!

Edited 1 time(s). Last edit at 10/13/2015 03:49AM by kellef.