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Da Vinci and PLA
#1
Hi,
I just did my first PLA on Da Vinci - I wanted compared ABS and PLA
After get rid off the Jam problem I got this print
Left is ABS and right is PLA. I do not have any extruder/fan modification as I have another printer which do PLA perfectly without extra fan so I wanted to give a try on DaVinci
I printed ABS extruder 230 / Bed 95 and speed 50, infill (??) - retractation 4 mm
I printed PLA extruder 240 / Bed 45 and speed 60, infill 50% - retractation 1 mm
I used blue tape / glue both worked, good adhesion and no wrapping - so far so good

but time to time I can hear the filament has issue in extruder - before I change retractation distance I even cannot print
I am also surprised that I need so high temperature (240) to avoid jam , same filament print perfectly at 220 on my other printer, I guess it is because thermistor table is not really accurate.

Anyway Is there something that could avoid the jam ? It is filament issue or extruder issue ?
[Image: 290ptfl.jpg]

Thanks in advance,
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#2
Hi
It's from the extruder, I also noticed that the retractation was a problem for the PLA, I turned off but still blocking after 10-15min ...
I put 220 ° C
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#3
Yes got same behaviour and seems ok after I have set 240 degres - I have also noticed it happen when filament has little bit tension - may be my holder is not smooth enought so extruder has some issue to pull/push filament and cause a little jam ?
My printing duration is little bit more than 1h

EDIT: I have done a new print putting extra filament out of holder during printing - so extruder did not have to do extra effort to pull/push filament, and I did not have any Jam in 1h10 of printing - seems good now, but not as good as ABS.
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#4
What was the fix for the "jam issue" you mentioned in the first post, luc?

Also to confirm, the printer has no mods to fans at all? No spare fan cooling the bed, and the hotend fan is mounted stock?

(I just got my first spool of PLA today, and my first attempt failed after about 15 minutes (but my temps were ~185/60). I have added the second fan but so far have left the hotend cooler stock -- if I don't have to modify the hotend cooler, that would make switching from PLA back to ABS a lot easier)
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#5
Here's my first take at PLA: it works, pretty much!

I've only printed a few items so far, with the longest print being a 2 hours job. With this semi-transparent Ocean Blue PLA that I got I need to print at 230-240ºC, since anything less than 220 means immediate extruder skipping. But even so, I still get some rare clicking/skipping from time to time, for no apparent reason, really. I also thought that it could be due to the filament dragging caused by the external spool, but sometimes it skips even with no tension whatsoever on the filament. The first day I did the so-called 'hotend seasoning' with olive oil, but I'm not sure if it has really helped. I couldn't get almost anything printed that day anyway because I was trying very 'low' temps, 180-200ºC, which is what my PLA filament is rated for.

As for cooling, I'm printing PLA with open lid and door, and with an additional extrusion cooling fan. The only other modding that could help is that the stock cooling fan is running faster at 8.8v, so it should provide a little extra air flow to prevent jamming. I'm also thinking of printing the mount for the stock fan available in thingiverse that improves the air flow to the extruder gear, which should help a little bit more.

The quality is good, but not as good as ABS, I think. Layering is sometimes a bit irregular, and the corners are not as straight as I'd expect, but the general result is acceptable. I do get quite a bit of stringing/oozing though so I guess I need to fine tune the retraction. The good thing is that it sticks to the bed (on which I use a sheet of BuildTak) very very good and there is no sign of warping so far. Here is what I have just finished printing for our Christmas tree:

[img]

Printed at 30mm/s for perimeters and 40mm/s for infill, 0.3mm layer height and 15% infill.

One thing I certainly do not like about PLA is its smell! Contrary to most people as it seems, with ABS I had never noticed any smell but the PLA's smell is quite strong and not exactly nice Tongue

All in all I'm quite surprised that I'm printing PLA this easily with very minor modding. I know that eventually I'll end up replacing the hot end (if not the entire extruder and carriages), because I want to be able to print reliably and hassle-free and with any other type of filament, but for now I'm glad that the stock hot end is also up to the job. It's great for learning Wink
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#6
Nice, work oscahie
Ian on my side no hardware change as mentioned - and me I was printing all door/top closed, I suspect the tension of filament change the shape and generate the click jam, so I pre-unroll the filament and no more click-jam sor far, but my printing is only 1h10 or something - what solved was :
1 - 240 degres for extruder / bed at 45 is really enough
2 - limit retractation to 1 mm
3 - pre-unroll filament
4 - before printing, extrude around 15 s to be sure filament is ok and extrusion is smooth
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#7
I'm having no luck at all yet trying to get Makerbot PLA to extrude longer then 3 seconds in RH using the extrude command. Sad

My last attempt was indicated on the LCD to be 240 C at 50 mm/s (I have tried a few slower speeds as well), but I have also measured with a thermocouple on my EXTECH 430 DMM and noticed both the bed and extruder are definitely out of calibration. I'll do some more testing to see by how much (not sure exactly where to take measurements on the extruder, I'm assuming as close as I can get to the hole in the nozzle.).

I'm curious if the tension on the extruder gears is too great. I have actually removed the extruder hot swap bay to expose the gears and when I try to insert the filament even with pulling the tension lever out it seems to grind the sides of my filament. I'm not sure if this is due to the way the filament is bending going in though. If I manually rotate the extruder motor shaft while the filament is in place I can feel the ridges of the gears on the filament coming out. Is this normal?

Do you guys have any issues trying to manually feed filament? Is there any way to lower the tension?
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#8
I have no issue to load filament (PLA/ABS) but I confirm the temperatures are not accurates - https://github.com/luc-github/Repetier-F.../issues/83
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#9
Good to know.

I was able to raise the temperature a good deal before seeing some more positive results. It still clicks like crazy if I try to extrude as little as 30 mm or so.

I had even tried 270 at 1,200 mm/min. The reading on my thermocouple was about 30 C off when I was at 250 C on the LCD. I think this Makerbot filament MP05790 is rated for 230 C or so (still sounds high for PLA) but running it at LCD reading of 270 was getting closer to actually allowing more continuous flow. O.o
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#10
My PLA temperatures usage are supposed 210-230 per supplier documentation, I use 220 on my other printer and it is fine.
So I guess the 240 is in the range considering the low accuracy of current thermistor tables
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#11
Oh the irony... yesterday, just after I finished printing the star, I wanted to print a few simple small christmas decorations together at the same time, and it failed miserably. I don't know why but only the first layer would print fine, then only skipping and more skipping until I had to stop it. I tried a few times more, priming several centimeters of filament while in parking position, but nothing, same result. I'm not sure what to make of it...

The only difference is that I had updated to Repetier 0.92, but I don't suppose that should make any difference...? I might rollback to 0.91, just to double check.
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#12
Should not - I only use 0.92 based and thermistor tables are identical
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#13
Ive been printing PLA exclusively for around a month now and one thing Ive noticed is I cant go below .3 layer height or the filament starts jamming. At .3 Ive cranked 5hr prints that come out perfect and I only use a front fan for organic curves, straight lines dont need it. U can probably work around the layer height with extruder offsets. Im using spool holder hanging off the back and routed through the same path as a cartridge. Spools sitting on top of the unit were jamming quite frequently for me or causing offsets from yanking the carriage really hard on long bed moves. This is with really cheap $15/kilo PLA @ 190/50 extruder/bed temps. Higher temps gave me smoother corners but the webs and jams werent worth it. I did yank a large heat sink from another board I had laying around, and cut it down so that it barely fit into the extruder housing and that seemed to reduce the jams significantly. I will still hear the extruder gear click every once in awhile, but its only a couple clicks and recovers. I didnt come up with the heatsink idea, but if pics would help anyone Ill gladly post some.
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#14
I did a few PLA prints today. The first was at the 185/60 generic PLA temps, it worked for 5-10 minutes and then constant clicking made the print fail.

After that, 240/50 as per luc's post was successful on a single-print basis, but if I tried a second print it would fail almost immediately -- I had to unload and reload. Also I got failures when I was printing things too slowly (which may also be the triggering issue with the first PLA print I did too, as it failed at a point in the print when it had to move slowly to ensure the minimum layer time). Retraction is off, also; haven't tried with it on yet except for the first failed print.

I've been lucky so far that heating the extruder to 230/240 has allowed me to get the filament out without breaking and I have yet to need to take apart my hotend to clear the jam.

So it seems that high temps and feeding filament fast enough is the key here, without extruder mods. Soon as the filament sits too long, it seems to jam and skip. Next week I'm going to see about using new hotend fan cooler flange on thingiverse, and since i've done the fan-replacement mod already maybe i'll add a manual PWM to the hotend fan so I can just turn it down a little when I use ABS.

Edit: I'm using repetier-firmware-0.91, custom built maybe two commits prior to beta2. I don't know if the temperature/thermistor updates for rc1 would make any difference??
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#15
nope- thermistor update is for the temperature around and under 20 degres to avoid a temperature defect from sensor - you use temperature range far from this one
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#16
Here is a message from XYZ for PLA (Found on another forum)

"Thank you for the interest in our printers.
Well besides the different color now the main door has magnet and sensor
as the top door has. Also the blue version is compatible with PLA and
ABS. But PLA cartridges are still not available.
Any other question please let us know."

"When will they be available ? - Will the 1.0 be upgradable to PLA?"

"Yes, you will be able to upgrade the 1.0 for PLA just changing the noozle. Price is not announced yet, we don’t have it yet to be honest."
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#17
Thanks for that info Edouard.

On a related note... I FINALLY GOT MY PLA TO PRINT!!! Big Grin

I had my flow rate (Speed value in RH when test extruding) and extruder temperature too high (to compensate for the high flow rate.). I was able to use 90 mm/min "Speed" and 235 - 238 C to do a calibration extrude of 100 mm of filament.

I was able to get to this conclusion as I FINALLY found some info on general flow rate for PLA and ABS (and not travel speed) and when I tried using luc's temp setting of 240 I noticed it would still click. I at first thought maybe the temp was too low, but then when I pulled out the filament I noticed the end closest to the extruder had expanded. I recall reading on this forum of people saying the stock extruder barrel getting too hot and allowing the PLA to expand and creep up the extruder and eventually blow out the top causing a jam. I started slowly dialing back the temp on the extruder until I found the ideal temp to keep the filament hot yet not expand and skip while doing slow test prints and even pauses between prints. I could definitely see how adding a slightly larger heat sink would help make PLA easier to print. I may just use a PC heat sink or something for now to improve the barrel cooling, but eventually I may just go the E3D hot end route Smile.

BTW when calibrating the extruder it was pretty much spot on already Smile. I then printed with pretty much the stock Slic3r settings and was able to get a test calibration print of a single wall object with wall width of 0.5mm on the first run. Given the fact that the 0.4mm nozzle will likely expand to say 0.48 or so at temp that is pretty damn good out the gate. (PS I used no glue, hairspray, or other bonding agent on the heat bed. Just glass heated to 60 C first layer and 55 C every other layer extruder temp was set to 238 C first layer and 235 C every other layer again this is not REAL temps just what the LCD displays currently.)

I hope this info helps someone else out. I'm probably going to do a nice blog post at some point of everything I'm picking up as there is still a decent amount of misinformation out there on general 3d printing topics. There is also a great deal of assumed knowledge that a first time printer would simply not know.
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#18
Xdye, Are you also finding that the first two layers are wider than the rest of the pla print. At first I thought it was due to addition of a brim, so I removed it. In your pic the right corner of the top arm of the star seems to exhibit this behavior, but the other corners look fine. After you took this star off the bed, did it have a ridge all around the bottom you can feel? I dunno if Im smashing the first layer too far into the bed or what, I do like not having to dork with tape or glue though and printing directly on a clean bed is a major bonus...enough to live with the ridge around the bottom. Just curious if youve experienced the same.
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#19
Does anyone else notice that the 2nd PLA layer is very rough, with alot of ridges and inconsistencies? This is where I experience all of my filament jams and If I make it past the 2nd layer I dont have to monitor it for the remaining layers. It does work itself out and layer 3 and above is very smooth and uniform. I do seem to be printing alot cooler than most with PLA, but Im using bargain bin filament too, until I have the hardware dialed in 100%. Has anyone else experienced this and corrected with higher extruder temps?
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#20
Just as an FYI. I did some more tests and came to the same conclusion that longer running prints will require some hardware modification. Mainly seems like beefing up the heat sink and possibly tweaking the fan airflow. I lowered the temp all the way down to the point where it is currently hard coded to disable the extruder motor at 170 C LED reading. I may go ahead and update my firmware to let me get a bit lower then that as I could still extrude manually.

I'm thinking E3Dv6 is the ideal solution in the end.
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