felt or wiper pad issue

Hi guys, I got my Lulzbot mini a few days ago, and I am happy with its built and printing quality. Although the design of auto nozzle cleaning and bed leveling is very clever, I found that a little felt pad fibers left on the nozzle right after auto cleaning is somehow annoying. It could impair auto leveling and PEI ( I also realized others have the same problem). I feel the wiper pad (one side) can be used only once, and it will start to leave some fibers on the nozzle during the second time wiping. To avoid fibers left on the nozzle, you seemingly need to either flip the wiper pad over or change a new one every time you start a new print. It seems to be wasteful.

Does anyone has suggestions to wiper pad replacement? I know some of you suggest using Scotch-Brite, but what kind of pad you are using. Those green or blue heavy-duty scour pad? Or those sponge-like pad?

Or, is there a way I can disable auto cleaning process and manually clean the nozzle myself before printing?

Thanks.

What filament are you using?

I’ve noticed that the wiping function works great with ABS. With PLA, I have to manually clean the nozzle after three or four prints because PLA smears itself all over the nozzle. I have noticed that the wiping function happens at a lower nozzle temperature for PLA – I could be wrong but I think it’s 140 for PLA and 160 (edit: actually 170) for ABS.

Hmmm, my nozzle is dirty right now and I have PLA loaded up … maybe I’ll try a test print with a higher wiping temp.

EDIT: Results – not awesome. It was the first print though and for me PLA always fails first print from cold startup, but the way it failed didn’t give me any confidence it would work. What I did was change the two M109 S140 lines prior to wiping in the start.gcode (expert settings), to S170 (ABS is actually 170). My nozzle was crusty and needed manual cleaning. I would say that at the higher temp it got cleaner, but not clean enough because it deflected the first washer when trying to sense it. So I hit the power switch after it released the first washer and before it could get to the second one. Turned it back on, homed Z, and manually cleaned the nozzle. Then I ran the same modified gcode. This time it worked fine, but of course I’d manually cleaned. I’ll keep testing though, maybe cleaning PLA at a higher temp will result in less frequent manual cleanings.

Note that there will be a seemingly unusual pause between wiping and probing – prior to probing the temp is set to 140. I decided to leave that alone in case the PLA wants to drool from a 170 nozzle.

There should not be a pause between wipe and probe. Make sure the nozzle is not heating during that pause.

If you are having PLA smear on the nozzle during the wipe, you might need to lower the wipe temp a bit for that particular PLA. 140 wipe and probe has worked without error for the two or three PLA brands I have on hand. I have never seen any fibers stick to my nozzle.

I sometimes notice the little fibers you’re talking about. In practice it hasn’t been an issue at all, and once I learned to ignore it I’ve had no problems.

IF it bugs you a lot, you can take a cloth, not terry, something with a tight weave (I use blue shop rags(The cloth kind, not paper)), and wipe the felt pad a couple times to remove those stray fibers.

This is true with the unmodified start.gcode, but not true unless you modify it in 3 places. I chose to modify it in only the the first two, in case filament tended to drool during the probing process if the head was set to 170. Notice the line in blue – that sets the temp for probing. If I set the temp to 170 in the two red lines, but leave the blue line at 140, it won’t probe till the temp falls to 140 (hence the pause). In normal operation, the head is at 140 when it finishes wiping and so it starts probing right away. To mimic that, I’d have to set the blue line to 170 as well in my experiment.

M109 S140 ; set to cleaning temp and wait
G1 Z150 E-30 F75 ; suck up XXmm of filament
M109 S140 ; heat up rest of way
G1 X45 Y174 F11520 ; move behind scraper
G1 Z0 F1200 ; CRITICAL: set Z to height of top of scraper
G1 X45 Y174 Z-.5 F4000 ; wiping ; plunge into wipe pad
G1 X55 Y172 Z-.5 F4000 ; wiping
[…snip…]
G1 X100 Y172 F4000 ; wiping
G1 X110 Y174 F4000 ; wiping
G1 X115 Y172 Z-0.5 F1000 ; wipe slower and bury noz in cleanish area
G1 Z10 ; raise z
G28 X0 Y0 ; home x and y
M109 S140 ; set to probing temp
M204 S300 ; Set probing acceleration
G29 ; Probe

The PLA I’m using (eSun) doesn’t smear when wiping at 140 – it seems excessively solid at that temperature. It seems like it smears during printing, specifically, when laying down the skirt, when it first starts to come out of the nozzle, it starts out too thin and that makes a little booger which sticks to the nozzle and then throughout the course of the print, sticks all over the cone surface of the nozzle, which encourages more stuff to stick.

For whatever reason, I’ve never had great luck with PLA – the prints come out OK but I have trouble getting it started and I have to clean the nozzle a lot manually. Maybe it’s the brand? What PLA are you using?

I should add, I seem to have less trouble with natural PLA. My beef is with the black and white filament I have.

I use Ultimachine, eSun and a little Matterhackers Pro. Play around with your printing temps. Not all PLA likes to print at 180 - 190C. The Ultimachine prints well at 225 on my Taz with an E3D V6 and 210 on my stock Taz 5.

You should be able to use the tweezers and pluck the plastic off the nozzle when it is at wiping temp. If it is hard to remove, raise the temp a few degrees. It should be soft, not hard and not runny.

When the Mini probes the corner washers, it should just tap them and not deflect them at all. If they are deflecting during probing, your nozzle tip is not clean. If that is the case, heat it up to printing temps and give it a good scrubbing with a folded up cotton cloth.

Thank you for all your replies. I think I got the idea that sticky filament on nozzle could potentially pick up fibers from wiper pad, and then causes further problems (incorrect auto leveling).

I first used natural PLA from MicroCenter (brand is Velleman), and now I changed to eSun’s silver ABS. It looks ABS doesn’t left much residue on nozzle like my PLA does, so I don’t need to clean the nozzle (or change wiper pad) every printing. Still, I feel it will get some residue on nozzle once in a while. I will make sure the nozzle is clean before printing, and thanks for the tips. :wink:

alexkychen wrote:
Does anyone has suggestions to wiper pad replacement? I know some of you suggest using Scotch-Brite, but what kind of pad you are using. Those green or blue heavy-duty scour pad? Or those sponge-like pad?

I use a piece of green 3M Scotch-Brite Scrubbing Pad (Amazon:http://www.amazon.com/3M-96-Scotch-Brite-Scrubbing-Pads/dp/B005SSJWLC/ref=sr_1_3?ie=UTF8&qid=1445081966&sr=8-3&keywords=3m+scrubbing+pads) to manually clean the nozzle tip before the auto cleaning cycle begins. I guess if you carefully trim this material you could use it as a replacement for the wiper strip, but I have only replaced one strip and they are pretty cheap (just buy a couple of kits to get over the free shipping limit on your next order from LulzBot). If you have to flip/change between each print there is something else going on: either too high a temperature during wiping or your Z settings are way off and you are digging too deeply into the wiper.

Here are my typical settings & procedure using HIPS on my Mini:

240 HE
100 Bed
2.85mm
90.0 flow
All Other Settings Unchanged (Cura Mini HIPS Medium Profile)

Preheat bed to 80 (just to speed things up) while heating HE to 250
Extrude 20mm to insure no issues, hit print & pre-wipe with 3M medium pad
Final pre-wipe when the HE has cooled to ~162; when the HE gets to 160 the GCode takes over

This has eliminated all auto leveling issues (I also occasionally polish the “corner” of the leveling washers to keep them clean) and extruding issues. I admit that I have been lazy and need to calibrate the extruder so I can go back to 100% flow.

'Hope this helps.