Mesh Leveling Causes Blob on Extruder  

RE: Mesh Leveling Causes Blob on Extruder

Can you give us a little more info to go on?

What filament, type and manufacture?

Default setting or modified, if modified what are they?

Providing photos is alway a good options, lots can be gleaned just based on photos. 

RE: Mesh Leveling Causes Blob on Extruder

@gkmakeit

I have done nothing since building the printer but use the calibration wizard and print from the sd card so I assume the settings are as default as can be. 

The filament is a brand new Prusa PLA galaxy silver that came with the printer. 

I cleaned up the extruder after the last print so I won't have a picture until I get a chance to try again. 

RE: Mesh Leveling Causes Blob on Extruder

It can happen without the Gcode modification because it takes longer for the bed to heat than the extruder, and gravity causes the drips.  I find that it is more apparent after printing multiple prints at a time.  e.g. print an hour or two print and then immediately print another and another, then the dripping starts.    Without the Gcode modification, what i found to work to minimize those blobs are two things:

Cleaning filament.  Run a piece through the extruder after you are done printing for the day.  after removing the filament,  load the cleaning filament and say no to the load question 2 or 3 times.  Leave it in the extruder and shut down the temps. it will not hurt anything.  then when you print again and bring to temp, you unload the cleaning filament and load the printing filament.  this pulls any excess melted filament out and prevents partial clogs.  downside is you have to buy cleaning filament but it is like $15 bucks for 500grams and lasts forever...  Esun makes some.  this is a Bobstro tip that I adopted early and has not failed me.

don't leave your filament in the extruder after a print.  eg if there is not a print going, i do not leave the filament in the extruder sitting at temp or not.  this prevents the melting and the drips.  unload and then reload when printing.   I have to remove my filament and box it or bag it up due to humidity, but it is good practice to not let the filament sit in the extruder and heating, even in the cooldown phase or startup phase as much as possible.

the best way to prevent it is the GCODE mod, but these two tips will greatly minimize it from happening from my experience.

RE: Mesh Leveling Causes Blob on Extruder

@jbinfl

Thanks for the tip on the cleaning filament, was unaware this was a thing.  It just so happens that around the time this response showed up I was sitting in front of my printer just trying things to see if I could get it to work and taking pictures to provide additional information if I failed.  I didn't fail!

So no matter what, it appears there's always going to be some dripping that occurs during warm up and if it's too much, the mesh leveling makes a mess of that. I found this technique worked for me:

1. Preheat the material, in my case PLA

2. Make sure the Z-axis is close to the bed but still high enough where you can get a pair of pliers in there easily.

3. Move to the file on the SD card you want to print.

4. Clean the nozzle and any dripping with the pliers

5. Start the print from the file immediately after cleaning.

Since everything is already warm, the print starts almost immediately (a few seconds) which doesn't give enough time for much more dripping and the Z-axis doesn't have to move much also minimizing the time.  I did this successfully about 3-4 times without any nozzle clog issue so it really seemed to be doing the trick.

If it was successful, why did I do it 3 times you might be thinking?  Well, my benchy decided it wanted to start bending away from the build plate.  First from the front, then from a back corner.  Quick search for adhesion and pointed me back to first layer calibration.  Did some re-adjustments for my z-axis and definitely found a better setting there for adhesion that wasn't too squashed.  I also found the too squashed setting, man that was a pain to cleanup a single strand of that zig zag pattern.

But after it was re-calibrated, used my preheat and cleanup technique, 2 short hours later...

RE: Mesh Leveling Causes Blob on Extruder

Nice Benchy!

RE: Mesh Leveling Causes Blob on Extruder

You could also modify your start gcode to eliminate it as well as get more reliable mesh levelling.  You could use something like -

M83 ; extruder relative mode
G28 W ; MUST FIRST home all without mesh bed level or else risk nozzle crash!
G0 X70 Y70 Z0.2 F2000; PINDA warms faster near bed
M140 S65; set bed temp to help warm PINDA
M104 S160 ; preheat extruder to no ooze temp to help warm PINDA
M190 S65 ; wait for bed temp
M109 S160 ; wait for extruder temp
M860 S30 ; wait for PINDA temp. For most stable PINDA temp during mesh, set temp here 1-2 deg below your actual PINDA temp at end of mesh cal. S30 to S35 is a good range but S35 is too high during the winter , takes ages to warm up.
M104 S100 ; drop extruder to lower temp to minimize PINDA temp rise during mesh
G80 N7 R1 ; mesh bed leveling with extra points but this requires 3.6.0c firmware
G1 Y-3.0 F1000.0 ; go outside print area
G92 E0.0
G1 Z3 ; raise head safely clear of bed before heating extruder
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M104 S[first_layer_temperature] ; we heat extruder AFTER mesh to minimize ooze
M109 S[first_layer_temperature] ; wait for extruder temp
G1 Z0.7 ; move slightly above bed for easy clean intro line
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line
G1 E-0.1 F2100; bobstro anti-stringing retract and wipe
G1 X99.0 E0 F1000.0 ; -1mm intro line @ 0.00
G1 X110.0 E0 F1000.0 ; +10mm intro line @ 0.00
G1 Z0 ;lower head back to normal Z after intro line
G92 E0.0
M221 S{if layer_height==0.05}100{else}95{endif}

as all the warm up happens at 160 degrees theres no drip for mesh levelling and because the pinda is at a known steady temp the levelling itself is better as the PINDA sensor is temperature dependent.  It does mean it takes longer for a print to start though so not good if you are impatient but I find that the extra time give the print bed heat time to equalise better anyway.

RE: Mesh Leveling Causes Blob on Extruder

perfect thread for me to chip in...

Thanks to some earlier advice I now also run a modified start up routine, pretty similar to the above one. Although I don't understand the "bobstro anti-stringing line".

I encountered a new thing though. Heating up the extruder to 160 before mesh bed levelling and using a Flashforge PLA leaves a nice array of little plastic blobs on the last two or three lines of calibration points. It looks as if the calibration movements shake a bit of plastic out of the extruder.

Is 160 degrees already too hot for PLA during bed levelling?

RE: Mesh Leveling Causes Blob on Extruder

Posted by: @h-waibel

[...] Although I don't understand the "bobstro anti-stringing line".

I've documented my startup gcode here. There are many variations, but I find this works well.

RE: Mesh Leveling Causes Blob on Extruder

Posted by: @neophyl

[...]
M860 S30 ; wait for PINDA temp. For most stable PINDA temp during mesh, set temp here 1-2 deg below your actual PINDA temp at end of mesh cal. S30 to S35 is a good range but S35 is too high during the winter , takes ages to warm up.

I've worked around the seasonal fluctuations by increasing my initial bed temp to 75C. I want to keep my PINDA leveling temp at 35C year-round for consistency. From the reading I've done, 35C is a sweet spot. I found that heating the bed to 75C for PINDA warmup, then immediately dropping it allows it to cool down to close to PLA ranges before the print starts. I also like the bed and cabinet warmer before starting a print. My "Winter Soldier" version has been updated here. It's also much quicker!

RE: Mesh Leveling Causes Blob on Extruder

Thanks for that Bob, I'll check it out when I'm back at home 🙂