Extrusion issue  

Re: Extrusion issue

The lines printed in the live-z calibration are much thinner than the purge strip at the beginning.

Can you post a picture? Maybe one of the whole live-z print and one of the final square at the end, as close as you can get and still have the camera focus.

Re: Extrusion issue

Thanks

Sorry, hard to get everything clearly in on the shot, I didn't get the final square because it often comes out a blob. (Though this will probably be a Z height issue when it does work its thin lines that don't touch)

BTW: During the Z calibration exercise the corners are sometimes square, sometimes not, again a z height issue that I can fix once I solve the extrusion issue

The top example is from the edge of the bed, before the actual print. (Note the change in width, this happens about halfway along)
The middle example is taken midway through the print
The last example is for reference; it comes from my old printer

BTW: The extruder appears to be working the whole time, and I can't hear any clicking

Many thanks

Re: Extrusion issue

Hi Peter,

the top line is the start line and is intentionally over extruded.

the middle line looks like filament that hasn't been squished aginst the build plate, because the extruder is too high

and the bottom line looks like raw 1,75mm filament

try Jeff Jordan's 'Life adjust My way' https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f62/life-adjust-z-my-way-t2981.html#p97199

there are V6.1 files at the bottom of the first page...

try that when adjusting Live Z...

if the filament is individual strands your extruder is too high, too small a negative number for live Z
If the filament has ripples or waves in the surface, then your extruder is too low, , your live Z value is too big and
If you have a lovely smooth layer with the edges of the filament merging with adjacent filaments, you are about right!

regards Joan

Re: Extrusion issue

Thank you for your reply,

The red strand has a diameter of .55mm; it was extruded from another printer. It is not 1.75mm raw filiment. I put it there to show what scale I'm expecting compared to what I'm getting

The middle line, from my new MK3, is far thinner, 0.25mm, than what I expect from a 0.4mm nozzle.

Even if I get the nozzle close to the bed the plastic does not stick; I believe this is because not enough plastic is being extruded, but I can't figure out why.

When I get the extrusion correct, I should then be able to adjust the z height

Re: Extrusion issue

0.25 mm is too thick string so you have to lower the Z level a bit.
The nozzle diameter is 0.4 mm but the string you are trying to create should be 0.2 mm thick and about 0.45 mm wide.

Then forget the other printer, its nozzle may be larger than 0.4 mm or wrong calibrated.

Re: Extrusion issue

Thanks heaps!

While its a surprise to learn that a 0.4mm nozzle extrudes a 0.25mm string, it's a great relief to learn that my new MK3 is extruding correctly.

I'll try again to get the z height correct, so that the plastic sticks to the surface, (the original problem).

Again, many, many thanks

Re: Extrusion issue

If it does not help to calibrate the Z level, you have problems with a dirty bed (grease).
Wash the bed with a dish detergent and water. Wipe with paper and do not touch the writing surface with your fingers.
This works much better than other chemicals.
Between the prints, you can then use 99.5% isopropanol for PLA and window cleaner (Windex) for PETG.

Re: Extrusion issue

I've had much more success calibrating the x-height. However, I'm still having issues with the print not sticking to the plate as well as it should. My lastest successful print is a calibration cube. This failed twice before I increased the bed temperature to 70 deg. The now successful print exhibited 'elephant foot' so I'm assuming the nozzle is too low.

I will clean the bed with soap and water as you suggest, and then see if I can print without raising the bed temp, and the nozzle at a better height.

Many thanks