Umo+2 (um2 hotend) Retract Calibration

[neotko 1,418]

Hi,

I want to share my initial tests.

I'm getting someweird backpreassure from too much retraction on my um2 hotend. It's a weird effect where too much retraction make's a instant blob when it comes back after retraction. I seen that on my umo+ 1.75 hotends but with this um2 hotend (olsson original + ptfe from 3dsolex + Bowden 6-2mm) the effect where quite high making too much blobs when returning from a wipe-retract-extrude.

So, I did a simple retraction calibration with one of my tecnical filaments (high quality but unusable color for me) from smartmaterials pla.

For the purpose of the test I used 220C/60-70mm/s 0.2 layer, I always print at 210 for this layer height but I wanted to generate more dripping than usual to refine the settings. Also travel move was at 180mm/s

The blob on the third row it's from stopping the print.

Well for umo+ 1.75 hotend I used always 3,2 retract for clean and blop-less results. Seems that for um2 hotend the good number it's around 2 and 2.5mm, I'll start to do some long prints with 2.25mm to check my prints.

Remember movements from each row from up to down don't count, only in between cubes rows (since the process kicks-in with the retract settings for each row)

First row 1mm, second 1,5, third 2mm, fourth 2,5mm, fifth 3mm

A cut from the print sequence:

 

Retract factory file with the process (remember this it's for 1.75mm)

https://www.dropbox.com/s/wc3b296sgb8v0ff/retractest.factory?dl=0

Edited April 6, 2016 by Guest

[neotko 1,418]

Final test for now

2.25mm retraction distance seems to be perfect. This needs more filament brands on the test but for smartmaterials and faber it's working great.

 

Edited April 7, 2016 by Guest

[neotko 1,418]

2.25 works fine but there's very small little drops on some areas. I think 2.35-2.40 should work better. And probably 2.5 for general use.

[neotko 1,418]

Carbonfill retract at 2.5mm, zero drips when moving hotend printing at 250C 10mm/s bottom layer retract speed for this filament it's 15-20mm/s (at least what works for me after 8+ kilos printed.

[frederiekpascal 193]

monologue?

but a very interesting one though

[neotko 1,418]

Yes weird

[neotko 1,418]

Just a small update 2.7mm retracts works on umo+ 1.75 and um2. So if someone (like me) has both hotends, you can set the same retract distance to keep the gcodes with minimum changes.