Filament change gcode problem

[nsanti 2]

I am having a problem in cura with the change filament post processing script. Before moving the head out of the way to do the filament change, a huge blob of plastic is deposited on the model as you can see on this small test cube. I have already tried the pause script, but this will not work with my machine. The only way I can do multi color is using this script, but I have this issue. I am using a Monoprice select mini v2 printer.

 

[nsanti 2]

I have just tried the pause and it worked. I changed the code to m600 to pause until I tell it to resume , but when returning to the part, a blob is deposited where is begins. I really want to print with more colors but I can’t figure this out. Please help.

[Fred- 0]

Hello,

 

I have the same problem with 'Filament change' and a Creality CR10.

The values in the plugin works in the wrong way. For the two values initial and later retraction, it extrudes instead of retracting (so your blob!)

Unfortunately, one can't type negative values in the fields (in fact, you can set negative values, but they are converted to null values the generated gCode file).

 

This option seems useless for now, you can try the post-processing script "pause at heigh".  It works better,  I don't know if it's perfect, I had one problem on my first attempt  using it, I have to try again...

 

[nsanti 2]

A few days ago I figured it out, so it may help you too! When I created a pause in cura, it worked except when the print head returned to the model it left a blob again. I fixed the issue by opening the gcode in a text editor and deleting a line in the code as you can see in the picture, it’s highlighted in blue. This didn’t change anything except the blob of plastic was never extruded, and my print came out perfect! This might also work with the change filament script, but I haven’t tried it yet.

[Fred- 0]

Hello,

 

Not related to the problem, but in case you didn't know, you can easily take a screenshot on a mac with the shortcut Command-shift-5 (you'll have options to capture  the screen, the window or a selection,  and where to save...)

 

I use finally pause at height, it's working fine, you just has to remember that the pause is done *after* the layer you specify.

If you want to change the color for the 11th layer, you must pause at the layer 10, not at layer 11.

 

 

[nsanti 2]

It is related 100%. After I delete this line of code, it works. Without doing that, it doesn’t.

Edited May 12, 2020 by nsanti

[Fred- 0]

Hello, please forgive me, I'm not a native english speaker...

I wanted to say that my advice to take a screenshot was not related to the problem, not your post, sorry!

Edited May 14, 2020 by Fred-

[nsanti 2]

Ok I understand now after reading it again. 😀

 

your English is very good by the way, I would never have guessed you spoke a different language.

[Plasma 0]

I had the same blobbing, and I changed the retract to -40 it allowed me to do this and now I have no blobbing. Definitely a bug in that its meant to be a retract but without the - it is extruding more filament.

[nsanti 2]

I have also had to change the m0 code to an m600, since the printer pauses and then resumes shortly after without waiting for you to push the button to resume.

[SeungsooKim 0]

Good news....

I have also this problem at 'pause at height' plugin.

I will try your deleting method.

If that problem is cleared, I will try changing the python code of pause at height plugin for me.

 

original source...is open by ultimaker as "PauseAtHeightMarlin.py"

# Copyright (c) 2018 Ultimaker B.V.
# Cura is released under the terms of the LGPLv3 or higher.
# Modified by Art Hoke - August 5, 2019

Edited February 22, 2021 by SeungsooKim

[SeungsooKim 0]

Still doesn't solve the problem. Your method didn't work at all. The more problematic is that this phenomenon does not always happen consistently.

[GregValiant 1,409]

What printer?  What firmware?  Does the printer have a TFT screen (as opposed to LCD)?

[icerabbit 0]

I have the problem with bad filament change post script.

 

Creality Ender 3.
Post-Processing to Switch Filament.

 

The printer completes the layers as desired.

Then moves to a coordinate over the print and purges a blob of filament onto the work piece.
Then moves to the corner on the build plate (10,1) and starts another filament push.
The printer is grinding loudly in the process ... because the head cannot print as fast as the line is asked to move.

The printer gives off an audible alarm.
Nothing responds (controller or octoprint) and the printer needs a hard shutdown to make it stop. 

Primary issue is that the printer stops unrequested over the printed item, pushes filament instead of retracting, then moves away to the corner and again instead of retracting pushes to seemingly purge. 


 

 

[GregValiant 1,409]

Post a gcode file that's broken.  It might be an Octoprint problem as well.

It's also possible that the filament change code M600 is not supported in your firmware.  Creality likes to play tricks and their firmware is no longer mainstream Marlin.

Edited May 30, 2021 by GregValiant

[HaLo2FrEeEk 0]

Here's my two cents. I've actually tried modifying the script to alleviate this issue.

 

Say I set a filament change for layer 10. What I experience is, after printing layer 9, the filament retracts according to my retraction distance setting, then the head moves to the corner and the filament pulls all the way out. I put in the new filament and let it purge, continue and pull off the purge right before printing starts again and...blob.

 

Why? Remember the retract at the end of layer 9? The printer thinks the filament is still 8mm up the nozzle, so it tries to move it back, but after the purge the filament is already at the tip. My simple solution was to edit the gcode, find the first G0 after the M600 filament change, should be something similar to G0 F1500 E# where the # is the *absolute* position of the extruder. Change the G0 to a G92 and remove the F parameter so you're left with G92 E#. That will reset your extruder position without actually moving the filament and voila, no blob.

 

What I'd like to know is how to access these values (absolute extruder position) from within a script. If I can do that I can modify the filament change plugin to automatically make that change.

 

I hope this helps, and I hope someone can point me in the direction of some help with the python scripts.

Edited May 30, 2021 by HaLo2FrEeEk

[GregValiant 1,409]

The Filament Change plugin consists of adding a single line that is the M600 command and it gets inserted at the target layer.  The file is "C:\Program Files\Ultimaker Cura 4.9.1\plugins\PostProcessingPlugin\scripts\FilamentChange.Py".

 

How "Filament Change" works is dependent on 3 things:

1. Where the user leaves the new filament in relation to the nozzle.  If the user remembers to pull the filament back "retraction distance" then there should be no blob.

2. How the firmware is configured to handle the two retractions that are within the M600 command.

3. Where the M600 line gets inserted within the retraction/prime cycle of the gcode file .  If it is: a) between a retraction and a prime, or b) just before a retraction, or just after a prime.

 

I use "Pause at Height".  It works well when the "By Layer" option is chosen.  If there are no Z-Hops in the file and you are not using "Adaptive Layers" then "By Height" will work.  I am a fan of the Manual Retraction method and I've found that about 3mm is perfect.