Still having issue when manually changing filament during a print  

RE: Still having issue when manually changing filament during a print

Yes, this happens every color change for me. It also happened on the Mk3 but the Mk4 seems to push out more filament at this point (nozzle lowered on to the print). There are several threads on this and I believe its "normal" behavior. It would make more sense to go to the start point of the layer rather than the end point of the previous layer but that isn't the way the gcode seems to be written.

The only way I have seen around it is to make the color change one layer higher which is fine if you have text or something multilayered above but doesn't work for things like HueForge prints.

RE: Still having issue when manually changing filament during a print

Thanks for the reply. I don't understand how it can be considered normal behavior if it doesn't happen consistently. I have never had this happen (this "forcefully") on the MK3. It may leave a tiny dot but it can be picked off without a problem. When this particular behavior occurs on the MK4 there is no way to remove this much bigger spot of filament. I completely agree that the nozzle should move to the start of the next layer before doing the filament change action. I do like the idea of moving the color change up a layer for MK4 but that means editing a few hundred files. 🙁

I will search again for other similar complaints, but if you happen to have a link to one handy I'd appreciate it! I must be using the wrong search terms.

RE:

For me it is consistent as it happens every color change.

Here are a couple of threads that mention the same issue,

https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-how-do-i-print-this-printing-help/color-change-dot-outside-printing-area/

https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-how-do-i-print-this-printing-help/manual-multi-material-extra-unnecessary-purge/

The second is not exactly the same but a very similar problem.

Another good suggestion mentioned by @fuchsr in the first thread, is to add a small object that is sort of a wipe tower and as long as it prints second then the blob will be on this object rather than your print. I haven't tried it but just adding a shape in prusaslicer that's as high as needed should eliminate the problem on your actual print.

RE:

You can fix this with a few settings in the slicer.  As noted, there have been a few forum threads on this, and I learned how to fix it from some other forum members.  My experience is in this post in particular, but the whole thread may help to give some background.  Following the lead of @minorhavoc, I've typed up my settings so that I can easily re-apply them to a new configuration.  I suspect that the three settings under point 4 ("Single extruder MM setup") will be sufficient to stop this giant blob, but the complete set of settings below makes a reliable, clean manual material setup.  They make use of the wipe tower to ensure that any mess associated with the filament swap happens away from your print.

EDIT: I see @ironfan72 has already linked to the same thread while I was typing my response, but I think it DOES tackle the same problem that you're having.

You can save the "Printer Settings" as a printer preset, and the "Print Settings" are easy to set on a per print basis.

In “Printer Settings”:

1. In "General"-->”Capabilities”:

• Set "Extruders" to desired number of colours
• Enable "Single Extruder Multi Material"

 

2. In "Custom G-code"-->"Tool change G-code" section:

• Put the following:

{if layer_num >= 0}

    local next_filament = filament_settings_id[next_extruder];

    "M117 " + next_filament + "

";

    M600 ; change to filament for extruder {next_extruder + 1}

{endif}

 

3. For each Extruder-->"Retraction when tool is disabled":

• Set "Length" to 0.

 

4. In "Single extruder MM setup":

• Set "Cooling tube position" to 10.
• Set "Filament parking position" to 0.
• Set "Extra loading distance" to 0.

 

In “Print Settings”:

5. In "Multiple Extruders"-->"Wipe tower":

• Enable “Wipe tower”
• Disable "Prime all printing extruders".

RE: Still having issue when manually changing filament during a print

@chris-hill

Thanks for the informative reply! All of my multi-color models simply change colors at varying layer heights. What is the proper method to use the process you describe (add 1 or more extruders if necessary, example single extruder MMU, etc.) that would have the least impact on my many models? I.E. can I just enable those settings and turn on a wipe tower? Or do I have to actually edit the profile and switch extruders for each color change?

RE: Still having issue when manually changing filament during a print

I think you'd have to specify a different extruder for each different colour if you want to make use of the wipe tower.  Once you've set up more than one extruder, you get an additional option to 'Change extruder' which you can use instead of 'Add color change'.