Mixed Filament Type Test Print

This very simple test print was created to try out an idea for making ink stamps.

Short version :

Test of a method for printing with two different filament types - in this case PLA and FLEX. The photos show a test disk with gray PLA and green FLEX.

Long version :

This method was used to try out an idea for making ink stamps. The idea is that the main part of the stamp would be made of PLA, and the stamp part would be made of FLEX. As it turned out, the method worked, but did not help with the actual stamp.

For more on the stamp I made with this method, see this print :

https://www.prusaprinters.org/prints/43190-42-version23

The method itself is fairly simple. The model for this test print is very simple - just a small disk. For the test, the disk is printed in two different "colors" using filament switching, except that instead of just switching colors for the second filament, I also switch filament types. For this to work, the GCode produced by PrusaSlicer needs to be modified. The general method is this:

1. In PrusaSlicer, slice the STL model to create GCode.
2. Save the GCode to a file.
3. Edit the Gcode to add settings for the second filament.
4. Save the edited GCode.
5. Upload the edited GCode to the printer and print.

To obtain the code needed for the edits, I did the following:

First, I used PrusaSlicer to produce GCode for printing with FLEX. From this GCode I extracted the code lines which set up the printer for printing with FLEX - the default settings for FLEX including the nozzle temperature (but not the bed temperature).

Second, to the above I added code to move the print head away from the print at the start of the filament switch. Result : GCode fragment for FLEX.

Third, using PrusaSlicer I generated GCode for printing in PLA with a "color change" filament switch. This produces GCode with an M600 code ("CHANGE FILAMENT") in the file. Result: PLA "color change" code.

Finally, I edited the code for the PLA "color change" to insert the GCode fragment for FLEX just before the M600 line. I saved the edited GCode as "PLA-FLEX". This is the code I used to print the test print.

Note : All of the above GCode is included here.

In practice, the print works as follows:

• printing starts with PLA and continues up to the "color change" layer
• at the "color change" layer the printer stops printing, moves the print head away from the print, and waits while it warms the nozzle up to the required temperature for FLEX.
• at this point the M600 code takes over - ther is a slight head movement followed by instructions to unload the current filament and load the new (FLEX) filament.
• with the FLEX filament loaded, the print proceeds normally.

Notes :

The FLEX I used was TPU - very flexible but still moderately hard. a very soft filament might make an improved stamp.

FLEX has a higher nozzle temperature than PLA so it has no problem sticking to a PLA layer. I am not sure this would work so well in reverse.

In switching filament types, I think it is worthwhile to give the print nozzle an extra "purge" by telling the printer that the "color change" did not work the first time - this causes it to extrude more filament.

The OnShape 3D CAD for this test print is here :

https://cad.onshape.com/documents/a0bf5e1bd9e0edaf1024617c/w/a671242f897f3c14071f2bb7/e/345fe6629bff940ce611ac51

Print instructions

Print the test print using the gcode provided. The print will not work with just a "color change" as the nozzle temperature will be too low for FLEX.