This document contains notes for a Dallas Makerspace class about multi-color printing using the PolyPrinters.

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1 Class Notes This document contains notes for a Dallas Makerspace class about multi-color printing using the PolyPrinters. Caution Like most 3D printers, the PolyPrinters perform limiting range checking. Which means that a printer can be damaged by sending bad G-code. If you have questions about customizing G-code then ask. If you have doubts then ask. If you have concerns then ask. There are people here who not only can help but are conversant in G-code. Modeling I m going to make a small name tag about the size of a business card (90 mm by 50 mm). A 2 mm thick base works well. I will use Arial Rounded MT font because it prints well. 18 mm high lettering works well for Brian and 9 mm high lettering works well for a phone number. A thickness of 0.5 mm works well for lettering. Color printing works best when each color is an independent solid. For the small name tag I ll make the base one solid and the lettering at least one separate solid; there will end up being one solid for each letter. Note: To create independent solids in SolidWorks ensure merge result is not checked when extruding. This pyramid is also a good example. It has been sliced into seven pieces. KISSlicer treats each slice as an independent solid building a bottom, walls, fill, and a top for each. Saving STL Files Saving each body as a separate file avoids a problem. Either SolidWorks incorrectly writes the individual solids when they are combined into one file or KISSlicer incorrectly interprets the individual solids when reading a combined file. Slicing Loading the complete model into KISSlicer is easy: just select all the files when opening. When loading multiple solids KISSlicer places them at the correct relative height. In my original model the text is resting on the top of the base rectangle so that is where KISSlicer places it. Once the combined solids are loaded just slice as you normally do. G-code Crash Course G-code is text. Each line is either a command, a comment, or a blank line. Blank lines are ignored. Comments are marked by a semicolon. Everything after a semicolon is ignored.

2 ; The following blank line is ignored. ; As are the comments before and after the blank line. G0 Z30 ; Everything after the semicolon is ignored on this line. A command starts with a single English alphabet letter (like G ) followed by a one to three digit number. Some commands have parameters. If a command has parameters they follow the command on the same line and are separated from the command by space. The commands of interest for this project are G-code G0 G1 G28 G90 G91 G92 M0 M104 M109 M117 Description Rapid Move Linear Move Move to Origin (Home) Switch to Absolute Positioning Switch to Relative Positioning Set Position Stop or Unconditional Stop / Program Pause Set Extruder Temperature Set Extruder Temperature and Wait Display Message Pause Overview The goal is to get the printer to gracefully pause so the filament can be easily changed. There is a G-code command that, at first blush, appears to be exactly what we want: M0 - Program Pause. The biggest problem is that M0 never makes it to the printer. OctoPrint traps it and interprets it to mean stop sending G-code. This works to our advantage but it also means we have to do more than just insert an M0. G-code Structure from KISSlicer KISSlicer outputs G-code in sections 1. Title block. This section is composed entirely of comments. Details include the KISSlicer version, the operating system, and some other mostly irrelevant trivia. 2. Printer settings. This section is composed entirely of comments. Details include a complete dump of all the KISSlicer settings. This section is useful for troubleshooting a failed print or reproducing a successful print. KISSlicer can import settings from a KISSlicer produced G-code file. 3. Printer initialization. This section prepares the printer for a new print. Steps include reseting the printer, ensuring the speed is 100%, and warming the bed and extruder. 4. Layer generation. This section consists of the steps to print each layer. Each layer is marked at the beginning by a comment like this ; BEGIN_LAYER_OBJECT z=0.250 z_thickness=0.250

3 Each layer is marked at the end by a comment like this ; END_LAYER_OBJECT z= Printer finalization. This section contains G-code to gracefully shutdown the printer including cooling the extruder and bed, turning the fan off, moving the bed all the way out, and disabling the motors. 6. Estimates. The last section is composed entirely of comments. This section has KISSlicer s estimates for time and material. Graceful Pause The steps performed by the pause code are 1. Turn off the extruder heater so filament will not ooze out while waiting for the human to change the filament. 2. Move the head to a convenient location away from the part (0, 0, 30). 3. Back the filament out of the extruder to make changing filament a little easier. 4. Pause. This step is performed by OctoPrint. It simply stops sending G-code until the resume button is clicked. 5. When printing is resumed, the extruder is heated to 260 C. 6. When the extruder reaches the target temperature 75 mm of filament are extruded to purge the previous color. 7. The extruder is cooled to 180 C without waiting. 8. A second pause. 9. When printing is resumed, a standard PolyPrinter wipe is performed. 10. The head is moved to a height just above the part. 11. Printing continues. Merging Process Armed with G-code to create the part and G-code to pause the printer the next step is to merge the two. 1. Load the KISSlicer created G-code in your favourite text editor. I prefer Notepad2. 2. Find the end of the layer where a filament change is needed. For example, the Business Card Name Tag base is 2 mm thick so a filament change is needed after the 2 mm layer is done / before the next layer starts. 3. Search the file for a END_LAYER_OBJECT comment with the target z value. For the Business Card Name Tag this is the line of interest

4 ; END_LAYER_OBJECT z= Open the Pause for filament change.gcode file in your favourite text editor. 5. Select the entire contents of the Pause for filament change.gcode file then copy. 6. Paste the entire contents of the Pause for filament change.gcode file into the KISSlicer created G-code file after the END_LAYER_OBJECT comment. 7. Towards the bottom of the G-code that was pasted is a line like this G0 Z2.50 ; <--- Change the value after "Z" to a bit more than the next layer height. ---< The Z value needs to be changed to be slightly more than the current layer height. For example, the value for the Business Card Name Tag needs to be greater than 2 (mm) because the part at this point is 2 mm high is a good choice. That G-code command moves the nozzle to the height (in millimeters) specified after Z. This command ensures the nozzle is above the part when the head moves back over the part to resume printing. 8. Save the KISSlicer created G-code file. Printing Printing starts the same way it always does. When the graceful pause runs 1. The extruder is cooled, the head is moved to the origin at a height of 30 mm the filament is backed out of the extruder, and OctoPrint suspends printing. 2. At this point it is safe to change the filament. 3. After changing the filament click Resume in OctoPrint. 4. The extruder is heated to 260 C, 75 mm of filament is extruded to flush out the previous color, the extruder temperature is set to 180 C to avoid oozing, and OctoPrint suspends printing. 5. At this point the mess below the head should be removed including the three small blobs sitting on the bed from the previous wipe. 6. After cleaning the mess click Resume in OctoPrint. 7. A standard PolyPrinter wipe is performed then printing continues. Fonts that Work Well The following fonts work well with the PolyPrinters Arial Rounded MT, Bold, 19.00mm (74pt) Arial Rounded MT, Bold, 9.00mm (35pt) Forte, Regular, 25.00mm (105pt)

5 Forte, Regular, 10.00mm (42pt)