Extrusion Calibration by Calipers

thingiverse

I had to recalibrate my extruder steps and wanted to try the SublimeLayers method using calipers attached to the filament. My inexpensive calipers lacked a depth rod so I was unable to use the originally designed holder. They also have a goofy boss at the bottom that won't let them sit flat against a surface (It's the pair you regret buying even though they were like $4 and you just hold on to hoping that there is something you can use them for... this is THAT!). Pretty much any 16m wide standard caliper will do, they can be dial type or electronic. They don't need a depth rod to work. These calipers would lose count if the caliper body was anywhere near the extruder motor. (I suspect that the reinforced plastic body acts as an antenna and the EM pulses of the motor interfere with the caliper encoder). So I remixed this so that the caliper holder sits on top of my Di3 sheet metal frame and gets secured with a binder clip. The caliper in turn gets secured with a M3x25 grub screw. The clip that captures the filament is similarly secured to the lower jaw of the caliper with 2- M3x10 grub screws. The filament clamp uses an M3x15 screw. I changed the position of the screw so that you don't have to unload the filament from the printer or remove the clamp screw to thread the filament in. I tweaked the original gcode script, so that the hotend heats up, beeps, displays a countdown and then extrudes 100mm of filament. The extrusion starts off slow and then speeds up then ramps down. See the linked video. https://youtu.be/RxmVA18I0-0 Tips: Filament is best fed from the top of the printer, or use a short length. It helps if you straighten your filament by running it through your fingers a few times. If the lower caliper jaw drops a bit after securing the filament and zero'g out the caliper, don't worry about it. The extruder will take up the slack and pull the assembly downwards and it will catch up on the dropped amount. Remember to calculate the steps per mm and store it to the EEPROM of your printer. Octoprint makes this easy for the major firmware flavors. If you are not using already, you should, and if you are, throw a few dollars Gina's way...