Although the main purpose of adding multiple extruder feature to the RepRap machines is to allow printing the dissoluble support material, the new RepRap X2V3 dual carriage design opens a few new interesting possibilities.
The machine supports driving each extruder hotend independently on the X axis (”Dual X Drive”, see video here http://www.youtube.com/watch?v=AEW-DNo0GxI). Its predecessor (RepRap X2) had both hotends fixed on the same carriage (similar to Makerbot’s dual extruder machines) and at relatively close distance of about 20mm. If printing simultaneously from both extruders the machine’s build volume on the X axis would be limited to the distance between the extruders (not quite useful). Because of that I’ve decided not to implement the “follow-me” mode while adding multiple extruder support to Marlin firmware.
Unlike it’s predecessor RepRap X2V3 is free to position the hotends at any distance the size of the machine allows. That makes it possible to effectively use all the build space (i.e. the build envelope for simultaneous printing on RepRap X2V3 is about 100×200x130mm). Moreover, independent carriage driving allows simultaneous printing of mirrored copy of the object. That is often required when printing parts for the dual extruding machine or any object that has mirror symmetry. These hardware capabilities have convinced me to add the “follow-me” support to the latest (v1.1.0 X2 Beta 1 as of this writing) version of MarlinX2 firmware. The command for turning it on/off is M322. Its description is available in the README.md file. The video below demonstrates the feature in action:
One of the most annoying problems with the dual extruder printing is the plastic leaking from the idle extruder. It is especially noticeable with PLA that flows easier than ABS. Lowering the temperature of the idle extruder while it is not needed and restore it when it is time to start printing with that extruder again helps to deal with leaking. It is tricky though since leaking has to be prevented during the teperature changes.
The technique being used with the current generation of the RepRap X2 printers (S/N: 020*) is to print a “parking space” besides the actual object. That “parking space” serves two purposes, one is to plug the nozzles while the temperature changes and the other is to “prime” the extruders (i.e. establish the consistent flow of plastic) before printing the actual object after the temperature change.
The video demostrates the RepRap X2 S/N 0203 (find it on eBay) printing a dual color whistle (pictured above) using the described technique during the tune-up procedure. The STL files used for the print with the parking space object are here:
1. The whistle body (”BASE”, for printing with the extruder 0): Whistle X2 body
2. The text (”INSERT”, for printing with the extruder 1): Whistle X2 text
The special Skeinforge profiles for the X2 printer are needed to generate the G-code. They can be deployed using x2Profile app from the from the X2SW software bundle.
The …0.5C-BASE profile has to be used for slicing the body and …0.5C-INSERT for slicing the text STL of the model. The penultimate G-code generated has to be then merged using the “x2Merge” application (a part of the X2SW software bundle).
The “x2Merge” application merges together the G-code generated for the body and the text STLs. It is merged layer-by-layer. The content from the chosen alteration files for extruder switching is inserted in the places where there is a need to change the extruder. The inserted G-code positions the nozzles above the “parking space” object and changes the active extruder while lowering the temperature of the idle and restoring it for the active hotend before letting the printing continue.
The technique works the best for printing a few layers of color, for example a colored text on the top and bottom of the object. It essentially elliminates the discoloration due to the plastic leaking, but because of the time needed to adjust the temperatures it slows down the print substantially when there are a lot of layers requiring extruder switching.
Note: in order to use the technique X2SW software bundle of at least v22.214.171.124 and X2 firmware of at least v1.0.0b2 are required.
Here are a few experiments with Slic3r advanced features.
The pucture shows the calibration cube printed with infill every 2 perimeter layers (perimeter height 0.2mm, infill height 0.4mm) and the same cube printed with infill from the second extruder (natural color ABS).
Slic3r dual infill height and dual extrusion (perimeter+infill)
Recently I’ve had several attempts to print http://www.thingiverse.com/thing:23365
That was a pretty hard print for 0.5mm nozzle especially given that I had to scale the model down to 125mm height. One of the failed attempts produced this:
Akiko print failed
which looks kind of nice, but still funny given thet the expected result was that: