When we first got our Makerbot Replicator last year, I was really excited about the promise of using the dual-extrusion machine to make more complex prints. Why add a second print head? In the beginning, the ability to print multiple colors of plastic, without having to swap filament mid-print was compelling. And while I did manage to print a handful of test designs using black and white filament on the Replicator, the process to prepare models for a dual-head print involved splitting the different colored parts of a model into two separate STL files, making each of them printer-ready separately, merging them in ReplicatorG, and then adding a couple of additional steps to the already lengthy slicing process. It kind of sucked.
Enter MakerWare, Makerbot’s custom, mostly-closed source ReplicatorG replacement. While Makerware lacked dual-extrusion support at launch, it was added earlier this year. Since the update, I reconfigured our printer so it was running PLA on one head and ABS on the other—this makes printing using whichever material I want much more convenient. However, I hadn’t had a chance to test it out printing multiple colors on a single object using Makerware. I picked up a couple of fresh spools of ABS last weekend at MakerFaire, and figured that was as good an excuse as any to try dual-extrusion again.
My first multi-color attempt using Makerware was one of the gorgeous multi-color vases listed on Thingiverse (also pictured above). I set it up using the highest resolution setting, 0.1mm, which is what I usually use for prints today. Users of Makerware probably know that the Low and Medium print quality settings use MiracleGrue, Makerbot’s proprietary slicing engine, while the High quality setting uses ReplicatorG. MiracleGrue is dramatically faster than ReplicatorG, but it produces prints that are much lower quality (0.27mm vertical resolution vs. 0.1mm). I wanted to test both MiracleGrue and ReplicatorG with multi-color prints.
The difference in speed was quite remarkable. On my laptop, slicing the Julia vase took just under 8 hours to run using Makerware’s High quality setting and the ReplicatorG slicer. The slicing process converts a three-dimensional model into a series of layers that can then be translated into toolhead movements. This may seem like a relatively simple task, but it isn’t. The software has to take into account everything from the amount of plastic going into the print head to the mechanical properties of the hot plastic to the amount that it shrinks when it cools. To slice for a dual-extrusion printer, the software has to cut up slices for each color separately, weave the tool path commands together for each layer, and then check the tool path for potential crashes or other errors. The MiracleGrue slicer took about 10 minutes to do the same thing.
But wait, there’s a twist. Only the simplest of the multi-color objects I tried to print using the Miracle Grue slicer actually printed—the sample Makerbot tag that’s pictured above. The other objects failed in similar ways—each printed a portion of the first color of the first layer of the model, then stalled. This seems like it's probably a bug with the slicer. The ReplicatorG prints weren’t much better though, despite taking much longer to slice. Every time I tried to print the Julia vase, the filament going into the extruder head stripped at about the same place, a problem I haven't taken the time to figure out yet.
There is some good news though. I was able to get the cat pictured at the top of this post to print after spending a significant portion of the last three days. Unfortunately, the print finished too late to make him this week’s Mystery Object, so instead of a Mystery Object, he'll be an object lesson. If I’m going to try to do a dual-extrusion Mystery Object in the future, I need to start earlier in the week (or with something less complex).