I first encountered 3D printing seven or eight years ago at Comic Con. In Artist’s Alley, a booth had a 3D printer set up and running a print. This was fascinating, but I made two observations that stopped me from jumping into the industry at that time. First, printing even a small object takes a lot more time than most people would assume. Like the characters in this Funny or Die video, I expected 3D printers to be more like ink printers, quickly producing a loaded file. Not quite! My second off-putting observation was how bland the finished product looked: it was a figurine made of a single color. It looked cheap and not worth the time spent printing it. At subsequent Designer Cons and Comic Cons, I continued to encounter 3D prints that simply didn’t sell me on 3D printing because they always were a single color.
When we first started on our 3D printing journey, we decided to build multiple colors into our designs by printing them in pieces (by color) and then building our final models. We experimented with hand-painting our printed models, and we quickly decided to upgrade one of our printers with a multi-material unit. We want color, and lots of it!
My goal for this post is to share three ways to create multi-color prints using an FDM (fused deposition modeling) printer. We use Prusas, but the methods described below should be translatable to other brands of FDM printers, as well as a variety of slicing applications.
This method involves pausing the printer mid-print and changing the filament roll to the desired color. This either can be a manual filament change, or it can be programmed into the G-code for the print. When doing so manually, use your printer’s LCD controls to pause the print, load/unload the filament, and then resume the print. If you are adept at using your slicing software, you can schedule the color change at a particular layer.
Advantages
Manually changing color mid-print is fairly straightforward and should be easy for beginners to handle. Programming the color swap using slicing software is slightly more challenging, but still achievable for those new to 3D printing.
The main advantage I see in using this method is that color bleeds can be avoided. When loading the new filament, I have the ability to extrude as much filament as I need before continuing the print. This allows me to purge any filament that has mixed with the previous color in the extruder so that only the true, intended color continues to build my model.
Disadvantages
One disadvantage to this method is that prints have to be actively monitored with the user nearby ready to jump in for the color swap at the desired layer. Even when programming the swap into the G-code, it’s still necessary to swap filament manually at the right layer, lest the nozzle and printed piece cool from a long pause between filaments. The longer the pause in the print, the more opportunities for errors such as layer shifts, collapsing, or detachment from the bed.
Print limitations are also a consideration. With the print and swap method, an individual layer is limited to a single filament, and consequently, a single color. So, as your print builds up from the plate and you pause and swap filaments, there will be a clear delineation between layers as show below:
I have always loved building models and Lego sets, so I’m partial to using this method of printing my multi-colored items. Each color of a model is printed on its own, with similarly colored model parts batched together for the print. That is, if I have a model with 5 colors, I will run 5 separate prints, each with its own filament loaded. I then have to piece together my model.
Advantages
Using this method eliminates the possibility of any color bleed between differently colored parts, as you can fully purge old filament from the extruder between prints. I also like aggressively scrubbing the hotend on my machine between prints so no debris from a previous print finds its way into my current one.
Another advantage is that there are fewer print limitations (if any), in this method of multi-color printing, as colors are no longer layer-dependent. A whole piece–like a dog’s brown muzzle or ear–can be a discrete color and then assembled with another piece of another color–like a dog’s gold head.
Printing models in parts also can save time as no print time is lost for filament swaps (as in Pause & Print) or maintaining wipe towers (MMU method). If you want to produce multiple copies of a print, you can batch print by color. For example, I can print ten sets of brown dog ears, along with ten brown muzzles and ten sets of brown eyebrows together in one run of the printer. Batch printing like this saves a little time and some filament, but more than anything, it’s very convenient to build inventory this way.
Disadvantages
Post-production times rise significantly when printing in parts as you have to assemble the final model. While I prefer to make my models with snap-fit parts, the reality is that it is often best to glue parts together so nothing falls off through normal wear and tear. Glue presents its own challenges as it can stain your model or leave unwanted marks anywhere the glue touches accidentally. Parts may break during assembly, often requiring a quick print of a single part for replacement.
This upgrade option only is available for Prusa printers, so it’s not relevant to many readers. My reason for including the Multi-Material Upgrade (MMU) in this blog post is to provide one example of an automated approach to printing multi-color models. Of course, there are dual extruder printers, as well as devices like Palette 3 Pro, available on the market. I’ve not had experience with these yet, but I would like to try them and report back to you! For now, let’s look at the pros and cons of the MMU.
Advantages
Two of the main advantages of printing with an MMU answer to some of the disadvantages of the previously mentioned multi-color printing methods. First, with the color changes built into the G-code of a print, the MMU automates the swapping of filaments so prints do not have to be actively monitored. Second, using an MMU eliminates much of the post-processing work necessary from the Print in Parts method.
I have a love/hate relationship with my MMU, but what I really love about it does something the other multi-color printing methods simply can’t: I can achieve multiple colors in a single layer. This allows me to take any vector graphic and extrude it to be printed in a 3D environment.
One Grindmonkey’s top selling products is a Lilo & Stitch themed surfboard. It would be close to impossible to piece the different colors together using the Print in Parts method, and entirely impossible to achieve with the Pause & Swap method.
Disadvantages
Colors can bleed after filament swaps. This can be addressed through your G-code for a model by purging volumes. That is, you can adjust how much filament is purged through the extruder before the print resumes with a new color. For example, I may set my black filament to unload, purging 150mm of filament so when a lighter color loads, it has less of a chance of being contaminated by the darker color. Of course, this “wastes” filament.
The MMU creates a wipe tower, which a non-usable block of extruded filament to wipe the extruder during color changes. This is a neat feature, but again, it wastes some filament. Additionally, each filament change adds up in terms of time. So if a layer has four colors, the printer has to stop at least four times to load and unload the next color. And the general gripe about the MMU is that it is extremely finicky. During the automated load/unload process, filament may get jammed, requiring manual intervention. But, then again, the MMU can achieve prints that Print & Swap and Print in Parts simply cannot.
Conclusion
Again, these methods apply to FDM printers, and I’m sharing my experience based on having used Prusa MK3S printers. Regardless of the brand of FDM printer you may have, the workflow (loading/unloading filament, for example) is very similar. There are other methods of printing with multiple colors, and I have no doubt this post will be outdated before my others, as the technology for 3D printing keeps advancing rapidly.
Which method do you prefer? Is there a method not mentioned here that you would like to share? I welcome you to post your comments.
Leave a Reply