Advances in materials science and polymer innovations are an increasingly powerful catalyst for change in the additive manufacturing industry at this time. As 3D printing gains popularity in the industrial sector as a major means of production, a broad range of applications drives a proliferation of specialized plastics uniquely suited to various purposes. In turn, the machines performing the extrusions must be engineered to possess the versatility needed to create optimum flow rates for these different materials. Hobbyists and DIYers are also often enthusiastic about having access to a multitude of printing materials and correspondingly look for a machine that can handle a variety of polymers.
Count us amongst the polymer nerds! Here at the Massive Dimension extrusion lab, we have prints running every day, and as often as not we are printing with feedstock material that we have not yet tried in some different permutation. As we have mentioned in a previous blog post (insert link to extrusion service blog post), we provide extrusion tests as a service to customers, but outside of those specific tests we push ourselves to constantly try to expand our knowledge or what is possible with our machines. Knowledge is power- and one of our goals is to be able to share that knowledge with the community. Though a certain subset of the polymers we have printed with are protected by non-disclosure agreements with particular clients or companies, we’d like to start providing blog posts sharing all of our findings that we can with our readers. Here is a list of some of the polymers we experimented with in the lab on the MDPH2 so far in 2021-
Ol’ faithful. A dependable and printer friendly polymer as ubiquitous as Sriracha. We recently switched from supplying 3D850, 3D870, and 4043D as our PLA variants to LX175, so most prints were run with LX175 though we also did some experiments printing with 3D850 regrind granules and pelletized recycled filament.
LX175 + 10% Brass powder
This polymer was mixed & extruded in the EX6 into 1.75mm filament then chopped in the Pelletizer before being fed into the MDPH2. Printed just like plain LX, with hot end temperature bumped up 5 degrees as it seems the added metal slows the melt flow just a touch. Produces a beautiful color and genuine metallic, glimmery surface finish. Stiffer & heavier in the hand.
LX175 + 20% Spent coffee grounds
This was made from coffee grinds collected over the course of a week or two in the Filabot office. Spent coffee grounds were dried in a kiln then mixed by hand at 20% weight with virgin LX175 pellets, then extruded with the EX2 into 1.75mm filament and chopped on the Pelletizer. This was a favorite in the lab - prints without issue at same settings as plain LX175 and smells like coffee while extruding! Gives a nice organic texture to the print and tints the polymer the same color as the grounds, a nice dark chocolate appearance. Check the Filabot blog for more on this combination!
Push Plastics Woodfill PLA
This composite polymer is also printer-friendly and requires little tweaking for a successful extrusion. If you turn up the hotend temperature a bit you can actually start to burn the wood a little bit, which gives you some ability to play with your final color tone. Don’t turn it up too high though, or it starts to stick to the screw! Very matte finish, like a blonde ceramic.
Mystery PLA + 50% Wood dust
This was definitely a wild card experiment - we found a 5-gallon bucket of this polymer in a forgotten corner of storage in the lab and figured we had to try it. The large amount of wood fiber meant that the pellets also had a significant amount of moisture in them, which required a lot of drying. The MDPH2 was capable of extruding the polymer, though we didn’t manage to print much more than a simple hexagonal honeycomb pattern a few layers high. The biggest obstacle was the pellet size, which are extremely large and jam in the feed throat. Further experiments could be done compounding these mystery pellets down with virgin polymer and creating a smaller pellet. If you enjoy the smell of sawdust, the scent of this extruding is thoroughly enjoyable!
Another reliable workhorse polymer. This is also a go-to in the lab for printing prototype parts with great success rate. As with the PLA variants, most of the lab trials involved additives.
PETG + 8% Aluminum powder
As with the other metal composites, this seemed to be happy extruding at 5 degrees higher on the hotend than plain PETG. Unlike many of the other composites we ran recently, this combination was not previously compounded on a Filabot extruder and chopped into pellets. We simply weighed out a ratio of metal powder to pellets and mixed it together in a bag before dumping it into the hopper of the MDPH2. Under a visual inspection of the resulting prints the mixing appears sufficiently consistent, though certainly pre-compounding would deliver superior consistency. The effect of the added aluminum seemed mostly visual, as opposed to the PLA/brass mixtures that were stiffer and heavier than the plain PLA. That being said, the visual effect of the aluminum additive is very striking- somehow both shiny and matte depending on how the light hits it. For a no-fuss additive it is very worthwhile.
PETG + 2% Ceramic pigment
We did a number of experiments simply playing around with adding different colors to standard PETG to see what combinations could be created, as well as trying transitions within a single print. The transitions are very hard to accomplish as the pigment coats the screw quite thoroughly and requires a large amount of polymer to pass through before being eliminated. An even lower ratio might be required in future tests to accomplish this effect. Lots of fun to be had making your own recipes for particular colors if you enjoy playing with different hues! These ceramic pigments are something we started offering on the Filabot store recently!
Part of our mission is to increase viability of recycled polymers for use in additive manufacturing, and to help shift industrial practices to reflect this. We ran a number of prints using rPETG, recycled from a variety of waste products. Admittedly, this recycled polymer can require a bit more fiddling with settings than virgin PETG, our best results were found with higher hotend temperatures than virgin PETG, by as much as 20 degrees.
Polycarbonate is a far less popular polymer at large as compared to PLA, PETG, ABS, etc. It is a bit more restrictive in terms of machine capabilities, mostly due to requiring higher bed temperatures than many machines can produce or enclosures to help slow cooling. The experimental system in the lab that the MDPH2 is currently mounted on (custom SCARA movement system with a ½” aluminum build plate) does not have an enclosure, and our tests also struggled to keep the print from warping as it cooled. We successfully printed some smaller diameter vase forms, and especially liked the visual effect of polycarbonate when the pellets had not been dried! Much like PETG, moisture in the PC creates small bubbles that give the finished print an appearance similar to antique glass. The polymer seemed less prone to oozing than PLA or PETG, reducing stringing.
TPU has taken off as a specialized polymer for industrial applications, being used for various products such as cell phone cases, sporting goods, power tool housings, and wheels. It is fairly easy to extrude with the MDPH2, and is very sticky so bed adhesion is no issue either. TPU is flexible, tough, and abrasion resistant - it comes in a huge variety of densities and durometers. While not suitable for all applications (thin walled prints or hollow forms will collapse under their own weight) there is something quite delightful about printing something that can be stretched, bent, and squished. We printed a frisbee-like dog toy and “stress-tested” it by playing tug-of-war and fetch with one of the shop dogs. It didn’t break, even with the full weight of the dog dangling off of it!
Those are the highlights from the first two months of the year, we hope you enjoyed reading along and encourage you to reach out with any comments or questions about extruding these different materials! We intend to make these “extrusion reports” a regular feature of the MD blog moving forward so check back in for further updates!