Of all the BigRep materials we’re reviewing, I was probably most concerned with TPU, a highly flexible material. I have used various brands of TPU in the past and have had great success printing flexible parts. I’ve also had a lot of failed and smeared prints with TPU, as well as clogged nozzles and filament wrapped around the drive gear. It can be frustrating stuff.
Flexible 3D printing materials have really expanded the range of desktop and professional 3D printers, allowing small businesses to make prototypes and functional parts that would normally be made from rubber through the expensive injection molding process. So, is BigRep’s TPU a material for professionals to make gaskets, sound and vibration dampers, seals, molds, dampers and more, or is it a headache on a reel that produces ugly parts and clogged nozzles? We will find out today!
The BigRep TPU filament is wound just like every other BigRep material we’ve reviewed, which is to say, perfectly. It’s incredibly flexible and seemingly impossible to tear; it’s somewhat elastic, too. The packaging indicates that the material is sensitive to moisture and should be stored in a dry place.
Standard TPU setups in Cura were used to load and print the material on an Ultimaker S5. The first two prints were printed with 0.15mm layers and the rest were printed at 0.2mm. Prints well at 225°C on a 60°C bed; the biggest differences in print settings for TPU are slower print speeds (25mm/s) and a longer shrink distance due to the aforementioned compression characteristics. Benchy!
Color me surprised. This is by leaps and bounds the prettiest TPU print I’ve produced to date. I know we’ve set the bar high with other materials, so it may not look as good as rigid materials, but that’s mostly a texture/lighting issue. Looking at the front of the arch, the smoothness of the walls is evident. Similarly, the corners of the pillars are straight and small details are present. There are some faint strings, but nothing that can’t be easily removed.
And none of the other Benchies can do that! He never gets old. It always returns to its form. I opted for the smaller torture test for this material as it better reflects its capabilities.
This print does a great job of showing off the distinctive finish of the material, which I personally enjoy. It has a professional touch. The corners of the plaza are incredibly sharp and the pillars withstand extreme flexing without breaking or warping. The hex and circle holes came out nice and the arch is great up to the top where it struggled a bit at the bottom of the bridge. The only other problem is a slight chord between the pillars, something that is almost impossible to avoid with flexible materials. That is not to say that the stringing cannot be reduced by increasing the retraction in the printing parameters. The default settings were used for consistency and to produce results that typical users can expect. The problem under the arch had me worried about the bridge test, and for good reason.
The bridge is somewhat complicated. If you look at a 3D printer when it’s connected to a rigid material like PLA, you’ll see something fascinating happen. When the stream of molten plastic is vented into the air from the first side of the bridge, it initially sinks a bit. After the nozzle connects the line to the other side of the bridge, the line cools and contracts, tightening into a straight line with little or no sag. It only works well if the printer is printing fast enough to beat the media cool down time. With TPU, slow print speeds are specifically used to allow for proper cooling because it’s a softer material and each layer still needs to be firm enough to support the next layer. It handled Benchy’s 6mm jumpers pretty well, but crossing anything larger than 12mm will be difficult with stock print settings. Still, the print didn’t fail, and the quality of the rest of the print wasn’t affected by the poor bridge, so it’s a win.
I performed ply adhesion tests by breaking three vertical drawbars on a hanging ladder. They broke at 25lbs, 30lbs and 30lbs, for an average of 28.3lbs, less than I would have expected for such a strong material.
The thermal deflection test of a rectangular bar was more promising. Also, let’s see that the other test bars do this:
- Original dimensions: 20.15mm x 119.9mm x 5.74mm
- Dimensions after annealing: 20.1mm x 119.5mm x 5.74mm
That’s virtually unchanged after being exposed to 170°F / 76.6°C, which means the material should hold up well to hot applications.
To really demonstrate what can be done with this TPU, I looked for another material: epoxy resin. I’ve recently been experimenting with 3D printed mixed media and resin parts, and when I print with rigid materials like PLA, the resin and PLA permanently bond as the resin cures into a solid. It is possible to use PLA to make resin molds, but the PLA must be broken to get the resin part out. I was hoping that the TPU would allow me to print reusable molds for resin. I couldn’t find anyone on the internet that prints TPU molds for resin. It is not a good sign.
But lo and behold, it really worked! I didn’t even spray it with mold release (cooking spray) before pouring the resin because I totally forgot. But after letting the resin cure for a day, I folded one of the edges under and it popped open. The resin piece will need some sanding and polishing to make it really shine, but the printed mold is ready for round two. An important lesson to learn here is to not let a lack of results on Google stop you from trying something interesting. It might work, and there’s nothing like finding out through good old-fashioned experimentation. I will definitely be adding this to my toolkit, and will be writing a tutorial on printing TPU molds in the near future, so stay tuned.
Conclusion
This material is delicious. Sure, it’s not good for bridging and it chains up a bit. Those aren’t deal breakers when you check all the other boxes and create boxes most other material has never heard of. It’s easy to print with as I had no stripped parts and no extrusion issues. It is aesthetically pleasing. It is hard and impact resistant (I dropped all my footprints on the tiles and none were damaged). It can take the heat. Best of all, it bends, straightens, stretches, flexes, and twists! That opens the door to use cases that rigid materials simply can’t handle, especially with consistent, repeatable printing like I experienced using the material. Professional engineers and designers can certainly benefit from having access to a 3D printable rubber-like material in BigRep’s TPU.
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