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3D Printing has become almost commonplace in both industrial and hobbyist spheres, enabling the rapid creation of functional prototypes, replacement parts, toys, models, and much more. We’ve seen this first-hand at Diabase Engineering, making industry-acclaimed products like our Flexion extruders, urethane filaments, and hybrid machine platforms. Our flagship product—the H-Series—doubles as a rotary 3D printer, among other things.
While there continues to be advancements in faster 3D deposition technology and Hybrid Additive-Subtractive manufacturing (as well as some new Multi-material and Hybrid manufacturing developments in your run-of-the-mill plastic-squirting FDM printers), we haven't even begun to utilize the full potential of existing technologies.
Case in point: Rotary 3D Printing.
What is a Rotary 3D Printer?
Before we jump in, first: What is a rotary 3D printer? Printing around a cylinder, rather than on a flat bad, offers a number of advantages that are both practically useful and delightfully novel. In this post we'll go through some of our favorite features of Rotary 3D Printing.
1. Printing Is Easier and Parts are Stronger
Because we are Diabase Engineering, and we care first and foremost about creating functional parts, we will start with functionality! There are many exciting post-processing techniques and technologies that engineers and designers use to make their 3D printed parts stronger. However, with rotary printing, you can make your parts stronger from the first layer up by using a different approach to fabrication.
Bed adhesion is often a concern when 3D printing because of thermal stresses and adhesion characteristics between the part and build platform materials. The root cause of these stresses and failures also leads to parts that are weak where you don't want them to be. If we can diverge into a bit of technical discussion:
The strength of polymers is dependent on the long carbon chains being interwoven and randomly oriented. When a polymer is extruded through a nozzle and pulled along a surface, the chains have a tendency to align with the flow. Further, each layer goes down hot and cools separately from the layer before and after. The plastic wants to shrink as it cools, and the molecular chains are all aligned within the layer, generating shear stress at the interface of each layer, exactly in the area where the chains are not interwoven. The net result of this is relatively weak inter-layer boundaries, which causes FDM-printed parts to curve upward either off the bed or separating the layers. Worse yet, these weak points can cause failures of parts in-the-field when they don't have nearly the desired strength orthogonal to the printed plane.
However, when printing around a cylinder, we generate hoop stresses rather than unresisted shear as in planar printing. This helps with both of our problems (bed adhesion and part strength/stability) by compacting the layers against against the center axis as the parts cools, improving bed and layer-to-layer adhesion, and resulting in a stronger part.
Sticking the parts to the build surface is easy enough, but what about getting them off? The first example in this video shows the quick removal of a part from the mandrel:
2. Use Less Support Material in 3D Prints
Support material is often the bane of any 3D print job for a few reasons: because of material compatibility, parts sometimes will not stick to the support material; removal can be difficult or impossible; the surface finish on the support-facing side is poor, and soluble support material is very expensive. For parts with roughly cylindrical geometry, rotary printing can reduce the separating volume between the part and build surface. This knee brace, for example, is only vaguely cylindrical but can be printed much more efficiently with a rotary setup:
Of course this isn't appropriate for all part types - many don't lend themselves whatsoever to rotary printing. But for a lot of parts, Rotary printing is the ONLY way to make it. A bellows, for example, has a lot of high-angle walls that would require mid-part support material. That isn't impossible with a planar setup, but it is difficult to find material combinations that work reliably, and a bellows is particular in the material that it needs to utilize.
3. 3D Print Impossible/Unique Parts
This should probably be #1 instead of 3, because it is probably the most exciting. What could we make around a cylinder that we truly could not make otherwise? How about infinite helical printing? (The axis rotation is theoretically infinite, but obvious you would run into a space limitation at some point). This is neat for labels and decorations, but also has enormous potential for belting, tie-downs, webbing, lashing, etc. when we use a tough, flexible material such as TPU.
How about printing permanently on something that is already cylindrical?
Similarly, rotary printing allows you to encapsulate a rigid component with a flexible (or other) material, which may be useful for certain types of prosthetics.
Adding a 4th axis to your motion system allows myriad new build strategies and pain-free manufacture of different part types than people would normally associate with 3D printing. What else could you do with this capability? Please leave any ideas in the comments below.
4. Better Surface Finish on 3D Printed Parts
For organic shaped parts, the topology lines of rotary prints are more intuitive and attractive. Look at the topographical layer lines on this rotary printed mask:
But more importantly than beautiful organic shapes, rotary 3D printing allows "top-side finishing" of every side of a part. This capability eliminates the issue of the differing characteristics of printed parts on the bottom side - which is often either a very smooth (when over build platform) or very rough (when over support material) finish. The external surfaces of parts can be more fully finished in rotary builds.
5. Access All Sides of a Part
Similar to how parts can be printed smooth on all sides, a 4th axis also allows parts to be finished in other ways on all sides. Here is an example of milling smooth and accurate pockets into a rotary printed part:
There are many other strategies that could make use of accessing and further-processing any side of a part. In the above example, you could implant objects in those cavities then continue to print above them. The ability to rotate a part to exact and known locations opens up a world of additional possibilities.
6. BONUS - MORE ROTARY PRINTING IDEAS!
Wearable items (often rubber/plastic combined with fabric):
Print on Fabric and Mesh (Fabric stretched over a cylindrical surface is held “down” tightly to the surface)
Helmets, Splints, braces, orthotics
Costumes and Cosplay - masks, wearables, etc.
Racing apparel (motorsports jackets, knee-pads, and such)
Tactical gear - gloves, holsters, etc.
Backpacks, duffels, tough-gear, etc.
Footwear and other sporting goods
Power transmission components: