3D printing enables rapid prototyping but lacks production-ready qualities such as smooth surfaces, temperature resistance and food safety. These attributes however can easily be added by combining 3D printing with casting silicone and urethane plastic for small batch production runs.
As long as you don’t need hundret thounsands of parts, this method should get you up and running without paying a fortune for a silicone injection molding setup.
When selecting mold making materials for 3D printed parts, it is important to be clear about the intended material for mold and cast .
Some points to consider are:
Silicone such as Dragon Skincan be extremely difficult to stick to surfaces, except silicone itself.
Urethane plastic such as Smooth Cast 310 is exotherm. This means it gets hot while it’s hardening.
Some 3D printing filaments are more temperature-sensitive than others.
Some 3D printing filaments are easier to post-process than others.
Having this in mind, the proper materials can be chosen basing on the desired material of the positive.
The center board has been glued with HK CA glue (HC-50-175). A small frame with screws through the four beam holder holes kept the sandwich layers aligned.
Note: Better do large areas with this glue outside as it generates a fume.
Using nylon spacers and screws, the top and bottom sandwich were assembled.
The beams were machined with a 1/32″ flat end mill and cut to length in the last run.
M3 nylon screws lock the beams and act as breaking point when crashing.
To attach the electronics to the center board, I chose two different approaches. Components which will not be used in every flight have been attached using Velcro. The other components were glued directly to capton tape I put to the center board. The ESCs were wrapped in capton tape to prevent short circuits. I hope the heat dissipation is reasonably low with the 30A ESCs.
HK CA glue (HC-50-175)
Loctite Vinyl, Fabric & Plastic Flexible Adhesive
HK 30min Slow Cure Epoxy
3M General Purpose 45 Spray Adhesive
Sandwich Bend Test
100x10mm x 1mm CFK, 3mm Fill, 1mm CFK
CFK 1mm, 3k plain weave carbon, orientation parallel (0°/90°) to centerline
Bend test showed best adhesion and no separation up to 6kg for HK CA glue (HC-50-175). All other separated well below this (usually at around 3-4kg). However glueing is tricky for large areas such as the center board.
During the first flights, the flight time was reasonably high at a bit over one hour with 1555 props.
Arms folded away during the first crash (I’d love to call it unplanned rapid decent though :-)) and the M3 nylon screws broke as planned, preventing damages to the rest of the drone.
With this setup, flight times above one hour have been achieved, even including the 180g 3-axis gimbal and GoPro.
In the diagram below various test flights for a 15″ 5.5 and 17″ 6.0 propeller were aggregated to show the effect the prop choice has on flight time.
Update: I’ve updated the battery with a 6600mAh 6S and the quad flies a lot more stable now.
Previously the flight recorder showed motors occasionally maxing out during sharp moves or wind gusts.
I’ll do some test flights and check the flight time. First flight was 2500mAh for 15min
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