Why print battery pads?
I’ve recently been building quads based on open-source frames, specifically a 7″ mid-range quad using the FR7 frame by Jeremy Mariscal, as well as a 5″ long-range quad using the #MiniLongRange frame by Dave_C_FPV. These are both absolutely great frames for their intended use, with an active community around them. But I’ve discovered one (albeit very minor) downside: There are no custom cut battery pads available for them, and it’s not easy getting one custom cut in small quantities.
When I was finishing my FR7, I planned on cutting some Ummagrip-like material to shape. Well, that turned to be quite the challenge. I tried all kinds of methods of cutting it (including using a leather hole punch on the curved sections), but I just couldn’t get it to cut very cleanly. I spent quite a bit of effort on the aesthetics of the rest of the build, so adding an irregularly shaped, cut-up piece of sticky stuff wasn’t going to cut it.
I remembered seeing a comment on a forum where someone was asking about 3D printing a battery pad in NinjaFlex. This sounded intriguing, so decided to order some NinjaFlex.
NinjaFlex
NinjaFlex is a TPU material, but unlike the TPU most printed quad parts are typically made out of (95A shore hardness), it is MUCH softer & squishier (85A shore hardness). It essentially feels like rubber.
Designing the pad
In the case of my FR7, the designer of the frame (Jeremy) made available a DXF file for a nice battery pad, so all I had to do was extrude it to my desired thickness of 2.2mm and export the STL. However, had this file not been available, I would have simply based my design off of the CAD drawing of the frame’s top plate (which has the shape and position of the cutouts, which is really all you need to design a pad).
I opted to keep the top surface smooth & flat. In the future I might experiment with some different textures.
Printing
NinjaFlex turned out to be a bit more challenging to print, but once dialed in, was great to work with. I started with my TPU print profile (which I previously dialed in for Sainsmart 95A filament), and went from there. I had to significantly increase flow (125%), print at a hotter temperature (225-230deg), and squish my first layer a bit more (via z-offset), but otherwise didn’t need to touch the rest of my TPU settings. I used 100% infill.
I’ll point out that a battery pad is clearly not the most difficult thing to print, so it’s possible that further tweaking would be required if printing something more exotic with NinjaFlex.
Attaching it to the quad
I was looking for double-sided tape that would stick well to both NinjaFlex and carbon fiber. I found one at Michael’s that claimed to stick to rubber, so gave that a try. It worked great, and was easy to apply and cut. It sticks extremely well to both the NinjaFlex and the frame. The specific one I used is this one, but you can probably find something similar elsewhere.
Performance
In my opinion, the printed pad looks great! Equally importantly, it performs really well. It’s not sticky like Ummagrip, but with normal tightening of the battery straps, the battery is held firmly in place and won’t budge.