Because of the rise of 3-D printing we now have several parts that can be custom made for our aircraft. A recent thread is proof of some stunningly designed pieces for adding lights to our experimental airplanes. I’m thankful for this technology and, not long ago, bought such a part made by another builder for my own plane.
But please do be careful as the following story tells a tale that is sad, and in truth, is the type of error, that perhaps, any builder could make if they don’t connect the dots:
I’m certainly not trying to put a damper on 3-D printing but rather to send a caution to be careful and think through the process. Good news is the pilot is OK …
I 100% agree. I do a lot of 3D modelling and printing, but would never use a 3D printed part in any kind of structural component or a critical part near a heat source. I’ve found it especially useful for fixtures/tooling when building where precision sizes matter for one-off use. And it can be used for non-critical parts that aren’t subject to heat, but they should be designed AND printed properly in those cases.
For example, while the cockpit isn’t inside the cowling, a hot summer day can cause the temperatures inside to rise to the point where most filament types will reach their glassing temperature and start to droop. I’ve seen it happen out in the open air in Georgia on a cloudless summer day. I’d printed a little glare shield for a tablet that was attached to a side-by-side vehicle for a project I was supporting at work. Around 2pm the glare shield started drooping and was malleable to the touch. It was printed in PLA, which has a very low glassing temperature, but is the filament that is most used for consumer 3D printers.
Definitely do some homework and select a material that can withstand high temps (ABS). Most consumer 3D printers don’t do very well with those high temp filaments, but there are places you can send a job to that can do it on high end printers than can handle it.
In the case of the article, it would be suggested to lay up some composite (carbon fiber?) around the part to make sure it holds its shape. Probably even better to use it to make a mold and use ONLY composite material.
My Brauniger Alpha MFD is an orphan. One of the switches died. Adam designed and printed a switch box and we saved it. Sitting outside for the first time at the airport fly-in, the print warped. It still works but we made a replacement to swap in out of HDPE and aluminum. I need to do that this annual.
I’d be interested to know what filament was used. I know some of the carbon types are being used on intakes for cars, so I’d imagine the under hood temps are as high as our cowl temps. Of course if you put anything close to an exhaust pipe all bets are off. I’d also imagine there’s quite a difference in the “carbon” I could print, vs what a professional machine could print.
made a replacement to swap in out of HDPE and aluminum
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That looks really nice!
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I’d also imagine there’s quite a difference in the “carbon” I could print, vs what a professional machine could print.
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I like PETG with Carbon Fiber for fairly simple parts that hold their shape, but even PETG has too low of a glassing temp for most outdoor use.
In general, I really like filaments with the CF particulates - the plastic in pretty much any filament expands and contracts with temperature, but the CF particles don’t, so it tends to be easier to print and hold its shape better. For example, ABS really shrinks when it cools and just keeping a part from peeling itself off the print bed mid-print can be tough. But the ABS-CF filament decreases that issue a bit.
Just to be clear, I think any 3D printed part under the cowl is a bad idea and suggested that he should have made a fully laid-up carbon fiber part (no 3D printing at all, apart from maybe to use in the mold).
I’ve used plenty of PETG parts on the outside of the plane, but I wouldn’t think of using one under the cowl unless it was just a trivial part, and maybe then just as a test to see if it would survive. I’ve never tried any of the carbon impregnated filaments, but only because I’ve never had an application I thought might require it.