Arms Finished Printing and Change of Colour Scheme

I’ve been using CAD models and renders in white plastic the whole time, but a while back you may have noticed that I switched to using grey plastic when it actually came to the 3D printing. The main reason for this is that I’d been having some trouble with the surface finish of the white PLA, and as I knew that grey worked I stuck with it for then.

I’d been planning to stay with grey for the rest of the quad, giving it a nice smart, industrial finish, however I hadn’t anticipated how much filament I would have to use and after printing the second arm it was evident that I wouldn’t have enough to print any more.
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CAD Design for Arm

Now that the main body is done, the next step is the arms. Now I know exactly how they have to fit into the frame, because I designed the fitting earlier, and the female part of this is already built into the frame centre.

The first problem I noticed is that the radius of the propellers I’ll be using is about 130mm – the same as the length I had set between the body and the motor centre. The frame is angled so that motors this distance from the frame will be equidistant, but I obviously need some clearance between the propellers and the frame, and so I have regretfully extended the arm length to 160mm to allow for this.
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Print of Main Frame Centre

The main frame centre has now finished printing, and it’s come out nicely. I had one failed print, where because I didn’t have any glue to put on the print bed, the corners warped to the extent that it would have been impossible to actually attach anything to the bottom:

Warped edge on left
Warped edge on left – you can see the shadow underneath

So I added lots of pritt stick (the recommended way to make prints stick better) to the bed, raised the bed temperature from 60 to 75deg, and tried again.

It came out perfectly:

Perfect print of main body
Perfect print of main body

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Final Design for Main Frame Centre

Right after modelling the main parametrics of the frame, I’ve gone on to make it ready for 3D printing.

First, I have added screw holes in the bottom of the frame for attachment of a battery holder, and I slightly thickened the top of the walls on the long sides to allow room for embedded nuts for attachment of a lid.

Here’s the bottom:

8 screw holes on the bottom for attachment of a battery holder.
8 screw holes on the bottom for attachment of a battery holder.

I may not use all 8 screws, but I have put all the holes there in case I do need to.

For the top I have modelled in four hexagonal cavities for nuts to be embedded in, as you can see in this section analysis:

Section analysis of top of frame
Section analysis of top of frame – the long walls had to be thickened to make space for the nuts

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