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

I’ll achieve this by setting the print to pause at a certain height (the height of the top of the hexagonal holes) and insert the nuts when is pauses, then letting it print over the top of them to hold them in place.

I actually had to write a plugin for this: although there is one built in to Cura, the slicer software I use, it is fairly limited and unreliable, and so I wrote a new one that mimics the normal pause and resume process of the printer as closely as possible. You can see it activated in the slicer software here:

Screenshot from Cura
Screenshot from Cura

Next, I inserted the framework that the components will be mounted to. Rather than remodelling everything into the new design, I just ‘cropped’ the one I’d already made and inserted it into the main frame.

Now it quickly became apparent that if I merged the component framework with the main frame there wouldn’t be any room to insert the ESC (which rests at the bottom, under the other components) once printed, and so instead I’ve made the component framework a separate part, so that now they print separately and I attach the component framework on top of the ESC with screws. For this, I did the same as for the lid, with four embedded nuts at the right places in the bottom of the frame, and corresponding countersunk screw holes in the component framework. Here’s what it all looks like together, once assembled:

Render of frame with component framework inserted inside.
Render of frame with component framework inserted inside.

And here’s the component framework by itself, which I’ll print seperately (using support material):

The framework is placed over the ESC and screwed into the main quad frame.
The framework is placed over the ESC and screwed into the main quad frame.

I have also removed the countersinks from all but the top screw hole on each fitting, as the bottom three screws will have their heads inside the fitting rather than outside.

Additionally, I’ve done some final touches – labelled USB and power ports for the Arduino on the side and slightly taller walls to give the PCB a little more room:

Side ports with labels.
Side ports with labels.

A small problem is created by the positioning of the power port for the Arduino on the outside: it means that I won’t be able to link it to the main battery power supply on the inside easily, and so will have to have a power cable plugged into the side of the quad connected to the battery as well as the main one going into the bottom. I don’t want to change the design now so I’ll have to live with it.

(The alternative is to try and power the Arduino using its VIN pin through the PCB, but this could be tricky. If I have time I’ll give it a go.)

Now to print it and move on to the arms, battery holder and lid.

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