With the driver board working, I need to put the turntable on the motor which means I have to build a structure around it.
Some designs print the turntable as a whole. Others print quadrants and attach them together with screws. I’m having a little problem with my prints curling. I know it’s related to the temperature of the hot end but it’s a pain to tweak when all I want to do is to print a flat circle. So, I purchased some pre-cut 7″ diameter wooden circles from Amazon (http://www.amazon.com/gp/product/B00TGFWNMI) for $10. The suggestions I’ve read talk about either painting the turntable with a rubber coating or using the non-slip rubber matting that can be cut to size. I intend to use the latter.
To build the structure, I’m working in parts and will merge some of them so they can print together.
First step, is to attach the structure to the stepper motor. The motor is a NEMA-17 size which has some specific dimension. Lots of drawings can be found online. I’m new to 3D printing so there must be some rule of thumb to apply when copying dimensions verbatim.
It’s supposed to be 42.3mm square with a 31mm gap between the screw holes. It took me several iterations to get the screw holes to line up with the holes in my design but I managed it.
Now that I have the design for the top part, I can merge that with the other parts later.
Next step is to couple the motor shaft to the turntable. The shaft is 5 mm diameter and around 21-22mm high. My first pass at the coupling is designed so that the turntable is screwed onto the coupler ( screws descending ).
While I didn’t allow for any slop in the coupler itself ( it’s a tight press-fit onto the shaft ), I’ve included a hole for an additional screw to clamp the coupler to the shaft. I haven’t tested this yet but I have concerns whether the coupler is too small to allow the turntable to move smoothly. I may need to extend top of the coupler in the 4 directions so that I can add more screws to attach it.
The coupler on its own is not enough to support the turntable so I have to build some support struts. Other designs include a large ring bearing but my plan is for 4 struts with a skateboard bearing on each one and the turntable sits on top of those bearings.
I designed an axle for the bearing with a split down the middle to allow the bearing to pop on but not come off without additional force.
This one took a few attempts to get right as the diameter of the axle has to wide enough to fit through the bearing hole and tight enough to allow the bearing to spin correctly. Also, the wider part seen on the left has to be bigger than the bearing hole to prevent the bearing coming off but, when both sides are squeezed together, it has to be able to fit through the bearing hole. Now you see why it took a few attempts. I’m not an engineer and I don’t play one on TV.
Anyhoo, once I had that to my liking, I designed a simple strut to attach it to.
That was fun to do because I could use the 3D design software to take the axle I made and merge it onto a basic strut.
I took another go because I wanted to make the struts a little more aesthetically-pleasing. So, this is the final design.
To give you an idea on how this is supposed to look, imagine 4 total struts supporting the turntable: