Optical Tube Assembly Printing

I have been test printing parts for the 3D printed telescope since early October. Starting with the two main rings for the optical tube assembly (OTA). Early on I knew I would be limited by the size of the print volume of my Dremel Idea Builder, which is 230mm x 150mm x 140mm. This led me to break up the rings into 6 equal parts of a circle. I tried four different ways to connect the parts together and settled on an interlocking system held together by 3 M4 x 20mm socket head cap screws arranged in a triangular pattern.

Each piece of the ring has a slot for a ~2 foot long piece of OpenBeam connecting the bottom and top rings. These slots have four holes (two inside and two outside) for M3 x 6mm button head screws to hold the OpenBeam in place. For the bottom ring there are 12 other M4 holes arranged every 120 degrees for the mirror cell blocks that connect the central mirror cell to the OTA. On the top ring there are M4 holes arranged every 90 degrees for the spider blocks that attach the spider and secondary mirror assembly to the OTA.

Below are a few pictures of the top ring that I have printed and assembled. In the first photo you can see the interlocking system at each end of every piece. There are 18 M4 x 20mm bolts and 18 nuts that hold the ring together. All the hardware is countersunk making all of the surfaces clean looking. You can also see the vertical holes made for the spider blocks placed at a separation of 90 degrees. There are 4 holes when the spider block is near the center of the piece and 2 holes when the block is over one of the OpenBeam slots. The OpenBeam will extend about 1cm into the spider block that is over the slots to add stability.

Again you can find all of my current .stl files at http://www.thingiverse.com/thing:1112195