Kossel Carbon Fiber Arms

Continuing the saga of converting a Rostock Max to a Kossel, the arms which attach the carriages to the effector platform from the Rostock were not long enough for the new build. The appropriate length for the Rostock Max was around 11.5″, while the new Kossel build needs ~16-17″ in order to reach the outside of the bed.

I sourced carbon fiber tubes from Goodwinds.com and inserts from Amazon. I divided up each of the 3 rods into two 15″ pieces using a dremel to form the 6 arms that attach the carriages to the effector platform. I used super glue to attach the inserts to the carbon fiber tubes. When fixing the inserts it is very important that all 6 rods are exactly the same length. This measurement plays an important role in the accuracy and resolution the printer can get. In order to achieve this I set up a simple jig to hold each rod in the same place while the glue dried:


A lot of information I read talked about the length of the carbon fiber rods themselves needing to be exact. Taking this approach allows you to simply slip the ends in and call it a day. I found that using this jig allowed me to “fudge” the lengths of the rods. Since the jig is holding the position of the ends exactly where they need to be, a slightly shorter rod doesn’t compromise the total length, the rod end simply sticks out a little farther from the rod. This allowed me to have small differences in my rod lengths (I was using a dremel free hand) without sacrificing precision in the total length.


I rotated the rod ends in the rods towards me so they touched the nut, ensuring each of the ends were completely flat as well. After trying out one rod I could see the printer would be able to print to the edge of the heated bed with ease, and hopefully better accuracy.


On an unrelated note I finalized the work on the 24v power supply by attached the 12v stepdown unit and the SSR to the PSU to keep things neat:


In the future I may make the PSU modular to ease the work required to move the printer.

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