Replacement Strut Arms

Discussion in 'Modifications' started by Mark G, Oct 4, 2017.

  1. Mark G

    Mark G Member

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    CompletedArmsInUse.jpg Jig.jpg OnePartAsPrinted.jpg I have had head crashes or other mishaps that have stressed the head platform and broken some of the orange acrylic plastic struts on my Deltaprintr Kickstarter printer. In the past, I have been able to purchase replacements/spares from Deltaprintr, but they no longer have a supply.
    Being down to no spares, and with one just glued back together, I decided to try designing and printing my own. I tried single-piece, but distortion at the edges of the print area were too severe to make usable parts. I also noticed that some of the print-area-edge-distortion seemed to be related to the strut end pinching against the u-joints.
    Also, the critical dimension of the strut arm is exactly 255mm between the 3mm screw hole centers, to within 0.1 mm or so. So I needed to be precise and consistent.
    In the end, I succeeded by designing a 2-piece strut (2 identical pieces per strut), with a jig to hold them while gluing to enforce the critical dimension. I used ABS for strength and because of the easy availability of ABS pipe glue.
    So, you first need to build a jig with two 3mm screws (I used nails) centers exaclty 255 mm apart.
    Then for each strut, print 2 parts. I used ABS settings with a brim. There are tabs at the ends of the pieces to tape down during printing to avoid warping (I do not have a heated bed). The tabs snip off easily.
    Trim the brim and tabs off each part, and then drill out the end hole to a smooth 3mm. Place each part on one of the jig pins, flat side up, apply glue (carefully) amd press together. Make sure they are nicely set on the pins. (ABS pipe glue is black, if you don't like that color you could make your own glue slurry with scrap ABS and acetone....)
    When you mount the assembled arms, make sure the flat side of the strut is on the side of the strut arm AWAY from the u-joint. This will stop the arm pinching distortion when the head platform is near the print area edges.
    RESULTS: After replacing all the arms (24 parts!) I have to say that the printer performs better than before! Far less distortion at the edges, and generally a little better behaved. I think these arms are actually stiffer than the original arms.
    Even if you don't want to do the while thing, it would be wise to print up a couple for spares, since Deltaprintr no longer supplies these strut arms.

    This is published in Thingiverse...
    https://www.thingiverse.com/thing:2569069
     

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    Last edited: Oct 4, 2017
  2. denys

    denys Active Member

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    That looks pretty good. I'll keep it in mind :)
     
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