Wednesday, May 29, 2013

Printing the JHack simple servo bed

Jhack's derivative of the simple servo bed seems to be an improvement over the original simple servo bed that Gael posted recently.  It is certainly simpler to mount servos in it.  It is, however, fragile, in a few places and it isn't obvious how you attach it to the forearm shell save using glue. The same can be said for the cover over the servos that fits on top of the bed.  Once glued down, it would seem to me that you'd have to tear the while forearm apart if a servo failed.  I'm probably going to try to modify that while I'm waiting for the rest of my HK15298B servos to arrive.

The simple servo bed was a touch too big for my UP! Pro 3D printer so I had to tilt 45 degrees on the vertical to fit into my print volume.  Given the height of the resulting print, I had to use the stable support option which took a lot of filament to make the support and a lot of extra print time.  You can see the finished print here.

The extent of the support structure needed is quite clear.

You can get an idea of the nature of the paper-thin support structure in this pic of the support structure being removed.

While the removal of the support structure looks like a formidable task, as a practical matter it took less than ten minutes to clean it from the print.

The cover, not pictured, required a similar support structure.  It was considerably more fragile than the bed and required greater care in removal from the support structure.  I was able to do that successfully, however.


  1. Hi Forrest, I haven't printed the derivative of Jha, but it seems it could easily be transformed into two separate parts for smaller print bed. Jha on his video doesn't seem to glue the cover but just clips it, is it so?

  2. As I said, the part is rather fragile so I suspect it would be a bit tricky to transformed as is into two parts that could be connected. The cover clips on. Whether it will stay on when the servos are loaded is a question I can not yet answer. :-)

  3. Hi the top part is hot glued on at the moment I've been looking at making it screwed on though it is possible to change a servo with out pulling ot apart, I've had to replace one. I can look at making the top part thicker. If you think it will help? Thank you for your feed back it helps a lot. And I'll try to answer any question you have.

  4. I've been looking at incorporating some blocks into the lower and upper shells of the lower forearm that block your servo bed in and extending the cover and making it a bit more robust so that it can be attached to the blocks with screws. That would let us access the servos and also let us remove the servo bed with servos in situ.

    I've done the blocks and hope to get to the redesign of the cover this weekend. Do you think that's worthwhile, or would you like to do the whole redesign yourself? I'm easy either way. :-)

  5. I'm happy for you to do it , if you happy to . I do have it on my todo list but with work I don't get any time to redesign until about 2 weeks time,