Tuesday, July 16, 2013

Prosthetic assembly test

I got a little time to test assemble a bit and I found a couple of problems right away. This is with the center servo holder part, the first actuator and the first finger piece held together with a piece of filament. The end of the actuator does not look as curved up as in the assembly drawings. I don't know if that is an actual problem or not. Also, the shape of the top of the actuator will not allow the next piece of the finger to fit together correctly. It will be easier to see in a later picture.

This picture includes the next piece of the finger and this is as well as the pieces will fit together. 

This one shows down into the second finger piece and shows the conflict with the actuator and the finger piece.

This picture shows the under side with the three pieces assembled and shows the conflict between the gear teeth and the under side of the servo holder. The interference here will not allow the gear piece to move at all.

I hope that helps some. 

I will work tomorrow on attaching the servo to the worm gear and getting the worm gear to rotate well in the holder.



  1. Hi Morris, I was just comparing your pictures and the assembly pictures I posted in Thingiverse, it seems I posted in the pics a previous version of the actuator. So what you need to do, is mount the actuator the other way around. Instead of having the head of it going up it should be going down.
    I will post a new assembly pic on Thingiverse.

  2. Hi again, okay I posted a new pic in Thingiverse. I understood why you got it wrongly mounted. My pics confused you, the second actuator looked as if it was the first actuator.
    Hope this helps.

  3. That definitely works better. I got the finger assembled but it still won't move due to the interference between the gear teeth and the frame of the servo holder as in picture # 4 above. I can move the other parts but not the first piece.

    1. I just checked that collision/interference you mention. And it should pass normally, now that being said, the parts are very close from each other, and I guess the first tooth of the gear had a bit of overhang during printing, that might cause the collision. Could you cut a bit with a knife the first tooth to see if you still get the problem. Let me know, I could modify a bit the frame of the servo holder or reduce a bit the length of the teeth.

    2. I had already removed some plastic from the servo holder when I saw this message so I won't know if taking some material off the first tooth would have worked.

    3. Oh okay. Well I know I should give a little more space to make sure others don't encounter this problem.
      Let me know if it now function and if you can actuate the whole finger just by turning the gear, parts should move easily by hand other wise the servo will be forcing.
      I have posted again your blog on the forum for others to follow your work.

    4. There is another blog post after this one that is a follow on about the assembly test. The finger now flexes with the gear turn but not the finger tip. I don't know if that is because of a design problem or because I put something together wrong.