Sourcing machined parts for actuators on the cheap

Mechanics
1

We’re currently in the beginning stages of planning our own ODRI 12dof build, with a focus on minimizing costs.

The main issue we’ve run into is that we can’t source the MicroDriver v2 boards–we’ve messaged BetaLayout and they estimate that this will be sorted out in a half year, but this doesn’t fit to our time-schedule at all (we would like to test motor control before the end of the year).

As an alternative, we think that a solution based on Tinymovr will do the trick; either using their motor controller with the standard 4004 motors or their bundle with a 5208 motor. It’s in stock and purchasable.

The problem is that this solution does not use the encoder kit from PWB Encoders GmbH, and as such, does not include the aluminum machined parts–and while we have the 3d printing capabilities, we don’t really have access to a machine shop and from what we’ve seen so far, having an external shop make them for us would be prohibitively expensive (like 80€ per piece).

So, some questions:

  • Can we purchase off-the-shelf aluminum parts from somewhere? Can we buy a normal AT3 pulley and then modify it?

  • Is there a way to get some MicroDriver boards?

  • Is it generally realistic to reduce the BOM per actuator to < 200€ for each motor/encoder/controller bundle?

  • General advice?

2

Hi,
the shortage of the chips for the Microdriver boards has been going on for a quite while now and is also a problem for us - we don’t have a solution for that.

Using a Tinymovr motor controller seems like a good alternative - one of the challenges is that it uses a magnetic sensor on the motor driver board to determine the rotor angle.
So to use that board you would have to integrate it into the actuator module which might be quite a bit of work.

David Gonzalez developed a similar design - so maybe you can get some inspiration here:

Regarding the machines parts:

  • You could try to 3d print the all the timing belt pulleys.
    We did that in the beginning - using a high precision polyjet printer (Projet). (picture below)
    The limitation is that the teeth of the small pulleys can shear off when experiencing violent impacts.
  • You could also use AT3 stock material to reduce the machining complexity. (picture below)
  • We started with the stock material but it was difficult to get and the long lead time was a problem.
  • Yes - you can also modify standard AT3 pulleys - the only drawback here is that the teeth are smaller and that the standard tooth profile has a bit more backlash than our version.

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Good luck and best wishes. Felix

3

Hi, Marmoset

I have some Aluminum AT3 pulleys lef, like 10€ per piece。