Set screw angle and securing the dispensing disc

[wke...@udel.edu]

Hi all,

We've been experiencing an issue where our dispensing discs gradually accumulate crumbs of pellets underneath them and eventually lose their grip on the motor rod. This leads to the dispensing disc coming unsecured from the motor.

In my efforts to try and better secure the dispensing disc to motor rod, I've had some success by changing the angle of the set screw, but this doesn't seem like the best solution, so I'm wondering where we're going wrong / what others have come up with to firmly secure the dispensing disc to the motor rod.

As designed, the set screw is angled at ~45 degrees. In our hands, this slightly downward tilt means the screw isn't flush with the motor rod and tightening the screw actually introduces a force that pushes the whole dispensing disc upward, away from the motor rod. I've tried tilting the set screw orientation to be closer to parallel to the plane of the dispensing disc, which leads to the screw meeting the motor rod perpendicularly and make more flush contact between screw and rod (I tried mocking up a simple diagram for what I'm describing). This approach seems to help prevent the dispensing disc from coming dislodged, but it's very tricky because the motor rod is so short; essentially, by tilting the set screw to be parallel with the disc, I risk melting through the disc falling out the bottom.

It would be a lot easier to secure the dispensing disc to the motor rod if the rod stuck up longer. But since that doesn't seem to be an option, I'm left wondering how else to get a more secure connection between disc and rod. One idea is to make a permanent extension to the rod with either metal or plastic and then designed our own version of the dispensing disc that could accommodate that. 

Does anyone have any advice for how to better secure the dispensing disc to the motor rod?

Cheers,

-Will

[Lex]

Hi Will!  I wish the motor had a longer spindle, it would make this connection much easier!  Unfortunately they don't seem to sell that motor with a longer spindle.  I spent a while messing with the angle and that was the best I could do.  If you find an improved position let me know and I can evaluate it and possibly update the design.

That said, the current disk design works for us.  I think there may be two reasons you're having trouble.  First, you are correct that it is critical that pellet pieces/dust do not get underneath the pellet disk.  We find that you need really good prints for the disk. Whereas other parts (covers especially) don't really matter, the pellet area of the housing and disk have to be perfect. I'm attaching a video showing what it should look like in terms of printing and stability.  When we've tried using poorer quality prints (or disks that weren't totally flat) we had these issues.  I recorded a video to show you how it should be.

Second, I found "cone point" set screws, which may help with the stability.  Whereas normal set screws are little cylinders, these have a cone point:

We started using these, I think they make a stronger connection with the 45 degree angle to the spindle.  I hope this helps! -Lex

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