PDA

View Full Version : Material strengths for mounting plates



Rogue
21-11-2011, 06:49 PM
Time for another MS Paint picture, I know how you love them so :smile:

I hope to mount the motor "internally" to the axis, so both the shaft and screw extend out in the same direction and can be connected by a pulley/belt system.

4946

The initial plans used a lovely thick block of aluminium for this - until I realised that the motor shafts aren't all that long in the first place. The second version (I think there's another picture I posted somewhere already) involved a pocket milled into the material to make it thinner where the motor mounted. This second version is No. 1 in the picture.

The question I have now is whether a pocket like this would substantially weaken the mount or otherwise weaken it in a way that makes it pointless, and what thickness is actually needed for a decent motor mount?

Is there a real benefit to using a thick mount, compared to a thinner piece with a standard mounting block, as in No. 2 in the image?

Edited to add: In the first image, the ballscrew is held by bearings (the green bit) in a pocket milled into the mount. In the second image, the ballscrew is held by a traditional bearing block (the green bit) or similar.

Jonathan
22-11-2011, 12:15 PM
Finally someone using pulleys from the start :tup:


The second version (I think there's another picture I posted somewhere already) involved a pocket milled into the material ... whether a pocket like this would substantially weaken the mount or otherwise weaken it in a way that makes it pointless, and what thickness is actually needed for a decent motor mount?

Sounds familiar, here's one I made earlier:
4948
4947

That was from 5/8" thick aluminum, motor is resting on about 2mm thick which is plenty as the 'wall' around it which is the full thickness supports it. It would be fine with say 1/2", but that needed to be thicker to fit a big bearing. I've made the pocket longer to allow changing of pulleys without changing the belt. You'll need some adjustment anyway to tension the belt.

You should mount the bearing as in number 2 as that allows freedom in the plane of the motor mount so you can get the screw aligned perfectly.