Tuesday, 10 November 2020

Latest progress on the Bantam CNC conversion - CAD assembly

So how's the CAD work going then, Fatty?

I've put lots of effort put into this recently. At least I seem to be making some sort of progress. I'm not the kind of guy who just holds a part up against the machine, screws it in place and then figures out how to add the next bit. There are a lot of moving parts here and not a lot of space.

I've modelled up most of the critical parts to a appropriate degree of accuracy, so I can design stuff to fit together with a fair degree of confidence that it will assemble and work.

Here's the section view through the cross slide ballscrew. I've got a simple rigid sleeve shown here but that wouldn't allow any float, which would make setup and adjustment rather tricky. In fact I plan to have a 14mm Rotex "spider" coupling joining the new ballscrew and the original leadscrew stub. 

The back of the machine is looking somewhere between "busy" and "tricky". I hadn't realised the mounts for the large ballscrew would be so large. Fitting them and the saddle and the ballscrew and the encoder scale in that space will take some juggling to end up with a tidy solution. Looks workable but isn't your slam dunk.

From another angle:

And stepping back a bit:

The "missing component" that houses the cross slide ballscrew thrust bearing, connects the saddle to the saddle ballnut and picks up the encoder read head will be a critical part. It also holds the servo motor, houses the drive belt and pulley and provides some adjustment to adjust the belt tension and align the saddle ballnut.

Next - figure out a sensible solution for the "missing part" that I can make without needing a PhD in machining....

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