RepRap: Blog

While I was away I did that panotgraph axis driver with the cranked arms. When trying to practically mount it, I realised it's a bit long. Here's a photo of the new one and a V0.03 Axis Driver:

The problem is the length. If I have to drive one end, and support the other, I need a structural member 140mm long, and that's going to have unavoidable flex to it. Ideally I'd have the supporting member no longer than the 60mm of the V0.03/4 driver. If I just shorten it up by half, the joints will have to bend beyond the limits of what I can do with PLA. There are a few options, and I'll probably take them all:

1. Fix the middle, not the end. This will work, but I'll need to change the ratio as fixing the middle on this version would give a 1:1 ratio, i.e. no advantage whatsoever. When I change that ratio I need to make the left-hand half a bit longer, but there's some benefit to he had there.

2. The arms don't have to be at 45 degree angles. It's the length of the arm that determines how much the flexures have to bend by. So if I scoot things together and sort of pre-flex the arm, I still get the mechanical advantage but there's less stress on the flexures. My model assumes 45 degrees, which is a pain, but that's fixable.

3. Make the beams narrower. They're a bit overkill at the moment. Can probably take a bit of overall length off there too.

There's probably a completely different solution involving clever linkages and complementary flexures. I remember seeing something a while ago, but to be honest couldn't figure out how it worked and can no longer find the references. May have been a fever dream or optimism. I'll give it one more go, and if I can't figure it out I'll get on with the depositing stuff again.