8x4 plasma cutter

**cropwell** · 10-12-2017

Hi Matt,

Maybe you could put a limit stop in to prevent the pinion disengaging from the rack and jumping, leaving the spring to keep the rack fully meshed at the end of a travel move.

Cheers,
Rob

**Neale** · 10-12-2017

Essentially, I think you have a geometry issue here. On the gantry, the arm is positioned and pivoted so that the pinion moves roughly at 90deg to the rack. However, the X pinion arm is pivoted so that the pinion moves almost parallel to the rack. I know that it's not quite parallel, but it's close enough that even with a very strong spring, there is relatively little force acting to keep the pinion engaged. Would it be possible to use a fixed vertical plate going down from the gantry with a pivoted horizontal arm carrying the pinion? I can see that that might give belt tension issues, but that might be an easier problem to fix!

**cropwell** · 12-12-2017

Originally Posted by Neale

Essentially, I think you have a geometry issue here. On the gantry, the arm is positioned and pivoted so that the pinion moves roughly at 90deg to the rack. However, the X pinion arm is pivoted so that the pinion moves almost parallel to the rack. I know that it's not quite parallel, but it's close enough that even with a very strong spring, there is relatively little force acting to keep the pinion engaged. Would it be possible to use a fixed vertical plate going down from the gantry with a pivoted horizontal arm carrying the pinion? I can see that that might give belt tension issues, but that might be an easier problem to fix!

The solution for belt tensioning would be to have two belts, one on the vertical arm and one on the horizontal, with two pulleys on a shaft at the pivot point.

**kingcreaky** · 12-12-2017

Thanks guys, am going to fix the shoulder drops, then pivot the plate on the same axis as the rack. this will require more belts. Matt

**Lee Roberts** · 13-12-2017

I was thinking split the plate, fix the top, pivot the bottom, use a bigger belt (probably) and design in a spring loaded cam follower feature that would auto adjust the timing belt tension as the pinion mechanism/plate adjusts in real time.