[HenryK]

Hello all,

I've been reading up on rack and pinion systems, and am in the process of building a 4x8 table utilizing many of the parts from Ahren's site, including the nema 23 4 axis package, linear carriages, and the gearing for the R&P system.

As a result of my unique setup, I'll be machining a custom pivot plate for the motor and pinion. Because my X axis has two rails (15inches apart) I'm considering not only backlash, but also racking as a possibility. From my basic understanding of physics, the placement of the pivot bolt will have an effect on both of these conditions.

The attached image is a top-down view of the z-axis sliding on the gantry, with the two potential positions of the pivot bolt. I was wondering if anyone had experiences or opinions regarding which position made the most sense, or if I should just split the difference!

(note: the pivot plate will be spring tensioned against the rack regardless)

Thanks for the help guys, I love this forum!
Hank

[ssutton]

Hi Henry,
I also have a one-off design and used a rack and pinion. Attached you will find a CAD image of my drive. The pivot point I decided on was just a best guess. It worked out fine for me, but one interesting thing I discovered was that in one direction the pinion would attempt to lift away from the rack and in the other direction the pinion would drive itself deeper into the rack. This is not an issue because my spring setup does not allow for the pinion to lift away from the rack. I found that a very heavy duty spring and a turnbuckle adjusted to where the spring just began to pull to be the optimum setup. As far as racking, if you have a 4 motor system want you install 2 motors on the x axis, one one each side? That is what I did and I do not have an issue with racking. Mach can home each side of the X axis individually so that the X is square to the Y. You will be pleased with the hardware from Ahren, I did not use his drives but mine are very close to his, the setup produces ample power and good speed.

-Scott