Re: Z-Axis Knee Woes

Hi Jake,

I powered the knee of a 9 x 42 mill with the same servos and Gecko
setup. Like yourself I ran into some of the same problems.

I cooked up a counterweight that hung behind the machine and
connected it by cable, over some pullies and down to the knee.
I also added two gas shocks with 175lb of force each.

With this system I only get about 30"/min max with .030" backlash.

It is usable like this but two things would make it better.

1) If I were able to exactly pinpoint the center of gravity of the
knee and counter balance the system from there.

2) Just get a bigger motor!


HTH
Matthew

> Hi folks. I'm retrofitting a G3102 Grizzly Knee Mill, a smaller

type

> mill somewhere bigger than a drill mill, but smaller than a full
> bridgeport.
>
> I just finished my Z-axis, after success with X and Y. I decided to
> motorize the knee for various reasons. I'm using Camtronics 600-in-

oz

> motors and a 2:1 ratio on the pulleys.
>
> The knee is driven by a shaft that is at 90-degrees to a jackscrew.
> The shaft is connected to the jackscrew via a set of helical spur

gears.

>
> Here are my problems:
>
> (1) the motors aren't powerful enough, apparently, to raise the

knee.

> They stall and eventually cause my geckos to fault. I'm pretty

sure

> I have the "limit" set to Max on the geckos.
>
> (2) when lowering the knee, the motor turns and every now again
> there's a 'thump' from the mill, as if the knee is not lowering
> smoothly, but in little increments.
>
>
> I guess I have two options:
>
> (a) go to a higher ratio, but 2:1 was the most practical. 3:1 is
> possible but expensive, and anything more is really not possible due
> to pulley size constraints.
>
> (b) counterweight the knee. I think this is complicated and

probably

> not a good idea.
>
> In either case I'm not sure it would solve problem #2. I'm

currently

> at a loss on how to proceed. Any suggestions are greatly

apprecaited.

>
> Thanks,
> Jake