Re: [CAD_CAM_EDM_DRO] Re: Z-Axis Knee Woes

Hi Everyone,
On this note how big a Servo motor do you recommend for the Knee?
oz/inch ? Anyone? Mine is sort of tough to turn. Well oiled but I think
just heavy. Could I go 4:1 or 5:1 on the pully? Would software setup
limit this? Since its lower and almost out of the way I have room to
play with
I think.
Any experience on this would be appreciated.
Vince

>
> 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
>
>
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