Re: What is the weak link in machine precision?

Peter,

Thanks for you input. What is the size of the motor you are using
for the knee? Are you using a stepper with encoder feedback, or a
servo system? Did you have to have the ways chromed after you bought
it or did they come chromed? Do you have any other kind of supports
to the table (air shocks, etc.) to help remove some of the static
weight from the knee?

Thanks.

Tom.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Peter Renolds <prenolds@s...>
wrote:

> You should have no trouble holding .001" if you use ground

ballscrews

> and quality components, tools, fixturing etc. You will have to

take

> thermal expansion into account - I just completed a big job (over

700

> hours) on my knee mill and was able to hold .02mm (about .0008") on

one

> dimension all day long. As the machine warmed up through the day,

I

> would take a couple of .01mm increments off my Z0 offset to

compensate.

> My part was about 5" x 4" x .75". My Z is via the knee and I have

not

> seen any significant wear - just a very nice, bright shine on the
> chromed ways.
>
> Cheers, Peter
>
> zipdrive2k wrote:
>
> >I am wanting to retro-fit a knee mill for prototyping aluminum and
> >some steel tooling dies. Many of the parts are complex surfaces

and

> >require 3 axis simutanious machining. I need to keep the machine
> >accurcy in the 0.001" to 0.003" range. Quill will be locked and

knee

> >will be moved for z-axis. Extreem speed is not a requirement.
> >
> >
> >