Re: [CAD_CAM_EDM_DRO] Mill recommendations needed for new CNC Project

mayfieldtm wrote:

> I'll be approaching my Boss on the possibility of putting together a
> small CNC Milling Station.
> Our need is quite specialized and it might be better suited if we
> build our own. I know a ready made commercial machine will be out of
> the question. All of our in-house CNC Machines are tied up in
> Production or tool making.
>
> So I'm asking you-all on your recommendations on a good new starter
> Mill that could be converted. Would like to keep the Mill price around
> and under $2500 (new). I'm figuring another $1500 for other parts.
>
> For my Home Shop, I converted a Grizzly (of the rong-fu type design).
> Although it's perfect for my hobby use, It would just not be tight or
> beefy enough for our application. And of course, you-all know about
> the round column problems.
>

There is the CNC-ready Taig, which is easily set up with size 23
motors. Just add motors, drives and your favorite CNC program.

Also, there is the 150-Lb minimill, a bit more rigid than the
Taig, but about the same envelope.

> We often design Forming Dies (two dimension) for various types and
> thicknesses of spring steels.
> The results of bending a part, often, is not quite as expected
> (calculated) and will fall out of tolerance, so the Die needs to be
> reworked or remade. The second try is usually successful.
> Most of our Dies are EDM'ed by an outside source, and can be expensive
> and most importantly, time consuming.
> I believe I can justify the concept of a small in-house CNC for this
> purpose only. I would not expect nor want the Machine to be used in
> Production.
>

If you just need to test a couple pressings with a die to verify
the geometry before having it made by EDM, you can make them out
of milder steels on the CNC. There are, of course, things you
can't mill, like square-corner die cavities.

> My Maximum Milling Envelope would be: X=6" Y=3" Z=1".

The Taig and the 150-Lb mills both handle about 4" Y, otherwise
plenty of travel on X and Z.

> The Typical size of a Die is 3"w x 1.5"h x 0.25"thk. with a profile
> along the 3" dimension.
> Most of the time I would be using an 1/8" Mill in 0.125 - 0.25" thick
> material. Typically "O1" or "D2" tool steel. (Annealed of course)
> Probably use Servo Motors, speed is of no importance, so Step Motors
> might be OK.

I have retrofitted servos to both the Taig CR machines and the
minimills.

> Dual Nut Ball screws mounted on Annular Bearings for Minimal Backlash.

The backlash on both these machines' standard screws is quite good.

> Will be using Gecko Drives, a Brute Force Power Supply, Computer
> Interface and a Computer running Mach3.
> I found that the most difficult part of converting the grizzly was the
> Z-axis, so the basic machine should be well suited for that.

Ahhh, good point. The Taig is better then, it comes with a
screw-drive for Z. The minimills have a rack and pinion, which
has to be replaced with a screw, as the rack has a lot of backlash.

Jon