Re: Beginner's Mill/Drill to CNC conversion questions

--- In CAD_CAM_EDM_DRO@y..., Bryan Pryor <bkpryor@y...> wrote:

> In my search for ways to get a 3-axis CNC mill for
> under $3000, I came across this page.
> http://www.homecnc.info/cnc-main.html Reading that, I
> believe I can actually obtain my goal. However, I
> have many questions still.
>
> I would like to use a mill/drill that has a dovetail Z
> axis, but if I cannot afford one I will get the same
> Enco that was used in the above webpage.

Most would prefer this however there are some cavets to this.
The dovetailed mill/Drills I know are nearly twice the price.
The good, you can rise and lower the head without losing position.
The bad, without the dovetail you can swing the head from one side
to the other inbetween machining and gain a much larger machineable
Area without reclamping. Can't do this with the tail.
Personally I do not belive the added price would be justified, if
I had the additional money for the dovetail version I would be
spending it on a larger machine to start with.

>
> 1. Once I purchase the Mill/Drill and computer, how
> much more will it cost to convert to a 3 axis CNC?
> 2. I would like a machine that will give me 0.001"
> accuracy. Can I expect that from this type of a
> setup?

Yes Mill/Drills are capable of this acuracy.
Most Drivers deliver resolutions higher then this.
There is a very wide range of cost here depending on the
performance you expect to get.
The more you want to get involved in assembly of your drivers
the more mony you can save, research and shop around.
The Hardware to mount the motors and such you will be stuck with
there are no vendors I know of that offer this.
There are some Kits offering drivers motors and software.
generaly anything less then $2000.- will likely not have powerful
enough motors to get satisfactory speeds.
You can always gear them down to get more torque but this will also
reduce the speeds to move the axes.
Between $2000-$5000 is what gets you into some respectable kits.
The sky the limit here there are kits for more then $10000.- out
there I have no Idea if they are any better, too much for me.

> 3. Will I need to install ballscrews, or are they
> just highly recommended?

Highly recommended.
Without Ballscrews your machine will have the same capability
as a manual machine just cnc controlled.
Dealing with backlash will be a pain, restricting to mostly
conventional cutting.
Acurate circle cutting one of the main benefits of cnc will
not be nearly as acurate eaven with backlash compensation.

> 4. Stepper or servo motors? and why?

This is to complex of a question to answer here, there
are many good webpages out there to explain the pos and cons.
Very generalised a machine this type can be retrofitted
with ether one and function very satisfactory.
A suitable stepper setup will likely be a little cheaper.

> 5. I am trying to get a mill/drill with a dovetail Z
> axis. would it be more difficult to convert this type
> mill?

No most I know still have rack and pinion drive.
This in any case is more difficult to archive backlash free
opperation.

>
> I'm glad I've found this group. there seem to be very
> knowledgable people here. I'm still reading through
> the FAQs and Archives. any advice or tips you could
> give me would be much appreciated. Thanks in advance.
>
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