Re: New Setup

--- In CAD_CAM_EDM_DRO@y..., "abbylynx" <abbylynx@y...> wrote:

> Hi Folks,
>
> I'm a newbie to the list, and have just ordered a Sherline CNC

Ready

> Mill, I live in London, England, so I'm expecting it to arrive here
> within the next month or so. In the meantime, I've been working on
> various plans and ideas for the controller part of the system -

which

> I shall be building myself. When I see the huge prices companies

and

> websites are demanding for simple parallel port drivers, it just
> doesn't make sense to buy from them when I know I could make
> something far superior for a much lower price.

Unless your goal is to learn more about the design of motor control
systems rather than doing projects on your machine, I suggest you
monitor the list and ask for low cost suggestions for CNCing your
Sherline. Many of the group members have already done this and there
are several low cost solutions for what you want to do...even PIC
based external pulse engines. There are low cost Controller Software
solutions that use a parallel port. Since I don't know your skill
level in electronics, programming and CNC I can't comment on
your "far superior at a lower price" statement.

>
> I have one main question right now before I commit: Steppers or
> Servos? So far I've been leaning towards steppers, driving them

with

> the L297/L298 and using a PIC uController to control them and take
> input from digitizing probes etc (it'd be a serial device with an
> error control protocol, and the PIC would take care of ramping
> up/down speed and providing steps instead of the PC, so I could

write

> Windows driver software and performance would not be an issue)
>
> I'm just wondering if anyone knows where cheap servo motors could

be

> found? Specifically, ones that are NEMA 23 compatible. If I could

get

> inexpensive enough servos, I'd most definately go with this route
> rather than trying to hack mouse-encoders onto my finished stepper
> setup at some distant point in the future.
>
> Any advice/tips etc before I release the wispy spirit from power
> drivers?

23 Frame Servos with encoders often appear on EBAY. Some of the
other members may know of additional sources. To keep your costs in
line with your expectations I suggest you stay with steppers and one
of the proven bridge type designs. Control of servo loops is an art
in of itself and introduces analog issues into a digital design.

One last note. I understand your desire to "roll your own". You are
obviously technical and technical people tend to want to do
everything themselves. I suffered from that for many years. In my
opinion, your waiting time would be better spent looking at CAM
programs and starting the learning curve of using those to make
parts. You can get free G-code simulation programs that will let you
take your designs and cut them on screen in a virtual environment.

One thing about this group: If you don't want advice (sometimes lot's
of it) don't ask :-)