Re: [CAD_CAM_EDM_DRO] CNC retro fit - Gray area , need help

Hi.... Good advice, hopefully I can add or clarify things..... The "controller" is usually software the takes your G-code information and sends it to your dirvers that power the steppers. The software sends "step" and "direction" information to the drivers via the parallel port or depending on the system, could use a special computer card in which to communicate from the software to the drivers.
Usually one draw there "part" in a cad software, then takes the drawing file into a cam software. This is were you set your cutting paths that will be coverted to g-code, to be used in your "controller" software......... This a very general description of the complex process, hope it helps.

Russ
Andrew Werby <drewid@...> wrote:Message: 13
Date: Sat, 11 Jan 2003 22:45:14 -0000
From: "pastypies
"

Subject: CNC retro fit - Gray aera , need help.

Hi all,

I am looking for the missing link between a Solidworks part and the
actual part being machined. I have a JFC-500C mill/drill (quite a
size as mill/drills go), I would like to make it a CNC mill/drill by
fitting NEMA 34 size stepper motors to the X and Y axis and perhaps
something smaller to the Z axis. I have researched the Internet for
about a month now and have found many informative sites, CNC Retro-
Fit website at http://www.mendonet.com/cnclinks/index.html is
especially good. From what I have read I conclude the following.

1.My mill/drill must have stepper motors fitted to the X/Y and Z
axis.

[Or servos.]

2.If possible I should change the standard Acme lead screws with
ball screws for greater accuracy.

[And speed.]

3.The motors must connect to some kind of driver or amplifier.

4.The driver(s) then connect to some kind of controller card fitted
inside my PC, or connect to an external controller that connects to
the parallel port etc.

[Some work that way (Flashcut, DeskWinNC), others (Gecko, Xylotex) use the
computer itself to generate pulses that activate the motors.]

5.Software on my PC needs to convert G and M codes into signals that
my controller card can understand (i.e. to be compatible with) to
drive the motors.

[Right- that's the controller software, like CNC Pro or Mach1.]

6.The software (be it the above or other) needs to convert my
Solidworks 3D model into G and M codes so the part can be machined.

[That's usually a different piece of software, called a CAM program. Try
VisualMill Free for this- it won't cost you anything to get started, and if
you decide you need more features, you can buy something later to provide
them.]

I understand that within reason a stepper motor is pretty generic be
it 4, 6 or 8 wire. In the same way so is a ball screw, its just a
ball screw, what you see is what you get. Presumably I can go out
and get any brand of stepper motor or ball screw and it will make no
difference what so ever?

[No, unfortunately it's not that simple. Steppers vary considerably in power
generated and power consumed, and there's some types (like 5-phase) that
aren't compatible with most drivers. You need to carefully match the
performance of your steppers to the loads they will be required to push
around. In general, for a mill-drill, you'll want at least a 34-frame
stepper capable of putting out 400 oz/in or (preferably) more.

Ballscrews vary as well. They can be too small in diameter to work
effectively in your unit, or too big to fit. Also, there are two major
types- precision-ground, which hold higher tolerances but are brutally
expensive (at least when new) and rolled, which are probably good enough for
what you're doing and a lot cheaper. The nuts can be individual or doubled
up to achieve preload, while eliminates (or at least reduces) backlash,
which is one of the main reasons you use ballscrews.]

The trouble for me comes when choosing drivers, controller cards and
the software to make the whole thing work. A lot of companies offer
motors and drivers but no controllers or software, or you can get
software but it can't translate g-codes. Or you get companies
that
just offer software and that's all, like Mach1 from Artsoft
(www.artofcnc.ca).

[There are also companies (like Flashcut, and AhHa) that offer everything
you need, from software to motors, drivers, and support. Of course buying
this complete retrofit kit will usually be more expensive (in money, if not
in time) than scrounging up and assembling everything yourself.]

There appears to be a grey area when it comes to this compatibility
issue. Perhaps I'm just being dim or something, or it is just
assumed that everyone knows what the score is here. Here is an
example. Suppose I buy three stepper motors from Pacific Scientific
(but it could be anyone) I also buy 6410 micro-stepping drivers from
the same suppler to drive my motors. I now need to find a controller
from a third party that will work with my drivers, and hopefully
they will also write software that I can use to control my mill g-
codes etc.

[Usually that will be a different piece of software from the control
program.]

I suppose what I am saying is `Is this whole thing generic'
by that I mean do all these controllers use a standard command
language?.

[They just about all use G-code, yes, but that basic language has many
"dialects", which are used by different controllers.]

If so I could then use any vendor's software to
control them.

[Any vendor's CAM software will usually work on a variety of mills, assuming
they provide a "post-processor" to adapt its version of G-code to the
dialect spoken by the particular controller you're using.]

As another example could I use the motors and drivers
above and say a controller card from someone else and software like
Mach1. This whole CNC retro business seems to be a bit of a black
art so any help or advice would be more than welcome.

Steve B...

[Sure, Steve. The more you get into it, the more options you'll discover. If
your main interest is in the wonderful world of CNC retrofitting in itself,
you'll find it's a fascinating hobby, and there are many very knowledgable
people here (much more so than me) to help you find your way. On the other
hand, if it's mainly a means to an end for you (ie. you'd rather be making
chips than soldering them to boards) then perhaps one of the ready-made
retrofits would be worth purchasing.]

Andrew Werby
www.computersculpture.com





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