CNC Retrofit of Smithy 1324 CNC

Message: 15
Date: Mon, 04 Mar 2002 12:01:23 -0000
From: "tmylen" <ted@...>
Subject: CNC Retrofit of Smithy 1324 CNC

Hi Everyone,

I am new to the list. Most of the posts are over my head but I am
beginning to get a general feel for the lingo of CNC.

I would like to give you a little history of my hobby and training
for that hobby.

I have been a computer buff since 1979. I have since owned or had
access to computers and write programs in C, C++, Visual Basic, and
Palm handhelds use C++ and basic. I also write embedded programs in
C and basic. My hobby extended into electronics about 4 years ago
and I have received training from the local community college through
digital circuits. I can program PIC, 68HC11, DSP, and Basic Stamp
devices. I have built one robot using the MIT Handyboard that uses
encoders and ultrasonic distance sensors. All it does is run around
and avoid "most" objects. I understand stepper motor technology and
have built and used several circuits to drive old floppy disk
steppers and many others I have salvaged from fax and old printers.
I have successfully used encoders to govern speed and position using
both stepper and reversable motors.

[It sounds like building a control box to drive your Smithy in CNC mode
should be well within your capabilities.]

I bought the Smithy about 4 months ago and have been reading as much
as I can, and can afford, to bring myself up to speed on various
techniques of machining metal, mostly aluminum and plastic, but I
have some ideas about using steel. My main interest initially is in
cutting gears and threads for drive systems.

I have a Vertex dividing head with three dividing plates. It can be
positioned from vertical to horizontal. I have a three-jaw chuck to
fit to the head.

The Smithy company refers me to Flashcut CNC for a retrofit package
for this Smithy. They quote me a three-axis outfit price of $3125
which includes controller and motors. I believe it is with stepper
motors and not servos.

[That will work, but it's expensive. I'm sure there are many on this list
who can tell you how to do the same job for a lot less, especially if you're
willing to scrounge motors and build a controller from parts or a kit. If
you want a bolt-on motion control system, look at MaxNC's doublestack
closed-loop setup for $1092.50 (my price). If you want to use more powerful
steppers in open-loop mode, I can also get you a discount on the gecko-based
controllers from Cyber-NC http://www.cyber-nc.com/cnc1.htm . ]

My first question is: What is the best CNC software for a home
hobbyist that can output DXP to the Flashcut system?

[Do you mean DXF?]

I have looked
at BobCad, Deskproto, and SurfCam. BobCad has a very attractive
price range and the version 17 can do 3D.

[BobCad won't import DXF drawings of any complexity. It really wants you to
do all the CAD work within the program, and its CAD capabilities are rather
limited. DeskProto is good at importation of DXF surfaces, but it won't
"see" linear drawings. It does "rastering" toolpaths, which traverse the
surface in a series of linear passes. Of these three, Surfcam sounds like
the best bet for what you are talking about. The full program is quite
pricy, but they have a free 2d version which might work for you, especially
if you're willing to tinker with the g-code. Other mid-priced programs to
consider would be Dolphin, Vector, and Rams (which imports linear drawings
as well as surfaced models.) ]

I looked at the "G" code
syntax and it looks pretty straight-forward. My initial goal with
CNC would be to set up standard cutting tool-paths for plastic
(Delrin) and aluminum gears for robotic drive gearboxes.

[Gears are more complicated than they seem upon casual inspection. Usually
they are produced using "hobs" which have the tooth profiles and spacing
pre-determined. These are used with a blank held in the dividing head, which
is indexed around to cut the whole perimeter. The toolpaths mostly involve
running the spinning hob into the blank, retracting, and incrementing the
rotary axis, so that part of it isn't too difficult.]

My second question is: What is an affordable CAD program that can
interface with the low end CAM programs above? I haven't looked at
any in this regard.

My money saved for this hobby has almost been depleted. I need some
type of "target" amount based on a hardware and software
configuration selected in the near term for future implementation
(when I can save the monies required).

[If you're really trying to save money, take a look at ProDesktop from
Parametric Technologies http://www.PTC.com/. They make ProEngineer, a highly
regarded but expensive program for machine design. But they are giving
ProDesktop away for free, and it has many of the same features. My personal
favorite for CAD is Rhino, but it isn't free, although it's well worth what
it costs (especially with the discount I offer).]

I have the computing power in my shop to handle any of these packages
already. I have computers that run DOS 6.2, Windows 3.1 and WFW
3.11, Win 95, Win 98, Win Me, Win 2k, and now my wife has a new Win
XP. The processors range from 286 and 386 (both retired but
revivable), Pentium II 233, 350, and 650, and Celeron 400. The
motherboards are mostly Abit with a new Gainward I am trying out.

[Use the fastest of these to run your CAD program (stuffed with memory). The
slower Pentiums should work fine to feed code into a machine controller.]

Any input would be most appreciated and highly valued. I have a
large learning curve but I am diligent and have the desire.

Thanks for your time.

Ted

ted@...

[There's really a lot you can do without spending much at all. Try what's
out there for free (or nearly) before plunking down the hard cash, and
meanwhile scrounge, scrounge, scrounge....]

Andrew Werby
www.computersculpture.com