Re: [CAD_CAM_EDM_DRO] Tutorial for 3d CAD???

Hi Bill:
The first thing you need to do is to find out if you have a 3D version
of Autocad or not.
If you have something like Mechanical Desktop it will be 3D.
Another way to check, is to see if you can find an icon or menu item for the
"world coordinate" system that Autocad uses to draw on planes other than the
"Top" plane.
If you got that, you're in.
Most CNC mill work is actually 2 1/2 D, in that it is a simple monoplanar
profile that is machined to a given depth.
The assignment of depth is provided by the CAM program, not by Autocad.
So you require for that, only your 2D profile drawn on the Top plane at Z=0
on your world coordinate system.
True 3D requires movement in Z at the same time motion is taking place in X
and Y, and is typically driven by a surface or a spline that has been
described in 3D space in your CAD program.
Learning that, will take buying a book...I have one by Mike Okuda that's
pretty good, but it's for R14.
Your CAM program will then turn it into G code consisting of a whole pile of
tiny linear moves that approximate the 3D path that you described in CAD.
3D milling is not rocket science, but it requires a bigger investment in
both the CAD and the CAM, as well as some learned strategies to rough down
the block before the finishing passes are taken.
It also requires a good bit of management when you have intersecting
surfaces, especially ones that are vertical or close to vertical.
You can easily overload a cutter if you power it into a 1" tall vertical
wall at 40 IPM, even if there's only 0.001" of stock left to cut on that
wall.
This is where experience is required to devise the most effective machining
strategy.
Hope this helps
Cheers

Marcus

----- Original Message -----
From: "Bill Kichman" <billkichman@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, January 05, 1988 6:48 PM
Subject: [CAD_CAM_EDM_DRO] Tutorial for 3d CAD???


> Woohoo! I just finished setting up my Van Norman Model 12 to CNC. I have
zero backlash in both ballscrews, x and y axes, and reduced the old z axis'
acme screw down to 4 thousandths backlash , which I certainly can live with.
>
> Now I am at a loss...although I use Autocad daily for my building
electrical designs, I have no clue how to do 3d parts designs...I suspect
it's not a huge transition but can anybody steer me in the direction of some
resources online to get through this quickly? I would rather avoid
coursework and/or textbooks, but as a last resort....thanks to all who
helped me with this retrofit, it wa much appreciated.
>
> P.S. I saw a big CNC mill at the scrapyard waiting to be cut up for scrap
on Saturday....can't remember the mfgr's name, but it sure was tempting to
bring that 2 ton beast home with me...
>
> R. William Kichman, P.E.
> Kichman Engineering Associates
> 103 Old Furnace Road
> Cornwall, PA 17016-0643
> tel/fax 717 270-0714