Re: How to go from 2.5 D to real 3 D ??

--- In CAD_CAM_EDM_DRO@y..., dougrasmussen@c... wrote:

> Rab & Fred,
>
> I agree the end result is what counts. Getting to that end result
> can sometimes be tremendousely easier with a machine that will do
> circular interpolation in three axis.
>
> Yes, it can be done in CAM with very large unmanageable files that
> have to be drip-fed to most current mainline type controllers

having

> limited memory.

Most current mainline controllers do not have limited memory. They
are PC technology based, have hard drives, and network connections.
File size is no longer an issure for modern controls, even in the
hobby market most of the manufacturers have eliminated file size
limitations in the last year. They ALL are working on continuous
contouring, especially after our little test program at NAMES last
year.

> Going back to my earlier simple example. Machine a hemi-spherical
> pocket, say, 4" diameter by 2" deep. For convience use a 1"

diameter

> ball end mill. You guys program it with short line segments, I'll
> program it using arcs.
>

I'll program it using arcs too, but if the controller can't generate
arcs where I can draw them, then and only then will I interpolate
them.

> To use the short segments you'll have to fire up your CAM program
> draw the part and process the Gcode. Load it into the controller,
> most likely drip-feed it. How many lines of code do you think

it'll

> take, a couple thousand, maybe? What if it turns out the segment
> length is unacceptible and leaves too faceted an appearance on the
> part? We all know from experience that can happen, sometimes you
> can't make a judgement on segment length until you run a trial.

Back

> to the computer, try again. Time is money.....
>
> I can program that part standing in front of the machine. My

program

> would have something like ten lines of code including the usual
> setup/housekeeping/tool business. Basically my program would cut

the

> arc, return the tool to starting position, rotate and repeat until
> the complete 360 degree pocket is cut. What if I don't like the
> surface appearance? Change one repeat parameter and I'm off and
> running.
>

Actually I would like to cut this shape with waterlines and not recut
the bottom over and over with each pass of the cutter. I would like
to control my scallop height externally while my machine was cutting
the previous job. I would also like to rough it out with maximum
depth of cut of .375 inches. My CAM system will only have to
generate my program one time and it will not be faceted, because I
know how to get the correct result from my tools on the first try.

> My point here is, it's very worthwhile paying a few bucks more and
> getting a controller that has the 3 axis circular interpolation
> capability. It may not give you the ability to do things you
> couldn't do otherwise, it might let you do them easier and in less
> time, though.
>

How many bucks, what kind of controller? Is it suitable for home
shop use? I don't know one hobby class controller that does what you
are recommending.

Best Regards,

Fred Smith
IMService