CAD CAM EDM DRO - Yahoo Group Archive

Re: 2.5 axis vs. 3 axis

Posted by yethdear0
on 2001-12-05 07:07:22 UTC
--- In CAD_CAM_EDM_DRO@y..., "Rob" <robv@s...> wrote:
> What's the difference?

Eric & others interested;

I sent this reply once and it didn't post right, excuse my ignorance,
I'm still getting use to this awkward Yahoo BBS.

As for your equipment Eric, If I remember right, your Sherline is a
bench top milling machine using stepper motors? If your machine is
say younger than 10 years old then I would almost bet money that it
could perform a full and true 3D contour.

The Ah-ha control software I am not familiar with. I have seen their
products and been to their web page. I could not tell you for sure if
the software and control would produce a 3D contour or not.

I have not heard of Dolphin software until a few days ago. I take it
that it is an extremely affordable software and it is still DOS
based. (Wow, how limiting!). I read somebody's posting that it was
also cheaper than Bobcad. I would be under the impression that "No",
Dolphin software probably does not have the capability of creating 3D
mesh surfaces and producing contouring toolpaths over those surfaces.
Most low end (cheaper) CAM/CNC software does not have this
capability. Why? Because of the math involved. If you think about it,
for every single move that the CAM software out puts in a 3D type
program, the software has to re-calculate a new contact point that
occurs between the tool and the surface. The results are huge G code
(machining) programs. I have created (with top of the line CAM
software) mold programs that were over 12mb in size and took hours to
run on the CNC.

Try this;
In your Dolphin software, can you construct a 3D dome (hemisphere)?
Will Dolphin then allow you to make a tool path straight across that
dome in the X axis, right across the center of the dome? At the same
time this tool path is made, the CAM software should also produce Z
movements that lift your tool up over the dome and then back down the
other side all the while keeping your tool tangent to the dome
surface. Now, can you rotate that same toolpath ½ degree and repeat
the path and do so for 180 degrees until you have completely machined
the dome surface?

The output from your will be a huge amount of XY and Z points, there
will be no arcs at all. Every single movement and program line should
have an X, Y and Z coordinate value in it. Only circular motion that
is made parallel to any of the 3 main planes (XY, XZ or YZ) can be
output as arcs, as soon as you rotate your motion that first ½
degree, you are no longer running parallel to any of these planes.
This forces the software and computer to output a bunch of straight
line moves (point to point) that will follow the dome. These straight
lines moves will only be as long as the resolution of your software.
Some moves may only be .001 inches or less in length.

If you cannot construct this geometry in Dolphin or if it does not
allow you to produce this type of tool path, then your Dolphin
software is only 2 or 2-1/2 axis.

As for your machine and its control, if you would like to see if it
can do full and true 3D contouring then e-mail at
yethdear@... and I will send you a program to run on your
Sherline mill that will cut this dome shape. This is a simple program
to use to verify what your machine capabilities are. The worst that
will happen is your machine will not simultaneously move all 3 axis
at the same time when it reads a line of data that includes an X, Y
and Z values all on the same line. It will move the X and Y first
then the Z axis last and separately. The result will be a big gouge
in your part. For this reason, you should use a piece of machining
wax, balsa foam, or even a piece of wood so that there is no damage
to your machine or cutting tool if the machine gouges the part.

Here's a freebie tip:

Use "Bondo" auto body filler to make blocks of machineable material
to practice with. The Bondo is nonabrasive and does not dull tools.
It is also cheap and soft enough that if you crash into it, it will
not damage your tool or machine. And if you make a programming
mistake and gouge your block, just add more Bondo and re-cut it. Wal-
mart carries this in the automotive department. Just mix it
separately in one container and then pour it into another container
for molding. This gets rid of air bubbles and ensures mixing. Do be
aware of the fumes and the dust when you machine it.

Discussion Thread

Rob 2001-10-25 13:35:05 UTC 2.5 axis vs. 3 axis dave_pearson@b... 2001-10-25 14:14:40 UTC Re: 2.5 axis vs. 3 axis shymu@b... 2001-10-25 15:12:02 UTC Re: 2.5 axis vs. 3 axis Bob Campbell 2001-10-25 17:50:30 UTC Re: [CAD_CAM_EDM_DRO] 2.5 axis vs. 3 axis yethdear0@y... 2001-12-04 18:18:39 UTC Re: 2.5 axis vs. 3 axis glee@i... 2001-12-04 18:44:15 UTC Re: [CAD_CAM_EDM_DRO] Re: 2.5 axis vs. 3 axis yethdear0 2001-12-05 07:07:22 UTC Re: 2.5 axis vs. 3 axis Michael Milligan 2001-12-05 08:44:01 UTC RE: [CAD_CAM_EDM_DRO] Re: 2.5 axis vs. 3 axis yethdear0 2001-12-05 11:11:35 UTC Re: 2.5 axis vs. 3 axis John Barnwell 2001-12-05 12:00:35 UTC RE: [CAD_CAM_EDM_DRO] Re: 2.5 axis vs. 3 axis verizon 2001-12-05 12:11:34 UTC RE: [CAD_CAM_EDM_DRO] Re: 2.5 axis vs. 3 axis yethdear0 2001-12-05 18:39:47 UTC Re: 2.5 axis vs. 3 axis John Barnwell 2001-12-05 18:58:27 UTC RE: [CAD_CAM_EDM_DRO] Re: 2.5 axis vs. 3 axis GC 2001-12-05 19:19:00 UTC RE: [CAD_CAM_EDM_DRO] Re: 2.5 axis vs. 3 axis yethdear0 2001-12-05 19:23:31 UTC Re: 2.5 axis vs. 3 axis IMService 2001-12-05 19:47:11 UTC Re: Re: 2.5 axis vs. 3 axis Ray 2001-12-06 06:23:45 UTC Re: Re: 2.5 axis vs. 3 axis yethdear0 2001-12-06 10:40:10 UTC Re: 2.5 axis vs. 3 axis