RE: [CAD_CAM_EDM_DRO] EMC, ISA and other Questions...

At 13:35 1/22/2003 -0500, you wrote:

>I had occasion to use my rotary table to cut 3 slots aligned with the
>circumference of the part. These slots needed to start and end in a 90
>degree arc and I needed to compensate for the 1/4 inch cutter diameter. So
>I needed to move the rotary axis 90 degrees and move the y axis .250 so that
>cut would stop in the proper place. I was able to make these cuts using
>TurboCNC with out any problems.
>
>EMC when configured for 80 steps per degree (400*72 / 360) moves the rotary
>table at a speed such that the motion is not noticeable.

You know I might have missed part of this thread, but I haven't seen how
you are programing feed rates for fourth axis contouring paths.

Here's how it's normally done;

First of all the fourth axis needs it's feed rate supplied in *inverse
time*. Most controls initiate this with G93. The feed rate number in the
"F" address needs to be the velocity in inches per minute divided by the
travel distance or "span length" and 60.

ie; feed rate number = (inches per minute)/(60)(span length)

The common way to figure the span length is to multiply the radius by
SIN(1) and then multiply by the angle in decimal degrees.

ie; span length = (radius)SIN(1)(angle)

example:

to mill at 30 ipm on a 8 inch diameter part for one full revolution,

G93
G01 B360 F.020

When you add another axis to the mix, you have to consider the linear
vector's span length as well. Use the Pythagorean theorem to determine the
move's total span length.

-Bob