# Re: Quick, Cliff another post of JB's for you to shoot down

Cliff,

Not again Cliffie O'King of the Clueless One's, you stepped in it
again.

Dan wrote:
So unless you program an M04 while the spindle is turned on with M03,
it's not going to reverse.

Cliff wrote:
But if you have a negative diameter ...

I told you before in SFM mode the CNC Lathe ignores the positive and
negative when calculating spindle speed. How do I know this, I've
programmed, setup and operated machinery where I use both X- and X+
values in the same program and SFM mode without reversing the spindle.

Example:

On a CNC Gang Tool Lathe running a very tight program and process I
often use tools to cut on both sides of the work piece. I will have two
tools opposing each other with just enough space between them to safely
clear the part.

I use an OD rougher and program X- values for the OD profile and on the
op side of the work piece is an OD finish tool that will run the part
profile in the X+ side. Both tools run exactly the same in SFM mode
with the same spindle rotation.

In SFM mode with both X- and X+ values as the tool moves away from
centerline the spindle speed decreases.

In SFM mode with both X- and X+ values as the tool moves toward
centerline the speed increases.

Tom

Cliff wrote:
On 15 Jul 2006 18:04:51 GMT, D Murphy <spamto154@xxxxxxxxxxx> wrote:

Cliff <Clhuprich@xxxxxxx> wrote in
news:rtkhb21l2l7q1jg34q9ji60vgmalq7gene@xxxxxxx:

Here is another clue, the centerline of the radius is just asmuch of
an imaginary point to program from as are the edges. At least the
edges are engaged in the cut, unlike the center.

Your imaginary point is not <G>.
Not too hard to look at ratios of TNR to geomerty radius either.

Now, about CSS on a facing operation ... say with a .250" R button
on a .500" OD face .... at what point in time should the spindle
reverse?

More proof you've never seen a lathe. Spindle reverse? what a hoot.

<Shh .. is jb watching <GG>>

A little CNC programming lesson for you:

M-codes (miscellaneous codes) turn on and off misc. machine functions.

M03 is spindle on clockwise direction.

M04 is spindle on counterclockwise direction.

But if you have a negative diameter ...

M05 is spindle off.

"S" is a program word which denotes a speed value in either rpms, or in
SFM.

So unless you program an M04 while the spindle is turned on with M03,
it's not going to reverse. S-codes do not have the magical power to
change commanded M-code values.

The tool will eventually reach the workpiece centerline, where the SFM
is zero. Before that happens, the lathe will hit it's maximum rpm and
will clamp the spindle speed there.

Except that with that imagined non-contact non-centerline point being
programmed it should *slow down* as the tool's tangent point gets closer
to center but past 1 TNR (radial) from center.
You would have max RPM at 1 TNR (tangent point) (radial) from center.

(Assuming no RPM limits hit.)
--
Cliff

.

• References:

## Relevant Pages

• Re: Quick, Cliff another post of JBs for you to shoot down
... Not too hard to look at ratios of TNR to geomerty radius either. ... at what point in time should the spindle ... Spindle reverse? ... You would have max RPM at 1 TNR from center. ...
(alt.machines.cnc)
• Re: Motor wiring for reversing rotation
... You don't need to reverse the lathe to back off when screwcutting ... chalk line, and a similar line on the leadscrew, when the halfnut was ... revolutions of the spindle. ... and the leadscrew pitch) and waiting for the half nuts to re-engage ...
(uk.rec.models.engineering)
• Re: 7.5 HP Lathe on a 10 HP idler?
... chucks - the mount by screwing them onto the headstock spindle. ... the blokes used to use reverse to brake the lathe and tried it while ...
(rec.crafts.metalworking)