G93 questions

[Robertspark]

G93, am I correct in that you need to set up the units as Degrees?

And, don't set the axis to roll over at 360 degrees?

With regards to the use of G93.

If I wanted a spindle to turn at say 2500 rpm (41.666r rev per sec OR 15000 degrees per second)

what would I enter?

Would it be say

Code: Select all

G1 G93 Z1 A360 F41.666

If I wanted the Z axis to move 1 mm, and the A axis to complete one revolution?
(I appreciate going from zero to 1 revolution in 24mSec requires accelerartion.... I'm just trying to understand what the F word should be?)

Thanks.... always learning...

[cncdrive]

Hi Rob,

I think it only depends on if your unit is Degrees or revolutions is how will you program it in your g-code files.
I think usually they are degrees though.

The controller takes the acceleration and decceleration times also into account to finish in the time defined by the F word.
Also the CV planner works on the motion just like how it works in G94 mode.

[Robertspark]

Thanks for that.

So would the F41.6666 be correct for 2500 rpm if the axis was set in degrees?

I am just trying to get an idea of the math as it may relate to a servo spindle driven through a step and direction signal with a 1000ppr servo encoder.

Thanks again

[ger21]

I think it should be .024? Maybe?

From Haas:

the time (in seconds) to complete the programmed motion using G93 is, 60 (seconds) divided by the F value.

Note the part about time to complete the move. You have 41.666 revolutions/second. You want to make one revolution, which should take .024 seconds.

Right?

[Robertspark]

I'll have a play tomorrow.... Been doing my screensets and setting up a spindle (servo) .... Hmm!

Extract from the uccnc manual

Inverse time feedrate mode: G93
In inverse time feed rate mode the F word means that the move should be completed in [one divided
by the F number] minutes. For example if the F number is 2, the move should be completed in half
a minute.
When the inverse time feedrate mode is active, an F word must appear on every line which has a
G1, G2, or G3. The inverse time feedrate mode does not effect the feedrate of the rapid (G0)
movements.

.... So if the f word is 2 = 30 seconds to complete the move (60/2)...... For my 2500 rpm equivalent.... 60/2500 should complete the move (1 revolution) in 0.024 seconds.... Which is correct (1/ [2500/60] ) ...

So I guess it should be

G1 G93 Z1 C360 F2500 to complete moving the z axis 1 unit in 1 revolution.... If c axis = 1 degree = 1 unit

[ger21]

While trying to wrap my head around it, I too came up with 2500 at one point.

[Robertspark]

Thanks for taking the time