[AviS]

Hello,
I have an old grinding machine in my work place with fanuc controller, i want to make the a axis rotate similar to a spindle according to a given RPM, is it possible?

[Al_The_Man]

Depends alot on the setup and how it is configured, but if there is nothing to prevent it turning, limit switches etc, there is program at a certain feed rate or high speed jog, but this may not be the rpm you are looking for?
Al.

[AviS]

Depends alot on the setup and how it is configured, but if there is nothing to prevent it turning, limit switches etc, there is program at a certain feed rate or high speed jog, but this may not be the rpm you are looking for?
Al.

i'm not looking for high rpm, just for constant rotation through the g code program, what g code can i use for this?

[zavateandu]

it is easy
is all about degrees on a rotary axes
if you have G1 A 180 F100 you will have half turn,if you have A360 you will have 1 full turn,A720 you have 2 turns and so on,A999999 you will have a lot of turns until reach the value,but this will end when the maximum 8 digits will reach so youi have to start over.

[drdos]

Normally you set up the axis to be PMC controlled axis. Then you fire an M Code in the part program to start the axis in a continuous jog mode rotating that will turn till you stop it with another M code. This must be written in the ladder. If you try to rotate it with a command in the program the program will not go to the next block until the axis reaches it's end point at which it will stop. Do you know any good Fanuc ladder programmers?

[AviS]

Normally you set up the axis to be PMC controlled axis. Then you fire an M Code in the part program to start the axis in a continuous jog mode rotating that will turn till you stop it with another M code. This must be written in the ladder. If you try to rotate it with a command in the program the program will not go to the next block until the axis reaches it's end point at which it will stop. Do you know any good Fanuc ladder programmers?

Hi drdos,
Thank you for the reply.
No i dont have any cnc programmers in my work place, i will make some homework about this myself.

[Superman]

I have not tried this myself, but if you ran a program in incremental telling it to rotate 360° with a loop
using the feed override switch to adjust to get your "RPM" in the ballpark

it should look like this

N1 G91 G1 A360. F500.
GOTO N1
M30

note.....you can't do anything else while the program is executing
( but you might, if, you have a way of a "live" handwheel to move other axis while the program runs )
you may have to adjust parameters for the A axis so it doesn't count over 360....ie the next step/pulse after 359.999 is 0.000

[fordav11]

Normally grinding machines use lathe controllers (at least ours do), so you could use U/W for incremental (G91 doesn't exist on lathe control). If it is a mill control then G91 will work.
assuming the grinding is something simple like a Z- movement you could probably just add that to the program then make it rotate again with another Z+ movement.
The Z start and end position would move the wheel off the part so you don't get a flat spot when the A axis stops rotating at the end of the block.
you would need to calculate the number of rotations in your movement Z length. lets say you want to move 0.5" per rotation. that would be 20 rotations in 10" of Z movement or 7200 degrees.
all of this kind of stuff depends on how the MTB implements the A axis. it may freak at 7200 or it may rotate the A axis 20 times.

something like....
N1 G91 G1 A7200. F500 Z-10.0
G91 G1 A7200. F500 Z10.0
GOTO N1
M30

if you have macro you can add a U value as well and you'll be able to adjust it as the cycle runs. add stops to check the size and adjust the macro amount.

something like....
N1 G91 G1 A7200. F500 Z-10.0 X-[#100]
/M0 (CHECK SIZE)
G91 G1 A7200. F500 Z10.0 X-[#100]
GOTO N1
M30


this is all in theory and pulled straight out of my ass ;-)
I remember reading several posts here about other people wanting to do similar things and the end result was failure to get it working.
to do grinding, you would really need a spindle that rotates independently, powered by a motor and belt or whatever. in theory it wouldn't be difficult to disengage the A axis motor gears and connect it to an electric motor from a washing machine or similar via a belt. basically the A axis just needs to rotate by itself without program control.
if the machine is a real grinding machine it should have this capability already? on our machines there is an M code to start the wheel (the RPM is fixed) and the code to start the spindle is M3 Sxxx. The spindle is your A axis. it sounds like its converted from a mill? if its an old junker anyway you may want to consider disconnecting the A axis and adding an independent motor so you can do real grinding.

[AviS]

Hi fordav11,
Dedicated M code will be the best solution, i'll keep looking for an option to add it.
Thank you for the reply.

[fordav11]

if you want that you would need to modify the ladder. so we have come full circle again.
what you want to do is not possible to obtain without help from Fanuc. that means $$$$