Help with rigid tapping

[bob1371]

Hello,
We have had a cnc machine in our maintenance shop for a few years now that is used mostly as a high dollar drill press. I recently decided to make some fixtures and various other items. I found myself drilling holes and then hand tapping. I thought I would start using cnc for tapping and started with the following. This was for M10 X 1.50 tap
O0002;
G92 X0. Y0. Z0.;
M29 S1000;
G84 X0. Y0. Z-25.0 R2.0 P0 F1500;
M30;

Manually moving axis to position tap just above hole this worked great. Thought I would dress it up a little and make it easy for all to use so ended up with following.
O0002
#1 =1000 (SPINDLE SPEED);
#2 =1500 (FEED RATE);
(SPINDLE SPEED TIMES THREAD PITCH EQUALS FEED RATE);
#3 =-25.0 (TAPPING DEPTH);
#4 =2.0 (RETRACT POINT);
G92 X0. Y0. Z0.;
M29 S#1;
G84 X0. Y0. Z#3 R#4 P0 F#2;
M30;

Again this worked great. Something easy for any of the maint techs to plug in thier numbers and power tap.


Today I had one of our engineers tell me I should add a little dwell before reversing so I tried P1.0 and threads looked messed up. I realized that during dwell that spindle was still rotating and trying to pull part out of vise.
More bookwork I find that I need to enable the parameter for G84. I find it, make it a 1. Now as soon as cnc reads second line I get a 200 alarm INVALID S COMMAND. Looking thru manual It says I have command a speed greater than max speed in parameter (forget exact para # 5243 maybe?) but find that I have a value of 5000 there. This should be max spindle speed for G84 command. Everything works great without G84 parameter turned up as long as I do not dwell but now I am curious as to why this didnt work. Any help greatly appreciated.
I have very limited program experience. Do know how to read the manual though.

Machine is a Fanuc Robodrill A10TC its about 8 years old. 16 control I believe We have 13 other identical machines on the production floor and they all are using G84 with no problems.

thanks,
Bob

[theemudracer]

how are you holding the tap?? tap collet or .....????

[Ozemale6t9]

I could be wrong, but you may find that with the parameter enabled for G84, the feed becomes the pitch of the tap (not pitch x rpm). The alarm you are getting would then be that you are trying to feed faster than maximum feedrate (1000x1500=1500000mm/min). As I said, could be wrong, but worth a try.

Incidently, for your macro above (to make it simpler for the others), I would do this:-

O0002
#1 = 1000 (SPINDLE SPEED);
#2 = 1.5 (PITCH OF TAP);
#3 = -25.0 (TAPPING DEPTH);
#4 = 2.0 (RETRACT POINT);
#5 = [#1*#2] (CALCULATES FEEDRATE);
G92 X0. Y0. Z0.;
M29 S#1;
G84 X0. Y0. Z#3 R#4 P0 F#5;
M30;

But this is only if what I said above is not correct. If it is drop the calculation line, and set F#2 on the G84 line.

regards, Oz

[lgreeves]

It looks like the problem happened after the engineer suggested you put a dwell in the tap cycle? I don't think that is needed, you will get a dwell from the stopping and reversing of the spindle. If it worked fine before, go back to before.

[bob1371]

Originally Posted by lgreeves It looks like the problem happened after the engineer suggested you put a dwell in the tap cycle? I don't think that is needed, you will get a dwell from the stopping and reversing of the spindle. If it worked fine before, go back to before.

Yeah it is working fine for me but cant figure out why it didnt work the other way. Looking at the machines on the floor they all seem to work fine with the G84 parameter=1.

Thanks for all the info. Will keep trying to see what I come up with.
Bob

[jmcd]

I suggest buying a Tapmatic syncroflex tapping head for ridged tapping. This will extend the life of your tap and absorb all the tourque when the machine gose into revese.( It will help to keep from pulling out the threds) I own one and it is worth every penny I spent.

[ALLtra Mach]

I am not familiar with this control at all, But I know that most of the time I have come across a spindle alarm associated with an M29 (usually it is something like "Can not command S) it is cause3d by the lack of a spindle direction command (M3/4/5)

You might try adding an M3 on M29 line?