how to program a gear change while using CSS

[BodoW]

Hello everybody,
I'm new here and my name is Bodo. I'm working as a fabricator and mostly do the machinig part in our shop.
We are producing conveyors and so most of my time I'm producing some Rollers with a lathe.
Since some months we have an older CNC Lathe. It's a NISSIN NSK40/150 with a Fanuc 6T Controller.
So far I got accustomed with the Lathe, read a lot here in this Forum, in Youtube several videos and I'm in the moment
making some shop tools and some small jobs for Orders.
But coming back to my reason I'm posting here my question.
The machine has 3 gears or gear ratios. The first is from 20 to 290 RPM, the second is from 290 to 900 and the highest is from 900 up to 2000 RPM.
They are switched with the commands M37, M38 and M39 and this works so far.
But when I use CSS or G96 the gears do not switch automatically.
So for example I need on the OD 800 RPM and while I face my workpiece at the inner end of the cut I need 1500 RPM.
This would involve to change the gear ratio from the middle range to the high range.
How are you handling these kind of speed adjustments?
I mean I could calculate up to which diameter I can go with the middle range, stop the cut, change the gear and cut to the end.
Is this the way to handle this or is there a better/easier way for this.
The original manual is not very helpful for this case and I haven't found any help in the internet so far.
It would be nice if somebody could give me some hint how they solve this.

Regards
Bodo

 

[angelw]

Hello Bodo.
Your machine is circa 1979 to early 1980s. Some modern machines have gear ranges that are achieved electrically and the gear changes happen seamlessly to accommodate the spindle revs required. Some early machines had clutches that could accomplish what you're wanting to do whilst others had no facility other than to stop the spindle and change gears. It all depends on the Machine Builder. From your explanation, it seems that you will have to program the Gear Range change where required.

Regards,

Bill

 

[BodoW]

Hi Bill,
Ya the machine is from 1984. The machine has 3 clutches controlled by 2 solenoids.
So I assume I have to calculate up to where the starting speed range ends, make the gear change by command and go on cutting.
When starting with 12 inch OD then something like
G01 X8. F (whatever)
M39
G01 X-.031(whatever)

Thanks and Regards to down-under
Bodo

 

[EmGo]

Ya the machine is from 1984. The machine has 3 clutches controlled by 2 solenoids.
So I assume I have to calculate up to where the starting speed range ends, make the gear change by command and go on cutting.

No. You don't need max horsepower for a light facing cut. You just put it in the top range and start from that speed heading outwards. They'll all run down to a pretty low speed in top gear, just no power. Taking ten or fifteen off you don't need any power.

 

[BodoW]

Hi,
do I have to face from the centre to do this or can I get the same when I start from the OD? A bit wondering.
Of course for facing I don't need all 50 horses working. ;-)
Regards
Bodo

 

[EmGo]

Hi,
do I have to face from the centre to do this or can I get the same when I start from the OD?

It works either way, I was just in the habit of making one finish pass, out then around and along, all one continuous operation, but you don't have to do it that way.

 

[BodoW]

I was a little bit confused but now I got what you mean.
In the case what I have just to do is a crowned pulley.
So I have to face and bore both sides first and make the crown on the OD. For the crown on the OD I have to hold the pipe between centres.
It's a mess. Making 1 side, flip it around, make the second side and the put it between centres.

Thanks
Bodo

 

[EmGo]

In the case what I have just to do is a crowned pulley.

Ja, those are more awkward, can't do a nice easy swoop around the whole part. In fact, if it's got shoulders, a lot of times you can't even do the crown section with one tool, have to go at it from both ends.

Life's a beech, then you die

You know, if it's not a big wide surface and aesthetics aren't super important, you don't even need to run constant. A single speed will do an area that's not too wide and it'll work fine. Many/most parts you can just run in top speed and it'll be fine, just big roughing or drilling need to drop down a gear or two.

 

[BodoW]

I think you mean: Life's a bitch ;-)
I saw last time a nice speech: Life is sucking, otherwise you fall off (the planet).

Last time I did a indicator holder for the chuck and my first attempt was in the wrong gear and the speed was too slow. I did it again with the highest gear and the look at the second was much better.
At least a new made tool should look nice. Later it becomes dents anyway. ;-)