How to configure 4th axis for Taig mill?

[Andy Fritz]

Hi,

I have a Taig CNC mill with Deepgroove drivers and 253 oz steppers and run it with Mach 2. Now I need to cut a part that requires using the A axis rotary.

First question is: How should Mach 2 be set up as far as motor tuning goes?
Should I reduce the steps per unit until I get one full revolution from G0 A360?
If that is correct it would be something like 4.44 steps per unit, since I work in metric. This would not give very smooth contours due to poor resolution.

I am trying to cut an o-ring groove on a cylindrical face. The cylinder is mounted in the rotary chuck which rotates about the X axis. I want it cut so that the Z barely moves. This means that Z goes down to its cutting depth and only Y, X and A moves simulateously to cut the groove.

I have tried using 4th axis rotary toolpaths is Master Cam X, but it only allows a ball cutter and keeps moving the Z up and down. In the MC reference manual they recommend using C axis toolpaths for things like engraving on a cylinder face. Engraving text or an oring groove is the same so it should work, but this is limited to only the C axis.

Any help is greatly appreciated!

Andy

[cartertool]

I don't know about the actual programming options with Mastercam, but in terms of setup, the rotary table has 72 teeth (5 deg per revolution), and you have 400 steps per rev, so 80 steps per degree...

[phil burman]

Hi Andy,

I don't have a Taig but I have recently setup and used a rotary table for engraving on the circumference of a 3" steel disc using Mach 2 so maybe I can help.

Firstly if you are trying to cut an 'O' ring groove why are you concerned with x and y. Position the cutter over the center of the work piece at the location of the groove. Lower the z axis the required depth then turn the A axis through 360 degrees. Or do I misunderstand something. Also, depending on a number of factors milling an 'O' ring is not the best alternative as surface finish may be important for sealing ability.

You cant set up Mach2 fourth axis for either steps per degree or steps per linear units (mm or inches what ever you are using) but I'm not sure this is your issue.

Also what you are trying to do appears so easy that I would not even bother with a CAM program. Use the machine manually or input gcode directly in the MDI.

Regards
Phil

Originally Posted by Andy Fritz Hi, I have a Taig CNC mill with Deepgroove drivers and 253 oz steppers and run it with Mach 2. Now I need to cut a part that requires using the A axis rotary. First question is: How should Mach 2 be set up as far as motor tuning goes? Should I reduce the steps per unit until I get one full revolution from G0 A360? If that is correct it would be something like 4.44 steps per unit, since I work in metric. This would not give very smooth contours due to poor resolution. I am trying to cut an o-ring groove on a cylindrical face. The cylinder is mounted in the rotary chuck which rotates about the X axis. I want it cut so that the Z barely moves. This means that Z goes down to its cutting depth and only Y, X and A moves simulateously to cut the groove. I have tried using 4th axis rotary toolpaths is Master Cam X, but it only allows a ball cutter and keeps moving the Z up and down. In the MC reference manual they recommend using C axis toolpaths for things like engraving on a cylinder face. Engraving text or an oring groove is the same so it should work, but this is limited to only the C axis. Any help is greatly appreciated! Andy

[Andy Fritz]

Hi Phil,

Thanks for the input! If the oring would be placed around the A I would rather cut it in a lathe. Since it is placed on the top face, (imagine you do a circular move with Y and X), but also warped over the round cylinder face it needs to be done with the A rotary. I would imagine it would be very similar to engraving on a cylinder face. Basically the only axis the should not move during the cut is the z axis. I will try to upload a picture so you can understand instantly. The trick is to interpolate the moves of A, X and Y for a smoothe continuous groove.

The rotary is merely a small chuck mounted on the stepper shaft.
I worked backwards with the steps per unit and found that the code G0 A360 needed 4.44 steps per unit in the motor tuning set up to move the A a full revolution. Now it remains to be seen how the CAM program needs to be set up to produce just that.

Andy

Originally Posted by phil burman Hi Andy, I don't have a Taig but I have recently setup and used a rotary table for engraving on the circumference of a 3" steel disc using Mach 2 so maybe I can help. Firstly if you are trying to cut an 'O' ring groove why are you concerned with x and y. Position the cutter over the center of the work piece at the location of the groove. Lower the z axis the required depth then turn the A axis through 360 degrees. Or do I misunderstand something. Also, depending on a number of factors milling an 'O' ring is not the best alternative as surface finish may be important for sealing ability. You cant set up Mach2 fourth axis for either steps per degree or steps per linear units (mm or inches what ever you are using) but I'm not sure this is your issue. Also what you are trying to do appears so easy that I would not even bother with a CAM program. Use the machine manually or input gcode directly in the MDI. Regards Phil

[philbur]

Hi Andy,

With the picture the problem is much clearer. It looks like the equivalent of engraving a circular “O” on the circumference of a disc. If so then I think you can do this easily with just the X (or Y) axis and the A axis. Basically you produce the tool path in X and Y (for a flat surface) then you search and replace all the Y axis moves to A axis moves and set the A axis to linear (not angular). You have to also put in a diameter compensation as I think the default in mach2 for steps on the A axis is degrees (that is you input number of steps per degree) which is easy enough to test before committing. Have a look in the Tormach operation manual - http://www.tormach.com/documents.htm - section 8.1.2. It goes some way toward explaining how to do what you are trying to do. But be a bit careful as it assumes your Mach2 is already set-up according to Tormach’s preconfigured version. Also as you are milling a circle that is symetrical, unlike text, so you don't need to mess with transposing of axis's. The manual is not so clear so you have to wrestle with it a bit.

Regards
Phil

Originally Posted by Andy Fritz Hi Phil, Thanks for the input! If the oring would be placed around the A I would rather cut it in a lathe. Since it is placed on the top face, (imagine you do a circular move with Y and X), but also warped over the round cylinder face it needs to be done with the A rotary. I would imagine it would be very similar to engraving on a cylinder face. Basically the only axis the should not move during the cut is the z axis. I will try to upload a picture so you can understand instantly. The trick is to interpolate the moves of A, X and Y for a smoothe continuous groove. The rotary is merely a small chuck mounted on the stepper shaft. I worked backwards with the steps per unit and found that the code G0 A360 needed 4.44 steps per unit in the motor tuning set up to move the A a full revolution. Now it remains to be seen how the CAM program needs to be set up to produce just that. Andy

[philbur]

Hi again Andy,

Another thought, I’m not sure what rotary set-up you are using but you may have a bit of an issue with backlash compensation to contend with.

Regards
Phil