Y Axis Trickery

Once you have a lathe with a Y-axis, you can’t imagine how you ever got by without it in the past. Gang slide CNC Swiss type lathes have long had Y-axis milling capability due to the kinematics of the gang tool design. Here are a couple of “outside the box” ideas for other ways to utilize the Y-axis on your Swiss.

Shaving

You can use the Y-axis to shave material off of the workpiece using a fixed tool similar to the way a shaper cuts material. http://en.wikipedia.org/wiki/Shaper

Figure B
Figure A

We have used this method to both deburr and to cut features into the part being machined. On the part in Figure A, the square flange was milled out of round stock which leaves a burr along the front and back edges along the square. We deburred the square by cutting in a small chamfer using a turning type tool and shaving along the Y-axis.

After milling the square we used a 90 degree chamfer/turning tool (Figure B) to shave in the chamfers along the edges of the square. We shaved first the front side, then the back, indexed the spindle 90 degrees, repeat. When the edge becomes dull simply offset the X and Z axes by an amount slightly greater than the chamfer amount to bring up a fresh cutting edge,

Recently we cut a rectangular shaped part that had serrations cross ways across the milled flats. We were considering getting a special dovetail key cutter made up to mill them in when we notice that the serrations were the same shape as a TPG style turning insert with an ).008” nose radius. We shaved them in by taking several passes on each serration using the Y-axis.

As far as the feed rate used, you can run the tool at full rapid traverse (G00 mode). On a machine with 32 m/min rapid traverse rate, that only equates to a little bit more than 13 surface feet per minute. This is nowhere near high enough to burn up the tool. The maximum depth of cut per pass depends on the machine, the rigidity of the part, and the shape being cut. A good starting point for chamfering is a 0.005” per pass on a 90 degree corner break.

Roll Stamping

Another trick use of the Y-axis motion is to perform roll stamping using an ordinary straight stamp. There are several advantages to this method; first, for a simple, single character like a directional arrow a=or a single letter, there is no need to buy an expensive roll stamp an holder. Second, most gang type Swiss have limited clearance in which to accommodate a conventional roll stamp. By using a straight stamp and feeding it along the Y-axis the amount of “stick-out” in the X-axis is greatly reduced.


Work Stamp

The idea here is to synchronize the spindle rotation with the Y-axis feed rate. A simple way to accomplish this is to program the spindle in constant surface speed mode (G96). Then feed the Y-axis at the feet per minute feed rate. Since the only mode available is G98, inch per minute feed, we will have to convert feet per minute to inches per minute by multiplying by 12. So, if we rotate the spindle at 10 SFM by commanding:

G96 M03 S10;

We will need to feed the Y-axis at 120 IPM.

Assuming a ½” diameter to be marked with ¼” square stamp, your program should look something like this:

T0202; (Position the stamp mounted in position 2)
G96 M03 S10; (Start the spindle clockwise at 10 SFM)
G00 X0.55 Y0.6 Z0.3; (Rapid traverse the tool close to the part)
X.48; (Position the tool so it will be 0.010” deep into the part during marking)
G98 G01 Y-0.6 F120.0; (Feed the stamp along the Y-axis synchronous to the spindle rpm)
G00 X1.18 T0; (Clear to safe index point and cancel offset)

Make sure the Y-axis start and end points are far enough away from the work that the axis will have room to accelerate and decelerate while the stamp is not contacting the work.