Ball Turning

[pressurerelief]

What is the best way to turn a Ball, G71, G02? I want to turn a 1" diameter ball and leave a 5/16" stub approximately 3/8" long on the one end to thread in order to install on a shaft. I am looking for a GCode example and have not been able to find one.

As far as tooling I used a VNMG insert on my old manual to do this and would assume it is appropriate for the cnc app.

Rick

[Bourne Bill]

do a search for Brian Rupnow on this site. he has a good ball turner.

[John Stevenson]

do a search for Brian Rupnow on this site. he has a good ball turner.

No he wants to do it via CNC not as a manual attachment.

.

[saltmine]

You could probably manually turn a ball long before you wrote the G codes for it. Amazing how well those old "stone age" manual lathe tools work.

[John Stevenson]

True but you wouldn't be posting on the Digital machinists forum, you would post under general.

The OP did ask about G Code examples.

[pressurerelief]

Folks, I am looking for CNC GCode. I have built and successfully used one of the varieties of the cross slide mounted manual turners. I have a new CNC and want to start moving in that direction. One of the challenges with CNC is getting it to do new and different things. As soon as I conquer one task I am looking for the next application.

Saltmine, could not agree with you more for one, but when it comes to making the fourth one and counting setup time as well as time to reinstall the tool post with reindicating it, CNC wins. I just did some piston work for a friend who blows motors continually. Pulling tractors are hard on motors. Set it up once and let it run while cleaning up the shop. 18 pistons with relatively no effort. Machine stops and load the next part and back to work. Next week he will have his no effort backhoe at my house increasing the size of my pond.

Rick

[Mark Hockett]

You could probably manually turn a ball long before you wrote the G codes for it. Amazing how well those old "stone age" manual lathe tools work.
My CAM system can write the code for that job faster than I can get my manual lathes radius cutter out of the storage box.

Rick,
I don't think a G71 will work on that. I use a grooving tool to generate the radius. The one I use the most is a Valenite VTG style holder, but for smaller stuff I use the Nikcole mini grooving inserts. I have the tool rough out the shape by plunge cutting and then finish with a profile cut. If you fax or email me a sketch I can help you with the code. My fax and email is on my web site below.

[toastydeath]

G71/G70 and G02/G03 will work, provided your control handles non-monotonous (the path has a direction change in X, in the case of turning, as Z increases) paths in the automatic stock removal cycles. Obviously, the accuracy of the ball is going to be a real finicky thing if you care about that. The tool nose type and radius will also have to be defined, because nose comp is always on in g70, and your path will be inaccurate without it.

This code hasn't been run on any machine, obviously, but here's a quick example of a ball radius followed by a short lil shaft. I'm imagining 1" stock, and a .5" stem. It's 11:38 and I've been up all night, so I'm not going to venture to calculate the ball Z/J values and have someone try to run this without checking numbers.


G28 U0 W0
T0101
G50 S2000 M41
G96 S500 M3
G0 X1.1 Z0 M8
G1 F.004 X-.05
G0 X1.1 Z.1
G71 U.05 R.01
G71 P100 Q100 U.010 W.005 F.005
N100 G0 X-.05
G01 Z0 F.002
X0
G03 X.5 Z(INTERSECTION) I0 J(RADIUS)
G01 Z-2.0
N200 X1.1
G70 P100 Q100
M9
G28 U0 W0
M30

The trick, obviously, is the XZ endpoint of the arc, as that will not only define the end of the ball, but X value will be the diameter of your shaft. I'd probably not use a radius, but if you do, it will probably have to be a negative radius to get the major arc (>180 degrees of arc instead of <180). I'd rather define I/J and remove all ambiguity since the I value will be zero and the J value will be the radius of the arc.

So really, once you pick a radius and a shaft diameter, the only thing you need to calculate will be the Z intersection between the shaft and the ball's arc.