Improvised CNC Lathe

Having been impressed by the gadget in the link in Buffer's recent post, I got thinking about how I could use what I already had to get me out of a problem.

I am currently machining a flywheel for my 6" traction engine build. Front face is easy, so is the bore. The rear face of the rim is not so easy needing a very long and funny shaped tool. Also, the rim of the flywheel is to be "crowned" to allow it to drive flatbelts.

The flywheel is almost on the limit for the lathe (700mm) and the toolpost doesn't come out far enough to be fully useful.

So, thinking outside the box, I codged up this set up. Which despite it's appearance actually works very well. I am happily cutting the edge of the rim with a good finish. Just got to get my head around the G code for the crowning cuts. Translating the existing milling machine axes to lathe axes temporarily...

Les

Bits of chunky metal to fall over, wires everywhere, and the emergency exit inaccessible

Glad I'm not alone where these things are concerned

And well done on getting some CNC up and running

… as I believe they put it, in review-land

MichaelG.

Can the g-code for the crown be derived from treating the rim of the flywheel as a section of a sphere?

Les

Well done for thinking outside the box that some would lock you into.

Emgee

Yes, that seems to be the standard for crowned flywheels. I used the radius of the outside of the wheel. The rim is 3" wide and has about 3/32 less diameter at the edges.

I also did the back edge at the same time so it would be parallel to the front.

It was a bit of a lash-up but did a beautiful job of it.

Les

Ronald, the Gcode for a curve is quite simple, you tell the controller where the tool is starting from, where the tool will end up (as either X and Y coordinates on a mill or X and Z on a lathe) if the path is clockwise or anti- clockwise and either the radius you want or where the centre of the curve is.

Typically this would look something like this:

g01 x15 z-1.5 (go to the start point)

g02 x15 z1.5 r12 (travel in a curved path to the end point with a radius of 12)

g02 or g03 determines if the path is clockwise or anticlockwise.

There are variations in different controllers so this may not be quite the way that Les would set it up.

Martin C

I used the other method.

The core is:-

G0 X7.4706 Y45.0
G1 F100.0 X-3.0933
G2 F5 Y-45.0 I-320.7083 J-45.0
G1 F400 X7.4706
G1 F400 Y45.0

This does a cut and returns to the start position where I added a few thou each time to the X for the next cut.

Les