[JohnLucas]

I'm new at this and would apreciate some hints for cutting a tapered column on the Taig cnc mill (4 axis) See attached rough drawing. It's in Al about 1" diameter and 3" long.

To cut the slope I'm thinking of tilting the mill column so that the end of an an end mill will run flat but then I need to compensate the Z motion. My other option is to tilt the rotating table and raise the tailstock. The second option seems easier to program but more difficult to set up. Another option I've considered is to just run the slope with a round end mill. So what if it takes for ever - this is a hobby!

Oh, I have BobCad and Mach3. Thanks.

[metalworkz]

Hello,
It seems to me that raising the tailstock and running the Z in straight passes would be the easiest to program and might not be too difficult to set up. How much taper will it have? If the taper is too large the blank may not run too well on centers? The other thing is this setup will require turning the cylindrical blank on centers also. What are you making with this item?

[JohnLucas]

It's a column for a small engine.

Following your sugestion I could mount the 4th axis (with chuck) and tailstock on a plate. The whole assembly could then be raised to the correct angle (about 10 deg). Cut and flute the tapered section then lower the whole assembly to the horizontal and cut the remaining features. Probably start with it horizontal and rough cut to neasr size before cutting the taper.

[metalworkz]

Hello John,

I don't know if you have software to support doing a 4th axis rotary cutting but since you do mention having a 4th axis for your mill the other option might be to do it with the 4th axis running rotary toolpaths? Here is a link to a wrapper program to wrap toolpaths around a circumference:
http://www.cnczone.com/forums/showthread.php?t=90805

This wrapper toolpath may be worth looking into if you are able to use the free version for this engine column, but if not it may come in handy for something else. Keep us posted on your progress.

[bill-the-cat]

.......it looks to me like this part would be better suited for a lathe.

[awerby]

It's not necessary to tilt the head. Use a large ball-nose cutter for the roughing pass, and for the finishing pass use one that's small enough to get into the tightest place under the capital. I'm not sure if BobCADCAM supports 4th axis machining, but if not just generate a STL file of the column mesh and import it into DeskProto, which will generate the toolpaths. (You can download DeskProto from www.deskproto.com and run it for free for a month - once you're hooked, ask me about the new special hobbyist pricing.)

Andrew Werby
www.computersculpture.com

[UUU]

> bill-the-cat said .......it looks to me like this part would be better suited for a lathe.

That's what I thought from the original post. But then I spotted the word "flute". It's possible, I suppose, to turn the taper on the lathe, then cut flutes in a mill separately.

In fact, that's not such a bad idea. You'd get a good finish on the tapered surface of the column, and it shouldn't be too hard to work out the G-code for the flute, with the Z-axis at an angle.

[bill-the-cat]

> bill-the-cat said .......it looks to me like this part would be better suited for a lathe.

That's what I thought from the original post. But then I spotted the word "flute". It's possible, I suppose, to turn the taper on the lathe, then cut flutes in a mill separately.

In fact, that's not such a bad idea. You'd get a good finish on the tapered surface of the column, and it shouldn't be too hard to work out the G-code for the flute, with the Z-axis at an angle.

....I agree that the "flutes" could be added on the mill after turning the cylindical features on a lathe.

[Odin]

I actually had a similar problem awhile ago. Mine was more complex- I needed to cut a proportionally tapering oval cam at a set taper, for a special device I'm prototyping.

I haven't got the material yet, but my solution without CNC took me 4 months to figure out. I needed an exact size and taper without CNC, on only a mill, with a 4th axis rotary table.

I figured it out- and it will work even easier for your column. Simply bolt the 4th axis rotary table to the x ways on angle blocks equal to your taper, and lower your endmill to the far
edge of your part. Crank x axis across, rotate a few degrees, and repeat. This method makes a precise round taper precisely with the mill, even better if you use a fly cutter.

For my oval cam, I figured I needed a pattern glued to one end of the stock, and had to readjust the z axis for each 1 degree step to the edge of the cam pattern at the far end, and then
make each pass across with the X axis.

I hope this helps someone, and it was the only way I could find to make a proportionally tapering oval cam with only 4 axes and a mill. Perhaps this is dead simple to others, but it took
me a while to realize, partly because I thought it would take too long, I thought of it early on and dismissed it. It was only after 4 months of thought on the invention design that I realized
this was the only way I could make it with what I had and not change my design.