Rotary modeling and toolpathing advice

[duster]

I'm trying to figure out how to model and toolpath this twisted column. I've done several basic things with my 4th axis successfully, but I'm at a loss on where to start with this project. Any advice would be appreciated!

[Rcnewcomb]

I need to think about how to do this in VCarve. In Aspire this would be done using the 2-rail sweep.

An alternate approach is to hand code the G-code and cut it from the side. You need a fairly robust setup for this. Using a large, long bit, the bit starts at one end of the column and Z is at or below the centerline. It travels in a straight line to the opposite end as the column turns 90 degrees. Repeat until all sides are done.

[duster]

I believe my equipment is up to the task. I have a 10hp spindle with 12" of Z clearance, and a stout rotary axis set up.
For tooling, I have a 1/2" x 4" downcut chipbreaker bit for roughing out, and a 3/8" x 3.5" ball nose for finishing.

This is at least twice as big in diameter as anything I've attempted. I'm thinking a 10" square blank by 26" long, with the
corners cut off @ 45 degrees to create a roughly 11" diameter octagon. I would do a test blank in blue foam before I'd
try it in wood.

I'm not sure how to model this, and hand coding the g-code is probably beyond my limited skill set.

[SteveNelson46]

I don't think you can model it in V-Carve. Modeling is in Aspire only.

[TReischl]

Not quite sure why you want to turn it into an octagon? Me thinks you would be better off starting with a cylinder.

If someone does not come up with a magic way of modeling this in VCarve maybe one of us could create an stl for you. You would need to give us the exact dimensions, not just estimates.

[duster]

I was thinking of starting with an octagon because it would allow me to get a larger blank under the Z axis.
A 10 x 10 square blank would be almost 14" diagonally, whereas an octagon would only be about 11". At
that point I could turn it into a cylinder.

I'll work up better dimensions and post those. Thanks!

[mezalick]

If you play your card correctly , using VCarve, you can do what you want with the Moulding ToolPath.
You can adjust the shape and depth of the twist as needed.
Here's just a quick example.
Michael

[4DThinker]

You can do this with the moulding toolpath if you start with a blank longer than you need.
I started with a 10 inch circle as a section view of a starting cylinder blank. I drew a square in it to represent the shape I wanted to cut from it. Did a little drafting to figure out the angle of a guide line to send the moulding profile down, and used the Unwrap selected Object tool to make the moulding profile needed. Result is a 24 inch tall twisted post, but the moulding toolpath being angled will extend 37.33" some above and some below the finished post area. You could shorten the needed blank if you broke this down to 4 moulding toolpaths, one for each face of the square.

[duster]

4D - you nailed the shape of my column, 4 flat sides with a 90 degree twist. Unfortunately, I can't open your attachments. (I'm using V Carve 9.5) I'm still not sure how to draw this. Any more thoughts on this?

[4DThinker]

As I still have 9.5 on my PC here is a .CRV file you should be able to open. Left in all the steps/vectors I used to get to the final toolpath for your edification.

Enjoy!

[duster]

4D - Thanks for the time and effort helping me with this project. I was able to open the new crv file and see how you did it. I edited the toolpath to make use of the tooling I have available, and glued up a foam blank to to test this. A few adjustments to my rotary axis and I'll be ready to give it a whirl.

[4DThinker]

Glad to help Duster. I actually enjoy the occasional challenges user present on this forum. Keeps my mind awake and humming. Post a photo or two of your outcome as I'm sure many here would live to see it.
4D