Quarter column

[dealguy11]

I'm struggling with how to draw and machine a quarter column, in the shape shown in the picture below (looking straight down the column from the top). The column will have a pocketed area with a carving in it, so it's not just rounding the column.

It's probably very simple, but I'm having a mental block. It would be simple if I could just glue up 4 pieces with paper between the pieces, turn them round and then split at the paper seams. My son doesn't want to do that because it's mahogany, there will be a small reveal on the straight edges, and he's afraid the glue will penetrate the wood and mess up the finish.

How do I draw this in Aspire so that it will machine the curve as the piece is indexed on the a-axis?

[metalworkz]

Hello Steve,
To do just the quarter round it seems like it would be easier to do on the table without the rotary to me. It is not hard to do up to a half round with the 3D toolpaths in Aspire and the material would not need to be rotated.
If you are going to insist on using the rotary function it seems it might be a better situation to perhaps cut the full diameter from a large enough blank so that it can be sectioned into 4 separate quarter rounds with the carving etc.? Even if you cut the diameter exact it seems you could get at least 3 quarter round sections from the finished blank by the time you lose material for the cut between sections. Perhaps the sections could be partially cut on the rotary and then finished with a saw etc.
Sorry this is all just my thoughts, and I have not done anything like this yet. i will have to give this a try when I get my rotary build finished. I hope you get some good advice from others and good luck with this.

[metalworkz]

Hello Steve,

I worked up a scenario for cutting a blank round and then making the 3" quarter rounds from it and parting it with a .25" dia. tool. I don't know how feasible this idea is but thought I would throw it out. If I am way off and this is not possible I am sure some of the more experienced rotary people will reply and offer better solutions.
It looks like a blank roughed to an approximate 3.375" dia. will yield 4ea. quarter round sections at 3.00" diameter. I hope this is not way off base, and I took a snip of what I had sketched. Now if this will work how do you set up the toolpaths for the rotary?

[gravirozo]

just put the hafround column in a prism... and you can generate all toolpath on the quarter...

viktor


http://www.vectric.com/forum/viewtopic. ... 8&t=5911&p

also very possible, without rotary you can mill the surface... but this prism shows aspire where the toolpath need..

[dealguy11]

Thanks everyone for your thoughts. The customer has already sent us the blanks for each quarter, separately, so I don't have a lot of space to play with in terms of extra cuts. He also changed the dimension of the sides of the quarter to 2.75".

This morning I woke up with another idea, which I have modeled as shown below. The wireframe toolpath looks encouraging, so I will try this on a piece of scrap fir later today.

The general idea is to set up a cylinder with a diameter of the hypotenuse of the sides - i.e., if the sides of the quarter are 2.75 inches, then the diameter of the cylinder is 3.8891 inches. With a little more math, it turns out that the height of the machined curve above the center of the hypotenuse is 0.8057" (man, it's been a long time since high school!).

The curve goes from the surface of the cylinder down to the center point and back up. Set up a 2-rail sweep, add the design elements, and voila. We'll see how it cuts.

[gravirozo]

great... this is what you need really... to model the radius of the actaul surface...

for the other point, i really suggest you use a piece of cheap pine for test.. thats extra time, but cost no material...

viktor

[dealguy11]

To close this topic out, at the end we chose to make a jig and carve these flat. I wanted to use the indexer so that I could cut the pockets with an end mill and get nice square corners on the steps. At the end of the day, we were taking more time to figure this out than it was worth, so just set up a fairly simple series of 2-rail sweeps and cut flat, then squared up the steps with a v-gouge by hand.