A mounting boss on a rotary job

Topics related to wrapped rotary machining in Aspire or VCarve Pro
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eph210
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Posts: 188
Joined: Mon Mar 11, 2013 1:23 am
Model of CNC Machine: Stinger 1 and Mabel, both with 4 axis
Location: southern Alberta, Canada

A mounting boss on a rotary job

Post by eph210 »

I am making gavel for a customer using a 3D model and the rotary axis. I would like the handle to mount into a round boss or column that is 90 degrees from the rotary axis. Wrapping distorts the column in the direction it is wrapped. I am wrapping X to A so the Y dimension remains straight but the X dimension is undercut.
The base cylinder is .860 radius and the outside dimension is 1.50 radius and I would like the mounting boss to be 1.20" diameter.
The mounting boss will need to be designed with an ellipsoid at the bottom and a circle at the top in order to end up straight.
Can anyone tell me how I can calculate that ellipsoid to end up with straight sides?
Drilling the hole true is taken care of using a flat PP.
I have attached a picture showing the undercut issue.
I am using Aspire 8.5.

Thanks
Euan
Attachments
20200322_223509.jpg

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TReischl
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Joined: Thu Jan 18, 2007 6:04 pm
Model of CNC Machine: 8020 Build 48X36X10 RP 2010 Screenset
Location: Leland NC

Re: A mounting boss on a rotary job

Post by TReischl »

One way is to construct points on the cylinder using geometry. That is the way this sort of thing was done before the advent of computers and solid modeling. You need to draw three views and then project points to surfaces. After you get the points you connect them.

That method is tedious at best. If you do that you only need to do 1/4 of the perimeter because it is symmetrical.

Another way is to get one of us with a solid modeling package to create it for you and share it as an stl file.

There might be a way to do this in Aspire by modeling the base cylinder, save that as an stl. Then model the projection as a vertical cylinder and save it as an stl also. Import them both back in to a new job and adjust the positions. Not sure at all if that will work because I use a solid modeler for things like that. But maybe one of the other folks has either already done that or can take off with the idea. We have some really sharp people on this forum.
"If you see a good fight, get in it." Dr. Vernon Jones

eph210
Vectric Craftsman
Posts: 188
Joined: Mon Mar 11, 2013 1:23 am
Model of CNC Machine: Stinger 1 and Mabel, both with 4 axis
Location: southern Alberta, Canada

Re: A mounting boss on a rotary job

Post by eph210 »

Thanks.
I designed a boss in a flat instance of Aspire using a guess for the amount of distortion. I imported this into the wrapped job and re-calculated.
There is still a little undercut but it came close enough to be useful.

Euan
Attachments
20200323_1135292.jpg
20200323_1133592.jpg

User avatar
TReischl
Vectric Wizard
Posts: 3330
Joined: Thu Jan 18, 2007 6:04 pm
Model of CNC Machine: 8020 Build 48X36X10 RP 2010 Screenset
Location: Leland NC

Re: A mounting boss on a rotary job

Post by TReischl »

Not too shabby at all! Looks good to me.

I would not pound that thing too hard with all that cross grain right at the head, LOL. Looks like it is more for ceremonial purposes or display than anything else.
"If you see a good fight, get in it." Dr. Vernon Jones

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