Routing a spherical object.

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czwalga
Posts: 6
Joined: Sun Jul 27, 2014 3:19 pm
Model of CNC Machine: cncrouterparts

Routing a spherical object.

Post by czwalga »

Hello, I have aspire but I've only used it for 2d toolpaths.

I need to machine 3 holes into a spherical object, all 3 are close to the top. I have been hand drilling the holes, which is easy on a drill press because you just rotate the ball.

I realize this could be done fairly close in 2d since the holes are so close that the curve doesn't effect it too much, however I'm very sensitive on the depth. There's multiple layers to the ball and I can only go through the first.


Here's a picture. I'd like to be able to align the bit very center at the top of the ball. Then drill 3 holes that are painted black. The depth is only 1/16" so a 3d machine with the right tooling should be able to get it close.

If this is extremely difficult, i'd be willing to pay someone to design the tool paths as well; ASAP PM me. Eventually i'd set something up to do a bunch of these at once.
Attachments
ball6.jpg

ohiolyons
Vectric Wizard
Posts: 474
Joined: Wed May 27, 2009 7:16 pm
Model of CNC Machine: Laguna IQ HHC, 3HP
Location: Kettering, Ohio

Re: Routing a spherical object.

Post by ohiolyons »

So it looks like a golf ball.

Will it always be a golf ball?

Does your CNC have multiple origins?

Could you leave a fixture semi permanently attached?

Sounds like you want to zero the Z from the top of the material, is this true?
John
CNC in Kettering, Ohio

czwalga
Posts: 6
Joined: Sun Jul 27, 2014 3:19 pm
Model of CNC Machine: cncrouterparts

Re: Routing a spherical object.

Post by czwalga »

John,

Everything you said is true. I've also, been able to 3d model it I believe. Working on the tool paths. Anything special I need to worry about for the 3d toolpaths? Right now I'm having trouble with the z-axis. I believe 0 is at the top of the wood.
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model.png

czwalga
Posts: 6
Joined: Sun Jul 27, 2014 3:19 pm
Model of CNC Machine: cncrouterparts

Re: Routing a spherical object.

Post by czwalga »

I think I'm getting it. If I run into any issues, ill report back. Thanks!

ohiolyons
Vectric Wizard
Posts: 474
Joined: Wed May 27, 2009 7:16 pm
Model of CNC Machine: Laguna IQ HHC, 3HP
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Re: Routing a spherical object.

Post by ohiolyons »

Your model is a good start.
Just make sure you have selected project toolpath onto 3d model.

Under the assumption you can dedicate an origin and space on your table for a semi permanent fixture.

You need to cut a 1/2 sphere into into your fixture so your actual golf ball will rest in it and help hold the ball.
On this fixture i would figure how to attach some clamps so your fingers aren't part of your clamping strategy.
Golf balls are small and round and will tend to rotate.

I would do this in all one file so you don't have to worry about registration issues.
Just turn on or off your different models when generating toolpaths.

So you mount a piece of material to be your fixture.
Cut the hemisphere your golf ball will sit in.
Place golf ball in the fixture and tighten your clamping mechanism.
Now zero your Z to the top of the golf ball and run your toolpath.

Zeroing from the top of a ball is critical since there is only a minimum dimension on a golf ball.

If I was going to make many of these I would cut another hemisphere into a scrap piece of wood.
Cut it in half and slide it in from either side to act as the clamping mechanism.

You can do this, you don't need to pay for something like this.
John
CNC in Kettering, Ohio

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adze_cnc
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Re: Routing a spherical object.

Post by adze_cnc »

Something to think about: when you drill the holes manually the centre-line of each drilling meet at a common point at the centre of the ball. The walls of the hole cut will all be the same depth.

If you try to cut all three holes at once with a 3-axis CNC machine neither of the two properties above will be true. With more axes you could replicate the manual method.

See image of a cross section of 1.68" minimum diameter golf ball:
  • blue: hole as you have manually drilled them going through the centre-line (red)
  • yellow: 2D toolpath when cutting all three holes without rotating ball
  • white: keeping each wall 1/16" long and adding a curve that parallels the surface of the ball
  • black: two 1/16" diameter bits (straight and ball-end) showing area that won't be milled by a 3D toolpath
golf-ball.png

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TReischl
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Re: Routing a spherical object.

Post by TReischl »

In addition to what Mr Adze wrote:

The holes will NOT be circular appearing when viewed looking straight into the center of the ball. Hopefully that is not an issue, it will be very slight, but it will still be there.
"If you see a good fight, get in it." Dr. Vernon Jones

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