Machining a Segment of a sphere

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Machining a Segment of a sphere

Postby Soapyjoe » Tue Sep 19, 2017 10:54 am

Hi Everybody,

I wish to make a sphere, say about 6 inches in diameter.... the actual size is not really important.
I would like to construct it from segments, like an orange, of different coloured hardwoods.
I have a few ideas myself but would like to draw upon the expertise of some of our more experienced workers.
Thanks in anticipation.

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Re: Machining a Segment of a sphere

Postby adze_cnc » Tue Sep 19, 2017 4:37 pm

  • Machine two halves and glue them together?
  • Use a lathe?
  • Use a circular saw (search for Izzy Swan's video)?
  • Machine six shallow domes and glue them to a cube core?
  • Get a six-axis machine?

Edit: Sorry. I thought you were going to glue up the wood first and wanted ideas on how to deal with the blank.

How about using a bandsaw to form tapered blanks then place them in a jig and use the CNC to round them over?
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Re: Machining a Segment of a sphere

Postby Leo » Tue Sep 19, 2017 4:53 pm

Like slices of an orange

Each slice a different wood.

Hmmmmm

First a cylinder of slices.

thin double sided tape the slices to make the cylinder

Second - a rotary axis turning to make the sphere.
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Re: Machining a Segment of a sphere

Postby mezalick » Tue Sep 19, 2017 5:53 pm

I'm thinking he's looking for something like this..
Given that it's in the V-Carve section....now if it was Aspire....a whole different story..
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Re: Machining a Segment of a sphere

Postby mezalick » Tue Sep 19, 2017 6:03 pm

I found an easier way using the molding toolpath option..

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Re: Machining a Segment of a sphere

Postby mezalick » Tue Sep 19, 2017 6:05 pm

In fact, if you lay it out correctly you should get 2 slices from the same block of material..

Okay,,I'll stop now.....LOL

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Re: Machining a Segment of a sphere

Postby FixitMike » Tue Sep 19, 2017 7:52 pm

mezalick wrote:In fact, if you lay it out correctly you should get 2 slices from the same block of material..

Okay,,I'll stop now.....LOL

Michael


Post the file. Please? I possibly could figure out how to do this myself, but I'm lazy.
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Re: Machining a Segment of a sphere

Postby Soapyjoe » Tue Sep 19, 2017 10:40 pm

Hi Everybody,

Yes, I wish to machine it with Aspire 9.

My idea is to make the sphere from many segments ....say 36 each with a 10 degree taper.

I was thinking of using 2 rail sweep.

Any other ideas would be appreciated.

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Re: Machining a Segment of a sphere

Postby mezalick » Wed Sep 20, 2017 9:34 am

The two rail sweep would be my first choice...just need to make sure all the mathematics add up..
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Re: Machining a Segment of a sphere

Postby 4DThinker » Thu Sep 21, 2017 12:35 am

It fairly easy to make 10 degree wedges. Both the moulding and fluting toolpaths could be used for that. There are even a couple of 3D toolpaths that could do that job. What has proven difficult for me to do is make those wedges with a perimeter that is a true 10 degree section/slice of a sphere skin.

It seems as though there should be a mathematical/logical way to subtract 170 degrees from a half sphere and be left with a 10 degree slice of that sphere as a component to carve.
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Re: Machining a Segment of a sphere

Postby Soapyjoe » Thu Sep 21, 2017 8:31 am

Thank you for your interest in my posting.

I am not quite sure that I fully understand exactly what you mean by.....[wedges with a perimeter that is a true 10 degree section/slice of a sphere skin].
Do you mean that the wedges will have a flat on them ?

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Re: Machining a Segment of a sphere

Postby 4DThinker » Thu Sep 21, 2017 2:49 pm

Soapyjoe wrote:I am not quite sure that I fully understand exactly what you mean by.....[wedges with a perimeter that is a true 10 degree section/slice of a sphere skin].
Do you mean that the wedges will have a flat on them ? Soapy

If you want the 10 degree slices of a sphere to just be glued together without needing to be lathe turned/trimmed and sanded down until they look like a smooth sphere then the CNC could do that, if only you/I/anyone was smart enough to know how to make that 3D model for cutting out. If you just want 10 degree slices that are rectangular and can be glued up into a cylinder, then lathe turned down into a sphere then that is easy to do using the Moulding toolpath or the fluting toolpath and an array of parallel lines.

If my explanation is still confusing I apologize. I am used to talking to college students who go blank when I'm trying to explain how we'll cut their creative creations out using a CNC. :shock:

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Re: Machining a Segment of a sphere

Postby Pete Cyr » Thu Sep 21, 2017 3:25 pm

Lots of good ideas in this thread but there is no need to create a process - -someone else already did all the hard work for us.

viewtopic.php?f=29&t=18525

This post shows:

Perfect 4" sphere on a 3-axis Joe's Hybrid machine.
Board thickness needs to be about 25% of ball diameter.
1/4" RN to ruff; 1/8" RN finish. White pine.

---------------------------
I believe this will achieve your goal.
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Re: Machining a Segment of a sphere

Postby 4DThinker » Thu Sep 21, 2017 3:50 pm

Pete Cyr wrote:Lots of good ideas in this thread but there is no need to create a process - -someone else already did all the hard work for us.

viewtopic.php?f=29&t=18525
His goal was to create the sphere using 10 degree slices.

Soapy wrote:"My idea is to make the sphere from many segments ....say 36 each with a 10 degree taper.
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Re: Machining a Segment of a sphere

Postby Leo » Thu Sep 21, 2017 5:27 pm

Here is a 10 degree slice from a sphere.

Done with a 2 rail sweep.

The outside radius is 3" and the spherical curve is 3" radius.

Because the sides are almost vertical it is going to be really difficult to machine

This is a toolpath preview

Material size is 7" x 4" x .6"

Tool used is 1/32 tapered ball nose - stepover is .003
I don't think there will be good definition on the spherical cut otherwise

toolpath preview.jpg
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