Hi

I need to build parabolic dishes of different shapes. I think that
spin forming should be the ideal method but I no nothing about that
method. I'm not a metal craftman.

I have some questions about that process.

The material I want to use is either cupper or aluminium. Thickness is
in the order of 20-28 ga.

I don't want to make a mold for every dish because I won't produce
many of each size & shape so it has to be "turned" on air.

Is spinning on air precise enough to produce an exact curve every
time ?

What should be the rotation speed of the machine for let's say a 2-4
feetd dia. dish ?

Can I use a modified small lathe for that or a simple spindle could do
the job ?

Thanks

Don't move....
The bright young men in their clean white coats are coming to take you away!


HaHa!

JR
Dweller in the cellar


Bill wrote:

Hi

I need to build parabolic dishes of different shapes. I think that
spin forming should be the ideal method but I no nothing about that
method. I'm not a metal craftman.

I have some questions about that process.

The material I want to use is either cupper or aluminium. Thickness is
in the order of 20-28 ga.

I don't want to make a mold for every dish because I won't produce
many of each size & shape so it has to be "turned" on air.

Is spinning on air precise enough to produce an exact curve every
time ?

What should be the rotation speed of the machine for let's say a 2-4
feetd dia. dish ?

Can I use a modified small lathe for that or a simple spindle could do
the job ?

Thanks



--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth
If you're not the lead dog, the view never changes
Doubt yourself, and the real world will eat you alive
The world doesn't revolve around you, it revolves around me
No skeletons in the closet; just decomposing corpses
--------------------------------------------------------------
Dependence is Vulnerability:
--------------------------------------------------------------
"Open the Pod Bay Doors please, Hal"
"I'm sorry, Dave, I'm afraid I can't do that.."

On Wed, 03 Oct 2007 07:31:51 -0700, Bill
wrote:

Hi

I need to build parabolic dishes of different shapes. I think that
spin forming should be the ideal method but I no nothing about that
method. I'm not a metal craftman.

I have some questions about that process.

The material I want to use is either cupper or aluminium. Thickness is
in the order of 20-28 ga.

I don't want to make a mold for every dish because I won't produce
many of each size & shape so it has to be "turned" on air.

Is spinning on air precise enough to produce an exact curve every
time ?

What should be the rotation speed of the machine for let's say a 2-4
feetd dia. dish ?

Can I use a modified small lathe for that or a simple spindle could do
the job ?

Thanks
You should google for metal spinning. There is also a yahoo group for
metal spinners. Whenever I spin something the part of metal being
"supported" by the air seems to almost always be conical. Sometimes I
get a curved shape that may or not be parabolic. But then I'm not
trying to get a particular shape in the air, I'm trying to get the
metal to conform to the chuck and it will take whatever shape it wants
from flat disc to fitting the chuck. Some production metal spinning is
done on CNC machines. Maybe if the material was consistent a tool path
could be programmed to get the desired shapes without too many scrap
parts.
ERS

On Wed, 03 Oct 2007 16:30:28 -0700, Eric R Snow
wrote:

On Wed, 03 Oct 2007 07:31:51 -0700, Bill
wrote:

Hi

I need to build parabolic dishes of different shapes. I think that
spin forming should be the ideal method but I no nothing about that
method. I'm not a metal craftman.

I have some questions about that process.

The material I want to use is either cupper or aluminium. Thickness is
in the order of 20-28 ga.

I don't want to make a mold for every dish because I won't produce
many of each size & shape so it has to be "turned" on air.

Is spinning on air precise enough to produce an exact curve every
time ?

What should be the rotation speed of the machine for let's say a 2-4
feetd dia. dish ?

Can I use a modified small lathe for that or a simple spindle could do
the job ?

Thanks
You should google for metal spinning. There is also a yahoo group for
metal spinners. Whenever I spin something the part of metal being
"supported" by the air seems to almost always be conical. Sometimes I
get a curved shape that may or not be parabolic. But then I'm not
trying to get a particular shape in the air, I'm trying to get the
metal to conform to the chuck and it will take whatever shape it wants
from flat disc to fitting the chuck. Some production metal spinning is
done on CNC machines. Maybe if the material was consistent a tool path
could be programmed to get the desired shapes without too many scrap
parts.
ERS


We specialize in metal spinning for more info:
www.debcomachinery.com
Daveb

....
We specialize in metal spinning for more info:
www.debcomachinery.com
Daveb

I went through your web site, watched your video, very interesting. Couple
of questions.
How are you quickly chucking the part?
Tell me more about the tool that's contacting the metal to spin.

I doubt that I ever do it, but it looks like most CNC lathes could be easily
modified for spinning, at least for HSM type runs.

Karl

You could try http://metalspinningworkshop.com/forum/upload/index.php
although you do have to register IIRC to post.

Bill wrote:

Hi

I need to build parabolic dishes of different shapes. I think that
spin forming should be the ideal method but I no nothing about that
method. I'm not a metal craftman.

I have some questions about that process.

The material I want to use is either cupper or aluminium. Thickness is
in the order of 20-28 ga.

I don't want to make a mold for every dish because I won't produce
many of each size & shape so it has to be "turned" on air.

Is spinning on air precise enough to produce an exact curve every
time ?

What should be the rotation speed of the machine for let's say a 2-4
feetd dia. dish ?

Can I use a modified small lathe for that or a simple spindle could do
the job ?

Thanks

On Thu, 4 Oct 2007 05:11:23 -0500, "Karl Townsend"
wrote:

...
We specialize in metal spinning for more info:
www.debcomachinery.com
Daveb

I went through your web site, watched your video, very interesting. Couple
of questions.
How are you quickly chucking the part?
Tell me more about the tool that's contacting the metal to spin.

I doubt that I ever do it, but it looks like most CNC lathes could be easily
modified for spinning, at least for HSM type runs.

Karl


The part (disk) has a hole in the center that locates over a pin on
the ejector and then the tailstock is closed.

Most machines have a centering device (hydraulic) the you set the disk
on then it extends upwards and the tailstock is then closed.

The tool is just a heat treated steel with a radius and a relief with
a bearing in the center.

When you do large diameters (as in the video) you see the backup
roller that extends out on a cylinder and as the part is being spun is
is pushbacked this is to keep the part from distorting or
bottlecapping.

Here is a good video we made:

http://s32.photobucket.com/albums/d1...nt=Spinvid.flv

Regards
Daveb

On Thu, 4 Oct 2007 05:11:23 -0500, "Karl Townsend"
wrote:

...
We specialize in metal spinning for more info:
www.debcomachinery.com
Daveb

I went through your web site, watched your video, very interesting. Couple
of questions.
How are you quickly chucking the part?
Tell me more about the tool that's contacting the metal to spin.

I doubt that I ever do it, but it looks like most CNC lathes could be easily
modified for spinning, at least for HSM type runs.

Karl


http://s32.photobucket.com/albums/d1...t=Dscf0002.jpg
Daveb

On Fri, 05 Oct 2007 01:46:39 GMT, (DaveB) wrote:

On Thu, 4 Oct 2007 05:11:23 -0500, "Karl Townsend"
wrote:

...
We specialize in metal spinning for more info:
www.debcomachinery.com
Daveb

I went through your web site, watched your video, very interesting. Couple
of questions.
How are you quickly chucking the part?
Tell me more about the tool that's contacting the metal to spin.

I doubt that I ever do it, but it looks like most CNC lathes could be easily
modified for spinning, at least for HSM type runs.

Karl


The part (disk) has a hole in the center that locates over a pin on
the ejector and then the tailstock is closed.

Most machines have a centering device (hydraulic) the you set the disk
on then it extends upwards and the tailstock is then closed.

The tool is just a heat treated steel with a radius and a relief with
a bearing in the center.

When you do large diameters (as in the video) you see the backup
roller that extends out on a cylinder and as the part is being spun is
is pushbacked this is to keep the part from distorting or
bottlecapping.

Aha! I've been puzzling over that one for a while, with mediocre
results. I did a little bit of spinning on my wood lathe, and the
"bottlecapping" made it seem impossible to do without making the disks
really oversized and then cutting off the remainder. Am I
interpreting the video correctly when it appears that the forming
roller is mechanically pushing back the backup roller as it goes, or
is that all computer controlled?

Thanks for the missing link!

Here is a good video we made:

http://s32.photobucket.com/albums/d1...nt=Spinvid.flv

Regards
Daveb

On Fri, 05 Oct 2007 06:25:48 -0500, Prometheus
wrote:

On Fri, 05 Oct 2007 01:46:39 GMT, (DaveB) wrote:

On Thu, 4 Oct 2007 05:11:23 -0500, "Karl Townsend"
wrote:

...
We specialize in metal spinning for more info:
www.debcomachinery.com
Daveb

I went through your web site, watched your video, very interesting. Couple
of questions.
How are you quickly chucking the part?
Tell me more about the tool that's contacting the metal to spin.

I doubt that I ever do it, but it looks like most CNC lathes could be easily
modified for spinning, at least for HSM type runs.

Karl


The part (disk) has a hole in the center that locates over a pin on
the ejector and then the tailstock is closed.

Most machines have a centering device (hydraulic) the you set the disk
on then it extends upwards and the tailstock is then closed.

The tool is just a heat treated steel with a radius and a relief with
a bearing in the center.

When you do large diameters (as in the video) you see the backup
roller that extends out on a cylinder and as the part is being spun is
is pushbacked this is to keep the part from distorting or
bottlecapping.

Aha! I've been puzzling over that one for a while, with mediocre
results. I did a little bit of spinning on my wood lathe, and the
"bottlecapping" made it seem impossible to do without making the disks
really oversized and then cutting off the remainder. Am I
interpreting the video correctly when it appears that the forming
roller is mechanically pushing back the backup roller as it goes, or
is that all computer controlled?

Thanks for the missing link!

Here is a good video we made:

http://s32.photobucket.com/albums/d1...nt=Spinvid.flv

Regards
Daveb

The part is pushing the backup roller, the pressure is adjustable.

Regards
Daveb