[chroniccodez]

How difficult would it be to create a spherical mold about 18-24" in diamater? I need two half spheres for casting an acrylic mold (i know this is for metal casting but i figured the technique is some what the same). I have an acrylic sphere that is the exact same diamater for what I need, but it is two brital when cut in half.

Is this something that I could do myself? If not, should I pay to have a mold made? How much do you think it may cost if I did have it made? I know this is hard to determine, but can anyone give me a general idea like $100-$200. I have a very low budget for my project.

Oh btw, the sphere needs to be hollow.

[keebler303]

does the mold need to be metal?
If not, use fiberglass. You can use your acrylic sphere as a pattern, coat it with a release agent, and make a mold off of it.
Any glass shop could do this easily or I can give more information on how you would do it if you want to do it yourself.

Matt

[chroniccodez]

Forgot to mention that I want it to be casted w/ an acrylic mold. I haven't done any calculations yet, but the walls will need to be 3/4-1" thick around the sides. I would also like the inside to have molded brackets. I do not know the technical term for this. I will be fastening aluminum inside the case.

I would prefer to do it myself, is this feasible? Any suggestions? I have never casted anything before so if you know of any helpful sites please link'em. Thank you.

[ltmquik]

This sounds like a perfect application for rotomolding. You can have a mold cast using aluminum and then finish machine the detail for your shere. This is probably going to cost you between $12k-$30K. I hope you are wanting to make more than one.

[tobyaxis]

How difficult would it be to create a spherical mold about 18-24" in diamater? I need two half spheres for casting an acrylic mold (i know this is for metal casting but i figured the technique is some what the same). I have an acrylic sphere that is the exact same diamater for what I need, but it is two brital when cut in half.

Is this something that I could do myself? If not, should I pay to have a mold made? How much do you think it may cost if I did have it made? I know this is hard to determine, but can anyone give me a general idea like $100-$200. I have a very low budget for my project.

Oh btw, the sphere needs to be hollow.

Just a Soild CAD Model or the Actual Sphere.

I'll do a CAD Model for you for $50.00 US. The Actual Part will cost a lot more than that.

[spider]

i'm not sure....would 3d printing work???

[chroniccodez]

This sounds like a perfect application for rotomolding. You can have a mold cast using aluminum and then finish machine the detail for your shere. This is probably going to cost you between $12k-$30K. I hope you are wanting to make more than one.

...yeah I do not have that sort of budget

[DSL PWR]

Do you need a solid sphere or 2 domes? If you need domes use a vac press like they have on mythbusters and do one half at a time.

[chroniccodez]

Do you need a solid sphere or 2 domes? If you need domes use a vac press like they have on mythbusters and do one half at a time.

I need two domes that when placed together, create a perfect sphere. I love mythbusters, but I can't remember the vac press. Will I be able to make a perfect sphere?

[holbieone]

what tolerance are we talking here ?

[chroniccodez]

Tolerance?

diameter: 18-24"
thickness: approx. 1"

[holbieone]

Tolerance?

diameter: 18-24"
thickness: approx. 1"

what tolerance on roundness

also do you have any pics or drawings of what you want to mold
or is this what you want to mold

[holbieone]

also what suffice finish do you need

[chroniccodez]

I am sorry, but what do you mean when you say "tolerance"? Do you mean how perfect do i want the overall shape to be?

Heres a very simple image of what i am trying to do:

http://i21.photobucket.com/albums/b2...8-Ballcopy.jpg

The green area is what will be inside the shell

[holbieone]

I am sorry, but what do you mean when you say "tolerance"? Do you mean how perfect do i want the overall shape to be?

Heres a very simple image of what i am trying to do:

http://i21.photobucket.com/albums/b2...8-Ballcopy.jpg

The green area is what will be inside the shell

yes that's what i mean

so you just need the shell

can this part be made in four pieces

also what material can it be made from

[chroniccodez]

I would prefer that it be done in two pieces. The top half of the shell needs to be one piece, it will look much better that way. Would it be easier to make four pieces? And if so, why?

I would prefer to cast an acrylic resin so that it is at least some what translucent.

[holbieone]

it all depends on how this sphere is made if its mill the tool would have to reach down 12 inches

what are you casting this sphere

or using this sphere to cast

[chroniccodez]

Let me describe what I am trying to do.

Imagine a spherical shadow-box. There will be something inside the sphere, approx. 20-25 lbs. I would like it to be some what translucent. Preferably a tinted black look, like tinted windows on a car. The top portion of the shell needs to have these features, the bottom half can be a solid color, and does not need to be translucent.

I do not want to go into too much detail at the moment.

[cbass]

Do you know anyone with a potter's wheel?

You could turn this on a wheel using some clay and a template of a quarter circle to create a hemisphere. The template will need some sort of jig to hold it steady. This might either hinge, or move in a linear motin relative to the rotating wheel. Or it could just be a surface you rest the template against. You can then cast a negative plaster mold directly off the clay positive. I assume you can then cast your plastic directly off of plaster...

I've done this before and it works. Just requires patience (like everything else!).

Carlo


BTW, this is called jiggering in ceramic manufacturing

http://www.pottery-books.com/axner/e...erarm-main.php

The image gives a good idea of how this works...

[holbieone]

Let me describe what I am trying to do.

Imagine a spherical shadow-box. There will be something inside the sphere, approx. 20-25 lbs. I would like it to be some what translucent. Preferably a tinted black look, like tinted windows on a car. The top portion of the shell needs to have these features, the bottom half can be a solid color, and does not need to be translucent.

I do not want to go into too much detail at the moment.

do you need the mold or the sphere?