Mold making complex shape

[malain]

Hi there,

My name is Pierre, french based in Nice.

I started ceramics couple of years ago,

Making all kind of things, fmostely kitchenware, objects, and deco.

 

I recently had a special order from a friend, 

Whom was asking for a Virgin Mary sculpture with a modern touch.

 

Because I am nowhere near from an artist and sculptor, 

I started researching mould making and obviously ended up learning about case slip method. 

I first tryied to make a 3 parts mold out of à 3D printed object, 

Which ended up as a Fail (half fail to be honnest)

 

So, then I decided to find the 3D model corresponding to one that I bought

in order to have a more precise understanding of the undercuts

And working around it in blender with multiple horizontal section planes

But with my lack of knowledge on undercuts, This still is quite a complicated task to do bymyself.

 

I recently came across a ceramic artist who would 3D print the outside shell of the future mold,

Fill it with plaster,

Then cut out the plastic,

then slip it.

Maybe this is worth a try?

 

This project has really been growing on me and I would really like to succeed!

 

So I was hopping someone on the forum could help out on to make such a complex mold, 

even if it were including many parts, or lots of post-prod work.

 

What do you think of this project?

 

Thanks in advance for your time and advice!

Pierre

 

 

 

 

 

 

[PeterH]

1 hour ago, malain said:

I recently came across a ceramic artist who would 3D print the outside shell of the future mold,

Fill it with plaster,

Then cut out the plastic,

then slip it.

Maybe this is worth a try?

Do you mean like this?
3D Printing a Mold for a Slipcasting Mold
https://www.instructables.com/3D-Printing-a-Mold-for-a-Mold/

Looks like a viable way of making individual parts of a multi-part mould.

[Jeff Longtin]

Hello Malain, 

Welcome to the forum. 

How tall is this piece? You intend to have the final product be ceramic, correct? Stoneware or porcelain?

In the picture there are several dark/shaded areas. Those would suggest undercuts. If you are willing to fill in those undercuts you may be able to make these with just a two part mold. (That would be best.)

[malain]

Hi,

@Peter - Yes. that's the method I was refering about. Although the Mary beeing much more complicated I was wondering if anyone would consider this option, and how many part I should consider making. Even by using the 3D software and horizontal section planes I find it  difficult to picture and split the mold efficiently.

@Jeff - The piece would be about 40cm height. Not Big. The final product would probably be stoneware . I had also considered  filling the undercuts, but then wondered if I'd be able to carve them afterward (like said before - not a sculptor), or if there were a risk of fragilizing the piece (uneven thickness) . If I were to use this metod would you suggest dividing front/back, or right/left ?

Maybe making the hands separately would also be best?

Thanks!

[Chilly]

Have you made moulds before?  Imagine making a mould for a banana.  Probably only needs 2 parts - one for the left side, one for the right.  Now think of an apple.  Might still only need 2 parts, but this time one for top and one for bottom, as an apple has dimples.  Now imagine a pineapple..........

Working out how many pieces you would need for a mould is a specialist job.  An experienced mould-maker could probably just look at it and know how to do it.  I wouldn't tackle anything that complex, but would think it would need at least 3-4 pieces.  If you look at the bottom third, you would need 3 pieces for that , as it curves outward and then in toward at ankle level, then back out at waist level.  Everytime you have bits that change direction and have shadows, you need more pieces.  You have to imagine shining a torch on it, and where the light shines you need a piece.   You might be able to do separate hands, and join them after casting.

[Jeff Longtin]

Mold Design decision - While you can make a multiple part mold for a complex form you need to also consider the usability of such a mold. Each part creates a seam.(That needs to be cleaned.) Each part needs to fit together, well, with its neighbor, so the mold holds together tightly.

If you have a mold with lots of small parts you then have to be really careful when you work with the mold. If you crack, chip, or break just one part does it ruin the whole mold?

For the aforementioned reasons it is best, if possible, to keep your parts to a minimum. (Less time spent cleaning, less worry about breakage.)

Undercuts - A way you can keep detail but reduce its impact is to design the undercuts so they face one direction, either front or back. If you alter the undercuts so they follow the "pull" of the mold, as you separate the two pieces, then you can keep detail but make it work for you and not against you.

Hope this helps.

[PeterH]

This earlier post by @Jeff Longtin may be of interest