Resin casting and color matching

[Hidronax]

Hi all!

Lately I am more and more intrigued by trying to make my own silicone molds for LEGO parts (mostly Bionicle) and make resin casts. I have had a look online and there's some good tips and tutorials.
This is an "old but gold" tutorial about how to make molds for lego hairpieces and helmets, I remember it from many years ago, but now sadly the images have gone missing.

Has anyone tried, and has experience to share? In particular brands of silicone and resin to use.
Another important thing will be trying to match as much as possible original LEGO colors. Does anyone have some experience to share on that regard? It would be very helpful!

Some people got very nice results but I doubt they'd want to share their secrets :P
I have never attempted silicone casting, so I only know what I could read online :)

Thanks for your help!

[JopieK]

You could use 3D printing and bake the parts (e.g. using fine salt).

[Hidronax]

5 hours ago, JopieK said:

You could use 3D printing and bake the parts (e.g. using fine salt).

Do you mean melting the parts in an oven and have the liquid ABS to drip into the mold?

[JopieK]

Here you go: https://hackaday.com/2020/09/23/reforming-3d-prints-with-salt-and-heat/

I haven't tried it yet, but my wife already brought the salt along :)

Of course you would also be able to use other techniques (e.g. vapor smoothing). 

 

[MAB]

Years ago I cast some large minifigures using two-part silicone to make the moulds and some off the shelf casting resin. They were based on the minifig torches.  They came out OK, in the sense that you could see they were minifigures. I tried the same for bricks and they were dreadful and for minifigure accessories they were passable but not great. Anywhere you need a decent tolerance to get the parts to work, you can probably forget it. Accessories are not too bad, as they don't have to align perfectly to work, so long as the grip is the right size for hands or you are willing to glue a hat on and so on. For example, for the Bionicle ball-snaps, if the ball is too big then it won't fit, too small then it won't hold tight. It will involve a lot of post moulding work to get it just right, either adding varnish coats to increase or sanding to decrease.

 

As for colouring, you will have to experiment. Paint matching is bad enough normally (and paint will be damaged in any moving / friction parts) to get the colourant inside will almost certainly depend on the exact resin you are using.

[Hidronax]

On 10/25/2020 at 9:21 AM, MAB said:

Years ago I cast some large minifigures using two-part silicone to make the moulds and some off the shelf casting resin. They were based on the minifig torches.  They came out OK, in the sense that you could see they were minifigures. I tried the same for bricks and they were dreadful and for minifigure accessories they were passable but not great. Anywhere you need a decent tolerance to get the parts to work, you can probably forget it. Accessories are not too bad, as they don't have to align perfectly to work, so long as the grip is the right size for hands or you are willing to glue a hat on and so on. For example, for the Bionicle ball-snaps, if the ball is too big then it won't fit, too small then it won't hold tight. It will involve a lot of post moulding work to get it just right, either adding varnish coats to increase or sanding to decrease.

 

As for colouring, you will have to experiment. Paint matching is bad enough normally (and paint will be damaged in any moving / friction parts) to get the colourant inside will almost certainly depend on the exact resin you are using.

I see! I would like to reproduce the Bionicle masks and pieces in the original LEGO colors though, I'm not sure how that could help...

On 10/25/2020 at 9:21 AM, MAB said:

Years ago I cast some large minifigures using two-part silicone to make the moulds and some off the shelf casting resin. They were based on the minifig torches.  They came out OK, in the sense that you could see they were minifigures. I tried the same for bricks and they were dreadful and for minifigure accessories they were passable but not great. Anywhere you need a decent tolerance to get the parts to work, you can probably forget it. Accessories are not too bad, as they don't have to align perfectly to work, so long as the grip is the right size for hands or you are willing to glue a hat on and so on. For example, for the Bionicle ball-snaps, if the ball is too big then it won't fit, too small then it won't hold tight. It will involve a lot of post moulding work to get it just right, either adding varnish coats to increase or sanding to decrease.

 

As for colouring, you will have to experiment. Paint matching is bad enough normally (and paint will be damaged in any moving / friction parts) to get the colourant inside will almost certainly depend on the exact resin you are using.

Well I am interested mainly in parts that only have axle and pin holes, nothing more complex than that... Yeah ball joints would be very tricky to obtain.

Yeah, matching colors seems something that would take a very long time to fine tune, without a starting point...

Edited November 4, 2020 by Hidronax

[Hidronax]

Double post (bug)

Edited November 4, 2020 by Hidronax

[MAB]

If you want a part with a pin or a hole, I suggest embedding or gluing a genuine LEGO pin into the casting. That way you are guaranteed a perfect fit.

[LEGO_duden]

Hi,

I once cast a polyurethane copy of Boba Fetts helmet.  I use it on RC parts mainly

Two component silicone is very good at replicating details. It does not stick to anything but silicone (problem with 2 part mould) 

There are a few things to be aware of. Through holes have to be blocked on one side, preferably on the inside of the piece, a piece of scotch tape is fine.

Silicone is kind of soft, so keep it mould int the Lego form while casting, else you risk deforming it while casting.

Suggest you use at least 10mm of silicone as minimum around the piece. Large pieces could need more or some stiffening, plastic sticks fx.

;Air pockets will happen if you dont plan on venting somehow or let the air out on top where you pour.

Lego is great for making the casting in, its not destroyed at all. It may be wise to use cling film anyway as it might leak between the bricks.

To make 2 part mould you could use clay, some clay contain sulphur that will inhibit the silicone cure. Make some marks in the clay so the 2 parts will  stay in place.

When casting the second part you need some wax or soemthing to prevent the silicone to stick to the first part.

Some cast all in one piece and cut it open with a scalpel to remove the piece inside and cut a pouring hole. Can work ok.

Silicone and polyurethane is hardly available here, so I have bought from UK. There are also several sellers in US if that is closer for you,

but I am not familiar with them, as postage is too expensive.

Color matching will be a trial and error.