Making the silicon mould

Yesterday we edited our last test piece from the cast-able resin. We printed a version which was not digitally restored and then tried to restore it manually with wax to see if this method works better than restoring it digitally. The restoring was done with a soldering iron to melt the wax and then dab it onto the surface. We also tried to scrape away material at the edges with some sculpting tools to make the ornaments on the crown more detailed. The cast-able resin has a soft wax layer at the surface, but is a lot harder beneath the surface layer. It turned out to be harder than we expected to edit the piece.

Restoring the cast-able resin piece with wax and a soldering iron

Dripping the wax onto the model

So now we have four different types of test pieces which will be casted.

Four types of test pieces

After the restoration we started with the production of the wax moulds. To make a piece of the crown from wax, we need a silicone mould where we can pour the wax into. We plan to make the silicone mould by pouring liquid silicone together with harderer in a wooden box. In the box we will stick our four crown pieces with some double sided tape on the bottom of the box. Then we will pour the silicon in and let it harden for twentyfour hours. Then we can break the walls of the box away and we have our silicon mould!

For the box we used a piece of mdf board. To assure that the silicone would not stick too much to the box we used clear tape to cover the inside of the wooden box. We also used sculpting clay to cover all the edged of the box so that there are no sharp corners in the silicon mould.

We found out that the cast-able resin pieces did not stick too well to the double sided tape, probably because of the thin wax layer, so we decided to stick them to the bottom of the box with the sculpting clay. We are not so sure if the pieces are well enough attached to the bottom. If that is the case, then the silicone can slip between the edges and fill up the cavity beneath the test pieces. Hopefully this will not be the case.

Making the wooden box for the silicone mould

 

The finished silicon mould

We mixed the silicon with the harderer and poured in into the wooden mould.

Pouring the silicon in the mould

Then we put the mould in the vacuum oven. Just to be sure we put the temperature a low as possible. The silicon rose a lot in the mould so it would have been better if we made the sides of the box a bit higher. To prevent the silicn from pooling over we let a little air in the oven bit by bit. This worked fine.

Removing air bubbles with the vacuum oven

There were quite a lot of large air bubbles so maybe some of the silicon slipped beneath the edged of the test pieces.

Inside the vacuum oven

This is the end result. It seems that most of the bubbles in the mould are gone so we are positive that the wax moulds will turn out fine. We let the silicon set over the weekend and on Monday we will start with the wax pouring.

 

 

Printing the cast-able resin test pieces

On Wednesday, we arranged to change the current grey resin for the newly arrived cast-able resin. This resin is used a lot for investment based jewelry casting. Because we want to use a similar method, the resin should fit our purpose perfectly. When heating cast-able resin, it will melt out of a mould, leaving space to pour liquid metal. We discussed this method in this post.

Another option is to create silicon moulds from these pieces. Hot, liquid wax can then be poured in the silicon moulds and the resulting wax models will be used for the investment or sand-casting. To make the silicon moulds, both the cast-able and non cast-able resin prints can be used, so in order to compare the two types of prints, we decided to print the same pieces as we did before and make a silicon mould of all four pieces.

First, we had to print the cast-able models, so we had to change the resin in the machine. Because Tessa never changed the resin in the Form2 yet, it was a new process to all of us. Being very cautious to not spil a single drop of resin on the clean glass, we managed to take out the printing platform and replacing the resin tank. Once everything was cleaned and changed correctly, we started our print and the tank started filling with the cast-able resin. Due to the orange cover of the machine, it looked like a black material.

The next day, Thursday, we returned to take out the print. When opening the cover, we were very suprised with the beautiful, bright, blue colour.

The two pieces printed in cast-able resin

After taking out the prints and taking off the support material, we noticed a clear difference with the non cast-able resin. The cast-able material is a lot softer, stickier and can even bend a little. Even though we were very careful taking off the support structure, we could not avoid scratching the surface a little.

The cleaned cast-able resin prints

Once the pieces were released from the support, we went to the city centre to meet Maaike and discuss the progress.

Resin print samples

We were able to collect our Form 2 resin prints on Monday morning and we are very happy with the results.

Finished pieces hanging on the building platform of the Form 2

Removing the pieces form the building platform with a scaper

It did require some work to clean up the samples but this was very easy to do for such a high quality result. First we soaked the prints in isopropyl alcohol and then we cut away the support material.

Prints soaking in isopropyl alcohol

Cutting away the support material

Cutting away the support material

Cutting away the support material

Now we could actually see very clearly the differences between the raw scanned data of the crown and the digitally re-touched version that we had made.

The hollow inside of the print

Left: retouched version. right: unedited version

We will still need to clean up some of the attachment points for the support material but this gives us a great insight into what the quality and finish is like compared to the Ultimaker printers.

The cast-able resin has also arrived so we will work with Tessa on Wednesday morning to change the resin over and print a sample in this resin to see how it differs from the normal grey resin that we used today.

In the meantime we will work on refining the digitally touched up model and attempt to re-create build the crown digitally in solidworks to see how this looks compared with the raw scanned and digitally touched up versions.