10. Molding and casting¶
This week I focused on designing an object for my final project. DITO is a device designed to facilitate the action of leafing throught the pages of a newspaper/book. It consists in a rubber thimble, with an external layer for grip.
To do that with molding and casting we will need three total pieces, two wax bricks for the external shape and a printed part for the internal part. For the modeling part I used Fusion 360. Here there’s the first sketch for the internal part.
Here’s the internal part and the actual object, which is a little bigger and has a fillet on the outside.
To create the mold shape we have to divide the object in half.
And subdivide it in a box, which is our wax brick.
This is the model we will 3D print, in order to stuck it on the wax bricks. It has a hole inside in order to let the material flow inside.
Save the file as .stl and upload it on Ultimaker Cura to print it.
This is a close-up of the mold with the interlocking keys.
Now it’s time to go in the manufacturing area of Fusion. First thing first make a new setup, with the following characteristics.
Then we have to decide the milling settings. I used a 6mm tip to remove most of the material, and a 1.5 mm tip for more precise processing.
Now we can make a simulation and post process to get to mill the mold.
Here I’m using the 6mm bit to smooth out the material.
This is the mold, once we divide it we can stuck the 3d printed mold and we’re done! Oh well, the molding part is done, the most difficult part is missing: casting!
The material I chose is Sintagom 730/40, which is a polyurethane elastomer that polymerizes in cold, giving rise to an elastic compound similar to rubber, stable and without shrinkage. It is normally used as a casting mass to obtain parts on silicone rubber molds. The apparent medium viscosity does not affect the smoothness of the product which is able to reach and reproduce every detail of the mold. The shore hardness is A 43.
Warnings
-
Do not use at temperatures below 17-18 ° C.
-
Do not use beyond the working time, after which, in the event of an increase in viscosity, it is absolutely necessary not to add thinners, believing that the useful life of the product will be increased.
Tips for safe use
-
Wear protective gloves and goggles both during the mixture and in the application
-
Wash rollers and tools with solvents as soon as you finish the job
-
Do not throw washing residues and solvents down the drain
-
Dispose of both the washing solvents and the empty packaging contaminated by the products at an authorized recoverer
Will it be a disaster? Probably. Will we stop trying? Absolutly not, but we just have to wait now.
Finally after one night, we can see the results. The mold was a little stuck, but with the help of compression air and fellow gents…
…I’m very pleased to introduce you to DEETO!
This is what you were looking for:
