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Week 13. Moulding and Casting

Hero Shot

Assignments for the Week

Group Assignment:

  • Review the safety data sheets for each of your molding and casting materials.

  • Make and compare test casts with each of them.

  • Compare printing vs milling molds.

Link to our group assignment is here

key takeaways from this week

  • Always use either polyurethane or hydrostone with silicon rubber mould because if you use same silicon rubber solution with silicon mould, there will be chemical reaction between same component resulting in the poor quality of mould.

  • Always use the negative mould obtained from the mother mould for the final product.

  • Always refer to the data sheets thoroughly while mixing the solutions during moulding.

  • Use silicone rubber solution with harder or rigid mould.

  • After pouring the mixter(A and B) in the mould, keep it on the stable place in order to avoid unnecessary spillages of the mixture and also to get the smooth finish of the mould at the end.

  • While using silicon rubber solution and catalyst for curing, remember to add either 30/50 percent of catalyst per the grams of silicon rubber solution added.

  • Take extra precautions while handling and mixing the solutions as they are toxic and can be harmful when it comes in coontact with our body.

Individual Assignment:

  • Design a mold around the process you’ll be using, produce it with a smooth surface finish, and use it to cast parts.

Designing Molds

For this week assignment, I had decided to make two part mold of pawn. At first I thought of designing by myself but since we had already completed our CAD week and also due to time constraints, I had directly downloaded the model from here. So after downloading I opened the fusion 360 and imported the stl file and started to work on it. For making cavity inside for the model and also to split body equally into two halves, I had gone through this tutorial for the reference.

I had sketched a rectangal on my model by diving equally after selecting one of the plane

Then I extruded the rectangular body symmetrically on the model on both sides ensuring that it covers the pawn fully.

After I had extruded the rectangular body on the pawn, next I did combine operation by selecting the target body as the mould and by selecting the tool bodies as the pawn.

In order to divide the body into two equal halves, I had selected on both sides of body and seperated it by midplane

Next I splitted the two bodies by selecting the Split body option and for that I had selected on both side of bodies and followed by that I had selected the splitting tools as the midplane.

After splitting the bodies I had renamed both part as mould front and mould back and hid the mould front and sketched the circle on the mould back.

In order to enclose two bodies with exact orientation while we do moulding, I created lock like structure by extruding the circle and created rectangular pattern by giving four numbers on the body of mould back.

After that I unhid the mould front and performed the combine option to create the hole on it so that two bodies will get enclose easily.

This is how my one part of body looked like after I finished creating the inside cavity and locks to enclose the two bodies.

In order to pour the moulding solution firmly with ease I had created hole on the top of my mould bodies so that I can pour the solution from there.

This were the steps I follwed to create hole on top of bodies. I had selected the revolve option and selected one of the axis for the rotation and performed cut option.

After that I had saved my models in stl files. Then I opened bambu slicer, did slicing and sent to printer for printing.

The step shows on the process of 3d printing my moulds using bambu printer.

After I finished printing my front and back mould, I went for preparing the moulding solution and as my mother mould was hard, I prepared solution consisting of silicone rubber with catalyst.

Different types of moulding solutions available in our Lab

  • LSR (Eco friendly)

  • Silicone rubber solution and catalyst

  • Polyurethane solution

  • Hydrostone

As per the definition from google; Hydro-Stone is a hard, strong gypsum cement, a type of plaster, often used for art and statuary castings, molds, and other applications requiring high strength and durability. It’s known for its fine detail duplication, paintability, and ability to withstand water absorption. Mix 1 part of water to 3 parts of hydrostone by weight.

Files for the week