Week 12. Molding & Casting

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Molding and casting are essential techniques in the manufacturing industry. Molds can be made using computer-aided design and manufacturing (CAD/CAM) technology. Traditionally, artisans would design models, then create molds from those original models, from which various replicas can be manufactured.

In our assignment we use CAD/CAM to create a digital 3D model of a design, which is then used to program a CNC machine to mill the design into a block of machinable wax. The resulting mold can then be used to cast a variety of materials, from plastics to metals. This process is commonly used in the automotive, aerospace, and medical industries, where precise and complex shapes are required for various components and parts.

Assignment Tasks:

Group Assignment: Review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them. Extra credit: try other molding and casting processes.
Individual Assignment: Design a mold around the stock and tooling that you’ll be using, mill it (rough cut + three-axis finish cut), and use it to cast parts. Extra credit: use more then two mold parts.

Group Assignment

Detailed Study Report on our Group Assignment Page.

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Design

When I started thinking about a design for casting something, a lot of ideas came to mind, and after a lot of brainstorming, I chose to try simple feather pendant made of clear resin with a real feather in it.

It all started from a simple line sketch.

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First I imported the Reference image into Fusion 360. Then made a sketch on top of that. After that I extruded to the required thickness and then used Fillet tool for top edge fillet. then added a small rectangular box as a head to the feather shape.

Final Design for CAM.

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Download Design File here

CAM

Step 1: Once the design is made, before moving into milling, we need to create CAm for machining. That is definig the toolpath. For thath we use Fusion 360 manufacture workspace. Go to Manufacture workspace from Design.

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Step 2: Create New Setup

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Step 3: While creating a new setup, we need to specify the stock material and size. Here we made a block in Fusion with exact dimension of our stock. And in Mode we can select the Relative size box.

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Step 4: Once stock is created we need to add the tools.

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Step 5: Tools can be added according to the available stocks. I needed 2 bits, 3mm Flat End & 3mm Ball End. I added both with specification cross checked with the actual tools available. And added Holder as well.

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Tool Specification for 3mm Flat End Mill

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Tool Specification for 3mm Ball End Mill

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Step 6: Once the tools are setup, now is the tie to play around the toolpaths. There are different option to chose according to the design.

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I tried different options and finally end up with 4 toolpaths and the result after simulation comes up like this.

Milling

Now is the time for milling. We use ProtoTrak RMX for milling.

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Milling came out nicely.

Molding

First stage of molding is to measure the quantity of material which need to be used. I measure using water filled inside the wax and transfer it to a glass and marked the level and weight.

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Now we will calculate the required quantity of silicon rubber with the help of the brand’s specification. For our make, it requires 25gms of hardner for 1000gms of silicon rubber.

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After taking the required amount of silicon and hardner, we will mix them well for about 2 minutes.

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Before pouring the same into the wax, we will use silicon spray for easy removal of the mold ince it is set.

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We will pour the silicon slowly from a height.

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Mold filling is finished and kept foe curing.

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After 24hrs of curing, its time to remold.

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And thats it, our mold came out neatly.

Casting

Step 1: For Casting Resin we used Aditya Brand Resin. Which comes with 2 parts. Part A & Part B, which has a mixing ratio of 1:2.

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Step 2: Now we will measure the quantity by pouring water into the mould and passing the same to a transparent glass and mark down the measurement and weight.

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Step 3: After getting the quantity we can mix the resin both parts to get the same quantity. The total weight required was 26gms. So Part A we will take 17.5gms & Part B 8.5gms.

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Step 4: Mix thoroughly. Mixing is very important. If the mix is not proper then the result will also get affected. While mixing air bubbles will form due to heat emission.

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We can use a hot air gun to remove the air bubbles. But this is limited to small mixes only.

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Since my plan was to add a real feathre, I collected a feather from a local pet shop and trim it into the size of my mold. And is ready to go into the resin.

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