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Molding and casting is a versatile manufacturing process used to replicate objects by creating a mold of a desired shape and then filling it with a casting material. This technique is widely used in industries for prototyping and production, allowing the creation of complex geometries with precision and repeatability in various materials.
Molding and casting are fundamental manufacturing processes used to create parts and prototypes by shaping materials inside a mold. Depending on the application, material, and production scale, different techniques are used. Below are some of the most commonly used types of molding and casting:
Compression Molding
This process involves placing a preheated material (usually a thermoset plastic) into a heated mold cavity. The mold is then closed and pressure is applied to force the material to conform to the mold shape. It is commonly used for making automotive parts, electrical components, and kitchenware.
Advantages: Low waste, good for large parts
Disadvantages: Slower process, limited to simple shapes
Injection Molding
Injection molding involves injecting molten material (usually plastic) under high pressure into a mold cavity. It is widely used in mass production of plastic products like bottle caps, toys, and phone cases.
Advantages: Fast, high precision, ideal for mass production
Disadvantages: High initial tooling cost
Blow Molding
Used primarily for making hollow plastic parts like bottles. A heated plastic tube is inflated inside a mold so it takes the shape of the mold cavity.
Advantages: Good for hollow objects, fast
Disadvantages: Limited to hollow shapes
Rotational Molding
In this process, a powdered plastic is placed inside a mold which is then rotated in multiple axes while being heated. The powder melts and coats the inside of the mold evenly.
Advantages: Uniform wall thickness, low tooling cost
Disadvantages: Slow, not ideal for fine details
Sand Casting
A traditional and widely used method where molten metal is poured into a sand mold. After solidification, the mold is broken to retrieve the part.
Advantages: Cost-effective, suitable for large parts
Disadvantages: Rough surface finish, less dimensional accuracy
Investment Casting (Lost Wax Casting)
A wax model of the part is made and coated with a ceramic shell. The wax is melted out, and molten metal is poured into the cavity. It’s used for complex shapes with fine details.
Advantages: High precision, good surface finish
Disadvantages: Expensive and time-consuming
Die Casting
Involves forcing molten metal under high pressure into a steel mold. It is mostly used for mass production of non-ferrous metal parts like zinc, aluminum, and magnesium components.
Advantages: Excellent dimensional accuracy, fast
Disadvantages: High setup cost, limited to non-ferrous metals
Plaster Casting
Similar to sand casting, but uses plaster instead of sand to make the mold. It’s good for casting non-ferrous metals and achieving better surface finish.
Advantages: Good for intricate details
Disadvantages: Weaker mold, limited to low-temperature metals
CNC machining is a subtractive process where a mold is carved from a solid block using computer-controlled cutting tools. It ensures high accuracy and repeatability, making it ideal for creating detailed and durable molds. Materials like wax, foam, or aluminum are commonly used depending on the casting material and application.
Material Preparation
Material preparation is a crucial step in molding and casting. It involves selecting suitable materials for both mold and cast, ensuring they are clean, dry, and properly mixed. Accurate measurement and thorough mixing of components like resins or silicones help prevent curing issues and ensure a smooth, high-quality final product.
For this assignment, I created a chocolate mold through a series of digital fabrication steps. I began by designing a solid model of a circular object in SolidWorks. Then, using ArtCAM, I generated a 3D milling toolpath to prepare the design for machining, ensuring precise dimensions and smooth contours.
During the Extrude feature in SolidWorks, I applied a 4-degree draft angle to the vertical walls of the model. This draft is essential to ensure the casted chocolate product can be easily released from the mold without damaging the design or causing sticking during the demolding process.
To avoid sharp corners that could hinder mold release or damage the cast, I added fillets to all necessary edges. However, the parting line edge was left without fillets or chamfers to maintain a clean mold separation. Finally, the completed model was exported in STL format for machining.
Here is the final designed output of the chocolate mold. The model includes smooth filleted edges, a proper 4-degree draft for easy release, and a clean parting line for accurate mold separation. It has been carefully prepared and exported in STL format, ready for the 3D milling and molding process.
For the milling process, MDF (Medium-Density Fiberboard) was selected as the base material due to its smooth surface and ease of machining. The toolpath was generated using ArtCAM to match the 3D model. The dimensions of the workpiece were set to 100x150 mm, ensuring enough space for the mold design.
The first step in ArtCAM is to save the relief layer, which stores the 3D surface data. After that, the STL file of the designed model is imported into the software. This imported 3D model is essential for generating an accurate 3D toolpath that guides the milling process.
After importing the STL file, the next step is aligning the model to the center of the workpiece in ArtCAM. This ensures that the milling is symmetrical and properly positioned within the 100x150 mm MDF board, preventing any part of the design from being cut off or misaligned during machining.
To define the boundary for the mold cavity, I created a rectangle with dimensions 80×80 mm in ArtCAM. This rectangle represents the negative space where the model will be milled out of the MDF block. It serves as the limit for the toolpath, ensuring precise and clean mold boundaries.
Then, I selected a 3 mm ball nose bit as the milling tool. This tool is ideal for 3D surface machining, allowing smooth curves and detailed contours to be milled accurately. The ball nose bit ensures the fine details of the chocolate mold are preserved during the roughing and finishing operations.
Next, I performed the material setup in ArtCAM. This involved defining the material thickness, setting the origin (usually at the top surface and center or corner of the block), and confirming the Z-zero position. Accurate material setup ensures the toolpath aligns perfectly with the MDF block and avoids any milling errors.
Then, I generated the toolpath for mold creation using the 3D roughing and finishing strategies in ArtCAM. The roughing pass removed excess material, while the finishing pass captured fine details of the design. These toolpaths were based on the imported STL model and ensured precise and smooth milling on the MDF surface.
Then, I exported the NC (Numerical Control) file, which contains the machine-readable instructions for the CNC router to execute the milling process. This file was generated from the finalized toolpath settings in ArtCAM.
The NC file is attached below to be used directly with the milling machine for mold creation.
