To manufacture a mould, a pattern of the desired shape is first made, then the moulding material (like sand, plaster, or metal) is packed or shaped around the pattern to form a cavity. After the material sets, the pattern is removed, leaving the mould ready for casting.
In this article:
How to Manufacture a Mould
Let’s go step by step. Manufacturing a mould is a core process in casting, injection molding, or die-casting, and involves designing a tool or cavity to shape molten material. I’ll explain it in detail, covering materials, steps, types, and finishing,
1. Understanding the Purpose
Before making a mould, you must know:
- Material to be cast: Metal, plastic, or composite
- Shape and complexity of the part
- Production quantity: Single-use (sand/ceramic) or reusable (metal)
- Tolerances and surface finish required
The mould design directly affects casting accuracy, surface finish, and cost.
2. Selecting Mould Material
Common mould materials
| Mould Type | Material | Applications |
|---|---|---|
| Sand mould | Silica sand + clay/binder | Metal casting (iron, steel, aluminum) |
| Permanent metal mould | Steel, cast iron, copper alloys | Die casting, gravity die casting |
| Ceramic mould | Refractory ceramic | Investment casting, precision components |
| Plaster mould | Plaster + silica | Small alloy castings, jewelry |
Note: Choice depends on melting point, part size, complexity, and production volume.
3. Designing the Mould
Steps in Design
- Part Analysis
- Identify critical features, undercuts, thin walls, and hollow sections
- Decide parting line for the mould
- Determine where cores are required
- Allowance Calculations
- Shrinkage allowance: for metal contraction
- Machining allowance: extra material for finishing
- Draft allowance: angle for easy mould removal
- Distortion allowance: for warped shapes
- Select Mould Type
- Sand mould, permanent mould, die-cast mould, shell mould
- Gate and Riser Design (for casting moulds)
- Decide where molten metal enters (sprues, runners)
- Decide risers for directional solidification
- Include vents for gases
4. Manufacturing the Mould (Step-by-Step)
For Sand Moulds (Single-use)
- Pattern Preparation
- Make pattern slightly larger with allowances
- Use solid, split, or sweep pattern depending on shape
- Mould Box Preparation
- Place pattern in drag (bottom) or cope (top) section of mould box
- Packing the Sand
- Use riddled sand to cover pattern
- Compact sand using rammer
- Repeat for top section if split mould
- Removing the Pattern
- Carefully withdraw the pattern
- Ensure cavity shape remains intact
- Core Insertion
- Place cores if internal cavities are required
- Finishing
- Smooth surfaces with trowel
- Make vents for gas escape
- Form sprues and risers
For Permanent (Metal/Die) Moulds
- CNC Machining
- Machine cavity from steel or aluminum using CNC milling, EDM
- High precision required
- Polishing and Surface Treatment
- Polish cavity surfaces for smooth casting
- Apply coatings if required (anti-stick or wear resistant)
- Assembly
- Assemble mould halves if two-piece
- Include sprue, runners, and ejector pins
- Testing
- Trial casting to ensure proper metal flow and cooling
- Adjust gates or vents if needed
For Ceramic / Investment Moulds
- Create Wax Pattern
- Wax replica of part
- Coating
- Dip wax in ceramic slurry repeatedly to form shell
- Dewaxing
- Melt or burn out wax, leaving ceramic cavity
- Firing
- Heat to strengthen ceramic
- Casting
- Pour molten metal into ceramic mould
5. Inspection and Testing
- Check cavity dimensions (using gauges or measuring tools)
- Trial pour (if metal)
- Check alignment of mould halves
- Ensure surface finish and venting are correct
This ensures the mould produces defect-free castings.
6. Summary Flowchart (Sand Mould Example)
Pattern → Mould Box → Sand Packing → Pattern Removal → Core Placement → Sprue & Vents → Finishing → Casting
7. Summary
- Material selection depends on metal type and production quantity
- Pattern design critical for accuracy
- Allowances and draft must be included
- Cores, gates, vents, and risers required for proper casting
- Permanent moulds are machined from metal, reusable
- Sand/ceramic moulds are usually single-use
Conclusion
Mould manufacturing is the process of creating a cavity, using sand, metal, or ceramic, with appropriate allowances, gates, risers, and vents, into which molten material is poured to produce a casting of desired shape and dimensions.
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