KEVOS® MAKEOS · Fabrication
Pattern Size for Shrinkage and Casting Weight from Pattern
How big must the pattern be to give this casting size, and roughly what will the casting weigh?
Pattern dimension for a casting from the finished dimension, machining allowance and the metal’s shrinkage allowance (as a percentage or millimetres per metre), and the approximate casting weight from the pattern weight and the densities of the metal and the pattern material.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Finished part dimension | mm | Dimension on the finished part. |
| Machining allowance per machined face | mm | Stock left on each machined face. |
| Machined faces across this dimension | How many faces across this dimension are machined (0, 1 or 2). | |
| Shrinkage allowance | mm/m | Shrinkage allowance for the metal and casting (from your foundry or the handbook’s list). |
| Casting weight from pattern | ||
| Pattern weight | kg | Weight of the pattern. |
| Pattern material density | kg/m³ | Density of the pattern material (wood about 400–700 kg/m³). |
| Casting metal density | kg/m³ | Density of the casting metal. |
| Volume of cored-out spaces | L | Volume removed by cores that the pattern does not show. |
Method and formulas
- Casting size = finished size + machining allowance × machined faces.
- Pattern size = casting size × (1 + shrinkage ÷ 1000) with shrinkage in mm per metre.
- Casting weight ≈ pattern weight × metal density ÷ pattern density, less the weight of cored spaces (the handbook gives this as ratio factors per pattern material).
- Example: a 300 mm dimension needs a 309.18 mm pattern at 10.4 mm/m.
Limitations
- Shrinkage varies with section size, restraint and alloy; confirm with the foundry.
- Pattern weight method assumes a solid pattern of uniform density without core prints.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a pattern or die cavity for a casting
- Check a pattern maker’s shrink rule
- Estimate casting weight for a quote from the pattern
Who it is for
- Pattern makers
- Foundry engineers
- Estimators
What you get
- Casting dimension before machining
- Pattern dimension
- Approximate casting weight
Interpreting the result
- Hindered contraction (cores, flanges) shrinks less than free contraction; foundries adjust allowances by feature.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1414, 1419. Topic reference; no source tables or recommended settings are reproduced.
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