Misrun or cold shut
- What may be observed
- Incomplete filling or a line where metal fronts meet
- What an investigation may review
- Filling path, component geometry, metal and mould conditions
Sand Casting Process: Steps, Defects and Method Selection
Sand casting forms a metal component by pouring molten metal into a cavity prepared in a sand mould. The mould may be made using a conventional pattern or, for suitable projects, produced from digital data using 3D sand printing.
This guide explains the main steps in the sand casting process, common casting defect categories and how sand casting compares with investment, permanent mould and die casting. The appropriate route depends on the component, alloy, quantity, tooling requirements and inspection scope.
Sand casting at a glance
External shape
The mould forms the external shape of the component.Internal cavities and passages
Cores can be placed inside the mould to create internal cavities or passages.Release after solidification
After the metal is poured and solidifies, the mould is opened or broken to release the casting.Project-specific sequence
The exact process sequence can vary with the component, alloy and foundry route.
The casting is then cleaned, finished and inspected according to the project requirements. Sand casting includes different moulding methods and materials.
Main steps in a sand casting process
Review the component and requirements
Review the available drawing, CAD model or physical component. Confirm the required alloy, quantity, delivery requirements, machining needs and inspection scope before selecting a manufacturing route.
Prepare the casting and mould design
Prepare the geometry and mould arrangement for the selected process. The engineering review may cover the parting arrangement, casting allowances, core positions, gating and feeding. Simulation may support this review where appropriate for the project.
Make the pattern or produce the mould and cores
In conventional sand casting, a pattern is commonly used to form the mould cavity. For suitable projects, binder-jet 3D sand printing can produce mould and core components from prepared digital data without making a conventional pattern for that mould-production stage. The metal component is still made through casting.
Assemble and check the mould
Position and assemble the mould sections and any required cores according to the prepared arrangement. Check that the components fit and are aligned before moving to the next production stage.
Melt and pour the metal
Prepare the specified alloy and pour it into the assembled mould according to the production plan. Pouring practice and mould conditions depend on the alloy, component and foundry process.
Allow the casting to solidify and remove it
After the metal has solidified and cooled sufficiently, open or break the mould to remove the casting. The timing and method depend on the material, geometry and moulding route.
Clean, finish and inspect
Remove sand and gating material. The casting may then undergo finishing, machining and inspection according to the agreed project scope.
Project example — 3D sand-printed moulds for an Engine Block
This Engine Block project used 3D sand printing to produce the sand mould and core components. The components were assembled for foundry production, and the metal Engine Block was formed by casting in the sand mould. The Engine Block itself was not 3D-printed.
The photographs show selected views of the mould components, assembly and Engine Block result. They document this project; other components may require a different sequence.
Printed sand mould and core components
Mould assembly before casting
Metal casting produced from the mould
Common sand casting defects
An indication on a casting does not establish its root cause by itself. Assessment may need to consider the indication’s location and appearance together with mould, metal, process and inspection information. These categories are starting points for investigation, not a defect-diagnosis chart.
| Defect category | What may be observed | What an investigation may review |
|---|---|---|
| Misrun or cold shut | Incomplete filling or a line where metal fronts meet | Filling path, component geometry, metal and mould conditions |
| Gas-related porosity | Rounded voids or porosity | Possible gas sources, mould or core condition, venting and metal handling |
| Shrinkage | Irregular voids or porosity within the casting | Feeding arrangement, component geometry and solidification sequence |
| Sand or oxide inclusions | Non-metallic material on or inside the casting | Mould and core condition, erosion, metal cleanliness and gating |
| Core shift or dimensional variation | An internal feature or passage is displaced | Core location, assembly and mould movement |
| Hot tear or crack | A crack-like indication | Component geometry, material and restraint during solidification |
Gas-related porosity
- What may be observed
- Rounded voids or porosity
- What an investigation may review
- Possible gas sources, mould or core condition, venting and metal handling
Shrinkage
- What may be observed
- Irregular voids or porosity within the casting
- What an investigation may review
- Feeding arrangement, component geometry and solidification sequence
Sand or oxide inclusions
- What may be observed
- Non-metallic material on or inside the casting
- What an investigation may review
- Mould and core condition, erosion, metal cleanliness and gating
Core shift or dimensional variation
- What may be observed
- An internal feature or passage is displaced
- What an investigation may review
- Core location, assembly and mould movement
Hot tear or crack
- What may be observed
- A crack-like indication
- What an investigation may review
- Component geometry, material and restraint during solidification
The cause and corrective action must be established for the specific casting.
Sand casting compared with other casting methods
The right process depends on the component, alloy, quantity, tooling needs and acceptance requirements. The table below is a general guide, not a recommendation for a specific part.
| Process | Mould approach | Factors to consider |
|---|---|---|
| Sand casting | Metal is poured into a cavity formed in a sand mould; cores can create internal features | Component geometry, alloy, quantity, mould route and finishing requirements |
| Investment casting | A ceramic mould is formed around a pattern | Detail requirements, pattern and shell preparation, geometry and quantity |
| Permanent mould casting | Metal is poured into a reusable metal mould | Tooling investment, repeat production, alloy and mould or core constraints |
| Die casting | Metal is injected under pressure into a reusable metal die | Production quantity, die investment, alloy and component design |
Sand casting
- Mould approach
- Metal is poured into a cavity formed in a sand mould; cores can create internal features
- Factors to consider
- Component geometry, alloy, quantity, mould route and finishing requirements
Investment casting
- Mould approach
- A ceramic mould is formed around a pattern
- Factors to consider
- Detail requirements, pattern and shell preparation, geometry and quantity
Permanent mould casting
- Mould approach
- Metal is poured into a reusable metal mould
- Factors to consider
- Tooling investment, repeat production, alloy and mould or core constraints
Die casting
- Mould approach
- Metal is injected under pressure into a reusable metal die
- Factors to consider
- Production quantity, die investment, alloy and component design
For a more detailed comparison, read Sand Casting vs Investment, Die and Permanent Mould Casting.
Investment casting, die casting and permanent mould casting are educational comparisons here, not services offered by Speed3D Mold.
Where 3D sand printing fits
3D sand printing is a method for producing sand moulds and cores from prepared digital data. It may be considered when the component geometry, quantity or tooling requirements make a patternless mould-production route useful.
It does not replace metal casting: the sand mould is printed, then used to form the metal component through casting. The Engine Block project above shows one example of that workflow.
Discuss a Casting Requirement
Frequently asked questions
What is the sand casting process?
Sand casting is a metal-casting process in which molten metal is poured into a cavity formed in a sand mould. After solidification, the mould is opened or broken to remove the casting.
What are the main steps in sand casting?
The main stages are reviewing the component, preparing the casting and mould design, producing the mould and cores, assembling and checking the mould, pouring, solidification and removal, then cleaning and inspection. The exact sequence depends on the process and component.
Can sand casting use 3D-printed moulds?
Yes. For suitable projects, 3D sand printing can produce the mould and core components from digital data. The metal part is still produced through casting.
What are common sand casting defects?
Common defect categories include misruns or cold shuts, gas-related porosity, shrinkage, inclusions, dimensional variation and hot tears. The cause of a specific indication requires investigation.
Can a casting defect be diagnosed from a photograph?
A photograph can help document an indication, but may not identify its root cause. Assessment may require more information about the location, process, material and inspection results.
