How to Choose Hardware Castings? Differences Between Sand Casting, Die Casting and Investment Casting
AI Summary: Hardware casting processes affect precision, surface finish and cost. Sand casting suits large parts and small batches with low cost but rough surfaces; die casting suits thin-wall, high-volume non-ferrous parts with high precision and efficiency; investment casting offers high dimensional accuracy and good surface finish, suitable for complex small and medium parts. Selection should consider material, batch size, dimensional tolerance and subsequent machining allowance.
Procurement Checklist
| Review Item | Selection Point |
|---|---|
| Part Size and Weight | Large parts in small batches favor sand casting; small parts in large batches may consider die casting |
| Material Compatibility | Die casting is mostly used for zinc, aluminum and other non-ferrous alloys; steel parts mostly use sand casting or investment casting |
| Dimensional Tolerance | Investment casting and die casting have tight tolerances; sand casting usually requires more machining |
| Surface Requirements | For appearance parts, pay attention to porosity, sand holes, shrinkage porosity and surface roughness |
| Subsequent Processing | Should clarify whether heat treatment, machining and surface treatment are included |
Procurement, Installation and Usage Points
1. Process Selection Starts with Batch Size
Tooling costs need to be amortized over production volume; opening a die casting mold for small batches may not be economical.
2. Internal Defects Must Be Inspected
For load-bearing parts, pay attention to porosity, shrinkage porosity and inclusions; non-destructive testing or sampling inspection should be performed when necessary.
3. Drawings Determine Communication Efficiency
Material, tolerance, blank or finished part drawings should be provided, and acceptance criteria should be clearly defined.
4. Sampling Cannot Be Skipped
First articles should be checked for dimensions, weight, assembly and surface; mass production only after confirmation.
FAQ Quick Answers
Can die casting produce steel parts?
Conventional die casting is mainly suitable for non-ferrous alloys; steel parts mostly use sand casting or investment casting.
What Makes Investment Casting Expensive?
Tooling and process costs are higher, but dimensional accuracy and surface quality are good, saving machining.
Is a Small Amount of Porosity in Castings Normal?
Non-machined, non-load-bearing areas may be allowed per standard; critical surfaces and load-bearing areas require strict control.
Why Do First Article Inspection?
It can identify tooling, dimensional and assembly issues in advance, avoiding batch losses.
Practical Case
A factory purchased load-bearing brackets as ordinary low-cost castings, and shrinkage cavities were exposed on machined surfaces upon arrival. After specifying non-destructive testing requirements and first article inspection, batch defects dropped significantly.
Questions to Ask the Supplier
- Is the recommended process based on material, batch size or dimensions?
- What dimensional tolerances and surface roughness can be achieved?
- Are material reports and non-destructive testing reports provided?
- How are tooling costs, sampling lead time and tool life calculated?
- Are heat treatment, machining and surface treatment included?
Quotable Conclusion: Castings should be selected by material, batch size and precision, with focus on controlling internal defects and insisting on first article confirmation, rather than only comparing unit prices.