Aluminium Casting · Creative Alucast
Sand Casting
Maximum Design Freedom — Any Size, Any Complexity
Tolerance: DCTG 11–14
Surface: Ra 6.3–25 µm
ISO 9001:2015
Process at a Glance
| Tolerance grade | DCTG 11–14 |
| Surface finish | Ra 6.3–25 µm |
| Min wall thickness | 3.0–4.0mm min |
| Draft (external) | 1° min |
| MA per face | 2.5–3.5mm per face |
| Tolerance standard | ISO 8062-3:2007 |
Overview
Maximum Design Freedom — Any Size, Any Complexity
Sand casting is the oldest and most versatile aluminium casting process, forming parts by pouring molten metal into expendable sand moulds. Each mould is destroyed after casting to retrieve the part, making it ideal for low-to-medium volumes, very large parts, and complex internal geometries that cannot be produced by permanent-mould processes. At Creative Alucast, sand casting uses resin-bonded or green sand systems with shell core capability for intricate internal passages.
The process imposes no practical limit on part size or shape complexity — internal cores of sand can create undercuts, passages, and cavities that would be impossible in die casting. Tooling is low-cost (wood, resin, or metal patterns) and can be produced in 1–3 weeks, making sand casting the fastest route from drawing to first cast for large or complex parts.Creative Alucast Facility
Creative Alucast Capability — Sand Casting
Creative Alucast operates sand casting alongside GDC and LPDC, enabling the same alloy to be specified across processes — critical for customers who need a family of parts from one supplier. Our maximum sand casting capability is 1,200 × 1,200 × 1,200mm and up to 25kg.
Process Comparison
Where Sand Casting sits relative to the other aluminium casting processes:
Sand Casting
DCTG 11–14
Ra 6.3–25 µm
Min wall 3–5mm
Tooling: Lowest
Tilt GDC
DCTG 8–12
Ra 3.2–12.5 µm
Min wall 3–4mm
Tooling: Medium
LPDC
DCTG 7–11
Ra 1.6–6.3 µm
Min wall 3–4mm
Tooling: Med–High
HPDC
DCTG 6–9
Ra 0.8–3.2 µm
Min wall 1–2mm
Tooling: Highest
Process
How Sand Casting Works — Step by Step
Step 01
Pattern Making
A pattern — the physical replica of the final part — is made from wood, resin, or metal. The pattern includes the part geometry plus allowances for shrinkage, draft, and machining stock.
Step 02
Mould Making
The pattern is pressed into bonded sand to create the mould cavity. Two halves (cope and drag) are made separately and assembled at the parting line. Sand cores are placed to form internal features.
Step 03
Melting & Treating
Aluminium alloy is melted in an induction or gas furnace, treated for degassing using our FOSECO GASTEC unit, and analysed by OES spectrometer before pouring.
Step 04
Pouring
Molten metal is poured by gravity into the assembled mould through a gating system. Risers feed molten metal into the casting as it solidifies and contracts.
Step 05
Shakeout & Fettling
After solidification the mould is broken apart, the casting removed, and gates, risers, and flash are removed by sawing, grinding, or shot blasting.
Step 06
Inspection & Finishing
Dimensional inspection, surface finishing, heat treatment (where specified), and machining are applied before despatch.
Materials
Maximum Design Freedom — Any Size, Any Complexity
Suitability ratings from BS 1490:1988 Table 8. Scale: 4 = Excellent, 3 = Good, 2 = Fair, n = Not normally recommended.
| Alloy | Nominal Composition | Suitability | Notes |
|---|---|---|---|
| LM4 | Al-Si5Cu3Mn0.5 | Excellent – the most widely used sand casting alloy. Available in M and TF conditions. | |
| LM5 | Al-Mg5Mn0.5 | Fair – difficult to cast due to no Si. Best corrosion resistance. Requires care. | |
| LM6 | Al-Si12 | Excellent – eutectic composition, best castability, excellent corrosion resistance. | |
| LM9 | Al-Si12Mg0.5 | Good – combines LM6 castability with T6 heat treatability. | |
| LM16 | Al-Si5Cu1Mg0.5 | Good – TB and TF conditions. Good pressure tightness. | |
| LM25 | Al-Si7Mg0.5 | Excellent – most versatile. Full T6 capability. Preferred structural sand casting alloy. | |
| LM27 | Al-Si7Cu2Mn0.5 | Excellent – general purpose. As-cast only. | |
| LM31 | Al-Zn5Mg0.7Cr | Good – naturally aged. Highest as-cast tensile (215 N/mm²) without heat treatment. | |
| LM2 | Al-Si10Cu2 | Not normally recommended – use GDC or HPDC for LM2. | |
| LM24 | Al-Si8Cu3.5 | Not normally recommended – HPDC specialist alloy. |
Heat Treatment on Sand Casting Castings
All BS 1490 heat treatment conditions are applicable to Sand Casting castings, including full T6 (TF condition) for LM25, LM9, LM16, and LM4. Creative Alucast performs full in-house T6 heat treatment with Brinell hardness verification on every batch.
Tolerances
Sand Casting Dimensional Tolerances — ISO 8062-3:2007
Dimensional Casting Tolerance Grade per ISO 8062-3:2007. Sand Casting achieves DCTG 11–14. Tolerances are symmetrically disposed (±half the total band) unless individually specified.
| Nominal Dimension | Tolerance Range | Best (DCTG 11) | Worst (14) |
|---|---|---|---|
| up to 10mm | ±0.55–2.0mm | ±0.55 | ±2.0 |
| 10–25mm | ±0.65–2.2mm | ±0.65 | ±2.2 |
| 25–100mm | ±0.9–3.2mm | ±0.9 | ±3.2 |
| 100–250mm | ±1.2–4.4mm | ±1.2 | ±4.4 |
| 250–400mm | ±1.6–6.2mm | ±1.6 | ±6.2 |
| Parting line | Add 0.5–1.0mm | — | — |
| Wall thickness | One DCTG grade coarser | — | — |
Wall Thickness — One Grade Coarser per ISO 8062-3
Per ISO 8062-3:2007 Clause 7: wall thickness tolerances are one DCTG grade coarser than the general stated DCTG. Account for this when specifying wall thickness tolerances on engineering drawings.
Surface Finish
Ra 6.3–25 µm as-cast. Shot blasting improves uniformity. Machining achieves Ra 0.4–1.6 µm on critical surfaces.
Machining Allowances (RMA) — ISO 8062-3 Annex B
| Surface Type | Required Machining Allowance |
|---|---|
| Small surfaces (≤100mm) | 2.5–3.5mm per face (RMAG E–F) |
| Medium surfaces (100–300mm) | 3.0–4.5mm per face (RMAG F–G) |
| Large surfaces (>300mm) | 4.0–5.0mm per face (RMAG G) |
| Bores and holes | 3.0–5.0mm on radius (larger than flat surfaces due to core shift) |
Design Guide
Sand Casting Design Rules — Wall Thickness, Draft & Tooling
Minimum Wall Thickness
| Section / Condition | Minimum Thickness |
|---|---|
| Small section (≤100mm from gate) | 3.0–4.0mm min |
| Medium section (100–300mm from gate) | 4.0–5.0mm min |
| Large section (>300mm from gate) | 5.0mm+ recommended |
| Isolated rib | 3.5mm min |
| Large flat panel | 5.0mm+ min |
Draft Angles
Draft is applied to all surfaces parallel to the die opening direction. Measured from the direction of draw.
| Surface Feature | Required Draft |
|---|---|
| External surfaces short draw ≤25mm | 1° min |
| External surfaces medium draw 25–100mm | 1.5° min |
| External surfaces long draw >100mm | 2°–3° |
| Internal sand cores | 0.5°–1° — cores provide own release |
| Internal metal cores / chaplets | 2°–5° |
Draft Calculation
At 1° draft over 100mm depth, the face offset is 100 × tan(1°) = 1.75mm. Calculate the resulting dimensional variation for all draft surfaces before finalising the design, especially on functional dimensions.
ToolinG
| Parameter | Details |
|---|---|
| Pattern material | Wood prototype / low volume · Resin medium volume · Aluminium high volume |
| Core boxes | Wood or resin. Shell core machines produce high-accuracy cores. |
| Tooling lead time | 1–3 weeks wood / resin · 3–6 weeks metal |
| Tooling life | Wood: 100–500 casts · Resin: 1,000–5,000 casts · Metal: 10,000+ casts |
| Tooling cost | Lowest of all casting processes — typically 30–50% of GDC tooling cost |
| Pattern modification | Easy and low-cost — wood / resin patterns can be modified without scrapping |
Quality
Quality Inspection — Sand Casting
All Sand Casting castings at Creative Alucast are subject to: chemical composition verification by OES (ARUN Technology MERLIN-4 ULTRA) before every pour; melt quality verification by RPT (FOSECO GASTEC) and density measurement (FOSECO DENSITEC); dimensional inspection on a 1,200 × 1,000mm granite surface plate; and Brinell hardness testing on all heat-treated batches (FIE digital Brinell tester). Certificate of conformance available on request.
Evaluation
Advantages & Limitations of Sand Casting
Advantages
- No practical limit on part size — the only casting process for very large parts
- Complex internal geometries achievable with sand cores
- Lowest tooling cost — fastest and cheapest route to first cast
- All heat treatment conditions applicable (M, TE, TB, TF, TF7)
- Suitable for all BS 1490 Group A and B alloys
- Economical for low volumes (single unit to a few thousand)
- Pattern modifications are simple and low-cost
- Weldable alloys can be used for complex fabricated assemblies
Limitations
- Lowest dimensional accuracy of all casting processes (DCTG 11–14)
- Roughest as-cast surface finish (Ra 6.3–25 µm)
- Highest machining allowances (2.5–5.0mm per face)
- Moderate porosity — not ideal for thin-wall pressure-tight parts
- Slowest cycle time — not suitable for high-volume production
- Higher per-piece cost than die casting at volumes above ~1,000 pieces
- Sand disposal and environmental management required
Applications
Typical Applications — Sand Casting
| Industry | Typical Parts | Why Sand Casting |
|---|---|---|
| Automotive | Large engine blocks, cylinder heads prototypes, gearbox cases, large structural brackets | Large size capability + complex internal passages |
| Power & Energy | Large pump casings, impellers, valve bodies, compressor casings | No size limit, complex internal water / fluid passages via cores |
| Industrial | Machine bases, frames, large housings, jigs and fixtures | Low tooling cost for one-off and short-run parts |
| Infrastructure | Architectural fittings, large lighting components, public fixtures | LM5 / LM31 for decorative anodised large parts |
| Prototyping | Pre-production prototypes, design validation castings, first articles | Lowest tooling cost, fastest lead time for first cast |
Frequently Asked Questions
Common Questions About Sand Casting
What is sand casting?
Sand casting is a process where molten aluminium is poured by gravity into a mould made from bonded sand. The mould is destroyed after each cast to retrieve the part. It is the most versatile casting process — capable of producing any size or shape without the high tooling cost of die casting.
What aluminium alloys can be sand cast?
All BS 1490 Group A and Group B alloys can be sand cast. The preferred alloys are LM4, LM6, LM25, and LM27 — all rated 4 (Excellent). LM25 in T6 condition gives 230 N/mm² minimum tensile from sand casting. LM2 and LM24 are rated 3n or 2n — not normally recommended for sand casting.
What tolerances are achievable in sand casting?
Sand casting achieves DCTG 11–14 per ISO 8062-3:2007. Typical linear tolerances are ±0.9–3.2mm for dimensions up to 100mm, and ±1.6–6.2mm for dimensions up to 400mm. Tighter tolerances are achieved through machining of critical surfaces with 2.5–5.0mm machining allowance.
What is the minimum wall thickness for sand casting?
The minimum wall thickness for sand casting of aluminium alloys is 3.0mm for small sections close to the gate, increasing to 5.0mm for large sections remote from the gate. Ribs minimum 3.5mm. Thin walls remote from the gate risk cold shuts and misruns.
What surface finish does sand casting produce?
Sand casting produces an as-cast surface finish of Ra 6.3–25 µm — the roughest of all casting processes. The sand grain texture is imprinted on the surface. Shot blasting improves appearance and uniformity. Machining achieves Ra 0.4–1.6 µm on critical surfaces.
How does sand casting compare to gravity die casting?
Sand casting offers lower tooling cost, unlimited part size, and more complex geometry — but gives lower dimensional accuracy (DCTG 11–14 vs DCTG 8–12), rougher surface finish (Ra 6.3–25 vs Ra 3.2–12.5 µm), and higher machining allowances. GDC is preferred for medium-to-high volumes where tolerances and surface finish matter.
Can sand castings be heat treated to T6?
Yes. All BS 1490 heat treatment conditions are applicable to sand castings including full T6 (TF condition). LM25 sand cast T6 delivers 230 N/mm² minimum tensile. Creative Alucast performs full in-house T6 heat treatment with batch Brinell hardness verification.
What is the tooling lead time for sand casting?
Wood or resin patterns: 1–3 weeks. Metal patterns: 3–6 weeks. Sand casting has the shortest tooling lead time of all casting processes, making it the fastest route from approved drawing to first cast.
Start Your
sand casting Project
Send us your drawing — we’ll review alloy selection, tool design, and process suitability, and provide a complete casting-to-finish quotation. Complex internal geometry? Ask about dissolving-core LPDC.