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Comparison of Lost Foam Process, Green Sand Process, Resin Sand Process, Investment Casting (Wax Pattern) Process and Coated Sand Process

Release time:

2026-10-19 15:33

Source:

Green Sand Casting VS Lost Foam Casting

Dimension	Green Sand Casting (Wet Clay Sand)	Lost Foam Casting (EPS/STMMA)
Pattern/Mold Sand	Wooden/Metal Patterns + Wet Clay Sand	Disposable Foam Patterns + Unbonded Dry Sand
Molding Method	Manual or High-Pressure Line Compaction, Requires Parting and Pattern Removal	Foam Pattern Buried in Dry Sand, Vacuum Casting, Pattern Vaporization
Dimensional Accuracy	CT10-11	CT7-9 (2-3 Grades Higher)
Surface Roughness	Ra 12.5-25 µm	Ra 6.3-12.5 µm
Wall Thickness Capability	≥4-5 mm	≥3 mm, Can Be Thinner
Complexity of Structure	★★★ Requires Sand Cores, Parting	★★★★★ No Parting, No Sand Cores
Applicable Weight	0.5 kg-400 kg (>400 kg Low Efficiency)	0.5 kg-2 t
Material Adaptability	Grey Iron, Ductile Iron, Aluminum Alloys (Cast Steel Prone to Sand Adhesion)	Grey Iron, Ductile Iron, Cast Steel, Stainless Steel, Non-Ferrous Alloys
Production Efficiency	High-Pressure Line 100-150 Molds per Hour	10-40 Molds per Hour
Economic Batch Size	Large Batches (≥10,000 Pieces per Year) Most Economical	100-10,000 Pieces per Year Most Economical
Tooling Investment	High-Pressure Line 20-60 Million RMB	Foam Patterns + Vacuum System 2-20 Million RMB
Running Cost	Cheap Molding Sand, 95% Old Sand Reused Online	EPS Pattern Consumption, Coating; Dry Sand 98% Reused
Environmental Emissions	Coal Powder VOCs, High Dust	Foam Pyrolysis Benzene Compounds, Requires Incineration/Catalysis
Main Defects	Gas Porosity, Sand Inclusions, Sand Expansion	Wrinkling, Carburization, Box Collapse
Scrap Rate	Internal Scrap Around 15%	Internal Scrap Around 3%
Typical Applications	Automotive Cylinder Blocks, Cylinder Heads, Pipe Fittings	Pump Casings, Valve Bodies, Machine Tool Parts, Gearbox Shells
Summary	-- Green Sand: Like "High-Speed Stamping", High Equipment Investment, Fast Cycle Time, Suitable for Large Batches, Relatively Simple Structures, and Cost-Sensitive Cast Iron Parts.	Lost Foam: Like "3D Printing + Casting", No Parting, No Pattern Removal, Complex Cavities Formed in One Operation, Suitable for Medium to Small Batches, Complex Structures, and High-Precision Castings.

On-Site Data Comparison (Same Specification 35# Steel Piece)

Dimensional Accuracy: Lost Foam CT7-8 vs. Green Sand CT11

Machining Allowance: Lost Foam 2-3 mm vs. Green Sand 3-6 mm

Cleaning Time: Lost Foam Saves Over 50%

Comprehensive Cost: Lost Foam Can Be 10-40% Lower

Summary

For Large Batches, Simple Parts, Grey Iron/Ductile Iron: Green Sand High-Pressure Line is the Cheapest.

For Medium Batches, Complex Cavities, Suitable for Steel/Iron/Non-Ferrous, High Precision: Lost Foam is Better.

2. Lost Foam vs. Resin Sand Casting

Dimension	Lost Foam (EPS/STMMA Foam)	Resin Sand Casting (Furan/Alkaline-Phenolic)
Pattern/Mold Sand	EPS/STMMA Foam Patterns + Unbonded Dry Sand	Wooden/Metal Patterns + Resin-Bonded Sand (Self-Hardening)
Pattern Removal and Parting	No Parting Surface, No Draft Angle, No Sand Cores	Must Part and Remove Pattern, Complex Parts Require Sand Cores
Dimensional Accuracy	CT7-9 (Close to Investment Casting)	CT8-10
Surface Roughness	Ra 6.3-12.5 µm	Ra 6.3-12.5 µm
Wall Thickness/Weight	Starting from 3 mm, 0.5 kg to 2 t	Starting from 4-5 mm, 1 kg to 10 t
Complexity of Structure	★★★★★ Arbitrary Cavities, Curved Surfaces Formed in One Operation	★★★ Complex Cavities Require Core Assembly
Material Adaptability	Grey Iron, Ductile Iron, Cast Steel, Stainless Steel, Non-Ferrous Alloys	Cast Steel, Cast Iron, Alloy Steel, Non-Ferrous Alloys
Economic Batch Size	100-10,000 Pieces per Year Optimal	Suitable for Multiple Varieties, Small to Medium Batches, or Single Pieces
Tooling Cost	High Initial Cost for EPS Patterns; Sand Boxes are Universal	Wooden Patterns are Cheap, Metal Patterns are Moderate; High Cost for Old Sand Regeneration Equipment
Running Cost	EPS Beads + Coating; Dry Sand Can Be Regenerated by 98%	Resin 800-1200 RMB/t; Requires Solvent Washing for Regeneration
Environmental Emissions	Foam Combustion VOCs Require Incineration Device; No Waste Sand Emissions	Resin Curing Agent VOCs, Waste Sand Requires Thermal Regeneration
Typical Defects	Wrinkling, Carbon Residue, Box Collapse	Gas Porosity, Sand Inclusions, Resin Thermal Cracking
Applicable Scenarios	Pump Casings, Valve Bodies, Manifolds, Boxes, Wear-Resistant Parts	Machine Tool Beds, Wind Turbine Hubs, Large Valve Bodies, Molds
Conclusion	For Complex Structures, Small to Medium Batches, and No Machining: Choose Lost Foam.	For Large Weight, Multiple Varieties, or High Steel Grades: Choose Resin Sand.

3. Lost Foam vs. Investment Casting (Wax Pattern)

Dimension	Lost Foam (EPS/STMMA Foam)	Investment Casting (Wax Pattern)
Pattern Material	Polystyrene Foam (Single Use)	Wax or Resin Wax (Reusable)
Mold Structure	No Parting, No Sand Cores, Metal Directly Occupies the Cavity After Foam Vaporization	Multi-Layer Ceramic Shell Encapsulates Wax Pattern, Cavity Formed After Wax Removal
Dimensional Accuracy	CT7-9	CT4-6 (Higher, Up to ±0.1 mm/25 mm)
Surface Roughness	Ra 6.3-12.5 µm	Ra 1.6-6.3 µm
Applicable Weight	0.5 kg to 2 t	A Few Grams to 100 kg (>100 kg Cost Increases Sharply)
Wall Thickness Capability	Starting from 3 mm	Starting from 0.8-1 mm, Can Be Thinner
Complexity of Structure	★★★★★ Arbitrary Cavities, Curved Surfaces Formed in One Operation	★★★★☆ Limited by Wax Removal Strength, Large Cavities Need Reinforcement
Material Adaptability	Grey Iron, Ductile Iron, Cast Steel, Stainless Steel, Non-Ferrous Alloys	Carbon Steel, Alloy Steel, Stainless Steel, Nickel-Based, Titanium Alloys
Economic Batch Size	Medium to Large Batches (≥100 Pieces per Pattern) Most Cost-Effective	Small to Medium Batches (<1000 Pieces per Year) Still Have Cost Advantages
Tooling/Mold	Medium Initial Cost for Foam Molds	High Cost for Wax Pressing Molds and Shell Molding Equipment
Production Cycle	Coating-Drying-Pouring 1-2 Days	Shell Making-Wax Removal-Firing-Pouring 5-7 Days
Main Defects	Wrinkling, Carbon Addition, Box Collapse, Bead Marks	Shell Cracking, Deformation, Incomplete Wax Removal, Insufficient Shell Strength
Environmental Emissions	EPS Pyrolysis VOCs Require Incineration Treatment	Wax Removal, Firing VOCs, Ammonium Chloride Hardening Liquid Requires Treatment
Typical Applications	Pump Casings, Valve Bodies, Machine Tool Parts, Automotive Intake Manifolds	Aviation Blades, Precision Pump Valve Parts, Jewelry, Medical Devices
Conclusion	For "Mirror Precision + Ultra-Thin Walls": Choose Investment Casting.	For "Medium to Large Parts, Complex Cavities, Medium to Large B

Lost foam VS shell molding(pre-coated resin)

The following uses "a table + five conclusions" to help you thoroughly compare the Expanded Polystyrene Casting (EPC) and Shell Molding processes. All data are excerpted from the latest public information, which is convenient for direct selection or report writing.

I. Quick Comparison Table (2025 Industry Average)

Dimension	Expanded Polystyrene Casting (EPC)/Lost foam	Shell Molding/precoated resin
Pattern/ Mould	EPS/STMMA foam pattern + dry sand (no binder)	Sand grains with pre-coated resin film, shell mold/core
Hardening/ Curing Method	Vacuum + metal liquid thermal shock to vaporize the foam pattern	Shell mold cured at 180-260 ℃
Casting Dimensional Accuracy	CT8-9 (Ra 25-200 µm)	CT7-8 (Ra 6.3-12.5 µm)
Applicable Weight	0.5 kg-10 t (wall thickness ≥ 4 mm)	0.1 kg-80 kg (wall thickness 2-30 mm)
Applicable Material	Grey iron, ductile iron, cast steel, aluminum, copper alloy	Grey iron, ductile iron, cast steel, aluminum, copper alloy
Mould Cost	Low foam pattern cost, no parting surface	Metal hot core box, high initial investment
Production Cycle per Piece	5-10 min/box (including moulding)	30-60 s/shell mold (shell thickness 5-8 mm)
Sand Consumption	1:3-1:5 (sand-to-metal ratio)	1:1-1:1.5 (thin shell saves sand)
Waste Sand Regeneration	Dry sand can be directly sieved and reused, extremely low cost	Requires 700 ℃ calcination to strip resin, high regeneration cost
On-site Environment	Vacuum extraction, less dust, but foam vaporization produces VOC	No dust, but shell mold combustion produces benzene compounds, requiring centralized treatment
Defect Tendency	Vaporization residue easily increases carbon content, causes wrinkling; large pieces require exhaust	High shell mold strength, less likely to expand, but poor heat dissipation for thick and large pieces

II. Five Conclusions (Helping You Make Quick Decisions)

Threshold for Large and Small Pieces
For pieces above 80 kg or extra-large boxes → prioritize Expanded Polystyrene Casting; for pieces below 80 kg and batch size ≥ 5000 pieces → prioritize Shell Molding.

Precision and Blank Value
If the subsequent machining allowance requirement is ≤ 1.5 mm and Ra ≤ 12.5 µm, Shell Molding has a higher first-time pass rate and can directly replace investment casting for medium and small precision parts.

Mould Investment Payback Period
A set of Shell Molding metal shell moulds costs 0.6-10,000 yuan, and the cost per piece drops sharply with the batch size; the cost of Expanded Polystyrene Casting foam patterns is 5-30 yuan per piece, but the mould investment is virtually zero, making it suitable for a variety of small batches.

Environmental Protection and Regeneration
The dry sand in Expanded Polystyrene Casting can be reused 100% on-site with little environmental pressure; Shell Molding must be sent out or a 700 ℃ calcination furnace must be built on-site, with a regeneration cost of 100-150 yuan/t.

Process Maturity and Risk
Shell Molding already has automated production lines and stable quality; Expanded Polystyrene Casting is sensitive to foam density, coating permeability, and vacuum degree, and requires "one process per piece," with a slightly higher technical threshold.

In a Nutshell
For "large pieces, complex shapes, and small batches," choose Expanded Polystyrene Casting; for "medium and small pieces, precision, and large batches," choose Shell Molding.

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