Sand Reclamation System for the No-Bake Sand Process is designed to recover and reuse foundry sand from chemically bonded molds and cores (typically using resin systems like furan, phenolic urethane, or alkaline phenolic). Since no-bake sands do not require heating for curing, reclamation focuses on mechanical, thermal, or chemical methods to remove spent binders and restore sand properties.
What Is No Bake Sand Process?
No-Bake Sand Process (also called Air-Set or Chemically Bonded Sand Process) is a foundry method for creating molds and cores using sand mixed with a chemical binder that cures at room temperature (without requiring heat or baking). This process is widely used in metal casting for producing high-precision, complex, and large castings with excellent dimensional accuracy.
Key Features of No-Bake Sand Process
Chemical Binders (No Heat Required)
- The sand is mixed with a two-part resin and a catalyst, which react to form a strong bond.
- Common binder systems:
- Furan (Furan-No-Bake) – Acid-catalyzed (e.g., sulfuric/phosphoric acid).
- Phenolic Urethane (Cold Box) – Uses amine vapor for curing.
- Alkaline Phenolic (Ester-Cured) – Uses organic esters as catalysts.
- Sodium Silicate (CO₂ or Ester-Cured) – Used for environmental and cost benefits.
Room-Temperature Curing
- Unlike green sand (clay-bonded) or shell molding (thermoset), no-bake molds harden without external heat.
- Curing time ranges from minutes to hours, depending on binder type and conditions.
High Strength & Precision
- Produces rigid molds with excellent dimensional stability.
- Suitable for large and heavy castings (e.g., engine blocks, pump housings, industrial machinery).
Low Moisture Content
- Unlike green sand, no-bake sand has almost no water, reducing gas defects in castings.
Steps in the No-Bake Sand Process
- Sand Preparation
- Clean silica, olivine, or chromite sand is mixed with a resin (Part A) and catalyst (Part B).
- Molding/Core Making
- The mixture is packed into a pattern or core box.
- Chemical reaction begins, hardening the sand.
- Curing
- The mold/core sets at room temperature (or with slight warming to accelerate curing).
- Pouring Metal
- Once fully cured, molten metal is poured into the mold.
- Shakeout & Reclamation
- After casting, the mold is broken, and sand is reclaimed for reuse.
Advantages of No-Bake Sand Process
- High Dimensional Accuracy – Minimal mold deformation.
- Excellent Surface Finish – Smoother than green sand castings.
- Versatility – Works with ferrous (iron, steel) and non-ferrous (aluminum, brass) metals.
- Low Gas Defects – No water means fewer blowholes.
- Suitable for Large Castings – Strong molds support heavy sections.
No-Bake Sand Process Applications
- Industrial Castings: Valves, pumps, gearboxes.
- Automotive: Engine blocks, cylinder heads.
- Heavy Machinery: Mining, construction equipment parts.
- Aerospace: High-precision components.
Key Components of a No-Bake Sand Reclamation System
- Primary Crushing & Screening
- Purpose: Break down large lumps of used sand molds/cores into smaller particles.
- Equipment: Jaw crushers, vibratory screens, or hammer mills.
- Mechanical Reclamation (Attrition Units)
- Purpose: Remove binder coatings from sand grains through friction and abrasion.
- Equipment: High-speed attrition scrubbers, vibratory reclaimers, or paddle mixers.
- Process: Sand grains are agitated to strip off residual binders, followed by dust extraction.
- Dust & Fines Removal
- Purpose: Eliminate fine particles and degraded sand to improve reusability.
- Equipment: Cyclone separators, baghouse filters, or air classifiers.
- Thermal Reclamation (Optional for High-Quality Reuse)
- Purpose: Burn off remaining organic binders at high temperatures (~600–800°C).
- Equipment: Fluidized bed furnaces or rotary kilns.
- Note: More energy-intensive but improves sand performance for critical castings.
- Sand Cooling & Conditioning
- Purpose: Reduce sand temperature (if thermally reclaimed) and adjust moisture levels.
- Equipment: Fluidized bed coolers or rotary drum coolers.
- Sand Testing & Reuse
- Tests: AFS grain fineness, LOI (Loss on Ignition), pH, and binder demand.
- Adjustments: New sand or additives may be blended to maintain optimal properties.
Benefits of a Sand Reclamation System
- Cost Reduction: Reduces the need for new sand, lowering raw material costs.
- Environmental Sustainability: Minimizes sand disposal and related pollution.
- Improved Casting Quality: Ensures consistent sand properties for better mold integrity.
- Energy Savings: Reclaimed sand requires less processing than new sand.
Conclusion
Sand Reclamation System for the No-Bake Sand Process is designed to recover and reuse sand used in foundries, reducing waste, improving cost efficiency, and enhancing environmental sustainability.
