Abstract:
This paper focuses on the sand casting process design and simulation optimization of a rotary disc, a critical component in drill press spindles. By analyzing the structural characteristics of the rotary disc and utilizing numerical simulation, an optimized casting process was developed. The paper presents the design of the pouring system, mold parting surface, gating system, risers, and chills, ultimately proposing the best sand casting process plan for the casting.
1. Introduction
The rotary disc, as a key part of the drill press spindle, requires high precision and hardness. Sand casting, particularly gravity casting with HT250 material, is commonly used for producing such components due to its high strength, good wear resistance, excellent vibration damping properties, and superior casting performance. This paper integrates relevant enterprise experience in inclined pouring, analyzes the structural characteristics of the component, and simulates and optimizes the casting process to determine the pouring position, mold parting surface, ingate, risers, and chill positions.
2. Structure Analysis
The rotary disc has an overall dimension of 1040mm × 375mm × 158mm, with a relatively symmetrical structure and a multi-ribbed, semi-open, and porous internal structure. The maximum wall thickness is 30mm, and the minimum is 10mm, while the smallest hole diameter is 6mm, classifying it as a thin-walled, medium-sized complex casting. High quality is required for the dovetail guide surface and threaded hole surfaces. The internal structure with multiple rib plates and hole positions makes coremaking a difficult aspect of this casting.
Table 1: Structural Characteristics of the Rotary Disc
| Characteristic | Description |
|---|---|
| Overall Dimension | 1040mm × 375mm × 158mm |
| Wall Thickness | Max: 30mm, Min: 10mm |
| Hole Diameter | Smallest: 6mm |
| Material | HT250 |
3. Sand Casting Process Design
3.1 Casting Process Analysis
The rotary disc is made of HT250 and is classified as a medium-sized complex casting for small-batch production. Due to the high quality requirements of the dovetail guide surface and threaded hole surfaces, furan resin self-hardening sand was selected as the molding material for both the sand mold and sand core, with alcohol-based coating used for manual molding and coremaking.
Table 2: Casting Specifications
| Specification | Value |
|---|---|
| Maximum Nominal Size | 1040mm |
| Casting Dimension Tolerance | CT11 |
| Casting Mass Tolerance Grade | MT10 |
| Casting Weight Tolerance | ±4% |
| Shrinkage Rate | 0.9% |
3.2 Pouring Position and Mold Parting Surface Determination
The pouring position is set with the dovetail guide surface facing downwards and the large plane facing upwards. This setup ensures better filling and crystallization quality for the slender dovetail guide surface. The mold parting surface is selected at the largest cross-section of the casting for easy mold withdrawal, simplified molding and mold plate structure, better dimensional accuracy, and ease of core insertion and mold closing.
3.3 Gating System Design
Based on production experience and the structural characteristics of the component, the ingate is placed at the bottom outer surface of one end of the casting for minimal filling resistance and stable filling. The mold is then tilted to utilize the self-weight pressure of the molten metal for inclined pouring, creating a pressure gradient in the mold cavity that maximizes the reduction of porosity and promotes simultaneous solidification, reducing the tendency for thermal cracking.
4. Numerical Simulation and Optimization
4.1 Bottom Pouring Inclined Gating System Simulation
Using Anycasting for numerical simulation and analysis, the simulation results showed that the filling process was relatively stable with no metal splash or gas entrapment. However, hot spots appeared in the thicker wall sections, requiring further optimization.
4.2 Process Optimization
To address the defects concentrated at the highest pouring position, two optimization measures were taken:
- Modifying the bottom pouring inclined gating system to a stepped inclined gating system.
- Placing risers at the highest point on the right side of the casting.
4.3 First Optimization Simulation and Analysis
The first optimization simulation showed improved solidification order and defect concentration at the risers. To ensure the crystallization quality of the threaded holes in the thicker sections, chills were placed to refine the grain size and increase the strength of the subsequently machined threaded holes.
4.4 Second Optimization Simulation and Analysis
To further ensure the crystallization quality of the threaded holes, chills were used for the second optimization. The simulation results showed significant improvement in hot spot reduction, with no apparent defects on the casting surface and shrinkage hot spots transferred to the risers, meeting the quality requirements of the casting.
Table 3: Casting Quality and Yield
| Item | Value |
|---|---|
| Casting Mass | 174.45kg |
| Gating System Mass | 85.25kg |
| Riser Mass | 9.8kg |
| Casting Process Yield | 64.73% |
5. Core Design
Given the rectangular shape of the casting, a multi-core approach was adopted. Small cores were embedded and fixed using steel pins and adhesive to prevent displacement. A hollow thin steel tube welded in a triangle shape was used as the core frame, with multiple holes on the tube serving as core supports, ventilation channels, and reducing mold weight.
6. Conclusion
- A complete and reasonable casting process plan was obtained for sand casting of rotary discs for small-batch production, utilizing resin sand cold-box precision core assembly for high-precision parts. Additionally, sand box and core bone designs were adopted to ensure the convenience and safety of core handling, mold closing, and pouring.
- The ingate was set at the side bottom and top surface of one end of the rotary disc casting length, using stepped pouring combined with inclined pouring to ensure stable filling and reduce overheating at the bottom dovetail guide. Risers and chills were placed to reduce casting defects, effectively ensuring the quality requirements of the dovetail guide surface and the large plane.
- The Anycasting simulation software was used to simulate and analyze the filling, solidification, and shrinkage defects, confirming the effectiveness and correctness of the design. The casting yield was high, reducing casting production costs and improving production efficiency.
The numerical simulation provided a good reference for quality control and defect improvement in sand casting, shortened development time, and indicated that reasonable process parameter adjustments and comprehensive considerations of casting structure, gating system, and venting system are crucial for ensuring casting quality.