Abstract
Based on the analysis of the structure and lost foam casting (LFC) process of a tractor transmission box, this paper summarizes the development of an lost foam casting process for large-sized and thin-walled shell parts. Through systematic research and numerical simulation, the optimal casting process is determined, effectively controlling deformation and ensuring no other defects. The use of numerical simulation technology and model comparison methods significantly reduces trial costs and time, highlighting the importance of lost foam casting in reducing overall production costs.
1. Introduction
Large-sized and thin-walled shell parts, such as transmission cases, are challenging to cast due to their complex structure, large volume, and small wall thickness. Traditional sand casting methods are costly and inefficient, with low sand recovery rates and high mold costs. In contrast, lost foam casting offers significant advantages, including lower costs, simplified processes, and high dry sand recovery rates. This paper focuses on the development of an lost foam casting process for a specific tractor transmission box, emphasizing the use of tables and images to enhance readability.
2. Product Structure and Process Analysis
The transmission box in question has a complex structure, large size, significant weight, and small minimum wall thickness, making it difficult to cast using lost foam casting. To facilitate subsequent process design, numerical simulation, and optimization in a virtual environment, a three-dimensional (3D) model was created based on the existing two-dimensional (2D) drawings. The dimensions of the part are summarized in Table 1.
Table 1. Dimensions of the Transmission Box
| Parameter | Value (mm) |
|---|---|
| Theoretical Mass | 265.1 |
| Maximum Outer Dimensions | 816 × 530 × 578 |
| Minimum Wall Thickness | 14 |
| Maximum Wall Thickness | 50 |
3. Mold Design
Based on the 3D model, the mold was designed with a parting plane in the middle, divided into two halves. The mold structure is automatic, with dimensions not exceeding 1100 mm × 900 mm × 600 mm. The mold material is GBZL106, with a surface roughness of Ra ≤ 1.6 μm, and TEFLON coating applied to the cavity, core, and inserts. Key dimensions are summarized in Table 2.
Table 2. Key Dimensions of the Mold
| Parameter | Value (mm) |
|---|---|
| Mold Outline Size | ≤ 1100 × 900 × 600 |
| Mold Body Wall Thickness | 12~15 |
| Outer Frame Wall Thickness | 18~20 |
| Processing Allowance | 3~5 |
4. Casting Process Design
Three lost foam casting process schemes were designed and numerically simulated to assess their feasibility, with key parameters summarized in Table 3.
Table 3. Key Parameters of Casting Process Schemes
| Scheme | Pouring Position | Gating System Dimensions (mm) | Head Pressure (mm) |
|---|---|---|---|
| Scheme 1 | Flat, Top Pouring | 50 (straight), 40×20 (cross), 40×7.5 (ingate) | 210 |
| Scheme 2 | Inclined, Side Pouring | 50 (straight), 60×55 (cross), 55×15 (ingate) | 190 |
| Scheme 3 | Vertical, Top Pouring | 50 (straight), 45×50 (cross), 60×15 (ingate) | 320 |
The numerical simulation results indicated that Scheme 2 was the most promising, with fewer defects and better temperature gradients during solidification. Based on this, Scheme 2 was optimized by adding additional ingates to increase filling speed and reduce temperature gradients. The optimized scheme.
5. Process Experiment
The optimized Scheme 2 was implemented, with key process steps including mold making, pattern assembly, coating application, drying, molding, pouring, and cleaning. The pattern assembly scheme.
After the casting process, the surface quality of the castings was good, with no obvious defects. The hardness of the end face was HB180~190.
6. Model Comparison and Processing Verification
The castings were scanned using a 3D scanner to obtain their 3D models, which were then compared with the theoretical 3D model to assess deformation and processing allowances. The comparison results, indicating that the deformation was within the process control range.
Further processing verification confirmed that the deformation was minimal and within acceptable limits, with no other defects observed. The finished castings.
7. Conclusion
The development of an lost foam casting process for large-sized and thin-walled shell parts, such as transmission boxes, presents significant challenges but also offers cost-saving advantages compared to traditional sand casting. Through systematic research and numerical simulation, an optimal casting process was developed, effectively controlling deformation and ensuring no other defects. The use of numerical simulation technology and model comparison methods significantly reduced trial costs and time, highlighting the potential of lost foam casting in the production of complex and large-sized castings.