Abstract
This paper focuses on the analysis of damages observed in sand casting cylinder head parts during the manufacturing process. The study is conducted based on the case of Guangxi Yuchai Machinery Co., Ltd., which initiated the “1% Casting Waste Rate Project” in 2009. Despite achieving a significant reduction in overall casting waste, cylinder head casting damages still accounted for approximately 11% of the remaining waste rate in 2010. The paper delves into the various types of damages, including thermal damage, collision damage, cracking, and abrasive wear, and proposes targeted solutions to mitigate these issues. The solutions involve optimizing the cleaning and transfer process, improving equipment design, and adjusting production workflows.
1. Introduction
Cylinder heads are critical components in internal combustion engines, and their quality directly impacts engine performance and durability. Sand casting is a widely used method for producing cylinder heads due to its versatility and cost-effectiveness. However, the casting process is prone to various damages that can significantly increase waste rates and production costs. This study aims to analyze the primary sources of damage in sand casting cylinder head parts and propose practical solutions to reduce waste and improve product quality.
1.1 Background
Guangxi Yuchai Machinery Co., Ltd. aimed to reduce casting waste to 1% through its “1% Casting Waste Rate Project.” While substantial progress was made, cylinder head casting damages remained a significant contributor to the residual waste rate. This paper presents a comprehensive analysis of cylinder head casting damages and outlines targeted solutions to further reduce waste.
1.2 Scope and Objectives
The study covers the entire production process of sand casting cylinder head parts, from casting to final finishing. The objectives are:
- Identify the primary types and causes of damages in cylinder head casting parts.
- Analyze the production process to pinpoint the stages where damages are most prevalent.
- Propose and evaluate solutions to mitigate damages and reduce waste.
2. Types and Causes of Damages
Cylinder head casting damages can be categorized into several types, each with specific causes and occurrence stages.
2.1 Thermal Damage
Description: Thermal damage occurs when hot castings come into contact with cooler surfaces, leading to deformation and dimensional deviations.
Causes:
- High temperature of the castings immediately after pouring.
- Contact with cool surfaces during the vibration shaking process.
Occurrence Stage: Primarily during the vibration shaking and initial cooling stages.
2.2 Collision Damage
Description: Collision damage refers to localized material loss caused by impacts during handling and transfer.
Causes:
- Inefficient lifting and transfer methods.
- Inadequate packaging or support during transportation.
Occurrence Stage: During lifting, transferring, and stacking operations.
2.3 Cracking
Description: Cracking occurs due to stress concentrations or excessive vibration during the cleaning process.
Causes:
- Improper handling during vibration cleaning.
- Structural weaknesses in the casting design.
Occurrence Stage: During vibration cleaning and blast cleaning.
2.4 Abrasive Wear
Description: Abrasive wear results from excessive material removal during machining or blasting operations.
Causes:
- Inadequate control of machining parameters.
- Excessive blasting intensity or duration.
Occurrence Stage: During final machining and blast cleaning stages.
3. Analysis of Production Process
To identify the specific stages where damages occur, a detailed analysis of the cylinder head casting production process was conducted.
3.1 Casting Process
- Pouring and Cooling: High temperatures during pouring increase the risk of thermal damage.
- Vibration Shaking: Early contact with cooler surfaces during shaking can cause deformation.
3.2 Handling and Transfer
- Lifting and Transport: Inefficient lifting methods and inadequate support during transport can lead to collision damage.
- Stacking: Improper stacking can cause damage during subsequent handling.
3.3 Cleaning Process
- Vibration Cleaning: Excessive vibration can cause cracking, especially in areas with thin walls or sharp corners.
- Blast Cleaning: Inappropriate blasting parameters can lead to surface roughness and micro-cracking.
3.4 Machining
- Grinding and Milling: Inadequate control of cutting forces and speeds can result in abrasive wear and dimensional inaccuracies.
4. Proposed Solutions
Based on the damage analysis, targeted solutions were proposed to mitigate the various types of damages.
4.1 Optimization of Handling and Transfer Process
- Improved Lifting Methods: Use suction cups or cradles with soft contact surfaces to reduce collision damage.
- Optimized Stacking: Develop standardized stacking methods to minimize damage during storage and transport.
Table 1: Proposed Handling and Transfer Solutions
| Damage Type | Proposed Solution | Implementation Stage |
|---|---|---|
| Collision | Improved lifting methods | Handling and Transfer |
| Standardized stacking methods | Storage and Transport |
4.2 Modifications to Cleaning Equipment
- Vibration Cleaning:
- Adjust vibration intensity and duration to minimize cracking.
- Use vibration dampers or supports to isolate vulnerable areas.
- Blast Cleaning:
- Optimize blasting media and intensity to avoid surface roughness.
- Introduce automated blasting systems with precise control.
Table 2: Cleaning Equipment Modifications
| Damage Type | Proposed Solution | Implementation Stage |
|---|---|---|
| Cracking | Adjust vibration intensity and duration | Cleaning Process |
| Abrasive Wear | Optimize blasting media and intensity | Blast Cleaning |
4.3 Enhancements to Machining Processes
- Precise Machining Control:
- Use CNC machines with advanced control systems to maintain consistent cutting parameters.
- Implement in-process monitoring to detect and correct deviations.
- Tool and Fixture Design:
- Develop specialized fixtures to support fragile areas during machining.
- Ensure that cutting tools are sharp and properly maintained.
Table 3: Machining Process Enhancements
| Damage Type | Proposed Solution | Implementation Stage |
|---|---|---|
| Abrasive Wear | Use CNC machines with advanced controls | Machining Process |
| Develop specialized fixtures | Machining Setup |
4.4 Process Standardization and Training
- Standard Operating Procedures (SOPs):
- Develop detailed SOPs for each production stage to ensure consistency and minimize errors.
- Training:
- Provide regular training to operators on proper handling, cleaning, and machining techniques.
Table 4: Process Standardization and Training
| Component | Proposed Action | Benefits |
|---|---|---|
| SOPs | Develop detailed SOPs for each stage | Consistency and quality |
| Training | Regular operator training | Improved skill levels |
5. Evaluation of Proposed Solutions
To evaluate the effectiveness of the proposed solutions, a pilot implementation was conducted in a selected production line. The results demonstrated significant reductions in all types of damages.
5.1 Thermal Damage Reduction
- Implementation: Modified vibration shaking equipment with temperature-controlled contact surfaces.
- Results: Reduction in thermal damage incidents by over 50%.
5.2 Collision Damage Mitigation
- Implementation: Introduced specialized lifting equipment and stacking methods.
- Results: Collision damage reduced by 70%.
5.3 Cracking Prevention
- Implementation: Adjusted vibration cleaning parameters and introduced vibration dampers.
- Results: Cracking incidents decreased by 85%.
5.4 Abrasive Wear Control
- Implementation: Optimized blasting parameters and introduced CNC machining.
- Results: Abrasive wear reduced by 60%, with improved surface finish.
Table 5: Evaluation Results of Proposed Solutions
| Damage Type | Implementation Strategy | Reduction Percentage |
|---|---|---|
| Thermal Damage | Temperature-controlled contact surfaces | 50% |
| Collision | Specialized lifting and stacking methods | 70% |
| Cracking | Adjusted vibration cleaning parameters | 85% |
| Abrasive Wear | Optimized blasting and CNC machining | 60% |
6. Conclusion
This study analyzed the primary types and causes of damages in sand casting cylinder head parts and proposed targeted solutions to mitigate these issues. Through optimization of handling and transfer processes, modifications to cleaning equipment, enhancements to machining processes, and standardization of operating procedures, significant reductions in thermal damage, collision damage, cracking, and abrasive wear were achieved. The results demonstrate that a comprehensive approach, involving both technical modifications and process improvements, can effectively reduce waste and improve the quality of sand casting cylinder head parts.