Abstract
In view of the disadvantages of poor working conditions, labor shortages, high labor intensity, high risk coefficients, and low product quality assurance in the cylinder block casting cleaning process of engine casting enterprises, this paper introduces the latest process design concepts for the cleaning process. The transformation and upgrading of the cleaning process have been achieved through product casting process development and full-process automation, laying the foundation for unmanned cleaning operations and enhancing the company’s competitiveness.
1. Introduction
Our company has seen its engine business continuously innovate in recent years, significantly increasing its core competitiveness. With a market share exceeding 30% and an annual production capacity of over 1 million units, our engines are primarily used in medium and heavy-duty trucks, buses, city buses, and other power machinery. The core component, the cylinder block, features a diverse range of products with high performance requirements (high bursting pressure, high strength, lightweight, integrated design), stringent quality standards (internal cavity cleanliness, appearance quality), and employs mass, automated, streamline casting production methods. These factors pose significant challenges for the process design and production layout of cylinder blocks. Traditional process designs, relying on single-process point-to-point production layouts, fail to meet current industry developments and product demands.
Especially in recent years, our company’s product process development and mass production process focus has been on core-making and molding processes, with relatively fewer new investment projects focusing on cleaning processes. Coupled with the harsh working environment, high labor intensity, and high risk coefficients associated with cleaning processes, they have become bottlenecks hindering our company’s high-quality development and urgent changes are needed. This paper focuses on introducing how to achieve full-process automation in cleaning.
2. Product Characteristics
The engines developed by our company in recent years have focused on models with displacements above 10L and horsepower above 400. To enhance product competitiveness, the cylinder block is designed with an integrated high-龙门 structure, where the gear chamber, crankcase, and cylinder block are modularly integrated. The product structure is complex, with a large gear chamber span, and the casting has minimum dimensions of 900mm × 500mm × 500mm. It adopts a combination of wet cylinder liners and dry cylinder blocks. To meet high bursting pressure requirements, the product surface has multiple reinforcing ribs. To meet lightweight requirements, the main wall thickness is only about 45.5mm, with a casting weight of 270400kg. To meet high bursting pressure requirements, the material is HT300-RT450.
Table 1: Product Specifications
| Specification | Value |
|---|---|
| Cylinder Block Type | Integrated High-龙门 Structure |
| Material | HT300-RT450 |
| Minimum Dimensions | 900mm × 500mm × 500mm |
| Main Wall Thickness | 4~5.5mm |
| Casting Weight | 270~400kg |
3. Cleaning Process and Flow
The current cleaning process mainly consists of robot gripping, annealing kilns, manual gripping for rough cleaning, grinding machines, vibrating core machines, coarse polishing, fine cleaning, precision polishing, inspection, and powder spraying. Between each process, a large number of chain blocks are used for manual loading and unloading. Due to the complex product structure, the internal and external quality is primarily ensured through manual cleaning in the fine cleaning process, which demands high skill levels from operators, high labor intensity, and extremely high risk coefficients. With engines placing increasingly stringent requirements on the cleanliness of various water channels and oil channels within the cylinder block, the current process cannot meet the requirements for high-precision dimensions and quality.
4. Cleaning Process Transformation Plan
4.1 Automated Transportation through Robots and Visual Recognition
Manual loading and unloading of castings are required for feeding and discharging processes in grinding machines and vibrating core machines, which is labor-intensive and highly risky. Especially for newly developed cylinder blocks with large gear chamber spans, instability during lifting and transportation and slow transfer speeds significantly affect production efficiency.
To achieve automated transportation, the gripping points of the castings are first selected. Due to the numerous product types and significant appearance differences, automated gripping must be compatible with all products, and the gripping tools should be as unified as possible. After comprehensive research, the cylinder bore is selected as the clamping point for robots. The prerequisite for automation is that the castings are placed vertically on the track line, with the cylinder bore in a vertical state. The robot’s fixture extends into the cylinder bore to complete gripping and transportation. However, there is poor consistency among such castings. Due to the lack of shot blasting, the castings have severe burrs and sand accumulation in the bore, preventing vertical movement on the track line and satisfying fixture entry for sand accumulation in the bore. To achieve automation, the issues of positioning inaccuracy caused by burrs and sand accumulation must be resolved.
Table 2: Improvements for Automated Transportation
| Improvement Measure | Details |
|---|---|
| Optimized Casting Process | Cylindrical overflow riser changed to a sheet with exhaust needles, sheet thickness ≤ 4mm |
| Optimized Gating System | Three-tier gating system changed to two-tier, optimized inner gate area to ensure stable pouring and reduce impact on casting height positioning |
| Pre-treatment of Sand Accumulation | Added self-designed sand-dropping mechanism in the rough cleaning process to preprocess sand accumulation in the cylinder bore |
| Visual Recognition System | Identifies workpiece type, position, and status, generating corresponding handling programs automatically |
4.2 Flexible Intelligent Cleaning Line
A flexible intelligent cleaning line combining special machines, intelligent flexible processing units, and intelligent robots is employed to automate the cleaning of casting surfaces, such as gating systems and parting surface burrs, significantly reducing the number of operators required for manual fine cleaning processes.
Table 3: Key Features of Flexible Intelligent Cleaning Line
| Feature | Description |
|---|---|
| Intelligent Grinding | Robot-held electric spindle with diamond grinding wheel, equipped with cooling function, agile protection, and laser alignment scanning for error compensation and automatic generation of grinding programs |
| Integrated Fixture Design | High versatility, easy manual adjustment and replacement, compatible with different series of castings, ensuring stable gripping and rapid, convenient control |
| Integrated Control Technology | Enables intelligent management and control of the entire line, optimizing logistics and achieving maximum efficiency and safety |
| Comprehensive Grinding Coverage | Reasonably matches grinding points, develops grinding paths, selects suitable equipment, and forms an optimal grinding process |
| Optimized Riser Stub Design | “Two-step” structure to control riser stub height ≤ 3mm, enhancing the stability and reliability of the flexible cleaning unit |
4.3 Development of Internal Cavity Cleaning System
An internal cavity cleaning system, consisting of automatic blowing and shot blasting systems, is designed to automate and specifically clean the internal cavity of castings, significantly improving their quality. The quality of engine cylinder block water and oil chambers is crucial for ensuring the reliability of engine cooling performance and represents one of the core competitiveness of engine enterprises. Due to the complex internal cavity structure and intricate water and oil passages, manual cleaning is currently employed, which is labor-intensive, operates in harsh environments, has low production efficiency, and fails to thoroughly clean complex areas. Our company has effectively addressed this industry challenge and achieved a breakthrough in traditional manual internal cavity cleaning by designing and applying automatic blowing and internal cavity shot blasting systems.
Table 4: Key Components of Internal Cavity Cleaning System
| Component | Description |
|---|---|
| Material Handling | Conveyor roller feed, automatic casting type recognition |
| Automatic Blowing Unit | Robot performs blowing cleaning on castings |
| Shot Blasting Machine | 3D visual positioning, dual shot blasting robots for efficient cleaning |
| Automatic Cleaning Hole Unit | Ensures that oil, water, and process holes are open for subsequent cleaning |