Advancing Axle Housing Production: Synergizing Stamping Operations with Precision Machining

This study explored optimization methods for processing vehicle axle housings. It aimed to tackle challenges found in traditional processes, which include cumbersome welding steps, difficulties in weld preparation, challenges in maintaining high precision control, and inconsistent product quality. To enhance processing efficiency and product quality, a solution was proposed that replaces some welding and bending steps with high-nominal pressure stamping. Additionally, by optimizing drilling, surface treatment, and material selection, the number of welds was reduced, leading to improved processing precision and durability.

 

01 Introduction

Traditional processing techniques, which involve cumbersome welding steps, challenging precision control, and low production efficiency, have obstructed the development of large-scale and effective production. To overcome these challenges, a new process has been proposed that replaces certain welding and bending steps with high-nominal pressure stamping. This approach, when combined with drilling, surface treatment, and material optimization, enhances processing precision and durability. The goal is to explore a more efficient and economical method for manufacturing axle housings.

02 Problems with Traditional Processing

2.1 Complicated Welding Steps Impact Production Efficiency.

Traditional manufacturing processes for vehicle axle housings often involve multiple welding steps, such as girth welds, rear cover welds, and straight seam welds, to ensure the axle housing’s structural integrity. This complexity arises from the need to assemble multiple components, requiring precise alignment, fixturing, and welding at each stage. Additionally, welded workpieces necessitate extra preparation, including slag removal, grinding, and inspection. These factors contribute to increased labor time and costs, ultimately reducing production efficiency and complicating large-scale manufacturing.

 

2.2 Weld Preparation is Difficult and Can Lead to Quality Issues.

During welding, high temperatures melt the metal to bond the workpieces; however, this process can lead to quality issues. Traditional welding techniques are prone to defects such as deformation, stress concentration, and porosity at the welded joints, which can compromise the overall strength and stability of the axle housing. The quality of the weld is closely tied to the operator’s skill, making it challenging to achieve consistent results manually. Even after careful weld preparation, defects can persist, leading to cracks or fatigue damage in the axle housing over time, ultimately impacting its service life.

Precision control is another significant challenge, resulting in poor product consistency. In traditional axle housing manufacturing, the accuracy of the workpiece depends on welding, assembly, and subsequent machining processes. However, heat-affected zones created during welding can lead to localized deformation, which affects the dimensional accuracy of the axle housing. Subsequent processes, such as drilling, often require multiple clamping steps. Each instance of clamping can introduce positioning errors, resulting in considerable dimensional variations between production batches. The heavy reliance on manual operation, combined with differing skill levels and experiences among operators, further complicates the issue of product consistency.

 

03 Improved vehicle bridge shell processing technology

3.1 Design ideas and goals of the new process

This process introduces a method that uses high nominal pressure stamping as the primary technique to replace certain welding and bending operations, thereby streamlining the manufacturing process. The rear cover, upper shell, and lower shell are all formed in a single step using a 1500-2000 kN punching machine, which reduces the number of welds and improves structural strength. The drilling process has been optimized by using a drilling machine with an adjustable drill bit, enhancing both drilling accuracy and production efficiency. Additionally, high-standard grinding and anti-corrosion spraying techniques significantly improve the product’s quality and durability. As a result, this method enables efficient, low-cost, and stable production of bridge shells.

 

3.2 Main process flow

(1) High-precision cutting and edge grinding

In the improved processing technology, high-precision CNC cutting equipment is used to accurately cut steel plate materials according to design specifications. This method reduces material waste and enhances material utilization. However, the edges of the cut steel plates often have burrs or irregular sections, necessitating a grinding process. An angle grinder is used to rough-grind the edges, removing burrs and improving the surface quality of the workpiece. This ensures a smooth transition to subsequent processes.

 

(2) High nominal pressure stamping replaces bending and welding.

This process utilizes a stamping machine with a nominal pressure of 1500-2000 kN to stamp the steel plate in a single step. Compared to traditional bending and welding methods, stamping effectively reduces the number of parts required for the bridge shell and enhances the overall structural strength. The stamping process eliminates the need for separate production of rear cover parts and removes several steps, such as girth welding, rear cover welding, and straight seam welding, thus creating a more integrated structure for the bridge shell.

This approach minimizes the risk of weld leaks, improving both the sealing and durability of the final product. Additionally, it boosts production efficiency and lowers energy consumption. The surface of the workpiece after stamping is smooth and uniform, which contributes to the quality of subsequent processing, decreases material waste, and enhances material utilization.

 

(3) Optimize welding structure and reduce the number of welds.

In the new process, the stamping method replaces part of the traditional welding process, resulting in a significant optimization of welding. The welding procedure is primarily used to assemble the parts after stamping, ensuring the structural strength of the assembly. We utilize argon arc welding or electric arc welding along with an assembly frame for precise positioning, which helps minimize welding deformation. By reducing the number of circumferential welds and rear cover welds, we significantly decrease the total number of welds. This reduction lowers welding stress and decreases defects such as pores and cracks, ultimately improving the structural stability of the bridge housing.

(4) Use an adjustable drilling machine to improve precision and efficiency.

The CNC drilling process utilizes a drilling machine equipped with an adjustable drill bit, allowing for the completion of all drilling holes in a single clamping. This enhances drilling accuracy and minimizes errors that can occur from repeatedly clamping the workpiece. In contrast, traditional drilling methods often require multiple clampings, which can complicate operations and result in precision errors between different hole positions. By using an adjustable drill bit, this process enables the drilling machine to accommodate the drilling needs for various positions and sizes, ensuring the accuracy of installation holes for the bridge housing and improving overall assembly precision.

 

(5) Fine grinding to improve surface quality.

After welding, the surface of the bridge housing may exhibit weld protrusions, burrs, and local defects, necessitating fine grinding. This process utilizes grinding wheels and specialized grinding tools to smooth and polish the welds, resulting in a more even surface for the bridge housing. By doing so, it reduces stress concentration points and enhances the structural durability of the housing.

To ensure the quality of the subsequent spraying process and improve overall appearance, the surface roughness of the bridge housing after grinding is maintained at Ra ≤ 10 μm. Fine grinding not only boosts the fatigue resistance of the surface but also minimizes dimensional errors in later processing stages. This approach makes the bridge housing more compliant with design standards and increases the yield rate.

 

(6) Ultrasonic cleaning and anti-corrosion spraying to improve durability

To enhance the durability and anti-corrosion performance of the bridge housing, ultrasonic cleaning is necessary before spraying. This process removes grease, stains, and impurities from the surface of the workpiece. Using an ultrasonic cleaning machine allows for deep cleaning, which effectively improves surface cleanliness and increases the adhesion of the paint.

After cleaning, the bridge housing is dried in specialized drying equipment to prevent residual moisture from causing defects during the subsequent spraying process.

High-performance anti-corrosion coatings are chosen for the spraying process to improve the corrosion resistance of the bridge housing and to minimize the effects of environmental factors. Additionally, alloy material is sprayed onto the inner side wall of the bridge housing end to enhance its wear resistance, high-temperature resistance, and oxidation resistance. This, in turn, improves the stability of vehicle operation and extends the service life of the bridge housing.

 

04 Key Technology Optimization Analysis

4.1 Stamping Process Optimization

1) The Impact of High-Nominal-Pressure Stamping on Processing Accuracy is critical in this process, which uses a stamping press with a nominal pressure of 1500-2000 kN to shape the axle housing. Unlike traditional bending and welding methods, the high pressure of the stamping press allows for uniform stress distribution during the forming process. This enhances dimensional accuracy and consistency.

High-nominal-pressure stamping minimizes deformation during part processing and reduces the need for subsequent machining adjustments. It ensures a uniform wall thickness of the axle housing, improves the structural strength and stability of the product, lowers scrap rates, and enhances material utilization.

 

2) This process eliminates the need to separately manufacture rear cover components, enhancing efficiency. In traditional methods, rear cover components are individually machined and welded to the axle housing body, which increases manufacturing complexity and welding costs. By using stamping technology to form the rear cover and axle housing body as a single unit, this method removes the need for girth welds, rear cover welding, and straight seam welding. As a result, the risk of weld leaks is reduced, and the sealing of the axle housing is improved.

 

4.2 Drilling Process Optimization
1) Use of adjustable drill bits to improve drilling accuracy and consistency. Traditional drilling processes often require multiple clamping of the workpiece, which can lead to significant errors in hole positioning and negatively impact the assembly accuracy of the axle housing. This process employs a drilling machine equipped with an adjustable drill bit, allowing for the flexible adjustment of both the drilling position and size according to design specifications. This ensures the accuracy of each hole. Utilizing an adjustable drill bit reduces human error and enhances drilling consistency, enabling the axle housing to align better with other components during subsequent assembly. As a result, this approach improves the overall accuracy of assembly and the stability of quality in the axle housing.

2) Design optimization for drilling multiple holes in a single clamping session. To enhance machining accuracy and minimize errors caused by repeated clamping, this process employs a high-precision fixture to secure the axle housing, allowing multiple holes to be drilled in a single clamping session. In contrast, traditional drilling methods require several clamping adjustments, which can easily result in deviations in hole positioning. This optimized solution reduces workpiece movement, improves positioning accuracy, and decreases cumulative errors. Additionally, the ability to process multiple holes in one clamping session boosts machining efficiency, shortens production time, and supports effective manufacturing in large-scale production environments.

 

4.3 Surface Treatment Process Optimization

1) Application of Ultrasonic Cleaning Technology. Grease, metal powder, and other contaminants can accumulate on the axle housing during machining, which may negatively impact the adhesion of spray coatings and the overall surface quality. To address this, we utilize ultrasonic cleaning technology. A cleaning agent is added to the cleaning tank, and the cavitation effect created by ultrasound effectively removes dirt and grease from the surface of the custom aluminum parts, ensuring it is thoroughly cleaned. Ultrasonic waves can penetrate deep into tiny crevices, enhancing cleaning effectiveness while avoiding the uneven results commonly associated with traditional manual cleaning methods. This process improves the quality of the axle housing spray coating and reduces the risk of subsequent loss of the anti-corrosion coating.

2) High-Standard Polishing Process. This process uses advanced polishing technology to achieve an axle housing surface roughness of Ra ≤ 10μm. A low surface roughness not only enhances the adhesion of anti-corrosion coatings but also decreases stress concentration, thereby reducing the risk of fatigue cracking. Additionally, the polished axle housing exhibits a smoother and more visually appealing finish, which contributes to improved product quality and greater competitiveness in the market.

Figure 1 illustrates a performance comparison of different surface roughness levels after polishing, where a score of 10 represents the best performance. The comparison visually assesses three key indicators: surface quality, corrosion resistance, and coating adhesion. The results demonstrate that the polishing process achieving Ra ≤ 10μm outperforms others in all aspects, leading to enhanced quality and extended service life of the bridge housing.

3) To extend the service life of the axle housing, an anti-corrosion coating is sprayed onto its surface. This high-performance coating enhances corrosion resistance, protecting the axle housing from moisture and chemicals, thereby reducing structural damage caused by rust. Additionally, an alloy material is applied to the inner sidewalls of the axle housing ends to improve wear and oxidation resistance. This helps minimize wear over prolonged use and enhances vehicle stability. Prior to spraying, thorough cleaning and drying of the surface ensure uniform adhesion of the coating, further increasing its durability and protective effectiveness.

 

4.4 Material Optimization
1) High-formability 485 MPa-grade steel plate is utilized to enhance the strength and durability of the axle housing. Given that axle housings experience heavy loads, both material strength and formability are vital. This process employs high-formability 485 MPa-grade steel plate, which offers a combination of high tensile strength and excellent formability. During the stamping process, this material effectively distributes stress, preventing cracks and localized thinning. As a result, it significantly improves the overall rigidity and impact resistance of the axle housing.

2) Applying an alloy spray to the inner sidewalls of the axle housing ends enhances both wear resistance and oxidation resistance. This process involves coating the inner sidewalls with an alloy that significantly improves high-temperature resistance and durability against wear. The alloy spray coating minimizes friction loss, extends the axle housing’s service life, and stabilizes vehicle operation. Additionally, the alloy’s high heat resistance helps prevent metal fatigue caused by prolonged exposure to high temperatures, further increasing the axle housing’s durability in harsh environments and enhancing its overall performance and reliability.

 

05 Conclusion

This paper discusses the challenges associated with traditional processing methods for vehicle axle housings. These challenges include cumbersome welding procedures, difficulties in achieving precise control, and inconsistent product quality. To address these issues, the paper proposes an optimized solution that substitutes some welding and bending operations with high-pressure stamping. Additionally, improvements in machining accuracy and structural strength of the axle housing are achieved through drilling, surface treatment, and material optimization. Research indicates that this enhanced process effectively reduces the number of welds required, boosts production efficiency, lowers manufacturing costs, and increases both the lifespan and stability of the axle housing.

 

 

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