Broaching and End Face Grinding Solutions for the Inner Cavity Machining of Oil Pump Stators

Introduction

The oil pump stator is the core static component of the oil pump (such as gear pump, vane pump, plunger pump, etc.) in the hydraulic system or fuel system, which cooperates with the rotor (or moving parts such as gears and blades) to form a sealed chamber to realize the suction, compression and discharge of oil, so as to provide stable hydraulic power or fuel supply.
The manufacturing process of the oil pump stator directly affects the efficiency, life and reliability of the pump, and the use of broaching machines and double-end face grinders for processing is to achieve extremely high dimensional accuracy, geometric accuracy and surface quality, so as to ensure that the oil pump achieves the key characteristics of high pressure, high efficiency, low noise and long life.

1.Core Objective of the Plan

This scheme takes “precision, efficiency, stability, and low cost” as the core, and achieves three core goals for the processing needs of the inner cavity and end face of the oil pump: first, to solve the problems of insufficient dimensional accuracy of the stator inner cavity, substandard surface finish, and deviation of end face parallelism, and ensure that the dimensional tolerance of the inner cavity is controlled within ±0.01mm. The parallelism of the end face is ≤0.003mm, and the surface roughness is Ra≤0.8μm, which meets the high-precision requirements of oil pump assembly. The second is to optimize the processing process, integrate broaching and grinding processes, reduce process switching time, improve mass production efficiency, and increase the processing efficiency by more than 60% compared with the traditional processing process. The third is to reduce the scrap rate in the processing process, through precise equipment selection, process optimization and quality control, the scrap rate is controlled within 1%, while reducing tool loss and energy consumption, and reducing the processing cost per product.

2.Manufacturing Pain Point Analysis

The difficulty of processing the structural particularity of the oil pump stator is mainly concentrated in the following four points, which is also the core problem that this scheme focuses on:

1. Complex inner cavity structure and strict precision requirements: the inner cavity of the oil pump stator is mostly irregular curved surface (such as spiral surface), multiple oil channels and sealing groove design, and the inner cavity depth is deep, which belongs to the closed or semi-closed deep cavity structure, which has extremely high requirements for dimensional accuracy, shape tolerance and surface roughness. Further increase the difficulty of precision control.
2. Thin wall is easy to deform, poor processing stability: most oil pump stators have thin-walled structures, poor rigidity, and are prone to elastic or plastic deformation under the action of cutting force, clamping force, residual stress and thermal stress, resulting in dimensional deviation (such as warping, drum degree) and shape change; At the same time, forced vibration and self-excited chatter are prone to occur during the machining process, which not only affects the surface quality and dimensional accuracy, but also accelerates tool wear and reduces machining stability.
3. Cumbersome process and low production efficiency: In the traditional processing mode, the rough machining, finishing, and end grinding of the stator cavity need to be completed by multiple equipment, with frequent process switching and repeated clamping and positioning, which not only increases labor costs, but also easily leads to a decrease in processing accuracy due to positioning deviation, and the processing time of a single piece is long, which cannot meet the needs of mass production; At the same time, the chip evacuation of the deep cavity structure is blocked, the chips are easy to scratch the processed surface, and the cutting heat is not easy to dissipate, which further affects the processing efficiency and quality.
4. Fast tool loss and high comprehensive cost: During the inner cavity machining process, the contact area between the tool and the workpiece is large, the cutting resistance is large, and chip removal is difficult, which can easily lead to tool wear and chipping, increasing the frequency and cost of tool replacement. At the same time, in the process of end face grinding, if the grinding wheel is improperly selected or the process parameters are unreasonable, problems such as fast grinding wheel loss and surface burning of the workpiece will occur, further increasing the comprehensive processing cost.

3.The Importance of Broaching for Internal Splines

The “broaching machine” here is mainly aimed at the internal spline in the oil pump stator that needs to be matched with the drive shaft.

• Efficient Machining of Complex Profiles: The tooth profile of the inner spline is a complex forming surface. A broach is a “combination cutter” on which the shape of a series of teeth gradually changes from the shape of a pre-machined hole to the final spline tooth shape. The broach cuts out all spline teeth efficiently and with high precision in a single linear motion, which is unmatched by other machining methods, such as shaping.
• Extremely high dimensional accuracy and consistency: The broach is a customized, high-precision forming tool that ensures that the size and tooth shape of each internal spline are highly consistent, making it ideal for large-scale production. This ensures optimal mating clearance with the drive shaft, neither too tight nor too loose to cause noise and shock.
• Excellent Surface Quality: Broaching results in smooth tooth surfaces, reducing friction and wear with the drive shaft.

Why is this important?
The inner spline is the key part of the torque transmission, and its processing quality directly determines:

• Transmission Smoothness: A spline with poor accuracy can cause rough transmission, resulting in vibration and noise.
• Reliability: Rough tooth surfaces are prone to wear and tear, which can even lead to serious failures such as broken teeth.
• Efficiency: Smooth and precise fit reduces unnecessary mechanical losses, improving the volumetric efficiency of oil pumps.

4.Equipment Selection and Configuration

Combined with the needs of oil pump stator inner cavity and end face processing, select and adapt high-speed broaching machines and precision end face grinders, with special tooling fixtures and tools to ensure the double improvement of processing accuracy and efficiency, equipment selection follows the principle of “precise adaptation, high efficiency and stability, easy operation, energy saving and environmental protection”, the specific configuration is as follows:

Face grinder selection: high-precision vertical double face grinder

The end face of the oil pump stator is the critical sealing interface. It fits snugly to the pump’s distribution pan or end cap and prevents high-pressure oil from leaking from the inside into the low-pressure zone.

• Guaranteed extremely high flatness and parallelism: this is the core value of double face grinders. It can grind two end faces at the same time, which naturally ensures the absolute parallelism of the two end faces, and the flatness of each end face itself is excellent. This is a level of craftsmanship that is difficult to achieve with single-sided grinding or turning.
• Control Precise Total Thickness: It controls the total thickness of the stator within extremely tight tolerances, ensuring that all parts are properly sized and the sealing pressure is uniform during assembly.
• Achieve Ideal Surface Texture: Grinding allows for microscopic surface topography that favors sealing.

Importance

Face seals are the lifeline of oil pumps (such as vane pumps, gear pumps).

• Prevent leakage: High-pressure oil can leak from anywhere there is a gap to the low-pressure area. If the end face is uneven or not parallel, it will lead to poor sealing and internal leakage. This is the main reason for the decrease in volumetric efficiency and low pressure construction of the oil pump.
• Guaranteed Pressure Stability: The uniform seal ensures stable output pressure.
• Reduced Wear: Good planar contact avoids localized wear and tear, extending the life of the pump.

5.Analysis of Plan Advantages and Benefits

The core advantages of the solution

1. Significant improvement in accuracy: Through the combination of high-speed precision broaching machine and high-precision end face grinder, combined with special tooling fixtures and optimized process parameters, it effectively solves the pain points such as insufficient accuracy of the inner cavity of the oil pump stator and the deviation of the parallelism of the end face, and the size tolerance of the inner cavity is controlled within ±0.01mm, the parallelism of the end face is ≤0.003mm, and the surface roughness Ra≤ is 0.8μm, which fully meets the high-precision requirements of oil pump assembly, and at the same time solves the problems of thin-walled parts deformation and thermal deformation, and the processing stability is greatly improved.
2. Doubling production efficiency: integrating broaching and grinding processes to realize one-time broaching and grinding of the inner cavity, reducing process switching and repeated clamping time, and shortening the processing time of a single piece by more than 60% compared with traditional processes; With automatic loading and unloading device, it realizes automated mass production, greatly improves production efficiency, adapts to large-scale mass production needs, and solves problems such as difficulty in chip removal and cumbersome processes, further improving processing continuity.
3. Comprehensive cost reduction: the optimization of special tools and grinding wheels reduces tool wear and replacement frequency, and reduces tool loss costs by more than 30%; The scrap rate is controlled within 1% to reduce raw material waste; Automated processing reduces manual intervention and labor costs; The application of cutting fluid filtration system extends the service life of cutting fluid, reduces the cost of consumables, and reduces the overall processing cost per unit product by 25%-40%.
4. Convenient operation and strong adaptability: the equipment adopts CNC system, simple operation, and operators can take up their posts after simple training; It can be adapted to the processing of oil pump stator of different specifications and materials, only need to adjust the process parameters and special tooling, no need to replace the equipment, strong flexibility, and the equipment has a high degree of intelligence, which can realize automatic monitoring and automatic compensation, and reduce the difficulty of operation and human error.

Benefit analysis

1. Economic benefits: Taking mass production (average daily production of 500 pieces) as an example, the processing cost of a single piece of traditional technology is about 100 yuan, and the processing cost of a single piece of this scheme can be reduced to 60-75 yuan, with an average daily cost saving of 12,500-20,000 yuan and an annual cost saving of 450-7.3 million yuan; At the same time, the production efficiency is increased by 60%, which can meet the demand for larger batches of orders, improve the production capacity and market competitiveness of enterprises, and further reduce the consumption of raw materials and processing process costs in combination with the application of precision forging blanks.
2. Quality and efficiency: the product qualification rate has been increased to more than 99%, reducing the rework and scrapping of non-conforming products, improving product reputation, and enhancing the market recognition of enterprises; High-precision processing quality can improve the volumetric efficiency and service life of oil pumps, help downstream customers improve product quality, achieve mutual benefit and win-win results, and avoid after-sales disputes and cost losses caused by insufficient product accuracy.
3. Management benefits: automated processing reduces manual intervention, reduces manual labor intensity, and reduces human operation errors; The whole process quality control system is convenient for the traceability and management of the production process, and the production management level of the enterprise is improved. Easy equipment maintenance and low failure rate reduce production downtime, ensuring a smooth production process while reducing equipment maintenance costs.

Plan Summary

This set of broaching machine and end grinding machine solutions for oil pump stator inner cavity processing aims at the core processing pain points of the industry, through precise equipment selection, optimized process flow, perfect quality control and after-sales guarantee, to achieve high-precision, high efficiency and low-cost processing of oil pump stator inner cavity and end face. The solution integrates the forming advantages of high-speed precision broaching machine and the grinding advantage of high-precision end grinding machine, combined with precision forging blank pretreatment and automatic auxiliary equipment, which effectively solves the problems of deformation, insufficient precision, low efficiency and high cost of thin-walled parts, and adapts to the mass production needs of various oil pump stators.
Compared with traditional processing solutions, this solution not only improves product processing accuracy and production efficiency, but also greatly reduces comprehensive processing costs, and improves the production management level and market competitiveness of enterprises. In the future, according to the specific stator specifications, materials and output needs of customers, we can further optimize equipment configuration and process parameters, provide customized processing solutions, help enterprises achieve refined and automated production, and promote the high-quality development of the oil pump parts processing industry.