Automotive Screw Production Line Solutions

Car lead screws are the core components of the vehicle transmission system, and their accuracy and quality directly affect the handling performance and safety of the vehicle. This solution aims to create a automotive lead screw production line that takes into account high precision and efficiency. Through optimization of process flow, precise equipment selection, strict quality control and other measures, it can achieve efficient production of the entire process from raw materials to finished products, ensuring that the products meet the strict standards of the automotive industry.

Screws Production Process

1. Raw material pretreatment

40Cr, 42CrMo and other alloy structural steels that meet GB/T 3077 standards are selected as production raw materials. The chemical composition is fully tested using a direct-read spectrometer to ensure that the content of key elements such as carbon, chromium, molybdenum meets the standards; a universal material testing machine is used to complete mechanical properties such as tensile and impact, and verify material strength and toughness indicators.

The straightening process is carried out through a high-precision hydraulic straightening machine, and the linearity error of the raw material is strictly controlled within 0.05mm/m, effectively reducing the risk of subsequent processing deformation.

2. Turning processing

• Rough processing: Use a high-precision CNC lathe equipped with FANUC 31i – MB5 CNC system, equipped with coated carbide tools, and efficient rough processing is carried out at a cutting speed of 150 – 200m/min and a feed capacity of 0.3 – 0.5mm/r, which reserves a single-sided 0.8 – 1.2mm processing allowance for subsequent finishing, and quickly removes most materials.
• Precision machining: Use a precision CNC lathe equipped with an online laser measurement system. By optimizing cutting parameters (cutting speed 80 – 120m/min, feeding amount 0.08 – 0.15mm/r), real-time monitoring and dynamic compensation of external circle dimensions are achieved, ensuring that the dimensional tolerance is controlled within ±0.008mm and the surface roughness Ra≤1.6μm.

3. Thread Processing

• Wire rolling molding: Use a planetary wire rolling machine for thread processing, and achieve high-precision thread cold forming by accurately controlling the phase, rolling pressure and rotation speed of the wire rolling wheel. The pitch error can be controlled to ±0.003mm and the half-angle error of the tooth type is less than ±5′, while the surface hardness of the thread is increased by 15-20%, significantly improving the thread strength and wear resistance.
• Milling machining: For large-lead, non-standard-specific threads, a five-axis linkage machining center is adopted, combined with a special thread milling cutter and CAM programming system, to achieve high-precision machining of complex threads, with machining accuracy up to IT5-IT6 levels, meeting special customized production needs.

4. Heat treatment process

• Quenching and tempering treatment: Place the workpiece in a vacuum quenching furnace, heat it to 840 – 860℃ for 1 – 1.5 hours, and then use oil quench to quickly cool it; the tempering process is insulated in the temperature range of 550 – 650℃ for 2 – 3 hours. By precisely controlling the heat treatment process parameters, the hardness of the workpiece reaches HRC48 – 52, and obtains good comprehensive mechanical properties.
• Aging treatment process: In order to eliminate processing stress, the workpiece is placed in an aging furnace, and then slowly cooled after 24 hours of insulation at a temperature of 180-200℃, effectively stabilize the internal structure of the workpiece, ensure long-term stability of dimensional accuracy, and reduce the probability of subsequent processing deformation.

5. Grinding processing

• External cylindrical grinding: Use a high-precision cylindrical grinding machine equipped with CBN superhard grinding wheel and an online automatic compensation system. The composite process of cutting grinding and longitudinal grinding is used to achieve high-precision processing of the outer cylindrical dimensions. The dimensional tolerance is controlled at ±0.003mm and the surface roughness Ra≤0.8μm.
• Thread grinding: For high-precision lead screws, professional thread grinders are used for processing, and high-precision pitch error compensation technology is used to precisely grind key parameters such as thread middle diameter, pitch, and tooth type to ensure that the thread middle diameter tolerance reaches ±0.002mm, significantly improving the thread transmission accuracy.

6. Surface treatment

According to the needs of automotive application scenarios, surface treatment processes such as chrome plating, nickel plating or blackening can be selected. Taking the chrome plating process as an example, an electrolytic deposition is used to form a chrome plating layer of 0.02 – 0.05mm thick on the surface of the workpiece, which effectively improves surface hardness, wear resistance and corrosion resistance, and meets the requirements of the complex use environment of the automobile.

7. Inspection and Packaging

• Quality inspection: The German Zeiss three-coordinate measuring instrument is used for full-size inspection, the thread parameters are accurately measured using a thread comprehensive measuring instrument, and the material performance and microstructure analysis is completed through a hardness meter and a metallographic microscope to ensure that the product 100% meets the quality standards.
• Protective packaging: After ultrasonic cleaning and hot air drying of qualified products, anti-rust paper and PE plastic film are used for multi-layer protective packaging, then put into customized cartons or wooden boxes, and place desiccants to ensure that the product is not damaged during transportation and storage.

Equipment Selection

Screw Process Route

Nut process route

Screw OP10 turning and milling composite

Single-piece beat approximate: screw rod 400S, nut 450S

The CX200 dual-spindle double-cutting frame turning and milling composite machine tool adopts a dual-spindle layout, arranged relatively, and the two sets of turrets are arranged up and down, and the upper turret has a Y-axis. Machine tool unique
The special dual-channel control system can realize the coordinated processing of dual spindles and dual turret towers. The sub-spindle connects the spindle to clamp the workpiece, continues to process the clamping end, and completes all processing steps of the workpiece.

Screw OP30 Whirling Machine

Mainly used for milling various cylindrical worms and lead screws in industries such as automobiles (steering systems, parking and braking systems), reducers, etc.

• Machining module: 2.5M (MAX)
• Machining diameter: 10 – 60mm
• Processing length: 400mm (Raw material length 500mm)
• Total weight: 4.5T
• Machine dimension: 2.5M3M2.3M (LMH)

Screw OP40 Thread Grinder Machine

Mainly used for grinding various cylindrical worms and lead screws in industries such as automobiles (steering systems, parking and braking systems), reducers, etc.

• Grinding wheel size: W 10 – 40mm/ OD 280 – 400mm
• Machine diameter: 10 – 200mm
• Machining length: 400mm
• Helix angle range: ± 45°
• Total weight: 5.5T
• Machine dimension: 2M * 3.2M * 1.8M (L * W * H)

Nut OP30 Hard lathe Machine

Single-piece beat: 300S (inner raceway + outer diameter)

Nut OP40 Thread Grinder Machine

Technical Parameters

• Grinding diameter: 10 – 100 mm
• Grinding length: ≤150 mm
• Helix angle: 0 – 25°
• Application: High – precision grinding of internal threads such as lead screw nuts, thread rings, etc.

Operational Details

• Loading/Unloading method: Manual/Gantry robot
• Clamping method: Chuck
• Workpiece rotation: DD motor direct drive
• Dressing method: Online dressing, online compensation
• Rotation axis resolution: ≤0.0001°
• Linear axis resolution: ≤0.0001 mm
• Rotation axis repeat positioning accuracy: ≤3″
• Linear axis repeat positioning accuracy: 0.001 mm
• Grinding electric spindle: 7.5 kW, 24000/36000/50000 rpm

Summary

UBright Solutions delivers comprehensive production line solutions for automotive lead screws, the core components of vehicle transmission systems. Starting from premium 40Cr and 42CrMo alloy steel preprocessing, our advanced manufacturing process includes high-precision CNC turning, planetary thread rolling, vacuum quenching and tempering, and CBN superhard grinding wheel processing. Achieving thread accuracy of ±0.003mm and surface roughness Ra≤0.8μm, our solution features dual-spindle turning-milling composites, whirling machines, and thread grinders to ensure IT5-IT6 precision levels. This complete solution meets the stringent quality standards and safety requirements of the automotive industry through optimized process flow and strict quality control.