From Basics to Applications: A Complete Guide to Turned Parts

1. Basic definition and core principle of turned parts: “rotational molder” in the manufacturing industry

Are you curious about how those precise rotating parts in machinery are created? In fact, the answer is turned parts – rotating body parts that are rotated and cut on a lathe through the principle of turning (a typical material removal process, which belongs to the category of subtractive manufacturing). To put it simply, it’s like cutting an apple with a knife, except that the processing of the turned parts is more precise and systematic.

The working principle of the lathe is the core of the turning process: the workpiece is fixed on the spindle by chuck and rotates at high speed with the spindle; The cutting tool mounted on the tool holder moves according to a preset path, gradually removing excess material from the workpiece, and finally forming a part that meets the design requirements. As the basic parts of the manufacturing industry and the core component of machining, the quality of the turned parts directly determines the performance of the end product, from the watch gear to the crankshaft of the automobile engine, which is inseparable from its support.

2. The main types and product forms of turned parts: classified according to “shape” to accurately match the needs

Turned parts come in a variety of forms, but can be divided into six categories based on structural characteristics, each with its typical application scenarios, helping you quickly identify and select:

1. Shaft parts: the “backbone” of mechanical transmission

Shaft parts are the most common type of turned parts and are mainly used to transmit torque and support other components, including optical shafts (smooth surfaces for simple transmission), step shafts (different segments have different diameters, suitable for complex assemblies), and eccentric shafts (shafts offset from the center of gravity to generate reciprocating motion, such as engine camshafts). For example, the stepped shaft in a car gearbox realizes gear positioning and power transmission through shaft segments of different diameters, and the tolerance is controlled within ±0.02mm.

2. Sleeve Parts: The Guardian of Precise Positioning

The common ones include bearing sleeves (protecting bearings and reducing wear), bushings (reducing friction on mating surfaces) and cylinder liners (core components of engine cylinders, which withstand high temperature and pressure). Taking the bearing sleeve in construction machinery as an example, it is made of stainless steel, and the surface finish of the inner wall needs to reach Ra0.8μm to ensure the smooth operation of the bearing.

3. Pan cover parts: the “key link” that connects and seals

Disc cover parts are disc-shaped and are mostly used to fix, seal, or transmit power, including flanges (the core components of pipe or equipment connections), end caps (sealing equipment cavities to prevent impurities from entering), and pulleys (transmitting power through belts). The flange in a wind power equipment has a diameter of 1.2 meters, and the flatness error needs to be ensured by multiple turning processes to ensure a flatness error of ≤0.03mm to ensure a tight connection with the tower.

4. Threaded Turned Parts: The “Core Component” of Fastening and Transmission

Threaded turned parts achieve fastening or transmission functions by machining external threads (such as bolts) or internal threads (such as nuts), and common products include screws (which convert rotational motion into linear motion, such as ball screws of machine tools), bolts (basic elements of mechanical connections). The pitch error of the high-precision screw needs to be controlled within 0.01mm/m to meet the feed requirements of precision machine tools.

5. Precision Turned Parts: The “Precision Dancer” in the Tiny Field

Precision turned parts focus on high precision and small size, and are commonly used in watch parts (such as gears, watch shafts), medical components (such as surgical instrument tips, implants) and other fields. For example, the tiny shaft parts in a minimally invasive surgical instrument have a diameter of only 0.8mm, a length of 5mm, and a tolerance requirement of ±0.005mm, which can only be achieved by using a Swiss lathe.

6. Non-standard turned parts: the “solution” for customized needs

Non-standard turned parts (also known as custom turned parts) are special-shaped parts designed for special scenarios, there is no unified standard, and they need to be customized according to customer drawings. For example, the special-shaped connection shaft in an automation equipment is designed into an L-shaped structure due to limited installation space, and is formed through multi-axis turning at one time, which solves the problem that traditional standard parts cannot be adapted.

3. Turning parts processing technology and technology: the evolution from tradition to intelligence

The turning process is constantly iterating, from traditional manual lathes to modern automation equipment, the precision and efficiency have been greatly improved, the following is a core process and technology analysis:

1. Comparison of mainstream processing methods

2. Core processing process steps

Turning operations typically follow the “roughing – finishing – auxiliary machining” process:

1. Rough turning: quickly remove most of the excess materials, improve processing efficiency, and leave 0.5~1mm processing allowance;
2. Precision turning: precise cutting to ensure dimensional accuracy and surface finish, which is the key process that determines the quality of parts;
3. Grooving/Cutting: Grooving on the surface of the part (such as ejector grooving) or cutting the workpiece according to the needs to complete the forming.

3. Cutting-edge processing technology

• High-speed turning: The cutting speed exceeds that of traditional turning by 3~5 times, greatly improving efficiency, and is suitable for easy-to-cut materials such as aluminum alloy and copper.
• Hard turning: Direct cutting hardened steel with a hardness > HRC55, eliminating the need for subsequent grinding and reducing machining costs;
• Dry turning: does not use cutting fluid, is environmentally friendly and pollution-free, suitable for stainless steel, cast iron and other materials, and needs to be equipped with special tools.

4. Material Science and Application of Turned Parts: Selecting the Right Material to Determine the “Life” of the Part

Material selection is the prerequisite for the processing of turned parts, and the mechanical properties, corrosion resistance, and machinability of different materials vary significantly, which need to be accurately matched according to the application scenario:

1. Metal Turned Parts: The mainstream choice with stable performance

• Steel turned parts: high strength and good toughness, suitable for mechanical structural parts, such as gears and shafts;
• Stainless steel turned parts: strong corrosion resistance, often used in medical and food machinery, such as surgical instruments and valves;
• Aluminum turning parts: lightweight, good thermal conductivity, suitable for electronic equipment and auto parts;
• Copper and copper alloy turned parts (such as brass, bronze): excellent conductivity and wear resistance, used for electrical joints and valve cores;
• Titanium alloy turned parts, superalloy turned parts: high temperature and high pressure resistance, suitable for aerospace and military fields, such as aircraft landing gear components.

2. Plastic Turned Parts: Lightweight, low-cost supplement

Plastic turned parts are mainly used in low-load, corrosion-resistant scenarios, common materials include POM (polyoxymethylene, high hardness, good wear resistance), nylon (strong toughness, impact resistance), PTFE (polytetrafluoroethylene, excellent corrosion resistance), suitable for gears, bearings, seals, etc.

3. Material selection guide

1. Prioritize mechanical properties: select materials with matching strength and hardness according to the load and rotational speed of the parts;
2. Focus on corrosion resistance: In humid and acid-alkali environments, give preference to stainless steel, PTFE and other materials;
3. Take into account machinability: easy cutting steel and aluminum alloy processing efficiency is high and the cost is low; Titanium alloys and superalloys are difficult to process and require special tools and processes.

5. Quality control and testing of turned parts: from “qualified” to “high-quality” guarantee

The accuracy of the turned parts directly affects the reliability of the end product, so quality control is crucial, and the core testing links and standards are as follows:

1. Core testing items

• Dimensional inspection: Measure key dimensions such as diameter, length, and pitch of parts to ensure they meet design requirements.
• Geometric tolerance measurement: including roundness, cylindricality, coaxiality, etc., such as the roundness error of shaft parts should be ≤ 0.005mm;
• Surface Roughness Detection: Ra values (arithmetic mean deviation) are measured by a profiler, and precision parts typically require Ra ≤ 0.8μm;
• Non-destructive testing: For important parts, ultrasonic and X-ray are used to detect internal defects.

2. Mainstream testing equipment

• Two-dimensional image measuring instrument: suitable for rapid measurement of plane size and shape and position tolerance, with an accuracy of 0.001mm;
• Coordinate measuring machine (CMM): It measures the three-dimensional dimensions and tolerances of complex parts in all directions, and is the core equipment for high-precision inspection;
• Hardness tester: Detects the hardness of materials to ensure that mechanical properties meet standards.

3. Quality control processes and standards

• Process: first article inspection (confirm that the parts are qualified before mass production), → process inspection (random sampling testing during processing), → final inspection (comprehensive inspection of finished products);
• Standards: Comply with ISO 9001 general quality standards, IATF 16949 for the automotive industry, and ISO 13485 for the medical industry.

6. Applications and cases in the turning parts industry: penetrate the core components of all walks of life

As basic mechanical parts, turned parts have been widely used in five core areas, the following are typical cases:

1. Automotive industry: the core support of power and transmission

Automotive industry turning parts cover engine parts (such as crankshafts, camshafts), transmission parts (such as gearbox gearshafts), oil nozzles, etc. The crankshaft of a car company’s 1.5T engine is processed with 42CrMo alloy steel, and is formed at one time through multi-axis turning-milling composite processing, with a spindle journal roundness error of ≤ 0.003mm, ensuring smooth engine operation and reducing fuel consumption by 0.3L per 100 kilometers.

2. Aerospace: Reliable protection for extreme environments

Aerospace turned parts are extremely demanding, such as landing gear components and aviation fasteners, which are subjected to high temperatures, high pressures, and severe vibrations. The hydraulic joints of the landing gear of a civil airliner are processed with titanium alloy, with a compressive strength of 35MPa, and have been tested for 100,000 fatigue tests without damage, meeting the aerospace EN 9100 quality standard.

3. Medical devices: the dual requirements of precision and safety

Medical device turning parts include surgical instruments (such as laparoscopic puncture needles), implants (such as artificial joint shafts), and endoscopic parts. The tip of the puncture needle of a minimally invasive surgical instrument is precision turned by stainless steel, with a diameter of 0.3mm and a sharpness error of ≤ 0.01mm, ensuring that the surgical trauma is small and the precision is high.

4. Electronic devices: lightweight and miniaturization

Electronic equipment turning parts focus on small and precise parts, such as connectors, heat sinks, and interface components. The charging interface terminal of a smartphone is brass turned, nickel plated on the surface, with a plugging life of more than 100,000 times and a contact resistance of ≤ 50mΩ.

5. Hydraulic and pneumatic systems: the key to sealing and transmission

Hydraulic and pneumatic system turning parts such as joints, valve spools, and pistons need to ensure sealing performance and movement accuracy. The spool of an industrial hydraulic valve is processed with stainless steel and a clearance ≤ of 0.005mm to ensure that the hydraulic system has no leakage and a response speed of ≤ 0.05s.

7. Yigu Technology’s view

As the basic core parts of the manufacturing industry, the technological iteration of turning parts is closely related to the development of the industry. In the future, with the advancement of Industry 4.0, the integration of CNC turning with automation and intelligent technology will become the mainstream, with high precision, high efficiency, and green (such as dry turning) as the core development direction. For enterprises, choosing the right processing technology, accurately matching materials and application scenarios, and strictly implementing quality control standards are the keys to enhancing product competitiveness. For purchasers, an in-depth understanding of the type, process and testing requirements of turned parts can better screen suppliers to ensure that the parts meet the needs of the end product.

8. FAQ: FAQ

1. Q: What is the core difference between turned and milled parts?

Answer: Turning parts are workpiece rotation, tool fixed (or moving), mainly processing rotating body parts; Milled parts are tools rotating and workpiece movements, mainly processing non-rotating body parts such as planes and grooves.

2. Q: How accurate can precision turned parts be achieved?

A: The tolerance of ordinary precision turned parts can be controlled at ±0.005mm, and the tolerance of small parts for Swiss turning can reach ±0.002mm, meeting the needs of high-precision scenarios such as medical and electronics.

3. Q: How do I choose the material for my turned parts?

Answer: First, clarify the working environment (temperature, humidity, medium), load and accuracy requirements of the parts, and then combine the mechanical properties, corrosion resistance and machinability of the material to select, and consult professional engineers if necessary.

4. Q: What is the impact of the surface roughness of the turned part on use?

Answer: Surface roughness directly affects the wear resistance, sealing and fit accuracy of parts, such as too low roughness of the inner wall of the bearing sleeve (too large Ra value) will aggravate bearing wear, and too high may affect the lubrication effect.