Design Key Points and Operation Maintenance of Machine Tool Pneumatic Systems

I. Basic Composition and Working Characteristics of Pneumatic Systems

1. Core Component Units

• Air supply devices: Including air compressors (providing 0.6-0.8MPa compressed air), air storage tanks (stabilizing pressure fluctuations), dryers (reducing the air dew point to below 5°C), and filters (removing moisture, oil, and particulate impurities). The accuracy of air supply treatment directly affects the service life of downstream components.

• Control components: Regulate the on-off, pressure, and speed of air flow through solenoid valves (for reversing control), pressure valves (pressure regulating valves, safety valves), and flow valves (throttle valves). For example, 3/2-way solenoid valves are used to control the expansion and contraction of single-acting cylinders.

• Actuators: Cylinders (for linear motion) and air motors (for rotational motion). Cylinders are structurally divided into piston-type, diaphragm-type, etc., with stroke ranges from a few millimeters to several meters, and their action time is usually controlled within 0.1-1 second.

• Auxiliary components: Including air pipes (PU pipes, nylon pipes, with inner diameters of 4-20mm), connectors (quick-plug type, threaded type), mufflers (reducing exhaust noise to below 85dB), and sensors (magnetic switches for detecting cylinder positions).

2. Working Characteristics

• Pressure and flow: The working pressure is generally 0.4-0.6MPa; excessively high pressure will accelerate component wear. The flow rate determines the action speed of actuators. Stepless speed regulation can be achieved through throttle valves, but it is greatly affected by pipeline resistance.

• Response speed: Pneumatic components have small action delays (solenoid valve response time ≤10ms), making them suitable for high-frequency cyclic actions (such as workpiece loading and unloading more than 30 times per minute).

• Environmental adaptability: They have strong resistance to dust and vibration, but in low-temperature environments (below 0°C), it is necessary to prevent condensed water from freezing and blocking pipelines.

II. Design Key Points of Pneumatic Systems

1. Air Supply Configuration Principles

• Matching air supply capacity: Select the air compressor displacement according to the total air consumption of the system (sum of air consumption of each actuator × simultaneous working coefficient). The volume of the air storage tank should be 1/3-1/2 of the air compressor's exhaust volume per minute to stabilize air pressure.

• Air supply treatment accuracy: Adopt a three-stage filtration scheme - main pipeline filter (filtration accuracy 5μm), oil mist separator (removing 0.3μm oil droplets), and precision filter (filtering 0.01μm particles) to ensure that the cleanliness of air entering solenoid valves meets ISO 8573-1 Class 2.

• Pipeline layout design: The main pipeline should have a slope of 1:500 along the air flow direction, with a drain valve set at the lowest point. The length of branch pipelines should be as short as possible to avoid excessive pressure loss (pressure loss per 10 meters of pipeline ≤0.02MPa).

2. Component Selection and Parameter Setting

• Cylinder selection: Calculate the required thrust according to the load size (F=P×A, where A is the effective area of the piston), with a safety factor of 1.5-2.0. A 10-20mm buffer margin should be reserved for the stroke to prevent the piston from directly impacting the cylinder head.

• Solenoid valve selection: Choose the number of valve positions according to the complexity of the control circuit (e.g., 5/3-way valves for bidirectional control of double-acting cylinders). The response time should match the action rhythm of the actuator. For high-frequency action scenarios, high-frequency solenoid valves (operating frequency ≥10Hz) should be selected.

• Pressure regulation: Set graded pressures for different load requirements. For example, 0.3MPa for light workpiece clamping and 0.5MPa for heavy workpieces to reduce unnecessary energy consumption.

III. Common Problems and Causes of Pneumatic Systems

1. Performance Degradation Manifestations

• Insufficient pressure: Normal air supply pressure but insufficient output force of actuators may be caused by pipeline leakage (loose connectors, aging air pipes), filter blockage (pressure difference exceeding 0.1MPa), or pressure reducing valve failure.

• Slow action: Slow expansion and contraction of cylinders are mostly caused by insufficient flow (insufficient throttle valve opening, too small pipeline inner diameter), worn seals (air leakage exceeding 0.5L/min), or poor lubrication (increased friction resistance).

• Noise and vibration: Excessive exhaust noise may be due to blocked or missing mufflers; pipeline vibration is mostly caused by air flow pulsation (unstable air compressor output) or loose pipe clamps.

2. Component Damage Types

• Solenoid valve jamming: Impurities entering the valve core or drying of lubricating grease cause commutation failure, manifested as incomplete cylinder action or no action.

• Cylinder air leakage: Wear of piston seals (normal service life is 1 million cycles) and scratches on the cylinder barrel inner wall can lead to internal leakage; external leakage at the piston rod is mostly due to damage to the dust seal.

• Sensor failure: Offset or weakened magnetism of magnetic switches can cause false signals; excessive environmental dust can also affect detection reliability.

IV. Maintenance and Optimization Measures for Pneumatic Systems

1. Daily Maintenance Points

• Air supply monitoring: Check the air compressor pressure (maintained at 0.6-0.8MPa) and dryer dew point (display ≤5°C) daily; manually drain water (at the bottom of air storage tanks and filters) weekly, and increase the frequency in rainy seasons.

• Component inspection: Observe whether the cylinder piston rod has scratches or deformation; check whether the exhaust port of the solenoid valve has continuous air leakage (no obvious air flow sound should be heard under normal conditions); check whether the muffler is blocked (judge exhaust smoothness by hand feel).

• Lubrication management: No additional oil supply is needed for oil-free lubrication components (such as food-grade cylinders); for components requiring lubrication (such as ordinary solenoid valves), add special pneumatic lubricating oil (ISO VG32) through an oil mist lubricator, with the oil drop rate controlled at 1-3 drops/minute.

2. Regular Maintenance Items

• Filter element replacement: Replace the main filter element every 3 months and the precision filter element every 6 months; shorten the cycle when the environmental dust is heavy.

• Seal replacement: Replace the cylinder piston rod seal every 1-2 years; check the solenoid valve core seal regularly according to the action frequency (check every six months for high-frequency use).

• Pipeline maintenance: Inspect air pipe aging (such as cracks, hardening) every year; prefer spiral pipes when replacing pipes longer than 5 meters to reduce vibration transmission; tighten connectors according to specified torque (usually 4-6N·m) to prevent thread damage due to over-tightening.

3. System Optimization Directions

• Energy-saving transformation: Cut off the air supply through solenoid valves during non-working hours; install pressure sensors to realize on-demand air supply, which can reduce energy consumption by 15%-20%.

• Pressure grading: Adopt independent pressure regulating valves for different load areas. For example, 0.3MPa for tool cooling and 0.5MPa for workpiece clamping to avoid high-pressure air waste.

• Intelligent monitoring: Install pressure transmitters and flow sensors at key nodes; monitor abnormal fluctuations (such as pressure drop exceeding 0.1MPa) through the PLC system, which can automatically alarm and cut off the air supply.