The machining center (CNC machining center) relies on compressed air in many key links, and its role covers cleaning, cooling, driving, chip removal and safety protection. The following are the detailed locations and specific application scenarios that require the use of compressed air in the machining center:
1. spindle and tool system
- Spindle internal blowing (Spindle Air Blow)
- role: In the process of tool replacement or machining, compressed air is blown to the tool through the center hole of the spindle to prevent chips, coolant or impurities from entering the spindle taper hole and avoid damage to the spindle or tool.
- Application Scenarios:
- tool replacement: blow the spindle taper hole and handle to ensure clamping accuracy.
- When machining high-precision holes or curved surfaces: Prevent surface scratches caused by chip residues.
- Pressure requirements: usually 0.4 ~ 0.6MPa, need to be equipped with precision filter (filtration accuracy 0.01μm) to avoid oil pollution of spindle bearings.
- Tool cooling and chip removal
- role: Spray compressed air to the cutting area through the nozzle to assist in cooling the tool and blow away the chips to prevent the chips from winding around the tool or scratching the surface of the workpiece.
- Application Scenarios:
- drilling, milling and other large cutting: to avoid chip accumulation caused by overheating or cutting tool.
- When machining soft metals (such as aluminum and copper): prevent chips from adhering to the tool or workpiece.
- Optimization recommendations:
- the nozzle angle should be aligned with the cutting area to avoid deformation caused by direct blowing to the workpiece.
- Can be combined with micro-lubrication (MQL) technology to reduce the amount of coolant used.
2. automatic tool changer (ATC)
- tool magazine cleaning and lubrication
- role: When changing tools in the tool magazine, use compressed air to blow off the chips and oil on the tool sleeve and handle to ensure smooth tool change.
- Application Scenarios:
- disc type tool magazine: each tool sleeve shall be equipped with an independent air blowing port.
- Chain tool magazine: centralized gas supply through pipelines, and regular purging of chains and tool sleeves.
- Pressure requirements: 0.3 ~ 0.5MPa oil-water separator shall be equipped to prevent lubricating oil from polluting the tool magazine.
- Tool changing arm drive
- role the tool changing arm of some machining centers adopts pneumatic drive, and the piston is pushed by compressed air to complete the action of grasping and loosening the knife.
- Application Scenarios:
- high-speed machining center: pneumatic tool change faster (usually <2 seconds), suitable for frequent tool change scenarios.
- Heavy machining center: need to cooperate with hydraulic buffer device to avoid pneumatic impact damage to mechanical structure.
- Precautions:
- A pressure regulating valve shall be equipped to control the stability of air pressure to prevent abnormal action of the tool changing arm.
- Regularly check the air tightness of the cylinder to avoid the failure of tool change caused by air leakage.
3. table and fixture system
- pneumatic clamp fixing
- role: The cylinder drives the clamp to clamp or loosen the workpiece to realize fast positioning and clamping.
- Application Scenarios:
- batch processing: pneumatic clamps can shorten the clamping time (such as from 5 minutes drop 1 minute).
- Flexible manufacturing system (FMS): with automated loading and unloading device, to achieve unmanned production.
- Pressure requirements: 0.5 ~ 0.7MPa A pressure switch is required to monitor the clamping force to avoid loosening or deformation of the workpiece.
- Bench cleaning
- role: Use compressed air to blow off the chips and coolant on the surface of the worktable to prevent impurities from entering the guide rail or screw and affecting the machining accuracy.
- Application Scenarios:
- after the processing is completed: automatic purge workbench to reduce manual cleaning time.
- Before precision machining: remove tiny particles to avoid scratching the surface of the workpiece.
- Optimization recommendations:
- equipped with dust suction device, linked with the blowing system to achieve chip recovery.
- Avoid blowing directly to the guide rail to prevent the lubricating oil from being blown away.
4. chip removal and cooling system
- chip removal machine drive
- role: The chain plate or scraper type chip conveyor is driven by compressed air to transport chips from the processing area to the chip collection box.
- Application Scenarios:
- when a large number of chips are generated (e. g. milling, turning): Avoid chip accumulation blocking the machining area.
- Unmanned production: the chip removal machine needs to be linked with the machining center to realize automatic chip removal.
- Pressure requirements: 0.4 ~ 0.6MPa, need to be equipped with flow control valve to control the chip removal speed.
- Coolant atomization cooling
- role: Compressed air and coolant are mixed to form an atomized airflow and spray it to the cutting area to enhance the cooling effect and reduce the amount of coolant.
- Application Scenarios:
- high speed machining (speed >10,000rpm): The traditional cooling method is difficult to penetrate the cutting zone, and atomized cooling can significantly reduce the tool temperature.
- Difficult to machine materials (such as titanium alloy, high temperature alloy): need to strengthen cooling to prevent tool overheating.
- Optimization recommendations:
- adjust the gas-liquid ratio (usually 1:5 to 1:10) to avoid waste of coolant.
- Equipped with oil-water separator to prevent blockage of atomization device.
5. protection and safety devices
- aerodynamic locking of protective door
- role when the machining center is running, use compressed air to drive the cylinder to lock the protective door to prevent personnel from misoperation and cause safety accidents.
- Application Scenarios:
- high-speed machining or five-axis machining: ensure that the protective door is completely closed to avoid chip splashing and injury.
- Comply with CE safety standards: When the protective door is not locked, the machining center cannot be started.
- Pressure requirements: 0.6 ~ 0.8MPa, need to be equipped with double electric control solenoid valve to achieve interlocking function.
- Emergency stop auxiliary
- role: In an emergency, compressed air can drive the pneumatic brake to quickly stop the spindle or worktable movement, shortening the braking distance.
- Application Scenarios:
- spindle speed >20,000rpm when: Traditional mechanical braking may cause equipment damage due to inertia, and pneumatic braking is safer.
- Heavy machining center: need to cooperate with hydraulic buffer device to avoid excessive brake impact.
- Precautions:
- it is necessary to regularly check the sealing of the pneumatic brake to prevent air leakage from causing brake failure.
- The braking air pressure shall be matched with the spindle speed to avoid excessive or slow braking.
6. other accessibility features
- pneumatic measuring device
- role: Pneumatic probe driven by compressed air to measure workpiece size or position accuracy.
- Application Scenarios:
- on-machine measurement (On-Machine Measurement): real-time detection of workpiece size during processing to avoid secondary clamping errors.
- Automatic production line: cooperate with robots to realize automatic sorting of workpieces.
- Pressure requirements: 0.3 ~ 0.5MPa A precision pressure regulating valve is required to ensure measurement stability.
- Pneumatic lubrication system
- role: Compressed air and lubricating oil are mixed to form pneumatic lubricating oil mist to lubricate moving parts such as guide rails and lead screws.
- Application Scenarios:
- high-speed machining center: Traditional grease lubrication is difficult to meet the needs of high-speed movement. Pneumatic lubrication can reduce friction and extend life.
- Clean workshop: pneumatic lubrication can avoid grease pollution of the environment.
- Optimization recommendations:
- adjust the oil mist concentration (usually 1:100~1:500) to avoid insufficient or excessive lubrication.
- Equipped with an oil mist separator to prevent oil mist from entering the processing area.
7. compressed air quality requirements
the machining center requires high quality of compressed air and must meet the following standards:
| parameters | requirements | impact |
|---|
| pressure | 0.3 ~ 0.8MPa(Adjusted according to application) | insufficient pressure can cause the pneumatic device to slow or fail. |
| Oil content | ≤0.01mg/m³(Oil-free compressor) | oil will contaminate the spindle bearing, tool magazine or workpiece surface |
| moisture content | dew point ≤-40 ℃(After dryer treatment) | moisture can cause corrosion or icing of pneumatic components |
| granularity | ≤ 0.01μm(after filtration by precision filter) | particles can wear cylinder seals or block nozzles |
**Summary
A wide range of compressed air locations are required in the machining center, covering the spindle, tool changer, workbench, chip removal system, protective devices and auxiliary functions. In order to ensure the processing accuracy and equipment life, it is necessary to strictly control the pressure, cleanliness and dryness of compressed air, and regularly maintain pneumatic components (such as cylinders, solenoid valves, nozzles, etc.). It is suggested that the compressed air system should be customized according to the model and processing requirements of the machining center, and equipped with pressure monitoring and alarm devices to achieve stable operation.
