CNC machining centers usually require compressed air its role runs through different links in the processing process, and is a key factor to ensure the normal operation of equipment and improve processing accuracy and efficiency. The following is a specific analysis:
main Uses of 1. Compressed Air in CNC Machining Centers
- spindle cooling and purging
- spindle cooling: The high-speed rotating spindle (the speed can reach thousands to tens of thousands of revolutions per minute) will generate a lot of heat. The compressed air passes through the cooling channel inside the spindle to take away the heat to prevent the spindle from thermal deformation or damage due to overheating, thereby ensuring Processing accuracy.
- Chip purging: The chips (such as metal chips and dust) generated during the machining process will adhere to the surface of the workpiece or tool, affecting the machining quality. Compressed air blows the chips away from the processing area through the nozzle to prevent the chips from scratching the surface of the workpiece or blocking the tool, while reducing tool wear.
- Pneumatic component drive
- pneumatic clamp CNC machining centers often use pneumatic clamps to fix the workpiece, and compressed air drives the clamping and loosening of the clamps through the cylinder to achieve fast and reliable workpiece positioning.
- Pneumatic tool changer in the automatic tool change system (ATC), compressed air is used to drive the rotation of the tool magazine and the grasping and releasing of the tool to ensure the efficient and accurate tool change process.
- Pneumatic spindle loose cutter: The spindle of some machining centers realizes the automatic tightening of the tool through compressed air, simplifying the tool change process.
- Machine Tool Protection and Cleaning
- protective door seal: Compressed air is used to drive the sealing strip of the protective door to prevent chips or coolant from entering the inside of the machine tool and protect precision parts.
- Machine internal cleaning: Regularly use compressed air to purge the inside of the machine tool (such as guide rails, lead screws, transmission parts) to remove dust and chips and extend the life of the equipment.
- Coolant atomization and transportation
- coolant atomization: Some machining centers mix compressed air with coolant to form atomized coolant, which improves the cooling effect and reduces the amount of coolant.
- Coolant delivery: Compressed air can drive the coolant pump to realize the circulating transportation of the coolant.
Quality requirements for 2. compressed air
to ensure stable operation of the CNC machining center, the compressed air must meet the following quality standards:
- pressure stability
- the compressed air pressure needs to be stabilized within the range required by the equipment (usually 0.5-0.8 MPa), and the pressure fluctuation is too high to affect the accuracy of the pneumatic components and even cause equipment failure.
- Oil content
- oil hazard: The oil in the compressed air (from the air compressor lubricating oil) will pollute the surface of the workpiece, the coolant and the inside of the machine tool, resulting in a decrease in machining accuracy, shortened tool life, and even electrical failure.
- Standard requirements: The oil content needs to be controlled at a very low level (usually ≤ 0.01 mg/m & sup3;) through precision filters, and some high-precision machining centers are required to reach Class 0 (oil content ≤ 0.001 mg/m & sup3;).
- Moisture content
- moisture hazard the moisture in the compressed air will corrode the pneumatic components, cause the pipeline to freeze (low temperature environment), and affect the emulsification effect of the coolant.
- Standard requirements: The dew point temperature should be controlled below -20 ℃ to -40 ℃ through a dryer (such as refrigeration type and adsorption type) to ensure air drying.
- Particulate matter
- particulate Hazards: dust, iron filings and other particles in the air will wear pneumatic components, block the nozzle, affecting the processing quality.
- Standard requirements: The particle size needs to be controlled below 1μm through the filter.
3. the Dependence of Different Types of CNC Machining Centers on Compressed Air
- economical machining center
- degree of dependence: Medium. Usually equipped with basic pneumatic clamps and spindle cooling function, the quality of compressed air in general.
- Typical applications: small parts processing, mold roughing.
- High precision machining center
- degree of dependence: high. Need to use precision pneumatic fixture, high-speed spindle cooling and efficient chip blowing, the pressure stability of compressed air, oil content, water content strict requirements.
- Typical applications: Aerospace parts, optical components processing.
- Five-axis machining center
- degree of dependence: Extremely high. Complex surface machining requires precise control of tool posture, the response speed and stability of pneumatic components directly affect the machining accuracy, and the quality requirements of compressed air are almost harsh.
- Typical applications: impeller, turbine blade processing.
Recommendations for the configuration of 4. compressed air supply systems
- selection of air compressor
- type according to the requirements of the machining center, screw or piston air compressor is selected, and oil-free or micro-oil type is preferred (if high cleanliness air is required).
- Power: Calculate the total demand according to the number of processing centers and gas consumption, and reserve 20%-30% allowance.
- Post-processing equipment
- dryer: Equipped with refrigeration or adsorption dryer to ensure that the dew point temperature meets the standard.
- Filter: Multi-stage filtration (coarse filtration, fine filtration, activated carbon filtration) is adopted to gradually remove particulate matter, oil and peculiar smell.
- Gas tank: Buffer pressure fluctuation to reduce frequent start and stop of air compressor.
- Pipeline Design
- material: Give priority to stainless steel pipe or aluminum-plastic pipe to avoid corrosion and air pollution.
- Layout: Shorten the length of the pipeline, reduce the elbow and reduce the pressure loss.
- Drainage: Set automatic drain valve at the low point of the pipeline to discharge condensate regularly.
