When the mechanical power press slips, it is necessary to immediately stop the machine for inspection. By investigating issues such as friction component wear, abnormal lubrication status, clutch/brake failure, or load overload, targeted adjustments or replacement of components can be made to restore power transmission efficiency. As the core equipment in metal processing, the slipping phenomenon of mechanical power press (such as flywheel idling and slow slider movement) will directly affect the machining accuracy and equipment life. It needs to be systematically analyzed from three dimensions: power transmission, friction control, and load management. The following are specific solutions:
The power transmission of mechanical power presss relies on the close contact of friction pairs, such as flywheels and clutches, sliders and guide rails. If the friction surface experiences wear, oil stains, or surface hardening due to long-term use, it can lead to a decrease in friction coefficient and cause slippage.
The clutch is a key component for power transmission in mechanical power presss, and the wear of its friction plates can lead to the failure of power transmission between the flywheel and the crankshaft. It is necessary to regularly check the thickness of the friction plate (usually replaced when it is ≤ 2mm) and clean the oil stains on the surface of the friction plate. When replacing, it is necessary to use friction plates that are consistent with the original specifications (such as paper-based, semi metallic, or ceramic materials) to ensure that the friction coefficient matches.
The brake is used to control the stop position of the slider. If the friction disc is worn or the brake spring pressure is insufficient, it will cause braking delay or slip. It is necessary to check the thickness of the brake disc (usually replaced when it is ≤ 3mm) and adjust the brake spring pressure to the design value (such as 0.5-1.0MPa). After adjustment, a no-load test run is required to ensure that the braking distance meets the standard (such as ≤ 10mm).
The friction coefficient between the slider and the guide rail affects the smoothness of motion. If there are scratches or insufficient lubrication on the surface of the guide rail, it will cause an increase in the resistance of the slider movement or local slippage. Regularly clean the iron filings on the surface of the guide rail, apply special lubricating grease (such as lithium based grease), and check the parallelism of the guide rail (error ≤ 0.05mm/m). For severely worn guide rails, chrome plating or laser cladding processes can be used to repair the surface.
The lubrication system of mechanical power presss needs to strike a balance between reducing wear and maintaining friction. Insufficient lubrication can cause overheating and expansion of components, reducing the effective contact area; Excessive lubrication will form an oil film, reducing the friction coefficient.
Select lubricating oil with appropriate viscosity based on the working conditions of the punch press, such as speed and load. Low viscosity oil (such as ISO VG 32) can be used for high-speed light load conditions (such as stamping thin plates); High viscosity oil (such as ISO VG 68) should be selected for low-speed heavy-duty working conditions (such as stamping thick plates). Regularly check the viscosity of lubricating oil (such as through a viscometer), and replace it with new oil if the viscosity drops by more than 20%.
Blockage of lubrication points or insufficient oil supply can cause local dry friction, leading to slippage. Regularly clean the lubrication pipeline (such as blowing with compressed air every 3 months) and check the oil supply of the lubrication pump (such as through a flow meter). For key friction parts such as clutches and bearings, a quantitative lubrication device (such as a progressive distributor) can be used to ensure stable oil supply per stroke (such as 0.1-0.5mL).
Traditional manual lubrication is prone to leakage or excessive injection problems. It can be upgraded to an automatic lubrication system (such as a central lubrication station), which controls the lubrication cycle and oil supply through PLC. For high-temperature parts (such as brakes), high-temperature resistant lubricating grease (such as molybdenum disulfide based grease) can be used to avoid lubricant loss at high temperatures.
The coordinated work of clutch and brake is the core to prevent slipping. If the clutch is not fully engaged or the brake release is delayed, it will cause interruption or overlap of power transmission, leading to slipping.
The pneumatic clutch uses compressed air to push the piston and engage the friction plates. If the cylinder pressure is insufficient (such as below 0.4 MPa), it will cause insufficient compression force of the friction plate. It is necessary to check the pressure of the gas source (such as through a pressure gauge) and adjust the pressure reducing valve to the design value (such as 0.6-0.8MPa). At the same time, it is necessary to clean the rust on the inner wall of the cylinder to ensure smooth piston movement.
The brake should respond quickly after the clutch is disengaged to prevent the slider from continuing to move due to inertia. The brake action time (such as the time from clutch disengagement to slider stop) needs to be detected through an oscilloscope. If it exceeds the design value (such as ≤ 0.2 seconds), the response speed of the brake solenoid valve needs to be adjusted or the spring needs to be replaced.
The safety double valve in the pneumatic system is used to prevent accidental engagement of the clutch. If the dual valve seal fails or the spring breaks, it will cause the clutch to malfunction in the braking state. It is necessary to regularly check the leakage of the double valve (such as using the bubble method). If the leakage exceeds the standard (such as ≤ 0.1L/min), the valve body should be replaced.
The design parameters of mechanical power presss (such as nominal force, number of slider strokes) need to be matched with the machining task. If the load exceeds the rated capacity of the equipment or the speed is set improperly, it can cause the motor to overload or the transmission components to slip.
Adjust the stamping speed (such as increasing the stamping speed of thin plates to 200-300spm and reducing it to 50-100spm for thick plates) and pressure (such as monitoring the actual stamping pressure through a pressure sensor to ensure that it does not exceed 80% of the nominal force) based on the thickness and hardness of the material. Long term continuous stamping of ultra thick materials should be avoided to prevent motor overheating or transmission shaft deformation.
The flywheel achieves stamping action through energy storage release. If the quality of the flywheel is insufficient or the speed is too low (such as below 90% of the design speed), it will lead to insufficient stamping energy and cause slippage. It is necessary to regularly check the kinetic energy of the flywheel (such as calculating it through a tachometer and the moment of inertia of the flywheel). If the kinetic energy decreases by more than 15%, the flywheel should be replaced or the motor power adjusted.
The transmission ratio of a gear or belt drive system affects the output torque. If the transmission ratio is too large (such as the reduction ratio exceeding the design value), it will result in insufficient output torque; If the transmission ratio is too small, it may cause motor overload. It is necessary to detect the actual output torque through a torque sensor and compare it with the design value. If necessary, replace the gear or adjust the belt tension.
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