Application of Pneumatic Fixture Design in Thread

by:Top Talent     2020-05-23
Now when working in the production workshop, manual fastening has gradually been eliminated. At present, pneumatic clamps are a kind of clamps that use compressed air as the power source. They convert the gas pressure into mechanical energy through the cylinder, and can complete a variety of actions such as fixture positioning and clamping. Today we will introduce a rotary pneumatic clamp used in the screw fastening of rod-shaped workpieces. The following will give an example to analyze and explain the design of rotary pneumatic fixture. Workpiece to be processed Rod-shaped workpiece A (external thread) Specification: φL84.5mm Weight: 25g Rod-shaped workpiece B (female thread) Specification: φL75.5mm Weight: 12g Rotating pneumatic clamp action Transfer rod-shaped workpiece A (external thread) and rod-shaped workpiece B (internal thread) to the assembly device through the robot. The device is mounted on a two-axis robot of X-axis and Z-axis, and moves forward and downward toward the position of rod-shaped workpiece B. Raise the cylinder with the guide rod, and clamp the rod-shaped workpiece B with a three-jaw pneumatic clamp. When the motor rotates, the rotation is transmitted to the three-jaw pneumatic clamp through the synchronous pulley and torque limiter (a device that releases and cuts off the transmission in the overload state and protects the rotating shaft), and the rod-shaped workpieces A and B are screw-fastened. After the thread is tightened, no force greater than the rated torque will be transmitted through the torque limiter. The action of the torque limiter can be detected by the proximity sensor to obtain a signal that the thread tightening is completed. Basis for selection of main parts Thread tightening torque required is 0.06-0.12N ・ m, change the torque limiter spring. According to the required torque (0.25N.m) and rotation speed (5.6-56rpm) of the motor, select the motor and gear head with motor output 0.005N.m and gear head reduction ratio i = 1/50. Calculation process of main parts 1. Verify that the clamping force of the pneumatic clamp has the required tightening torque. 2. Confirm the clamping force of the three-jaw pneumatic clamp. Conditional values: torque required for thread tightening T1 = 0.12N? M, workpiece shape d = φ12mm, friction coefficient μ = 0.6 (rubber and metal), supply pressure p = 0.6MPa. According to the chart in the product catalog, when the supply pressure is p, the clamping force of the three-jaw pneumatic clamp is F = 38N. Three-jaw pneumatic clamp transmission torque: T = F × μ × (d / 2), T = 38 × 0.6 × {(12/2) × 10-3} = 0.14N? M? T1
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