Details for Pneumatic Presses:
Definition, Function, Use
Pneumatic presses are used when the manpower is not strong enough to generate the force required, or the number of parts to be machined is too large.
Pneumatic presses are manufactured with various force transission mechanisms. Their movement is based on compressed and dried air. Usually the air pressure applied is in between 3 bar to 6 bar (44 psi to 87 psi). Pneumatic presses reach their nominal force at 6 bar (87 psi). A controller is needed t operate a pneumatic. Normally 2-hand controller are used at manual work stations. In case the pneumatic press is integrated into an automated process a plc takes over the control.
Pneumatic presses are manufactured in three different force transmissions: The toggle mechanism, direct acting, and hydro-pneumatic transmission.
The optimum transmission ratio of the toggle lever produces large forces at the end of the stroke and ensures low air consumption. The relatively high ram speed and the defined length of the stroke are the adantage of the toggle mechanism. Pneumatic toggle presses are therefore especially used for riveting, punching, and adge cutting.
Direct acting pneumatic presses are the most widely used pneumatic presses. Their advantage is that they produce a constant force over the whole length of stroke. The air pressure used is directly related to the generated force of the press. A particular advantage of the direct-acting pnumatic press is the precise adjustment of the stroke length. This allows for flexible use in various applications: such as assembling, bending, press-fit, and crimping.
Hydro-pneumatic presses are a variation of direct acting pneumatic presses. Hydro-pneumatic presses are driven with compressed air only, but have integrated high pressure oil chamber in which the high force of this press type is generated. With hydro-pneumatic presses, therefore, a distinction is made between the pneumatic rapid stroke and the hydraulic power stroke. In the pneumatically driven rapid stroke, the workpiece is approached with high speed and low force. The hydraulic power stroke is then activated automatically when resistance of the work piece is encountered. Now a plunger is pressurised with compressed air, moves out and closes an oil chamber causing the power transmission to take place. The ram oves out at reduced speed and with increased force in the power stroke. Hydro-pneumatic presses are perfect, if high pressure over a short stroke is needed: for example for press-fit, assembling, and embossing. /p>