模具设计与制造专业英语黄义俊_统一模板(模具)Unit6课件教学.pptVIP

Unit 6 The Forming and Molding Equipment Unit 6 The Forming and Molding Equipment 6.1 Lesson 14 Types of Press For the applications, there are many types of the presses, such as the single-action straight-slide eccentric mechanical press, punch press, hydro-former press, hydraulic press, press brake, triple-action press, turret press, two-point press, twin-drive press, two point single-action press, watch press, trimming press, closed-type single-action crank press, knuckle-lever press, one-point single-action press, open-back inclinable press, open-side press, four-point press, four-crank press, flywheel-type screw press, friction screw press, straight-side single-action double-crank press, rocker-arm press, screw press and top-drive sheet-metal stamping automatic press and so on. A double-action press is used for large, or deep drawing operations on sheet metal parts．This type of press has an outer ram（blank holder）and a section inner ram（punch holder）. During the operating cycle, the blank holder contacts the material first and applies pressure to allow the punch holder to properly draw the part (Figure 6-1). A triple-action press has the same inner and outer ram as the double-action press, but a third ram in the press bed moves up allowing a reverse draw to be made in one press cycle[1]. The triple-action press is not widely used． A knuckle press is used for coining operation. The design of the drive allows for very high pressures at the bottom of the ram stroke．This type uses a crank, which moves a joint consisting of two levers that oscillate to and from dead center and results in a short, powerful movement of the slide with slow travel near the bottom of the stroke． A hydraulic press is used basically for forming operations and has a slower operating cycle time than most mechanical presses. The advantages of hydraulic presses are that the working pressure, stroke, and speed of the ram are adju