模具设计与制造专业英语 教学课件 ppt 黄义俊_ 电子教案统一模板(模具)Unit6

1、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-poin

2、t 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 partsThis type of press has an outer ram（blank holder）and a section inner ram（punch holder）. During the operating cycle, the

3、 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 cycle1. 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 strokeThis type uses

4、 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 adjustable (Figure 6-2). Hydraulic presses belong to the force-constrained ty

5、pe of forming machines. Their main use is found in those areas of forming technology where the force along the path of the ram must remain constant or under accurate control. The drive mechanism of piston and cylinder acts in a linear manner and is directly connected to the ram,The form of frame construction of hydraulic presses is largely similar to that of mechanical presses. The hydraulic drive units are easily accommodated in the machine frame. Consequently, several hydraulic drives can read

6、ily be built into a single machine for complicated forming and cutting operations (drawing, extruding, cutting, swaging, etc), and the required motions may be easily coordinated.,A press brake is essentially same as a gap-frame press except for its long bed from 6 to 20 feet (1.86m) or more. It is used basically for various bending operations on large sheet metal partsIt can also be used with a series of separate sets of press tools to do light piercing, notching, and forming (Figure 6-3)This al

7、lows parts of a complex design to be accurately made without a high-cost press tool by simply breaking the complex part down into several simple operationsThis type of operation is used on low-run or prototype parts.,Sheet metal can be bent easily with simple fixtures using a press brake. This press brake utilizes long dies in a mechanical or hydraulic press and is suitable for small production runs. The tooling is simple, and it is adaptable to a wide variety of shapes, furthermore, the process

8、 can be easily automated. Die materials for press brakes may range from hardwood (for low-strength materials and small production runs) to carbides. For most applications, carbon-steel or gray-iron dies are generally used.,6.2 Lesson 15 The Injection-molding Machine,The injection-molding machines are usually horizontal (Figure 6-4). Vertical machines are used for making small close-tolerance parts and for insert molding. The clamping force on the molds is generally supplied by hydraulic means. T

9、he injection-molding machines are rated according to the capacity of the mold and the clamping force. In most machines, this force ranges from 100 to 250 tons. The largest machine in operation has a capacity of 5000 tons, and it can produce parts weighing 25kg (most parts weigh from 100g to 600g). The tonnage is the force applied to keep the molds closed during injection of molten plastics into the mold cavities.,There are two basic units to an injection-molding machine, one for injecting the heated plastic and one for opening and closing the mold.1 The first unit includes a feed hopper, heated injection cylinder, and an injection plunger or reciprocating-screw systemThe second unit comprises a hydraulic operated moving platen and a stationary platen on which the halves of the mold are mountedInjection-molding machines are also available in vertical models.,There are many variations in injection-molding machine design, however, the basic machines are of either the recip

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