1.2 Press Forming Devices_聚合物成型工艺与技术-QQ阅读男生轻小说网

书名：聚合物成型工艺与技术
作者名：林志丹
本章字数：635字
更新时间：2020-08-29 14:57:33

1.2 Press Forming Devices

The core equipment of press forming is press.Compression molding needs to use die and some kinds of press forming need auxiliary equipment.In this chapter，we will only introduce the press.

1.2.1 Types of Press

Press is known as a pressure machine which uses a plate to put pressure on plastics during the forming process.According to the transmission styles，press can be divided into hydraulic press 液压机 and mechanical press.The more widely used one is the hydraulic press and the commonly used hydraulic press is the oil hydraulic press.Hydraulic press can be divided into general hydraulic press and multi-layer hydraulic press.

1.General Hydraulic Press

According to the characteristics of the frame，general hydraulic press can be divided into column hydraulic press 柱式液压机 and frame hydraulic press 框式液压机 . According to the setting position of working cylinder，the general hydraulic press has pressurizing-down style and pressurizing-up style.General hydraulic press has three kinds of operation methods：manual method，semi-automatic method and automatic method respectively.The specifications of general hydraulic press are 450 kN，630 kN，1，000 kN，1，600 kN，2，500 kN，3，000 kN，5，000 kN，etc.

The structure of the pressurizing-up style hydraulic press is shown in Fig.1-1（a）.The working cylinder 工作油缸 is designed on the top of the hydraulic press，and the lower plate is fixed.The main pressure plunger pushes the upper plate to press from the top to the bottom，depending on the rise and fall of the upper plate to complete the opening and closing of the mold and add pressure to the material.

Fig.1-1 pressurizing-up style hydraulic press and multilayer hydraulic press structural diagram

（1—master cylinder；2—master cylinder piston；3—upper beam；4—pillar；5—activities board；6—the upper template；7—plug；8—mold；9—the lower template；10—the machine；11—ejection cylinder piston；12—ejection cylinder；13—engine base；14—layered activities board；15—laminate plastic）

The position of working cylinder of pressurizing-down style hydraulic press is located at the foot of the hydraulic press and the upper press plate is fixed.The main pressure plunger is located under the lower pressure plate，and the main pressure piston pushes the lower plate to go up，so as to realize the closing and opening of the die.

2.Multilayer Hydraulic Press

Multilayer hydraulic press is a specialized hydraulic press，between the upper compressor and the lower compressor of press.There exists many heating plates 加热板 which can move up and down.Its structure is shown in Fig.1-1（b）.Multilayer hydraulic press can simultaneously form three to dozens of layers of different slabs，thus its production efficiency is high.Multilayer hydraulic press can produce laminate，rigid PVC 聚氯乙烯 lumber，foam plastic product 发泡塑料制品，etc.The specifications of multilayer hydraulic press are 10NM，15NM，20NM，25NM，30NM，etc.

1.2.2 The Parameters of Press

The main parameters of press are the nominal pressure 公称力，the plunger diameter，the size of pressure plate and the working stroke.The size of pressure plate determines the scale of products which the press can make.The working stroke determines the height of the mold or products.The nominal pressure of hydraulic press is the main parameter which can demonstrate the pressing capability of the press.The specification of hydraulic press is usually expressed by nominal pressure.Nominal pressure—F can be calculated as follow：

In the formula，D is the diameter of the oil hydraulic plunger，PL is the greatest pressure that press can bear.