Introduction to mold manufacturing technology

The first part of the concept and classification of the mold

First, the mold

The mold belongs to precision mechanical products. It is mainly composed of mechanical parts and mechanisms, such as forming working parts, guiding parts, supporting parts, positioning parts and feeding mechanism, core pulling mechanism and pushing mechanism.

When the mold is used with the corresponding forming equipment (such as punching machine, plastic injection machine, die casting machine, etc.), the shape, size, relative position and performance of the metal or non-metal material can be directly changed to form a qualified part.

Second, the classification of the mold

Generally speaking, molds can be divided into two categories: metal material forming molds, such as die, forging die, die-casting die, etc.; non-metallic material forming die, such as plastic injection mold, die-casting mold and injection mold, rubber Parts, glass parts and ceramic parts forming molds.

There are many specific classification methods for molds. Commonly used are: according to the form of mold structure, the die can be divided into single-process mold, composite mold, progressive mold, etc.; plastic mold can be divided into single-part plastic mold, double-part plastic Mould and so on. According to the nature of the process, the die can be divided into a punching die, a blanking die, a drawing die, and a bending die; the plastic die can be divided into a compression die, a press die, an injection die, and the like.

The classification of commonly used molds can be as follows:

The basic structure of the second part of the mold

This section mainly introduces the basic structure of cold die and plastic mold which are widely used in production.

First, the basic structure of the die

Although there are many types of dies, any pair of dies is composed of two parts, an upper mold and a lower mold. The upper mold is mounted on the slider of the press through the die shank or the upper die holder, and can move up and down with the slider, and is the movable part of the die; the lower die is fixed on the press table or the pad by the lower die holder, which is a die The fixed part.

The figure above shows a composite die with a complete set of punched washers.

1. The composition of the upper mold: the upper mold consists of a mold handle 8, an upper mold base 7, a backing plate 6, a punch fixing plate 5, a punching punch 1, a blanking die 2, a pushing device (by a bar 9, a push plate) 10. The push rod 11 and the push block 12 are combined, the guide sleeve 4, and the connecting screws and pins are composed of components.

2. Composition of the lower mold: the lower mold is composed of a convex and concave mold 16, a discharge device (consisting of the discharge plate 15, the discharge screw 21, the spring 22), the guide pins 14 and 20, the stopper pin 13, and the convex and concave mold fixing plate. 17. The pad 18, the lower die holder 19, the guide post 3, and the connecting screws and pins are composed of components.

3. Working principle: When working, the strips are sent along the guide pins 14, 20 to the position of the stopper pin 13, and the press is started. The upper mold moves downward with the slider, and the punching punch with sharp edges is blanked. The die 2 is passed through the strip together with the male and female molds 16 to separate the workpiece and the punching waste from the strip to complete the blanking work. When the sliding method drives the upper mold to rise, the unloading device removes the strip hung on the convex and concave mold, and the pushing device pushes the workpiece between the blanking die and the punching punch (ie, hooping on the punching punch) Falling on the lower die face, and the punching waste stuck in the convex and concave die is successively pushed out from the convex and concave die by the punching punch in the one-time punching process. After the part pushed down on the lower mold is removed, the next punching cycle can be performed.

According to the role of each component in the mold, the die can generally be divided into the following parts:

1) Working parts: parts for directly separating or plastically forming the blank, the punch 1, the die 2, and the convex and concave die 16 as shown in the above figure. The working part is the most important part of the die.

2) Positioning parts: The parts that determine the correct position of the blank or process part in the die, the block pin 13 and the guide pins 14 and 20 as shown in the figure above.

3) Pressing and unloading parts: These parts act to press the blank and ensure that the scrap or parts that are hooped on the punch or stuck in the die are removed to ensure that the stamping work can continue, as above The discharge plate 15, the discharge screw 21, the spring 22, the strut 9, the push plate 10, the connecting push rod 11, and the pusher block 12 are shown.

4) Guide parts: parts that determine the relative position of the upper and lower molds and ensure the accuracy of the motion guidance, as shown in the figure above, the guide post 3 and the guide sleeve 4.

5) Fixed parts: parts that are fixed to the upper and lower dies and the upper and lower dies are fixed on the press, as shown in the figure above, the fixed plates 5 and 17, the slats 6 and 18, and the upper dies Seat 7, lower die holder 19, die holder 8. These parts are the basic parts of the die.

6) Other parts: Parts other than the above parts, such as fasteners (mainly screws, pins).

Of course, not all dies have the above types of parts, but the working parts and the necessary fixed parts are indispensable.

Second, the basic structure of the plastic mold

The basic structure of any pair of plastic molds consists of two parts: moving, fixed or upper and lower. For fixed plastic molds, the fixed mold is generally fixed on the fixed template (or lower table) of the molding equipment, which is a fixed part of the mold; and the movable mold is generally fixed on the moving template (or upper work table) of the molding equipment, Reciprocating with the moving template is the active part of the mold. During molding, the movable mold and the fixed mold close constitute a cavity and a pouring system, and when the mold is opened, the movable mold and the fixed mold are separately taken out to take out the workpiece. For mobile plastic molds, the mold is generally not fixed on the molding equipment. After molding on the equipment, the mold is manually removed, and then the upper and lower molds are opened by the mold release tool to take out the parts.

The picture above shows a typical plastic injection mold.

1. The composition of the fixed mold: the fixed mold consists of fixed mold seat plate 9, concave mold 5, fixed template 10, positioning ring 7, sprue sleeve 8 and other parts.

2. The composition of the movable mold: the movable mold consists of the movable template 11, the core 4, the guide post 3, the support plate 12, the movable mold bracket 13, the push rod 2, the pulling rod 1, the push rod fixing plate 14, the push plate 15, etc. The composition of the parts.

3. Parting surface: the joint surface AA parting surface between the moving mold and the fixed mold.

4. Mounting of the mold: The mold is positioned on the injection machine by the positioning ring 7, and fixed to the fixed template and the moving template of the injection machine by the fixed mold plate 9 and the movable mold support 13 by screws and pressure plates, respectively.

5. Working principle: Before injection molding, the mold is closed and locked under the action of the injection molding device. During molding, the plastic melt injected from the nozzle through the nozzle is passed through the mold sprue sleeve 8 and the flow passage on the parting surface to enter the cavity and after being pressed, filled and twisted, the mold clamping device of the injection machine is formed. The movable mold is left to retreat, so that the movable mold and the fixed mold are opened from the parting surface AA. Since the plastic has a packing effect on the core after cooling and the pulling action of the pulling rod 1 on the flow channel, the plastic part and the flow channel aggregate will remain on the side of the moving mold after the mold is opened. When the movable mold is opened to a certain position, the pushing mechanism composed of the push rod 2, the pulling rod 1, the push rod fixing plate 14 and the pushing plate 15 will be generated under the action of the ejector rod of the injection molding device and other parts of the moving mold. Relative movement, so that the parts and runners will be pushed out by the pusher and the drawbar from the core and the parting surface flow path, thus completing an injection molding process.

Analysis of the plastic mold structure shown in the above figure shows that the plastic mold can be seen as consisting of the following functionally similar parts:

1) Molded parts: Parts that directly contact the plastic and determine the shape and dimensional accuracy of the part, that is, the parts that make up the cavity. The core 4 and the female die 5 shown in the above figure are the main parts of the mold.

2) Gating system: A set of feed channels that direct the plastic melt from the injector nozzle or mold feed chamber to the cavity. The sprue bushing 8 shown in the above figure and the flow path opened on the parting surface.

3) Guide parts: parts used to ensure the relative position of the moving mold, the fixed mold or the upper and lower molds to ensure the size and dimensional accuracy of the plastic parts. The guide post 3 and the guide hole on the fixed plate 10 are as shown in the above figure.

4) Push-out mechanism: A component used to push or pull plastic parts and runners from molded parts and runners during the mold opening process. The push-out mechanism shown in the above figure is composed of a push rod 2, a pull rod 1, a push rod fixing plate 14, and a push plate 15.

5) Lateral parting core-pulling mechanism: used to extract the parts of the side core before the mold is opened.

6) Exhaust system: The structure used to discharge the air in the cavity and the gas volatilized by the plastic itself during the molding process. The exhaust system can be a specially configured venting groove or some matching clearance near the cavity. The exhaust system shown in the above figure is exhausted by the gap between the parting surface and the core and the push rod.

7) Cooling and heating device: A device used to meet the mold temperature requirements of the molding process. When cooling, a cooling passage is generally provided around the mold cavity, and when heated, a heating element is installed inside or around the mold. The mold shown in the above figure is an injection-molded thermoplastic. The mold generally does not require special heating, but a cooling passage 6 is opened on the core and the die to accelerate the cooling and setting speed of the plastic part.

8) Supporting and fixing parts: mainly functioning as assembly, positioning and coupling. The fixed mold base plate 9, the positioning ring 7, the fixed die plate 10, the movable die plate 11, the support plate 12, the movable mold bracket 13, and the screws and pins are shown in the above figure.

The plastic mold relies on the coordination of the above various types of parts to complete the plastic forming function. Of course, not all plastic molds have the above types of parts, but the molded parts, the gating system, the push-out mechanism and the necessary support fixing parts are indispensable.

The third part of the mold engineering

Mold engineering is the forming machinery and equipment related to the mold, processing raw materials, parts, molding process, mold design and manufacturing, materials and cost, precision and life, installation and commissioning, use and maintenance, and mold standardization. Problems that systematically conduct research, understand the relationship between them, and master their objective laws. Therefore, mold engineering is a systematic project to study molds and related problems.

In the production process of parts, from the raw materials to the parts, the production system must be passed through the parts; the production system of the parts requires the development of a reasonable and perfect production process; while the production of modern large-scale parts necessarily requires mold forming. Processing; the correct mold forming process, high-efficiency forming machinery and equipment, advanced molds are the three important factors affecting the production of parts.

The mold plays an important role in the realization of the forming process, ensuring the shape, size and tolerance of the part; the high-efficiency and fully automatic equipment can only be used if it is equipped with a mold suitable for automated production; the product is also updated by the mold and Updated to the premise.

As a precision and efficient process equipment for production, the mold itself is also a sophisticated mechanical product. Whether the mechanical product can meet the requirements of its use performance and forming precision, it is necessary to solve the problems related to the mold in various aspects such as mold design and manufacture, precision and life.

As shown in the above figure, molds can be subdivided into mold design, manufacturing, materials, cost, precision, life, installation, use, and standardization. Mold design is the basis of mold manufacturing. Reasonable and correct design is the guarantee for the correct manufacturing of molds. The development of mold manufacturing technology is of great significance to improve mold quality, precision and shorten the cycle of manufacturing molds; mold quality, service life and manufacturing precision. And the pass rate depends to a large extent on the material of the mold and the heat treatment process; the cost of the mold is directly related to the cost of the part and the economic benefit of the mold manufacturer; the precision of the part of the mold determines the precision of the part; It is related to many factors such as mold material and heat treatment, mold structure and processed materials. The installation and use of mold is directly related to the performance and safety of the mold. The standardization of mold is the basis of mold design and manufacturing. The production of molds has a very important role, and the level of mold standardization is a sign of the development level of the mold industry.

The fourth part of the development of advanced mold manufacturing technology

First, the cutting edge technology of mold processing - high-speed CNC machining

The key technology of high-speed CNC machining is 1 high-speed spindle and high-speed feed drive system machine; 2 high-speed machining tool system; 3 based on CAD/CAM automatic CNC programming

1. High-speed CNC cutting

Mainly for turning and milling. Generally, the spindle speed of high-speed CNC cutting is 1 to 10 times higher than that of ordinary CNC cutting. Another connotation of high-speed CNC cutting is the use of high feed rates. Maintaining the cutting force constant, increasing the rotation speed can increase the cutting rate and reduce the cutting time; maintaining the feed rate at the normal cutting level, increasing the rotation speed can reduce the cutting force, and can process thinner or thinner mold parts.

The high speed spindle is the primary condition for high speed CNC cutting. At present, the spindle speed can reach 100,000 rpm, and the high speed cutting speed is 5 to 100 m/s. Mirror turning and mirror milling of mold parts are fully possible.

1) The high speed spindle has the following gradient forms

(1) The cage adopts ceramic ball bearing high-speed electric spindle, the spindle rotation precision is 0.5μm, and the rotation speed reaches 15000 rev/min or more.

(2) High-speed electric spindle with hydrostatic bearing, the spindle rotation accuracy is below 0.2μm, and the rotation speed reaches 100000 rev/min.

(3) High-speed electric spindle with aerostatic bearing, the spindle rotation precision can be below 50nm, and the rotation speed can be as high as 200,000 rpm. Under development.

(4) High-speed motorized spindle with magnetic suspension shaft, the spindle rotation precision can reach 0.2μm, and the rigidity is very good. Under development.

2) Structure of high-speed CNC cutting machine

(1) The high speed of the feed drive system, that is, the use of large lead ball screws and high speed servo motors; linear motors and precision linear guides. The feed rate can reach 60~120m/min.

(2) The weight of the moving parts and the servo feed control are refined.

(3) Three-, four-, five-axis linkage high-speed CNC cutting machine tools have been developed. A mold that can machine complex profiles.

(4) New motion principle Machine tool: Six-bar machine tool, three-bar five-axis machine tool and four-bar machine tool with parallel structure appear in the field of high-speed CNC cutting. It is constantly improving and developing.

3) High-speed CNC cutting tool system

(1) Tool materials : coated and uncoated cemented carbide, cermet, alumina-based and silica-based ceramics, polycrystalline diamond and polycrystalline cubic boron nitride.

(2) Tool holder structure: requires high geometric accuracy and clamping repeatability, high clamping rigidity and complete reliability at high speed operation.

(3) Modularization of the installation tool: There are typical HSK type shank and its connection structure, hydraulic expansion clamp and so on.

4) Development trend of high speed data cutting

Develop high-power high-speed spindle, power ≥100kW, speed ≥100000 rev / min.

2, high-speed CNC grinding key technology

1) High speed spindle

It is required to have high-speed dynamic balance, and an electric balance system or an electro-hydraulic balance system can be used.

2) High-speed CNC grinding machine structure

Combines multiple grinding functions with high dynamic accuracy, high damping, high vibration resistance, high stability, high automation and high reliability.

3) High-speed CNC grinding wheel

It is required to have a high mechanical strength as a whole, which is completely reliable at high speed and has a sharp appearance. The bonding agent must have high bonding strength and wear resistance to reduce the wear of the grinding wheel. The high-speed grinding wheel is designed with equal strength to optimize the structure and shape.

4) Cooling system

The coolant is required to have a high heat capacity and thermal conductivity to improve the cooling efficiency, can withstand higher pressure, has good filterability, good corrosion resistance and high adhesion, has high stability, does not blister, does not Discoloration, harmless to health, easy to clean, and conducive to environmental protection.

5) Development trend of high speed CNC grinding

Develop high-power high-speed spindle, develop a new type of grinding wheel suitable for high-speed grinding, improve the structure of the grinding machine, optimize the cooling system, and develop the grinding speed to supersonic speed of 250-350m/s. ?

3, based on CAD / CAM automated CNC programming

High-speed CNC machining As the cutting-edge technology of mold processing, one of the key technologies is the use of advanced CAD/CAM integrated design and manufacturing system for automatic NC programming of graphical interaction. This method is fast, accurate, intuitive, easy to use and easy to use. an examination. The key to solving high-speed CNC machining programming is NURBS interpolation technology, which has the following features:

(1) Spline interpolation calculation can be performed under the NC controller .

(2) Reduce the amount of data and increase the speed of data transmission.

(3) Accurate data transfer between CAD-CAM-CNC.

(4) It is easy to generate a smooth tool path. This is extremely advantageous for machining high quality, complex profiled molds.

Second, rapid prototyping and rapid molding technology

Rapid prototyping technology, also known as rapid prototyping technology (RPM technology), was born in the late 1980s and is a high-tech manufacturing technology based on material accumulation. It is considered to be a revolutionary breakthrough in the manufacturing field of the 20th century. According to experts, its development speed is faster than that of CNC technology. Rapid prototyping technology is an advanced technology that integrates CAD, CAM, CNC, precision servo drive and new materials. Its forming process is based on the three-dimensional design model of the product on the computer. The contours of the cross-sections of the layers are formed by superimposing different materials layer by layer according to different processes, thereby obtaining a three-dimensional solid product.

Although the rapid prototyping technology has not been available for a long time, the application of this technology has become more and more extensive due to its huge benefits to the manufacturing industry, especially for the design and manufacture of molds. In the molding process of various packaging products, a variety of different molds, such as injection molds, plastic molds, and pulp molding molds, and the like are used in large quantities. Due to the application of the new technology of rapid prototyping (RPM), the design and manufacture of packaging molds tends to be digital and rapid, which makes the mold manufacturing process a step forward in the process of shortening the cycle and reducing the cost.

Third, the conclusion

There are many types of advanced mold manufacturing technologies, and almost all of the advanced manufacturing techniques can be applied to mold manufacturing, and they are constantly evolving and cannot be summarized here. Starting from China's national conditions, it is unrealistic for all mold companies to adopt high-speed CNC machining technology as soon as possible, because equipment and technical equipment are expensive. Appropriate use of relatively inexpensive special processing technology for rapid manufacturing is worthy of consideration by some mold companies. From different perspectives, in addition to the advanced mold manufacturing technology mentioned above, there are also Reverse Engineering, VirtualManufacruring, FMS and MIMS. Wait. It has been suggested that the next generation of advanced manufacturing technologies use reconfigurable and scalable manufacturing equipment and systems, knowledge supply chains and independent manufacturing islands.

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