Plastic mold is a tool for plastic processing industry and plastic molding machine to give plastic products with complete shape and precise size.
Because of the variety of plastic and processing methods, plastic molding machine and plastic products and the structure of the simple and complicated, so, the plastic mold types and structures are also a variety of.
Molds are used in a variety of industries to create products. Plastic molding is a popular process used to create a variety of plastic items.
In this blog post, we&#;ll discuss everything you need to know about plastic molding! We&#;ll cover the basics, such as what it is and how it works, as well as more advanced topics, such as the different types of molds and the materials they use.
We hope this blog post will provide you with all the information you need to make an informed decision about using plastic molds.
Source: https://www.pinterest.com/pin//Basic Introduction to Plastic Moulds
A combination plastic mold for compression molding, extrusion molding, injection molding, blow molding and low foam molding, which mainly includes a concave mold with variable cavities consisting of a concave mold combination substrate, a concave mold assembly and a concave mold combination card plate, and a convex mold with variable cores consisting of a convex mold combination substrate, a convex mold assembly, a convex mold combination card plate, a cavity cut-off assembly and a side cut-off combination plate.
Coordinated change of mold convex and concave dies and auxiliary molding system. It can process a series of plastic parts of different shapes and sizes.
It is a tool used in the plastic processing industry and plastic molding machine to give plastic products a complete shape and precise size.
Because of the variety of plastic and processing methods, plastic molding machine and plastic products and the structure of the simple and complex, so, the plastic mold types and structures are also a variety of.
With the rapid development of the plastics industry and the continuous improvement of general and engineering plastics in terms of strength and other aspects, the application of plastic products is also expanding, and the amount of plastic products is rising.
Plastic mold is a kind of tool for producing plastic products. It consists of several groups of parts parts, and this combination contains the molding cavity.
During injection molding, the injection mold tool is clamped on the injection molding machine, the molten plastic is injected into the molding cavity and cooled and shaped in the cavity, then the upper and lower molds are separated and the product is ejected from the cavity and leaves the mold through the ejector system, and finally the mold is closed again for the next injection, the whole injection process is cyclic.
Generally speaking, the plastic mold consists of two parts: the moving mold and the fixed mold. The moving mold is mounted on the moving template of the injection molding machine, and the fixed mold is mounted on the fixed template of the injection molding machine. The moving mold template and the fixed mold template are the injection molding machine consists, which are used to fix the mold.
During injection molding, the mold and the fixed mold are closed to form the pouring system and cavity, and when the mold is opened, the mold and the fixed mold are separated in order to remove the plastic products.
Although the structure of the mold may vary depending on the variety and properties of plastics, the shape and structure of plastic products and the type of injection machine, the basic structure is the same.
The mold is mainly composed of pouring system, temperature regulating system, molding parts and structural parts.
Among them, the pouring system and molding parts are the parts in direct contact with plastic and change with plastic and products, which are the most complicated and changeable parts of the mold and require the highest processing finish and precision.
The pouring system is the part of the flow channel before the plastic enters the cavity from the injection nozzle, including the main flow channel, cold cavity, manifold and gate. Molding parts are the various parts that constitute the shape of the product, including moving mold, fixed mold and cavity, core, molding rod and exhaust port, etc.
China&#;s plastic mold in high technology drive and pillar industry application demand, the formation of a huge industrial chain, from the upstream of the raw and auxiliary materials industry and processing, testing equipment to the downstream of machinery, automobiles, motorcycles, home appliances, electronic communications, construction and building materials and several other major applications of industry, plastic mold development a vibrant.
Main classification of plastic moulds
According to the different molding methods, we can divide the types of plastic processing molds corresponding to different process requirements, mainly injection molding molds, extrusion molding molds, blister molding molds, high foaming polystyrene molding molds, etc.
According to our know about plastic injection moulds, it is mainly a kind of molding mold most commonly used in the production of thermoplastic plastic injection molded parts.
The plastic injection mold corresponds to the processing equipment of plastic injection molding machines, in which the plastic material is firstly heated and melted in the barrel at the bottom of the injection machine, and then pushed by the screw or plunger of the injection machine, it enters the mold cavity through the injection nozzle and the pouring system of the mold, the plastic is cooled and hardened, and the product is obtained by demolding, this is the entire injection molding cycle process.
The structure usually consists of molding parts, pouring system, guiding parts, pushing mechanism, temperature regulating system, exhaust system, supporting parts and other parts.
The injection molding manufacturing typically material usually adopts plastic mold steel module, the common materials are mainly carbon structural steel, carbon tool steel, alloy tool steel, high-speed steel, etc.
Entire injection molding process method is usually only applicable to the mass production of thermoplastic material products, with plastic injection molding process to produce a wide range of plastic products, from daily necessities to all kinds of complex machinery, electrical appliances, transportation parts, etc. are molded with injection, it is the most widely used in the production of plastic products a processing method.
There are two types of structural molds, compression molding and compression injection molding. They are mainly used to mold thermosetting plastics, and their corresponding equipment is pressure molding machine.
Compression molding method is based on the characteristics of plastics, the mold is heated to the molding temperature (generally at 103°-108°), then the measured compression molding powder is put into the mold cavity and the filling chamber, and the mold is closed.
Press injection molding is different from compression molding in that there is a separate filling chamber, and the mold is closed before molding, and the plastic is preheated in the filling chamber and is in a viscous flow state, then it is adjusted and squeezed into the mold cavity under pressure to harden and mold.
Compression molds are also used to mold certain special thermoplastics such as thermoplastics that are difficult to melt (such as polygafluoroethylene) blanks (cold compression molding), resin lenses with very high optical properties, nitrocellulose car steering wheels with slight foaming, etc.
Compression molding molds are mainly composed of cavities, filling cavities, guiding mechanism, push out parts, heating system, etc. Compression injection molds are widely used in encapsulating electrical components.
The materials used in the manufacture of compression molding molds are basically the same as injection molds.
It is also called extrusion molding head, which is widely used for processing pipes, rods, monofilaments, plates, films, wire and cable cladding, profiles and so on.
Its corresponding production equipment is a plastic extruder, whose principle is to melt and plasticize solid plastic under the conditions of heating and extruder&#;s screw rotation and pressure, and make continuous plastic products with the same cross-section as the shape of the mouth mold through a specific shape of the mouth mold.
Its manufacturing materials are mainly carbon structural steel, alloy tools, etc. Some extrusion dies are also inlaid with wear-resistant materials such as diamond in the parts that need to be wear-resistant.
The extrusion medium process is usually only applicable to the production of thermoplastic products, and its structure is distinctly different from that of injection molds and compression molds.
It is a kind of mold used for molding plastic container hollow products (such as beverage bottles, daily chemical products and other packaging containers), and the forms of blow molding are mainly extrusion blow molding, injection blow molding, injection extension blow molding (commonly known as &#;injection pull blow&#;), multi-layer blow molding, sheet blow molding, etc. Forming, etc.
Blow molding of hollow products corresponding to the equipment is usually called plastic blow molding machine, blow molding is only applicable to the production of thermoplastic varieties of products.
Blow molding mold structure is relatively simple, the materials used are mostly made of carbon more then.
It is a kind of mold which takes plastic plate or sheet as raw material to form some simple plastic products.
Its principle is to use the method of vacuum opening or compressed air forming method to make the plastic plate or sheet fixed on the concave or convex mold, deforming under the condition of heating and softening and sticking on the cavity of the mold to get the required formed products, mainly used in the production of some daily necessities, food, toys and other packaging products.
Because the pressure of blister mold is low, so the mold material is mostly made of cast aluminum or non-metal material, and the structure is simple.
It is a mold for molding foam packaging materials of various shapes by applying the raw material of EPS (beads of polystyrene and blowing agent).
The principle is that EPS can be molded into steam in the mold, including simple hand-operated molds and hydraulic machine straight-through foam molds of two types, mainly used for the production of industrial packaging products.
The materials used in the manufacture of such molds are cast aluminum, stainless steel, bronze, etc.
Plastic Mold Design Elements
Mold design and manufacturing have a close relationship with plastic processing. The success or failure of plastic processing depends largely on the effect of mold design and the quality of mold manufacturing, while plastic mold design is based on the correct design of plastic products.
1. Parting surface, i.e. the contact surface where the concave mold and convex mold fit each other when the mold is closed.
Its location and form are influenced by the shape and appearance of the product, uniform wall thickness, molding method, post-processing process, mold type and structure, demolding method and molding machine structure, etc.
2. Structural parts, i.e. slider, slant top, straight top block of complex molds, etc.
The design of the structural parts is very critical, which is related to the life of the mold, processing cycle, cost, product quality, etc. Therefore, the design of the core structure of complex molds requires high comprehensive ability of the designer, pursuing simpler, more durable and more economical design solutions as much as possible.
3. Mold accuracy, i.e. card avoidance, fine positioning, guide pillar, positioning pin, etc.
Positioning system is related to product appearance quality, mold quality and life, according to different mold structure, choose different positioning methods, positioning accuracy control mainly relies on processing, internal mold positioning is mainly the designer to fully consider, design a more reasonable and easy to adjust the positioning method.
4. Pouring system, that is, from the injection molding machine nozzle to the cavity between the feed channel, including the main flow channel, diversion channel, gate and cold cavity.
In particular, the location of the gate should be selected to facilitate the molten plastic in a good flow state filled cavity, attached to the product of the solid runner and gate cold material is easy to eject from the mold and be removed when the mold is opened (except for hot runner mold).
5. plastic shrinkage rate and the factors affecting the dimensional accuracy of the product, such as mold manufacturing and assembly errors, mold wear and tear, etc..
In addition, the design of compression and injection molds, should also consider the molding machine process and structural parameters of the match. Computer-aided design technology has been widely used in the design of plastic molds.
Plastic Mold Accessories
Punch, head, guide pillar, guide sleeve, fine positioning, ejector rod, ejector pin, sleeve, slider device, slant top device, steel ball sleeve, date stamp, plastic mold spring, seal, cooling joint, water plunger, positioning ring, gate sleeve, pulling material pin, tie bar, limit nail, garbage nail, support post, opener, mold opening sequence controller (mold locking buckle assembly), etc.
Plastic Mould Structure Parts
The structure of blow molding mold, casting mold and thermoforming mold is relatively simple.
Compression mold, injection mold and transfer mold structure is more complex, constitute the parts of this kind of mold is also more.
The basic parts are
1. Forming parts, including concave mold, convex mold, a variety of molding core, are molding products inside and outside the surface or the upper and lower end, side holes, side concave and threaded parts.
2. Support fixed parts, including mold base plate, fixed plate, support plate, pad, etc., to fix the mold or support the pressure.
3. Guide parts, including guide pillar and guide bush, to determine the relative position of the mold or launch mechanism movement.
4. Core extraction parts, including tilting pins, sliders, etc., are used to extract the movable core when the mold is opened, so that the product is released from the mold.
5. Push out parts, including push rod, push tube, push block, push piece plate, push piece ring, push rod fixed plate, push plate, etc., to make the products out of the mold.
This kind of mold frame is made of basic parts whose structure, form and size have been standardized and serialized, and the cavity can be processed according to the shape of products. The use of standard mold frame is conducive to shorten the mold making cycle.
Fixed mold base plate (panel): the front mold fixed on the injection molding machine.
Runner plate (spout plate): remove the waste stalk when opening the mold, so that it automatically fall off (three-plate mold).
Fixing plate (A plate): the front part of the molded product.
Fixed plate of moving die (B plate): the rear part of the molded products.
Pad: the foot of the mold, its role is to let the top plate have enough space to move.
Push plate: push out the product from the mold by pushing out the parts such as top bar, top block and inclined top when opening the mold.
Movable mold base plate (bottom plate): to fix the rear mold on the injection molding machine.
Guide pillar and guide bush: play a guiding and positioning role, assist the front and rear mold opening, and mold and basic positioning.
Support column (support head): improve the strength of the B plate, effectively avoid the deformation of the B plate caused by long-term production.
Top plate guide pillar (middle toast): guide and position the push plate to ensure smooth ejection.
Plastic Mold Material Requirements
The working conditions of plastic moulds are different from those of cold punching moulds, which are generally required to work at 150°C-200°C. Besides being subject to certain pressure, they also have to bear the influence of temperature.
Now according to the plastic molding mold using conditions, processing methods of the different plastic mold with the basic performance requirements of steel is roughly summarized as follows.
Plastic mold hardness is usually below 50-60HRC, after heat treatment of the mold should be enough surface hardness to ensure that the mold has sufficient rigidity.
Mold in the work due to the filling and flow of plastic to withstand large compressive stress and friction, requiring the mold to maintain the accuracy of the shape and dimensional accuracy of stability, to ensure that the mold has sufficient service life.
Mold wear resistance depends on the chemical composition of steel and heat treatment hardness, so improve the hardness of the mold is conducive to improve its wear resistance.
Most plastic molding molds, in addition to EMD processing also need to carry out a certain amount of cutting processing and clamping repair.
In order to extend the service life of cutting tools, improve cutting performance, reduce surface roughness, plastic mold steel hardness must be appropriate.
High-quality plastic products, requiring the cavity surface roughness value is small.
For example, the injection mold cavity surface roughness value required less than Ra0.1 ~ 0.25 level, the optical surface requires Ra<0.01nm, the cavity shall be polished to reduce the surface roughness value.
For this reason, the choice of steel requires less material impurities, tissue microfine uniformity, no fiber directional, polishing should not appear pockmark or orange peel defects.
Plastic injection mold parts are often complex in shape, hard to process after quenching, so should try to use a good thermal stability.
When the mold molding process after heat treatment due to the coefficient of linear expansion, heat treatment deformation is small, the temperature difference caused by the small rate of change in size, metallographic organization and mold size stability, can be reduced or no longer processed to ensure the mold size accuracy and surface roughness requirements.
45, 50 grades of carbon steel has a certain strength and wear resistance, after tempering treatment is mostly used for mold frame materials.
High-carbon tool steel, low-alloy tool steel after heat treatment has high strength and wear resistance, more for molding parts.
But high carbon tool steel because of its heat treatment deformation, only for the manufacture of small size, simple shape of the molding parts.
With the development of the plastics industry, the complexity of plastic products, precision and other requirements are increasingly high, the mold material also put forward higher requirements.
For the manufacture of complex, precision and corrosion-resistant plastic mold, can be used pre-hardened steel (such as PMS), corrosion-resistant steel (such as PCR) and low-carbon martensitic aging steel (such as 18Ni-250), have better cutting, heat treatment and polishing properties and higher strength.
In addition, in the selection of materials must also consider the prevention of abrasion and gluing, such as the existence of relative movement of the two surfaces, try to avoid the selection of materials with the same organizational structure, special conditions can be plated or nitride on one side, so that the two sides have different surface structure.
Plastic Mold Material Selection
Due to the development of plastic and plastic molding industry, the quality requirements of plastic moulds are getting higher and higher, thus the failure of plastic moulds and their influencing factors have become important research topics.
The main working parts of plastic mold are molding parts, such as convex mold, concave mold, etc. They constitute the cavity of plastic mold to mold various surfaces of plastic parts and directly contact with plastic, subject to pressure, temperature, friction and corrosion, etc.
General mold manufacturing includes mold design, selection of materials, heat treatment, cnc machining, commissioning and installation processes.
According to the survey shows: mold failure factors, the mold used in the material and heat treatment is the main factor affecting the service life.
From the perspective of total quality management, the factors affecting the service life of the mold can not be measured as the sum of polynomials, but should be the product of multiple factors, so that the advantages and disadvantages of mold materials and heat treatment in the entire mold manufacturing process is particularly important.
From the analysis of the common phenomenon of mold failure, plastic mold in the service process, can produce wear loss, localized deformation failure and fracture failure.
Important failure forms of plastic mold can be divided into wear loss failure, local plastic deformation failure and fracture failure.
With the rapid development of the manufacturing industry, plastic mold is an indispensable tool in plastic molding process, the proportion of the total mold production increased year by year.
with the development of high-performance plastics and continuous production, the increasing variety of plastic products, expanding the use of products to precision, large, complex development.
Molding production to high-speed development, the working conditions of the mold is also more and more complex.
Plastic melt to a certain pressure in the mold cavity flow, solidification of plastic parts from the mold, are caused by friction on the mold molding surface, causing wear.
The root cause of plastic mold wear is the friction between the mold and the material. However, the specific form of wear and wear process is related to many factors, such as the pressure, temperature, material deformation speed and lubrication condition of the mold in the working process.
When the material and heat treatment of plastic mold is unreasonable, the cavity surface of plastic mold has low hardness and poor wear resistance, which is manifested as follows: the size of cavity surface is super poor due to wear and deformation; the roughness value becomes high due to hair pulling and the surface quality deteriorates.
Especially when the use of solid materials into the cavity of the plastic model, it will intensify the wear of the cavity surface.
Plus the plastic processing contains chlorine, fluorine and other components of the heat decomposition of corrosive gases HC1, HF, so that the plastic mold cavity surface corrosion wear, resulting in failure.
If there is wear damage at the same time as the wear, so that the cavity surface of the plating or other protective layer is damaged, it will promote the corrosion process.
Two kinds of damage cross-action, accelerate the corrosion of a wear loss effect.
Plastic model cavity surface pressure, heat can cause plastic deformation failure, especially when the small mold in the large tonnage equipment, more likely to produce overload plastic deformation.
Plastic mold used in the material strength and toughness is not enough, low deformation resistance; plastic deformation failure another reason, mainly is the mold cavity surface hardening layer is too thin, deformation resistance is not enough or the working temperature is higher than the tempering temperature and phase change softening, and early failure of the mold.
The main reason for fracture is due to the structure, temperature difference and structural stress, thermal stress or due to insufficient tempering, in the use of temperature, so that the residual austenite into martensite, causing local volume expansion, the tissue stress generated inside the mold.
The working conditions of plastic moulds are different from those of cold stamping moulds, which generally have to work at 150&#;-200&#;, and are subject to temperature effects in addition to certain pressure.
The same mold will have a variety of failure forms, even in the same mold may also appear a variety of damage.
From the failure form of plastic mold, it is known that the reasonable choice of plastic mold material and heat treatment is very important, because they are directly related to the service life of the mold.
With the emergence of high-speed molding machinery, the running speed of plastic products is accelerated.
As the molding temperature is between 200 &#; 350 &#;, if the plastic flow is not good and the molding speed is fast, it will make the mold part of the molding surface temperature exceed 400 &#; in a very short time.
In order to ensure the accuracy of the mold in use and the deformation is small, mold steel should have high heat resistance performance.
With the expansion of the use of plastic products, in plastic often need to add glass fiber and other inorganic materials to enhance plasticity, due to the addition of additives, so that the fluidity of plastic greatly reduced, resulting in mold wear, so it requires a good wear resistance.
Most plastic molding molds, in addition to EDM processing also need to carry out a certain amount of cutting processing and clamping repair.
In order to prolong the service life of cutting tools, processing hardening in the cutting process is small.
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In order to avoid mold deformation and affect the accuracy, hope that the processing residual stress can be controlled to a minimum.
Plastic injection mold parts are often complex in shape, hard to process after quenching, so should try to use a good thermal stability of the material.
The surface of the cavity is smooth and the molding surface is polished to a mirror surface with a surface roughness of less than Ra0.4μm to ensure the appearance of the plastic pressed parts and facilitate demolding.
In the mold failure accident, the accident caused by heat treatment is generally 52.3%, so the heat treatment in the entire mold manufacturing process occupies an important position, the heat treatment process has a greater impact on the quality of the mold.
General requirements of heat treatment deformation is small, quenching temperature range, superheat sensitivity is small, especially to have greater hardenability and hardenability and so on.
In the forming process may release corrosive gas decomposition of corrosive gases, such as HC1, HF and other corrosive mold, sometimes in the air runner mouth to make the mold rust and damage, so the requirements of mold steel has good corrosion resistance.
General plastic mold is often used to normalize the state of 45 steel or 40Cr steel by tempering manufacturing.
Hardness requirements of high plastic mold using CrWMn or Crl2MoV and other steel manufacturing.
For the working temperature of the plastic mold, you can choose to use the high toughness of the hot work mold steel.
In order to meet the higher requirements of the plastic cavity on the dimensional accuracy and surface quality, and recently developed a series of new mold steel.
Carburized plastic mold steel is mainly used for cold extrusion molding cavity complex plastic mold, the carbon content of such steel is low, often add the element Cr, while adding the right amount of Ni, Mo and v, the role is to improve the hardenability and carburizing ability, in order to facilitate cold extrusion molding, such steel in the annealed state must have high plasticity and low deformation resistance, annealed hardness &#; 1 00HBS.
After cold extrusion forming for carburizing and quenching and tempering treatment, the surface hardness can reach 58 &#; 62 HRC.
These steels have special steel grades abroad, such as Sweden&#;s , the United States P2 and P4, etc..
Domestic often use 12CrNi3A and 12Cr2Ni4A steel, 20Cr2Ni4A, good wear resistance, no collapse and surface flaking phenomenon, mold life increased.
Steel elements cr, Ni, Mo, V increase the hardness and wear resistance of the carburized layer and the strong toughness of the heart.
The carbon content of this type of steel is 0.3% -O.55%, commonly used alloying elements are Cr, Ni, Mn, v, etc.. In order to improve its machinability, adding s, ca and other elements.
Through the development, introduction and development of several typical plastic mold steel Y55CrNiMn-MoVS (SMI) is developed in China containing S system of easy-to-cut plastic mold steel, which is characterized by pre-hardened delivery hardness of 35_40 HRC, a good machinability, no longer heat treatment after processing, can be used directly.
Add Ni solid solution strengthening and increase toughness, add Mn and S form the cutting phase MnS; add Cr, Mo, V, increase the hardenability of steel 8Cr2S steel is sufficient to belong to the cutting precision mold steel.
The development of low cobalt, no cobalt, low nickel martensitic aging steel, MASI is a typical martensitic aging steel.
After solid solution treatment by C, the hardness is 28-32 HRC, ding for mechanical processing, and then by C aging, aging fold out Ni3Mo, Ni3Ti and other intermetallic compounds, so that the hardness of 48-52 HRC. high toughness of steel, small dimensional changes during aging, good welding performance, but the steel Expensive, less popular in the country.
Polyvinyl chloride (Pvc) and ABS plus flame-resistant resin as raw materials for plastic products, the decomposition of corrosive gases generated during the molding process, will corrode the mold.
Therefore, plastic mold steel is required to have good corrosion resistance. Foreign commonly used corrosion-resistant plastic mold steel martensitic stainless steel and precipitation hardening stainless steel two types.
Foreign have such as the Swedish ASSAB STVAX (4Crl3) and A SSAB a , etc.
Plastic Mould Products
All kinds of tools and products used in our daily production and life, from the base of machine tools and machine shells to a small embryonic head screw, button and the shell of various household appliances, all have a close relationship with the mold.
The shape of the mold determines the shape of these products, and the processing quality and precision of the mold also determines the quality of these products.
Because of the different materials, appearance, specifications and uses of various products, the moulds are divided into casting moulds, forging moulds, die-casting moulds, stamping moulds and other non-plastic moulds, as well as plastic moulds.
1. such as: household appliances, instruments and meters, construction equipment, automotive industry, daily hardware and many other fields, the proportion of plastic products is rapidly increasing.
A reasonably designed plastic parts can often replace multiple traditional metal parts. The trend of plasticization of industrial products and daily-use products is rising.
2. the general definition of mold: in industrial production, with a variety of presses and special tools mounted on the press, through the pressure of metal or non-metallic materials to make parts or products of the required shape, this special tool is collectively known as the mold.
3. Injection molding process description: mold is a tool for producing plastic products.
4. the general classification of the mold: can be divided into plastic molds and non-plastic molds.
(1) non-plastic molds are: casting mold, forging mold, stamping mold, die-casting mold, etc.
A. Casting mold &#; faucet, pig iron platform
B. Forging mold &#; car body
C. Stamping mold &#; computer panel
D. Die-casting mold &#; super alloy, cylinder block
(2) Plastic mold according to the production process and production products are divided into.
A. injection molding mold &#; TV shell, keyboard buttons (the most common application)
B. Air blowing mold &#; beverage bottles
C. compression molding mold &#; bakelite switches, scientific porcelain dishes
D. Transfer molding die &#; integrated circuit products
E. Extrusion molding mold &#; glue tube, plastic bags
F. Thermoforming mold&#;transparent molding packaging shell
G. Rotational molding mold &#; soft rubber doll toys
Injection molding is the most common method used in plastics processing.
The method is applicable to all thermoplastics and some thermosetting plastics, and the quantity of plastic products made is unparalleled by other molding methods.
As one of the main tools of injection molding process, the injection mold, in terms of quality accuracy, manufacturing cycle and production efficiency in the injection molding process, directly affects the quality, output, cost and product renewal of products, and also determines the responsiveness and speed of enterprises in the market competition.
It also determines the responsiveness and speed of the enterprise in the market competition.
The injection molding tool is composed of several steel plates with various parts, basically divided into.
A Molding device (concave mold, convex mold)
B positioning device (guide pillar, guide bush)
C fixed device (I-plate, mold pit)
D cooling system (water transport hole)
E Constant temperature system (heating tube, hot wire)
F Runner system (chirp hole, runner slot, runner hole)
G Ejector system (ejector pin, ejector stick)
5. The molds can be divided into three categories according to the different types of pouring system.
(1) Large spout mold: the runner and gate are on the parting line, and the product is demolded together when the mold is opened, the design is the simplest, easy to process, and the cost is low, so more people adopt the large spout system operation.
(2) Fine spout mold: the runner and gate are not on the parting line, generally directly on the product, so it is necessary to design more than one group of spout parting line, the design is more complicated, processing is more difficult, generally depending on the product requirements and choose the fine spout system.
(3) hot runner mold: the structure of this kind of mold is roughly the same as that of fine spout, the biggest difference is that the runner is in one or more hot runner plates and hot spout with constant temperature, no cold material demoulding, the runner and gate are directly on the product, so the runner does not need to be demoulded, this system is also called no spout system, it can save raw material, it is suitable for the case of expensive raw material and high product requirements, the design and processing is difficult, the mold cost is higher.
Hot runner system, also known as hot sprue system, mainly consists of hot sprue sleeve, hot sprue plate, temperature control electric box.
There are two types of hot runner systems we commonly use: single point hot gates and multi-point hot gates.
Single point hot gate is to use single hot gate sleeve to shoot molten plastic into the cavity directly, it is suitable for single cavity single gate plastic mold; multi-point hot gate is to branch the molten material into each sub hot gate sleeve and then into the cavity through the hot gate plate, it is suitable for single cavity multi-point feeding or multi-cavity mold.
(1) No sprues, no post-processing, so that the whole molding process is fully automated, saving working time and improving working efficiency.
(2) Small pressure loss. The hot runner temperature is equal to the injection machine nozzle temperature, which avoids the surface condensation of the raw material in the runner, and the injection pressure loss is small.
(3) Repeated use of sprues will degrade the plastic performance, while using hot runner system without sprues can reduce the loss of raw materials, thus reducing the product cost.
With uniform temperature and pressure in the cavity, the plastic parts have low stress and uniform density, and better products can be injected than general injection molding system in a shorter molding time under a smaller injection pressure.
For transparent parts, thin parts, large plastic parts or high requirements plastic parts can show its advantages, and can use smaller models to produce larger products.
(4) Heat nozzle adopts standardized and serialized design, equipped with various optional nozzle heads, and good interchangeability.
Unique design and processing of electric heating ring can achieve uniform heating temperature and long service life.
The hot runner system is equipped with hot runner plates, temperature controllers, etc., with delicate design, various types, easy to use, stable and reliable quality.
(1) The overall mold closing height increases, and the overall height of the mold increases due to the addition of hot runner plates, etc.
(2) The heat radiation is difficult to control, the biggest fault of hot runner is the heat loss of the sprue, which is a major issue that needs to be solved.
(3) There is thermal expansion, thermal expansion and contraction is a problem to be considered when we design.
(4) The mold manufacturing cost is increased, the standard parts of hot sprue system are more expensive, which affects the popularity of hot sprue mold.
Common software for plastic moulds
PTC&#;s EMX, Siemens&#; NX Mold Wizard, CimatronE, Topsoild, Delcam Moldmaker, Missler&#;s Topsolid Mold, Think3&#;s Mold Design, Manusoft&#;s IMOLD, R&B&#;s MoldWorks, Solidworks, Pro-e, UG (the last three are mainly product design, but can do mold design integration), etc.
Plastic Mold Polishing Process
To get high quality polishing effect, the most important thing is to have high quality polishing tools and auxiliary products such as oil stone, sandpaper and diamond abrasive paste.
Fine polishing mainly uses diamond polishing paste. If the polishing cloth wheel mixed with diamond grinding powder or paste for grinding, the usual grinding order is 9μm (#) to 6μm (#) to 3μm (#). 9μm diamond grinding paste and polishing cloth wheel can be used to remove the hair-like grinding marks left by # and # sandpaper.
Next, polishing is done with sticky felt and diamond polishing paste in the order of 1μm (#) ~ 1/2μm (#) ~ 1/4μm (#). Polishing processes requiring a precision of 1μm or more (including 1μm) can be performed in a clean polishing room in the mold shop.
For more precise polishing, an absolutely clean space is necessary. Dust, smoke, dandruff and saliva foam are likely to scrap several hours of work to get a high precision polished surface.
After milling, EDM, grinding and other processes, the surface can be polished by choosing a rotary surface polishing machine with a speed of 35 000-40 000 rpm or an ultrasonic grinding machine.
Commonly used methods include removing the white EDM layer using a wheel of Φ3mm diameter, WA # 400. This is followed by manual oilstone polishing with strips of oilstone with kerosene as lubricant or coolant.
The general order of use is #180 ~ #240 ~ #320 ~ #400 ~ #600 ~ #800 ~ #. many mold makers choose to start from #400 to save time.
Semi-finish polishing mainly uses sandpaper and kerosene. In fact, # sandpaper is only suitable for hardened mold steels (52 HRC and above) and not for pre-hardened steels, as this may cause surface burns on the pre-hardened parts.
Fine polishing with abrasive paste, , 10,000 to achieve a mirror finish.
Plastic Mold Polishing Method
Mechanical polishing is by cutting, material surface plastic deformation to remove the convex part of the polished and smooth surface polishing method, generally using oil stone, wool wheel, sandpaper, etc., mainly by hand, special parts such as the surface of the rotary body, can use the rotary table and other auxiliary tools, the surface quality requirements of high can be used to ultra-precision polishing method.
Ultra-precision grinding and polishing is the use of special abrasives, containing abrasives in the grinding and polishing fluid, pressed on the surface of the workpiece being processed, for high-speed rotary motion.
Using this technology can achieve Ra0.008μm surface roughness, is the highest among various polishing methods. This method is often used for optical lens molds.
Chemical polishing is to allow the material to dissolve the microscopic projections of the surface in the chemical medium in preference to the concave parts, thus obtaining a smooth surface.
The main advantage of this method is that it does not need complicated equipment, can polish complex shape workpieces, can polish many workpieces at the same time, and high efficiency.
The core problem of chemical polishing is the preparation of polishing solution. The surface roughness obtained by chemical polishing is generally several 10μm.
The basic principle of electrolytic polishing is the same as chemical polishing, that is, by selectively dissolving the tiny projections on the surface of the material to make the surface smooth.
Compared with chemical polishing, the effect of cathodic reaction can be eliminated, and the effect is better.
Electrochemical polishing process is divided into two steps: (1) macro leveling Dissolution products diffuse into the electrolyte, the geometric roughness of the material surface decreases, Ra>1μm. (2) micro light leveling Anodic polarization, surface brightness increases, Ra<1μm.
The workpiece is put into the abrasive suspension and placed in the ultrasonic field together, and the abrasive is ground and polished on the surface of the workpiece by relying on the oscillating effect of ultrasonic waves.
Ultrasonic processing macro force is small, will not cause workpiece deformation, but the tooling production and installation is more difficult. Ultrasonic processing can be combined with chemical or electrochemical methods.
On the basis of solution corrosion and electrolysis, ultrasonic vibration is then applied to agitate the solution, so that the dissolution products on the surface of the workpiece are detached and the corrosion or electrolyte near the surface is uniform; the cavitation effect of ultrasonic waves in the liquid can also inhibit the corrosion process and facilitate the surface brightening.
Fluid polishing is to rely on the high-speed flow of liquid and the abrasive particles carried by the workpiece surface to achieve the purpose of polishing.
Commonly used methods are: abrasive jet processing, liquid jet processing, fluid power grinding, etc. Fluid power polishing is driven by hydraulic pressure, so that the liquid medium carrying abrasive particles flows over the surface of the workpiece at high speed reciprocally.
The medium is mainly made of a special compound (polymer-like substance) with good flowability under low pressure and mixed with abrasive, and the abrasive can be made of silicon carbide powder.
Magnetic grinding and polishing is the use of magnetic abrasives to form abrasive brushes under the action of a magnetic field to grind and process the workpiece.
This method has high processing efficiency, good quality, easy control of processing conditions and good working conditions.
Using suitable abrasives, the surface roughness can reach Ra0.1μm.
Mechanical polishing based on the method, the polishing said in plastic mold processing is very different from the surface polishing required in other industries, strictly speaking, the polishing of the mold should be called mirror processing.
Required in other industries, strictly speaking, the polishing of the mold should be called mirror surface processing.
It not only has high requirements for polishing itself but also has high standards for surface flatness, smoothness and geometric accuracy.
Surface polishing is generally only required to obtain a shiny surface. Mirror processing standards are divided into four levels: AO = Ra0.008μm, A1 = Ra0.016μm, A3 = Ra0.032μm, A4 = Ra0.063μm, due to electrolytic polishing, fluid polishing and other methods are difficult to accurately control the geometric accuracy of the parts, while chemical polishing, ultrasonic polishing, magnetic polishing and other methods of surface quality can not meet the requirements, so precision The mirror surface processing of the mold is still mainly mechanical polishing.
To obtain high quality polishing effect, the most important thing is to have high quality polishing tools and auxiliary products such as oil stone, sandpaper and diamond polishing paste.
And the choice of polishing procedure depends on the surface condition after pre-processing, such as mechanical processing, EDM, grinding processing, etc.
Mould Development
China&#;s annual plastic mold output reached about 53.4 billion RMB? Do you believe it?
Due to the rapid development of China&#;s economy, the requirements of plastic mould industry are more and more strict, so it provides a huge impetus for the development of plastic mould industry.
According to accurate statistics, the annual output value of plastic moulds in China reaches 53.4 billion RMB, which is a fact that already exists.
With the rapid development of automobile manufacturing industry and IT manufacturing industry, the domestic mould industry has made rapid development, it is understood that the proportion of plastic moulds in China&#;s mould industry can reach 30%, it is expected that in the future mould market, the proportion of plastic moulds to the total moulds will still gradually increase, and the development speed will be faster than other moulds.
It is reported that the mold industry since with an annual speed of 20% rapid growth, pulling the mold grade, sophisticated mold manufacturing equipment for the mold technology level to provide a guarantee.
Analysis that, due to the import of mold, precision, large, complex, long-life mold accounted for most, so, from the perspective of reducing imports, improve the localization rate, the share of such high-grade mold in the market will also gradually increase.
The rapid development of the construction industry, so that a variety of profile extrusion molds, PVC plastic pipe joint molds become a new economic growth point in the mold market.
The rapid development of highways, automotive tires also put forward higher requirements, so radial rubber tire molds, especially the development of the live mold will also be higher than the total average; plastic instead of wood, plastic instead of metal to make plastic molds in the automotive and motorcycle industry, the demand for Huge; household appliances industry in the &#;12th Five-Year Plan&#; period will have greater development, especially refrigerators, air conditioners and microwave ovens, etc. plastic mold spare parts demand is great
At the same time, the pace of structural adjustment of plastic mold industry is accelerating, the number and capacity of professional plastic mold manufacturers for the market is also growing rapidly.
According to the analysis of the production, sales, market situation, industry structure, products and import and export of plastic mold manufacturing industry, with reference to the development trend of plastic mold related industries, predict the future development direction of China&#;s plastic mold manufacturing industry where exactly, in the end how much development potential of China&#;s plastic mold manufacturing industry, these are needed to verify.
So you need a custom plastic part or product, but you don&#;t know how to get it made.
Is it large or small? Should it be flexible or stiff? Is it round, square, or some weird shape? Do you already have a mold, or do you need to have one made?
This guide will explain the different kinds of molding processes available today to help you discover the ideal process for your product.
*Disclaimer: Even though Fibertech exclusively offers rotational molding, we&#;ve gone to great lengths to make sure this guide accurately helps you choose the best form of molding for your product. Sometimes, the best choice is rotational molding&#; other times, it&#;s another kind of molding. Our goal with this guide is to be as objective as possible while pointing you in the best direction to get your part or product made with the ideal method. If you have questions or comments about this guide, feel free to contact us.
Molding, also sometimes spelled moulding, is the process of manufacturing by shaping liquid or pliable material using a rigid frame called a mold or matrix. [1]
When molding plastics, a powder or liquid polymer such as polyethylene or polypropylene is placed into a hollow mold so the polymer can take its shape. Depending on the type of process used, various ranges of heat and pressure are used to create an end product.