Injection molding is the most efficient and widespread method for producing various products. Plastic injection equipment is a wide range of devices that allow you to transform plastic and give it a certain shape.
Features of casting as a chemical process
When casting, plastic under the influence of pressure changes its viscous-flowing consistency in order to flow through the channels of the equipment. A certain form is prepared in advance, where the molten mass enters, where it becomes solid. Like equipment for molding plastic, the material itself can be different - the choice depends on the mode in which the casting will take place and in what form.
Plastic molding occurs most often at a pressure of 80-140 MPa. If it is higher, there is an opportunity to get products that will be highly durable. In addition, ultra-high pressure allows you to accurately transfer the dimensions of the parts of the product. The pressure level is selected depending on the degree of viscosity, the melt of the plastic, the type of mold and the result that is planned to be achieved.
Types of casting
Equipment for plastic injection molding is selected depending on what type of molding will be taken as the basis. There are several of them:
- Injection. With it, products are obtained with minimally thin or maximally thick walls, they give less shrinkage. The process itself is the injection of molten plastic into a mold that does not fully close.
- Intrusion. This method is necessary to obtain products with thick walls. The basis of his work is the injection into the form of a smaller amount of material than is required. The mold is filled with a low-pressure fluid composition. As soon as it is filled, a small amount of material is fed there under high pressure - it is it that finally forms the product and compensates for its shrinkage.
Injection molding machines - basic equipment
The equipment for molding plastic is used differently, but, as a rule, piece products are produced on its basis. The advantages of high pressure casting are as follows:
- The ability to use different types of plastic.
- The effectiveness of equipment that provides an automated process.
- The ability to produce parts of complex geometry, which cannot be done by other technologies.
- Products created by casting can be reinforced, be hybrid or hollow, multi-color and made of foam plastic.
- The ability to mold products of different weights - from a few grams to several kilograms.
Technology features
Using equipment for molding plastic products, you can create different products. Moreover, the method itself is cyclical, and its essence can be reduced to the following:
- First, the polymer melts, which accumulates in the cylinder of the injection machine for further feeding into the mold.
- Plasticizer melt moves into a mold that is uniformly filled with a polymer composition.
- The melt hardens, while the material cylinder is still closed with the shape system.
- After the product hardens, the form opens, the product is removed from it.
Plastic injection equipment consists of the following elements:
- a block that prepares the melt and feeds it into a mold (injection unit);
- block locking (and opening) form, which is a press device with a slider (node closure);
- drive unit: it provides all types of movement of mobile devices and equipment;
- injection machine control devices: it is designed to provide important parameters for operation, due to which the casting is performed efficiently.
Injection molding machines are complex and quite expensive devices that incorporate modern technical solutions.
Types of TPA
TPA is a modern equipment for plastic molding, presented in various versions. Depending on the method of plasticization, they are single- or double-worm, piston or worm-piston. Plasticization itself can be combined or separate. The number of plasticizers is also different. The drive in the injection molding machine can be electric or hydromechanical. In addition, all injection machines are horizontal, vertical, angular - with a horizontal or vertical press part.
Corner equipment for injection molding of plastic allows you to create large products that are difficult to remove from the mold, and vertical injection molding machines, on the contrary, are good for the production of small products, including reinforced ones.
How does an injection machine work?
The principle of operation of injection molding machines is simple. The raw material to be processed is placed in the hopper of the plasticization unit, then it is discharged into the cylinder, where the friction force acts under the influence of the screw . As a result, the raw material is heated, plasticized, and then fed into a space with a homogeneous mass. As the necessary amount of melt builds up, material is injected into the mold. The finished product is removed from it, and the cycle starts again.
Equipment for plastic molding in silicone molds is used in several modes:
- Manual, when operations are started by pressing a button and adjusting the end positions of moving mobile nodes.
- Semi-automatic. In this mode, the mobile fence door opens and closes in order to complete one work cycle.
- Automatic (photocell). In this case, the cycles follow each other, but the command to execute the next cycle is transmitted by the photosensors at the moment when the finished product falls between them.
- Automatic (time), when the cycle is in automatic mode, and the next cycle starts after the delay time between them expires.
Security systems
Any devices, including equipment for molding plastic at home, must work based on safety rules. Modern injection molding machines are always equipped with systems that ensure the safety of personnel, responding in emergency situations. All protective devices are electronic, mechanical, safety, as well as in the form of a protective casing for heating elements.
Electronic devices can protect the mechanism of the hydraulic system. In case of emergency, the “emergency stop” button can be used to shut off the oil pump drive. Mechanical systems simply close molds. Using the protective casing of the heating elements ensures the safe operation of the equipment.
Major brands
Modern manufacturers offer a wide selection of injection molding machines, and for plastic molding equipment, the price is very different and depends on technical parameters, power and other indicators. The most popular to date are Japanese, Chinese and South Korean brands. So, a new series of TPA was released by the Japanese company Nissei. The features of this product are as follows:
- The presence of a 5-zone temperature control, including heating of the loading port.
- TPA can work not only from a network.
An interesting solution is offered by Sumitomo: in its lineup there are 4 models that have a direct screw drive on ball bearings. The model is highly accurate. The plastic molding equipment created by the popular Toshiba brand has a high price, but it justifies itself with the excellent quality of the systems. The distinctive features of the products of this brand include:
- a new control system that directly controls robots;
- software packages can be downloaded over the Internet;
- the device can be tuned to sound limits.
Nadem by Meiki
The Meiki Nadem model has direct control and is complemented by an injection compression system. This device is fully electric, operating at high speed. The JSW Plastics Machinery brand offers an equally perfect unit: high-speed injection molding machines allow the production of a wide selection of products of different thicknesses. The largest toy injection molding equipment has been developed under the Toyo brand. The price of such equipment can reach a million rubles, while the machine is resistant to vibration, equipped with a special injection mechanism, which is associated with balancing the columns.
JONWAI injection molding machines produce various automotive parts. Initially, the company focused on the fact that they use recycled polymeric materials. Moreover, the products of this brand are widely used by popular car manufacturers HYUNDAI, PEUGEOT, FORD, DACIA, FIAT. TPA are widely used when casting plastic bumpers. Manufacturing equipment for these processes is one of JONWAI's business lines.
Silicone casting: what is the point?
Vacuum molding in elastic forms involves the production of plastic, rubber, plastic. This method is used for different purposes: when creating prototypes and prototypes, small batches of goods of varying degrees of complexity, shape and size. Forms are created on the basis of pouring silicone into the formwork, where the master model is located. Silicone polymerizes, after which it is cast into molds.
Equipment for molding plastic into silicone molds allows you to get products that perfectly reproduce the dimensions and surface texture of the master model. In addition, vacuum casting prevents the appearance of porosity on the surface and defects on it. It is also important that silicone molds allow you to create products of any complexity and configuration, which cannot be achieved using other technologies.
Rotational molding of plastics
The manufacture of equipment for the rotational molding of plastic products is a difficult process, which allows to obtain large-sized products. The peculiarity of their production is that there are no seams in such a product, and its walls are of equal thickness. Rotoforming involves the absence of pressure on the material, so the finished product does not have internal stresses, which affects greater strength. This type of molding consists of three stages of work:
- First, polymer material is poured into the mold.
- The form is sent to the chamber where it heats up. This stage is the rotational molding.
- At the last stage, the rotation form is cooled.