HOW THE MOLD IS MANUFACTURED: PRODUCTION STAGES
Manufacturing of molds is the way to the production of plastic products of any design and level of complexity. The price of a plastic injection mold depends on its performance. Equipment for injection molding of plastics is a system of complex elements, each of which must be ideally matched to each other. Therefore, the manufacture of molds for plastic injection begins with a critical stage – design.
To begin with, a 3D model of the finished product is created, and on its basis a mold is designed. It is believed that the most important part of the design is the 3D modeling of the technological parts of the mold. Of course, the shape of the parts (matrix and punch) must match – mistakes cannot be made here, because the appearance and quality of the final product depends on this. However, this task is not at all as difficult as designing a gating system, a system of ejection, cooling, etc. The entire production depends on the efficiency of their work – from quality to the final cost of the product. Well-designed and optimized parts can save you significant money and increase productivity.
All parts of the plastic injection mold are turned on high precision CNC machines from hardened steel. Individual parts are coated with a wear-resistant layer. After that, they are assembled and ideally rubbed against each other.
MOLD TEST AND TEST CASTING
The mold is launched on the injection molding machine. About a hundred closings are carried out to identify defects or inaccuracies. The mold casts the first piece. In case of revealing any shortcomings, the mold is refined until it becomes perfect.
Depending on the scale of production, there are five types of molds, which are shown below. All molds are made of high quality materials and anti-corrosion steel, and the column guides are coated with a special wear-resistant layer.
TYPES OF PRESS FORMS DEPENDING ON THE CIRCULATION
1. Molds with a resource of 1,000,000 cycles. These molds are designed for the highest production runs and are highly durable. The upper limit of the number of products is practically unlimited, since the parts of the mold can be replaced as they wear out. Also, the duration of their use can be increased by making products from non-abrasive plastics. These are the most expensive molds.
2. Molds with a resource from 100,000 to 499,999 cycles. They perfectly cope with the tasks of medium and small production. The cost of a mold for medium-sized casting is reduced due to the fact that there are fewer requirements for technical equipment. For example, cooling channels do not have such a complex design as a high-performance mold.
3. Molds with a resource from 500,000 to 999,999 cycles. These molds are designed for high tolerance parts and have medium to high productivity. The creation of a mold of this type takes into account the fact that the molds will be in contact with the abrasive plastic – the forming parts are hardened to a hardness of more than 49HRC.
4. Molds with a service life of up to 99,999 cycles. For the production of a limited batch of products, molds with a small resource are used.
WHY TO PRODUCE PRESS MOLDS?
Press forms apply to obtain any plastic products – from the ballpoint pen cap to the rocket parts. With their help, components and cases for household appliances, office supplies, children’s toys, medical devices, automotive and engineering industries, construction needs, etc. are manufactured. Molds are used to produce all kinds of containers and packaging materials.
TYPES OF MOLDS BY MANUFACTURING METHOD
DIRECT PRESS FORMS
In such molds, the material is loaded into a die, after which it is heated, becomes plastic and compacted under the action of a punch. When the product is finished, the mold is closed. Depending on the design of the design nest, this type of mold is divided into three kinds …
1. Open. The creation of a mold of this kind does not imply the installation of a loading chamber. Such molds are used for the production of large-area plastic products (for example, trays). Their disadvantage is the increased percentage of rejects due to underpressure in some cases.
2. Reciprocating. In them, the shaping nest directly continues the loading plane. Their operation requires an exact match between the mass of the loaded material and the resulting product. In such molds, plastic products can be made from difficult-to-press plastics. Their main disadvantage is the rapid wear of the punch and die.
3. With overflow. Molds of this type are the most common. Their design provides for a minimum clearance between the punch and the loading chamber. In this case, a release belt is formed, which ensures complete locking of the design nest.
Depending on the loading chamber allocate:
- with a common (for the production of small products of simple design);
- with individual (have a high accuracy of the forming nest).
Depending on the the location of the loading chamber The molds are divided into two types:
- c top loading chamber (its use is more preferable when using cassette packages);
- with bottom loading chamber (used on presses with increased force of the lower hydraulic cylinder).
PRESSURE MOLDING FOR PLASTICS
In this type of mold, the loading chamber is connected to the mold nest by means of a gating system. Plastic injection molding is the most popular form of mass production. The injection molds do not have a loading chamber, but the gating system remains. Such molds have a high degree of process automation and allow obtaining finished products that do not require additional processing.
1. Stationary. They do not have removable elements, so the mold is fixed on an injection molding machine for the entire period of manufacturing a batch of the product.
2. Semi-stationary. For such molds, removable elements are made that can be alternately installed in the mold, which allows you to speed up the casting process.
3. Removable. These molds are not fixed to the plates and each time they must be removed from the injection molding machine to remove the product. This allows significant cost savings in the manufacture of the mold due to the absence of a system for ejecting parts. However, such molds have low productivity, so they are used in one-off production.
The mold consists of two types of parts – technological and constructive. Let’s take a closer look at these two groups of parts. …
CONSTRUCTION FEATURES OF CREATION OF PRESS FORMS
TECHNOLOGICAL DETAILS OF THE MOLD
These parts are directly involved in the formation of products and come into contact with plastic. These include the following details.
- Matrix. Participates in the formation of the outer surface of the plastic product. Most often, matrices are made not integral, but composite, especially for the production of large-sized products. In the manufacture of the matrix, it is necessary to completely exclude the possibility of accidental ingress of material into the gap between the matrix and the loading chamber.
- Punch. Press punches form the inner surface of the product. Like matrices, they are usually prefabricated.
- Magazines. These are the details that connect the design elements. They are characterized by a simple design. Although they are not directly involved in the formation of products, they are under heavy stress and wear out quickly.
- Liners. Small parts that fit into a die and / or punch to create depressions or holes in a product. Inserts significantly save time and money in the production of the matrix, because machining on machines can be too complex.
- Thread. To obtain an internal thread, threaded marks are installed, and for an external thread, threaded rings.
CONSTRUCTION DETAILS OF THE MOLD
This group unites parts that do not take part in the formation of the product. However, they are very important, because they ensure the work of parts from the first group. For example, column guides, pushers, etc.
The gating system is a channel system that transfers the molding material from the nozzle of the injection molding machine to the mold cavity. Gating systems are hot and cold. Hot runner systems are capable of providing “runnerless” casting – when using them, a sprue is not formed, which is a part of the casting and goes to waste.
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HOW TO ORDER A PRESS FORM?
We have prepared for you contact list who are engaged production of molds and plastic products large batch …
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