Due to the presence of uneven carbides distributed in a certain direction in the mold steel used for metal and plastic mold processing, the expansion coefficient of carbides is about 30% smaller than that of the steel matrix structure. When heated, it prevents the expansion of the mold holes, and when cooled, it prevents the shrinkage of the mold holes, causing uneven deformation of the mold holes and resulting in elliptical circular holes in the mold. Causes and preventive measures:

When choosing a plastic mold processing enterprise, the first thing to consider is the selection of the mold being processed. Generally speaking, machines with high precision, multiple curved surfaces, and high-speed light cutting should be chosen. In addition to these factors, cost-effectiveness is also a consideration.

The various tools and products we use in our daily production and life, from the base and shell of machine tools to the shell of various household appliances, are all closely related to molds. The shape of the mold determines the appearance of these products, and the processing quality and accuracy of the mold also determine the quality of these products. Due to the different materials, appearances, specifications, and uses of various products, molds are divided into non plastic molds such as casting molds, forging molds, die-casting molds, stamping molds, and plastic molds.

In recent years, with the rapid development of hardware and plastic mold processing in Dongguan and the continuous improvement of strength and accuracy of general and engineering plastics, the application scope of hardware and plastic mold processing has also been expanding, 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 well-designed plastic component can often replace multiple traditional metal components. The trend of plasticization of industrial and daily products is constantly increasing.

The general definition of metal and plastic mold processing mold: In industrial production, various press machines and specialized tools mounted on the press machines are used to produce metal or non-metal materials into parts or products of the desired shape through pressure. These specialized tools are collectively referred to as molds.

Injection molding process description: Mold is a tool for producing plastic products. It consists of several sets of component parts, and this combination contains a molding cavity. During injection molding, the mold is clamped onto the injection molding machine, and molten plastic is injected into the molding cavity, where it is cooled and shaped. Then, the upper and lower molds are separated, and the product is ejected from the mold cavity through the ejection system. After that, the mold is closed for the next injection molding, and the entire injection molding process is cyclical.

(1) Large water mouth mold: The runner and gate are located on the parting line and are demolded together with the product during mold opening. The design is simple, easy to process, and the cost is low, so many people use the large water mouth system for operation.

(2) Fine nozzle mold: The runner and gate are not on the parting line, usually directly on the product, so it is necessary to design an additional set of water nozzle parting lines, which is more complex and difficult to process. Generally, a fine nozzle system should be selected according to product requirements.

(3) Hot runner mold: This type of mold has a structure similar to that of a fine nozzle, with the main difference being that the flow channel is located in one or more hot runner plates and hot nozzles with constant temperature, without cold material demolding. The flow channel and sprue are directly on the product, so the flow channel does not need to be demolded. This system is also known as a water free mouth system, which can save raw materials and is suitable for situations where raw materials are expensive and product requirements are high. The design and processing are difficult, and the mold cost is high.

Hot runner system, also known as hot runner system, mainly consists of hot runner sleeve, hot runner plate, and temperature control electrical box. Our common hot runner systems come in two forms: single point hot runner and multi-point hot runner. Single point hot gate is a plastic mold that uses a single hot gate sleeve to directly inject molten plastic into the mold cavity. It is suitable for plastic molds with a single cavity and a single gate; Multi point hot runner is a method of branching molten material into different hot runner sleeves through a hot runner plate before entering the mold cavity. It is suitable for single cavity multi-point feeding or multi cavity molds

Advantages of hot runner system

(1) No water mouth material, no need for post-processing, making the entire molding process fully automated, saving work time, and improving work efficiency.

(2) Low pressure loss. The temperature of the hot runner is equal to that of the injection nozzle of the injection molding machine, avoiding surface condensation of raw materials in the runner and reducing injection pressure loss.

(3) The repeated use of nozzle materials will degrade the performance of plastics, while the use of hot runner systems without nozzle materials can reduce the loss of raw materials and thus lower product costs. In the mold cavity, the temperature and pressure are uniform, the plastic part has low stress, and the density is uniform. Under lower injection pressure and shorter molding time, better products can be injected than general injection molding systems. For transparent parts, thin parts, large plastic parts or high demand plastic parts, their advantages can be better demonstrated, and larger products can be produced with smaller models.

(4) The hot nozzle adopts standardized and serialized design, equipped with various nozzle heads to choose from, and has good interchangeability. The uniquely designed and processed electric heating coil can achieve uniform heating temperature and long service life. The hot runner system is equipped with hot runner plates, temperature controllers, etc., with exquisite design, diverse types, convenient use, stable and reliable quality.

Shortcomings in the application of hot runner systems

(1) The overall height of the mold closure has increased due to the installation of hot runner plates, etc.

(2) The difficulty in controlling thermal radiation and the major problem with hot runners is the heat loss, which is a major issue that needs to be addressed.

(3) There is thermal expansion, and thermal expansion and contraction are issues that we need to consider when designing.

(4) The increase in mold manufacturing costs and the higher prices of standard components for hot runner systems have affected the popularity of hot runner molds.