Packaging machinery parts-the basic composition of injection molds
Update Time: 2019-09-10 Hits: 264
Although the structure and performance variety of plastic molds, the shape and structure of plastic products and the types of injection molding machines may vary, the basic structure is the same. It is mainly composed of die-casting systems, cooling systems, molded parts and structural parts. Plastic parts are in direct contact and change with plastics and products.They are the most complicated, mold replacement, parts processing accuracy requirements and highest finishing.
The gating system refers to the plastic before it enters the runner cavity from the nozzle, including the main flow, cold materials, runners and gates. Molded parts refer to various parts in the shape of the product, including movable molds, cavities, cores, molded rods and exhaust ports. A typical mold structure is shown below.
The gating system is also called the runner system. It is a plastic melt from the nozzle injection molding machine to the cavity of a group of feeding channels. It is usually composed of runners, runners, gates and cold materials. It is directly related to the molding quality and production efficiency of plastic products.
(1). Main channel
It is the channel that connects the injection molding machine nozzle to the shunt or cavity. The top of the main stream is connected to the concave surface with the nozzle. The diameter of the inlet of the main flow channel should be slightly larger than the diameter of the nozzle (O.8mm) to avoid overflow and prevent it from occurring due to cohesion. The inlet diameter depends on the product size and is generally 4-8mm. The gate diameter should be enlarged to an angle of 3 ° to 5 ° for a new release channel.
(2). Cold material
It is a hole at the end of the main flow path to capture cold material between the nozzle ends of the two shots to prevent clogging of the flow path or gate. If cold material enters the cavity, the system is prone to stress products. The cold material has a diameter of 8 lOmm and a depth of 6mm. For ease of release, the bottom is usually carried by the release lever. The top of the ejector pin should be designed as a winding hook or sinker so that the mold can smoothly cast the pull block.
It is the channel connecting the gate and cavity multi-slot die. Since the molten material has a constant velocity in the mold, the diverting devices should be symmetrical and equally spaced. The shape and size of the plastic melt flow in the runner are affected by the difficulty of demolding and mold manufacturing. If the material flow is equal, the flow resistance of the circular section is the smallest. However, because the specific surface area of the cylindrical channel is small, it is not conducive to blocking the cooling channel, and the rotor must be opened in two modules, which is time-consuming and easy to align. Therefore, it is often used to divert trapezoidal or semi-circular cross-sections and open with a stripper in the half mold. The channel surface must be polished to reduce the flow resistance of the mold filling speed. Size flow depends on the type, size and thickness of the plastic product. For most thermoplastics, the cross-section width of the flow channel is less than 8 meters, especially as high as 10 12M and as small as 2-3 meters. It should be reduced as much as possible in order to avoid increasing cross-sectional area, shunting blocks and extending cooling time.
It connects to the main (or shunt) and channel cavity. The zone channel can be equal to the main channel (or shunt), but is usually smaller. It is therefore the smallest part of a cross-section runner system. The size and shape of the gate have a great impact on product quality.
The role of the door of Shandong injection molding factory is:
A, control the material flow rate.
B, the injection prevents the molten material from flowing back in this part of the early solidification.
C, the molten material is subjected to strong shear and elevated temperatures, thereby reducing the apparent viscosity and improving the fluidity.
D, it is convenient to separate the product from the runner system. The size and structural design depend on the shape, size, and location of the door in the plastic product. Generally, the cross-sectional shape of the gate is rectangular or circular, and the cross-sectional area should be small and the length should be short. This is not only based on the action, but also because the smaller gate becomes easier, and the larger gate becomes narrower. Generally it should be in the thick door position without affecting the appearance. The design of the gate size should consider the nature of the plastic melt. The cavity is the space in which the plastic mold is molded. The forms used as cavity parts are collectively referred to as molded parts. Each molded part usually has a special name. The shape that forms the part is called a mold (also called a mold) and forms the internal shape of the product
(Such as holes, grooves) are called cores or punches (also called males). The design of the molded part must first determine the overall structural cavity based on performance, plastic geometry, size and required tolerances. The second is determined according to the structure of the parting surface, the positions of the gates and vent holes, and the demolding method. Finally, according to the design control size of each part, determine the combination between each part. High-pressure plastic melts into the cavity, so the molded parts should use reasonable materials and their strength and stiffness. In order to ensure that the surface of plastic products is smooth and easy to release, all plastic contact surfaces are used, with a roughness Ra> 0.32um and corrosion resistance.
2. Temperature control system:
In order to meet the requirements of the mold temperature injection process, the mold temperature control system is required to adjust the temperature. For the injection molding of thermoplastics, the design of the mold cooling system is mainly. A common method is to open the mold cooling cooling water channel in the mold and eliminate it by circulating cooling water; the mold heating and cooling water channels can use hot water or steam, and electric heating elements can also be set inside and around the mold.
3. Moulded parts:
The molded part consists of a core and a cavity. The core forms the inner surface product, and the mold forms the outer surface shape product. A cavity mold is formed after the core and the cavity. According to the process and manufacturing requirements, sometimes the core and mold are combined by multiple parts, sometimes as a whole, only inserted when the parts are easily damaged and the parts are difficult to use.
It is a groove provided at the exit of the mold shape, which uses gas to exhaust the original and melt it. Melt into the cavity, the gas originally stored in the cavity and the fluid flowing from the melt must reach the end of the mold through the exhaust port, otherwise it will make the product porous, poor contact, filled and expired compressed air temperature and Product burns. Generally, the vent hole can be located at the melting end of the flow cavity, or it can be set on the mold parting surface. The latter is to create 0.03-0.2mm deep and 1.5-6mm shallow groove width on the side of the mold. During the injection, there will not be a large amount of melt oozing out of the vent, because the melt will block the channel when it cools and solidifies. The location is not opposite the operator's exhaust vent to prevent accidental injuries.
4. Structural parts
It refers to the composition of each part, the mold structure includes: the guidance of various parts, mold, core drawing and typing. Such as splint front and back, buckle template, support plate, bearing column, guide column, ejection template, ejector rod and return rod.
In order to ensure that the movable mold and the fixed mold in the mold can accurately guide the components, they must be set in the mold. In injection molds, four sets of guide posts and guide sleeves are often used to guide the invisible. Sometimes, the inner side and the outer side are tapered to assist positioning.
(2). Release mechanism
During the mold opening process, plastics and aggregates need to be fired in the runner to be fired or pulled out. The introduction of the clamp rod putter is a fixed plate and a push plate. The push rod is fixed on the general reset lever, the dynamic reset lever, and the mold is reset in combination with the push plate.
(3). Side core pulling mechanism
Some plastic products with undercuts or side holes must be separated first when introduced into the former, and the mold can be removed smoothly after taking the side core. At this time, the side needs to be arranged in the core pulling mechanism.
(4). Standard mold Shandong injection molding factory
In order to reduce the heavy workload of mold design and manufacturing, injection molds use standard molds.