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2021-10
Several elements in plastic molds
1. Parting surface: the contact surface between the plastic mold and the convex mold when it is closed. The choice of its location and form is affected by factors such as product shape and appearance, wall thickness, forming method, post-processing technology, mold type and structure, demoulding method and forming machine structure.
2. Structural parts: that is, the slider, inclined top, and straight top of the complex mold. The design of structural parts is very critical, related to product life, processing cycle, cost, product quality, etc. Therefore, the design of the complex core structure requires the comprehensive ability of the designer, and strives to pursue a simpler, more durable, and more economical design solution.
3. Mold accuracy: namely avoiding jams, positioning, guide posts, positioning pins, etc. The positioning system is related to the appearance quality of the product, mold quality and mold life. According to the different mold structure, choose different positioning methods. The control of positioning accuracy mainly depends on processing. The positioning of the internal mold is mainly considered by the designer, and a more reasonable and easy-to-adjust positioning method is designed.
4. Pouring system: the feeding channel from the nozzle to the cavity of the injection molding machine, including the main runner, branch runner, gate and cold cavity. In particular, the selection of the gate position should be conducive to filling the cavity with molten plastic in a good flow state, and when the mold is opened (except for the hot runner mold), the solid runner and gate cold material attached to the product can be very effective. Easily eject and remove from the mold.
5. Plastic shrinkage rate and factors affecting product dimensional accuracy: such as plastic mold manufacturing and assembly errors, mold wear, etc. In addition, when designing compression molds and injection molds, the matching of process parameters and structural parameters of the molding machine should also be considered.
27
2021-10
Injection molding and temperature issues
The higher the mold temperature, the lower the flow resistance. On many injection molding machines, this naturally means that the flow through the sprue, gate and cavity is faster, because the injection flow control valve used cannot correct this change, and faster filling will result in a greater flow in the sprue and cavity. High effective pressure. May cause flashing. Since the hotter mold does not freeze the plastic that enters the edge area of the flash before the high pressure is formed, the melt will flash around the ejector pin and overflow into the gap of the dividing line. This shows that good injection rate control is required, and some modern flow control programmers can indeed do this.
Generally speaking, a higher mold temperature will reduce the amount of plastic that has a condensation layer in the mold cavity, making it easier for the molten material to flow through the mold cavity, thereby increasing the weight of the part and improving the surface quality. At the same time, the mold temperature will also increase the tensile strength of the part.
Mold insulation. Many molds, especially thermoplastics, work at relatively high temperatures, such as 80 degrees Celsius or 176 degrees Fahrenheit. If the mold is not insulated, the heat lost to the air and injection molding machine can easily be as much as the heat lost from the injection barrel. Therefore, the mold and the board should be insulated, and if possible, the mold surface should be insulated. If considering the hot runner mold, the heat exchange between the hot runner part and the cooling injection part should be minimized. This can reduce energy loss and warm-up time.
27
2021-10
Model manufacturing is inseparable from high-precision molds, communication that developers cannot ignore
When developing products or trial-manufacturing new products, one should not only focus on R&D and neglect the communication with the model manufacturing unit. After the product design plan is initially determined, there are two advantages to contacting the manufacturer in advance:
27
2021-10
Xiaobian takes you to understand the content of mold processing
With the increasingly fierce competition in the manufacturing field. Shortening the production cycle is a development trend. Some foreign fixture manufacturers have realized the unified benchmark interchange of milling, turning, measuring, EDM and other processes through the use of stable and accurate benchmark systems. It only takes about 1 minute to complete the clamping and alignment on the machine tool, and the repeatability is set within 3μm, which shortens a lot of setting time and improves the actual running time of the machine tool. Facts have proved that this is a necessary condition for modern production. When using the clamping and setting system, it already has the basis for automation.
27
2021-10
What will be the impact of injection molding
Mold designers have rich experience in design and injection molding, and consider the relationship between these factors and injection molding conditions and their apparent factors, such as injection pressure, cavity pressure and filling speed, injection melt temperature and mold temperature, mold Structure and gate type and distribution, and discussed the influence of gate area, wall thickness, filler content in plastic, plastic crystallinity and orientation. The influence of the above factors also varies with plastic materials or other molding conditions such as temperature, humidity, continuous crystallization and molding machine.
Because the injection molding process is a process of plastic from solid (powder or granule) to liquid (melt) to solid (product). From particulate matter to melt, and then from melt to product, it passes through the temperature field, flow field, and density field. Under the action of these fields, different plastics (thermosetting or thermoplastic, crystalline or non-crystalline, reinforced or non-reinforced, etc.) have different polymer structures and rheological properties. All the factors that affect the "field" will affect the physical and mechanical properties, size, shape, precision and appearance quality of plastic products.
27
2021-10
What factors should the material of the injection mold have?
Do you know the basic principles that need to be achieved when selecting materials for injection molds? If you are still unclear, let's take a look at it with the editor now.
1. Abrasion resistance
During the plastic degeneration of the blank in the cavity, the blank flows and slides along the surface of the cavity, causing friction between the surface of the cavity and the blank. Therefore, the wear resistance of the material is one of the most basic and important properties of the mold.
The main factor affecting wear resistance is hardness. Generally, the higher the hardness of injection mold parts, the smaller the wear and the better the wear resistance.
2. Toughness
Most of the researches on the working environment conditions of the mold are very harsh, and some of them are often able to withstand large impact loads, which can lead to brittle fracture. In order to prevent sudden brittle fracture of mold design parts during work, the mold must have relatively high strength and toughness.
The toughness of the mold mainly depends on the carbon content, grain size and microstructure of the material.
3. Fatigue fracture performance
In the development process of mold design work, under the long-term influence of cyclic stress, it can often lead to fatigue and fracture of students. Its forms include small energy fatigue fracture through multiple impacts, tensile fatigue fracture, contact fatigue fracture, and bending fatigue fracture.
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