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Injection Mold

In modern industrial production, mold is an important technology used in shaping products (including metal products and nonmetal products) for all of the industries. Meanwhile, it is the ‘magnifying glass of efficiency and profit’ to the raw material and equipment, because the value of the final product made in the mold is often tens of, even hundreds of times as valuable as that of the mold itself.

The mold industry is the basic industry of the national economy, and it is called ‘the mother of industry’. Every aspect of human life such as clothes, food, housing, and transportation is closely connected with the mold industry. Therefore, the level of injection mold technology has been a significant symbol to measure a country’s developing level of mechanical industry.

And mold can be divided into two kinds of them: mold for metal products and nonmetal products.
The metal products mold include cold-press mold, pressing mold, forging mold, press casting mold, precise casting mold, stamping tool, punch tool, and dust metallurgy mold, etc. These kinds of mold have extensive apply-cation in electrode-cranial products, automobiles, aviation instruments, and other metal products.
The nonmetal products include plastic injection mold, ceramic mold, rubber mold, glass mold, food mold, and ornament mold. These kinds of molds have extensive apply cation in our lives, at this page we are talking about injection mold. this is the most papular modern technology which used in our life everywhere.

An injection mold used to form a plastic product using the injection molding process. A standard injection mould is made of a stationary or injection side containing one or more cavities and a moving or ejection side.

The resin, or raw material for injection moulding, is usually in pellet form and is melted by heat and shearing forces shortly before being injected into the mould. The channels through which the plastic flows toward the chamber will also solidify, forming an attached frame. This frame is composed of the sprue, which is the main channel from the reservoir of molten resin, parallel with the direction of the nozzle, and runners, which are perpendicular to the direction of the nozzle and are used to convey molten resin to the gate(s), or point(s) of the gate and feeding the molten material into the mold cavity. The sprue and runner system can be cut off and recycled after molding. Some moulds are designed such that it is automatically stripped from the part through the action of the mould. For example, the submarine gate or banana gate, if using hot runner systems then there will be no runners.

The quality of the injection molded part depends on the quality of the mould, the care taken during the moulding process, and upon details of the design of the part itself. It is essential that the molten resin is at just the right pressure and temperature so that it flows easily to all parts of the mold. The parts of the injection mold must also come together extremely precisely, otherwise small leakages of molten plastic can form, a phenomenon known as flash. When filling a new or unfamiliar mould for the first time, where shot size for that particular mould is unknown, a technician should reduce the nozzle pressure so that the mold fills, but does not flash. Then, using that now-known shot volume, pressure can be raised without fear of damaging the mould. Sometimes factors such as venting, temperature, and resin moisture content, can affect the formation of flash as well.

Injection Mold Material

Traditionally, molds have been very expensive to manufacture therefore they were usually only used in mass production where thousands of parts are being produced. Injection Molds are typically constructed from hardened steel or aluminum. The choice of material to build a mold is primarily one of economics. Steel molds generally cost more to construct, but their longer lifespan will offset the higher initial cost over a higher number of parts made in the mold before wearing out. Aluminum molds can cost substantially less, and when designed and machined with modern computerized equipment, can be economical for moulding hundreds or even tens of parts.

Requirements for the injection mold

ejection system

An ejection system is needed to eject the molded part from the cavity at the end of the molding cycle. Ejector pins built into the moving half of the mold usually accomplish this function. The cavity is divided between the two mold halves in such a way that the natural shrinkage of the molding causes the part to stick to the moving half. When the mold opens, the ejector pins push the part out of the mold cavity.

cooling system

A cooling system is required for the mold. This consists of an external pump connected to passageways in the mold, through which water is circulated to remove heat from the hot plastic. Air must be evacuated from the mold cavity as the polymer rushes in. Much of the air passes through the small ejector pin clearances in the mold. In addition, narrow air vents are often machined into the parting surface; only about 0.03 mm (0.001 in.) deep and 12 to 25 mm (0.5 to 1.0 in.) wide, these channels permit air to escape to the outside but are too small for the viscous polymer melt to flow through.

All of the information we referred from Wikipedia, but we sort out together for easy to read, if you want to know more, please go to injection mold Wikipedia.


Injection Molding Process:Plastic Processing, Make Parts From Plastic Material

Finding the right source for your injection molded thermoplastic parts is as easy as selecting DONGGUAN SINCERE TECH CO.LTD. With SINERE TECH, you are guaranteed professional quality assurance standards, the latest in technological equipment, and innovative, cost-efficient manufacturing techniques.

Injection Molding Process: A Brief Description

Thermoplastic injection molding is the most widely used of all plastic processing methods. Injection molding is a manufacturing technique for making parts from plastic material. Molten plastic is injected at high pressure into a mold, which is the inverse of the desired shape.

Thermoplastics are those which, once formed, can be heated and reformed over and over again.

PP injection molding

PP injection molding

The mold is made from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part. SINCERE TECH provides the highest quality economical plastic molds available today, with less moving parts to reduce maintenance and repair costs.

The injection molding machine reduces pelletized resins and coloring agents into a hot liquid. This slurry, or “melt”, is forced into a cooled mold under tremendous pressure. After the material solidifies, the mold is unclamped and a finished part is ejected.

An injection-molding machine performs the entire process of plastic molding.  These machines serve to both heat the plastic material and form it.  Using different molds the shape of the produced components may be changed.

Injection molding machines have two basic parts, the injection unit, which melts the plastic and then injects or moves it into the mold, and the clamping unit, which holds the mold shut during filling. The unit clamps the mold in a closed position during injection, opens the mold after cooling, and ejects the finished part.

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injection molding parting line

What is Plastic Injection Mold Parting Line

Plastic injection mold parting line is the boundary or separation between the two halves of a mold used in the injection molding process. Injection molding is a manufacturing technique where molten plastic material is injected into a mold cavity to create a shaped product. The mold is typically made up of two halves – the stationary half, called the “fixed” or “A” side, and the moving half, called the “cavity” or “B” side.

The parting line is the meeting point of these two mold halves. When the mold opens after the plastic has been injected and cooled, the parting line is where the two halves separate, allowing the molded part to be ejected. The location and design of the parting line are crucial aspects of mold design and can have significant implications for the final product.

In Injection Molding (or almost in any type of molding), one of the most basic concepts is Parting line. A Mould is divided into two parts (more for complex designs) so that it comes apart in order to remove the product and reuse it again and again. These two parts are, namely, Core and Cavity.

While doing injection molding the cavity needs to be placed inside the core before pouring the molten plastic in. The line where these two parts meet is called the mold parting line. The component produced thus has a single continuous line around its perimeter. This line is usually visible naked eye as a slight discontinuity on the surface of the element after it is removed from the mold.

Plastic Injection Mold Parting Line

Key consideration when design plastic injection mold parting line

Designing the plastic injection mold parting line is a critical aspect of the overall mold design process. The parting line’s placement and design can impact the quality, functionality, and manufacturability of the final plastic product. Here are key considerations when designing a plastic injection mold parting line:

  1. Functionality:

    • Ensure that the parting line does not interfere with the functionality of the final product. It should not affect critical features or assembly.
  2. Aesthetics:

    • Minimize the visibility of the parting line on the finished product. Consider the overall appearance and surface finish of the molded part.
  3. Draft Angles:

    • Incorporate draft angles on the part geometry to facilitate easy ejection from the mold. Draft angles help prevent the part from getting stuck and reduce the likelihood of damage during ejection.
  4. Material Flow:

    • Analyze the material flow during the injection molding process. The parting line should allow for even material distribution to avoid defects such as flow lines, warping, or sink marks.
  5. Gate Location:

    • Coordinate the parting line with the gate location. Proper gate placement helps control material flow and minimizes visible gate marks on the final part.
  6. Moldability:

    • Optimize the mold design for ease of manufacturing. A well-designed parting line can simplify the mold construction, reduce production costs, and improve overall efficiency.
  7. Complexity:

    • Minimize the complexity of the mold design. While some parts may require complex parting lines, simpler designs are often more cost-effective and easier to manufacture.
  8. Assembly Considerations:

    • If the molded part is part of an assembly, consider how the parting line aligns with other components. Ensure that the parting line allows for easy assembly and alignment.
  9. Undercuts and Side Actions:

    • Identify and address any undercuts or features that may require side actions. Side actions can impact the complexity of the mold design and affect part ejection.
  10. Tolerance and Precision:

    • Ensure tight tolerances and precision in the mold design to produce high-quality parts. Pay attention to the alignment and accuracy of the mold components along the parting line.
  11. Mold Release Agents:

    • Consider the use of mold release agents to aid in part ejection and minimize friction along the parting line.
  12. Simulation and Analysis:

    • Utilize computer-aided design (CAD) tools and mold flow analysis to simulate the molding process and assess the impact of different parting line configurations on the final product.
  13. Material Selection:

    • Consider the type of plastic material being used and its properties. Different materials may have specific requirements for mold design and parting line placement.

By carefully addressing these considerations during the mold design process, engineers can optimize the parting line for successful plastic injection molding, resulting in high-quality and cost-effective production.

What is plastic injection mold gate

In plastic injection molding, the gate is a crucial element in the mold design. It serves as the point through which molten plastic enters the cavity of the mold. The gate is essentially the opening that allows the plastic material to flow from the runner (a channel that distributes the molten plastic) into the mold cavity where the final part is formed.

There are several types of gates used in injection molding, and the choice of gate design depends on factors such as the type of plastic material, the geometry of the part, and the desired properties of the finished product.

Types of Plastic Injection Mold Gates

There are several types of gates used in plastic injection molding, each with its own advantages and considerations. The choice of gate type depends on factors such as the part design, material properties, and production requirements. Here are some common types of plastic injection mold gates:

  1. Sprue Gate:

    • The sprue gate is the primary channel through which molten plastic enters the mold cavity.
    • Located at the thickest part of the mold, it is connected to the runner system.
    • It is easy to design and is often used in molds with single-cavity configurations.
  2. Runner Gate:

    • The runner gate is a channel that distributes the molten plastic from the sprue to multiple cavities in the mold.
    • It can have various configurations, including a single runner, multiple runners, or a hot/cold runner system.
    • Runner gates are commonly used in multi-cavity molds to facilitate efficient material distribution.
  3. Direct (or Edge) Gate:

    • The direct gate is connected directly to the part, typically at the edge.
    • It is suitable for simple part geometries and is relatively easy to design.
    • However, it may leave visible gate marks on the finished product.
  4. Submarine Gate:

    • The submarine gate is located beneath the surface of the part, making the gate mark less visible.
    • It is often used when aesthetics are a significant concern, and a clean appearance is required on the finished part.
  5. Tab Gate:

    • The tab gate is a small gate type often used for small parts or parts with intricate details.
    • It leaves a small tab or vestige on the part, which may need to be removed in secondary operations.
  6. Fan Gate:

    • The fan gate distributes molten plastic in a fan-shaped pattern across the mold cavity.
    • It helps reduce the pressure on the mold and minimizes visible gate marks on the finished part.
    • Commonly used for cosmetic parts where gate visibility is a concern.
  7. Tunnel Gate:

    • The tunnel gate is a type of gate designed to minimize gate marks on the finished product.
    • It is often used for parts with specific cosmetic requirements.
  8. Cashew Gate:

    • The cashew gate is named for its shape, which resembles a cashew nut.
    • It is a variation of the fan gate and is designed to minimize gate vestiges on the part.

The selection of the appropriate gate type is a critical aspect of mold design, and it depends on factors such as part geometry, material characteristics, production volume, and desired part quality. Mold designers carefully consider these factors to optimize the injection molding process and achieve the best results.

These are the two types of irregularities that appear on the surface of a component manufactured by the injection molding process. In order to separate the element from the mold easily, any part of the element must not have any indentation or protrusion that prohibits part ejection from an image. This type of intrusion is called an undercut feature. Any overhanging features must also be avoided during the process although these intrusions are used in processes like overmolding or double shot injection molding. 

In order to prevent these intrusions and to remove the part easily from the mold, a draft angle is needed. The draft angle is defined relative to the Plastic Injection Mold Parting. If these measures are not taken while the mold manufacturing process, more complex types of moulds can be made, but this adds significantly to the cost of manufacturing.

In all, Parting lines are one of the main aesthetic problems that can happen with Injection molded plastic parts. In order to have an aesthetically pleasing design which is robust at the same time, one needs to take care of the parting line as it affects how fast the molten plastic cools and solidifies as well as how many layers it forms which affects the friction coefficient of the part.
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