You need to know how to fix the mold issue, plastic Mold Maintenance, repair the plastic mold, if you are working in plastic injection mould, mold Maintenance in important.

Mould, indispensable in modern industry development and technological level improvement, is one kind of widely-used process equipment during mid-period of industrial production. According to statistics, moulding accounts for 75% of rough machining of industrial parts and 50% of precision machining. Mould can be classified as cold-punching mold, injection mold (or plastic injection mold), die casting mold, rubber mold and so on.plastic mold

1. Introduction of Injection Mould

1.1 Range of Application:

Injection mould is suitable for thermoplastic like ABS, PP, PC, POM, etc. while rubber mould is fit for thermosetting plastic, such as phenolic plastic, epoxy plastic and so on.

1.1.1 Classification of Injection Mould:

By structure: two-plate mould, three-plate mould

By gate type: edge gate mould, pin gate mould, hot runner mold

1.1.2 Structure of Injection Mould

A. Molding parts/components: normally called as cavity and core, which are the closest part with plastic products.

B. Feeding/casting system: Runner for molten plastic to flow from nozzle to cavity. It is classified as the main runner, sub-runner, runner gate, cold slag well, etc.

C. Leading/Guiding system: The system, determining the relative position of cavity and core during clamping/mold closing, is normally made up by guide pin and guide bushing. the ejector plates also need positioning by guide pin and guide bushing.

D. Demoulding structure: It is the structure ejecting the plastic part from the mold. Commonly, it consists of ejector pin, ejector plate/stripper plate, ejector sleeve, etc.

E. Temperature conditioning system: Cooling water must installed at both cavity and core site to meet the requirement of mold temperature during the injection molding process.

F. Side parting line and side action: Slide should be adopted when there is under-cut structure on the product design, i.e. the structure inconsonant with demoulding direction. It is usually made up by slide, lifter, loose core, etc.

G. Venting system: It consists of two forms: the venting groove and gap between mould components. In order to discharge air in cavity and gas caused in moulding process, venting groove is usually set at parting line, with the principle of designing venting groove as big as possible in compliance with smooth overflow and flashing. Meanwhile, insert pin, ejector pin and mould insert discharge air through gaps between mold components.

2. Plastic Mould Repair

Mould repair is needed during occasions of normal or abnormal abrasion and various abnormal phenomena occurred during plastic molding production.

2.1 Preparations for moldmaster (moldmaker)

A. Make it clear the mould is damaged to what extent;

B. Develop a repair plan according to the damaged molding sample.

C. Precise understanding for repair work needed to be done: Mould repair is usually carried out without drawing with the principle of no change of the plastic parts structure and dimension. Therefore, it is prerequisite for our technician to understand precisely where and to what size should the part be repaired.

2.2 The Dos and Donts during assembly and Disassembly Mould

A. Sign mark: The corresponding sign mark in mould base must be remembered clearly when removing guide pin, ejector sleeve, ejector pin, mould insert, holder block, etc, to assure the right re-installation for the mould, especially for those with direction requirements. The following two items should be paid attention to in this process:

  • The signed mark is the exclusive one without duplication;
  • Sign mark should be made on each mould insert accordingly

B. Anti-Damage proofing: Anti-Damage proofing should be carried out for parts easy to install. In other words, parts cannot be installed back with Incorrect installation;

C. Placement: Parts removed should be placed in order while screws, springs, O-ring should be stored in the plastic box.

D. Protection: Protection measures should be made for precision parts such as mould core, cavity and so on, to avoid careless damage by people.

2.3 The Dos and Donts when Repairing Mould texture surface

A. Polishing: Protection measures for texture surface component should be made prior to repair work when polishing is needed for plastic parts with mould sticking and scrapes. It is forbidden to polish texture surface area. Mould shutoff repair should be done if it is unsure for the repair result.

B. Welding line: The following items should be paid attention to during welding on texture surface:

  • Welding rod material should be consistent with that of mould core;
  • Tempering should be done after welding;

C. Re-texture: When mould repair is finished and ready to take it out for re-texture, moldmaker should make good protection of texture area covered with paper, mark position to make texture area and attach texture template with the mould. After mould texturing, moldmaker should examine textured surface carefully to guarantee good quality and then install mould back.

If it is not sure about the repairing result, mold test should be made first. If it is OK, then take mould out to make the textureplastic mold maintenance

3. Plastic Mold Maintenance

Plastic Mold maintenance is more important than mould repair. The more frequently repaired, the shorter the molds life would last. And vice versa.

3.1 The necessity for Mould Maintenance

  • Keep normal movement of the mould and avoid unnecessary abrasion of moving parts;
  • Maintain the mould to normal service lifetime;
  • Reduce oil contamination during production.

3.2 Classification of Mould Maintenance

  • Routine maintenance for the mould;
  • Scheduled maintenance for the mould;
  • Appearance maintenance for the mould.

3.3 Items for Plastic Mould Maintenance

a. Routine maintenance:

  • Oil filling on moving parts like ejector pin, slide, leader pin and ejector sleeve;
  • Mould surface cleaning;
  • Cooling channel dredging;

b. Scheduled maintenance, following the above items;

  • Venting slot cleaning. Add venting slot at air trapping places and position burnt mark area;
  • Repair of damaged and wearing places;

c. Appearance maintenance:

  • Make painting for outside of mould base to avoid rusting;
  • The cavity should be coated with anti-rusting oil/grease after mould dropping/shutoff.
  • Mould should be closed tightly for storage to avoid dust coming into mould core.

3.4 The Dos and Donts for Mould Maintenance

a. For moving parts, oil filling during routine maintenance is necessary;

b. Mould surface must be clean enough: Tag paper cannot be stuck on P/L side. Do not close the mold when molding part is sticking to the cavity or core side, clean the plastic residues at P/L position.

c. Abnormal condition identification, Prompt repair should be made if there is ejection abnormity, great noise during mold-opening and mold-closing.

4. Safety Issues during Mould Repair and Maintenance

Safety should be put in the first place whenever and wherever. Mould repair and maintenance, with close contact with mold machine and steel equipment, is no exception. It is necessary to pay high attention to safety issues during this process.

  • Examine carefully before use to make the sure hanging ring in perfect condition.
  • The worker must wear safety goggle when operating mold machine to avoid flying chip into eyes
  • The worker must wear protective clothing and safety goggle during the welding process.
  • It is forbidden to operate at the bottom of the mould.
  • Injection moulding machine must be in stopped state and nameplate should be hung on it before operating machine.

plastic mouldingPlastic moulding is the plastic work through the Injection moulding machine, The melted plastic will automatically molten after erupting out in all of the plastic moulding methods, injection moulding has been the most widely used. The method comprises the following steps: getting the thermoplastic plastic or the thermosetting plastic imported into the heating cylinder of the injection moulding machine, and when it is completely melted, it will produce heat and frictional heat by the pressure of the plunger or the screw, and is injected into the mould cavity of the closed mould, after curing, and then open the mould and take out the finished product.

Plastic Moulding Knowledge Guidance

1 The basic knowledge of plastic molding.
1.1 The characteristics and composition of plastic injection moulding.
Plastic Injection moulding is to fill the molten moulding material in a closed mould with high pressure. The pressure that the plastic molding cavity needs to be subjected to about 400 KGF / CM2, approximately 400 atmospheres. With such a high pressure to make a product is its characteristic which is not the only an advantage but also disadvantages. In other words, the mold always has to be made stable, therefore its’ price is always high. So must be mass-produced in order to buckle with high-priced mould costs. For example, the production of each batch must be more than 10000PCS to be reasonable. In other words, plastic molding work surely has to be a mass-production.

A few steps of the plastic molding process :
1.1.1 Closing
Close the security and then start moulding
1.1.2 Clamping mold
Moving forward the moving board in order to get the mould closed. When the mould is closed which means is also locked.

1.1.3 Injecting (including holding press)
The screw is quickly pushing forward, injecting the molten formed plastic material into the mould cavity to full fill it. Keeping the press at the same time after full filling it, this action is particularly named “holding press.” The pressing that the mold has to bear when it just gets full filled, generally called ‘Injection Press’ or ‘one press’.

1.1.4 Cooling off (and the next step of the plasticization project)
The process of waiting for the material getting cool formed in the mould cavity is called “cooling off”, At this time the injection device is also ready for the next step, this process is called “plasticization process. The moulded material is placed in the hopper, inflow into the heated tube to heat, it is based on the rotation of the screw turning the raw material into the molten status.
1.1.5 Opening the mould
Move the moving board to the backward and the mould will be opened.
1.1.6 Opening the security door
Opening the security door, then the machine will be in the standby status.
1.1.7 Picking up
Taking out the product, checking carefully if there is anything left in the mould cavity, and this whole forming operation is called moulding cycle time. The finished product is shaped by the shape of the mould. The mold is composed of the left mould and the right mould, These two sides of moulds are left with voids, and the material would flow into the voids and get compressed to finish the product. There are three main lines of the path of the molding material before it flows into the left side and right side, sprue, runner, gate, and so on.
1.2 Injection molding machine
Injection moulding machine is distinguished from two large projects, they are divided into two, clamping device and injection device.
1.2.2 clamping device
Closing the mould, the molding material would be cooled off and solidified in the mould cavity. Opening the mould cavity and take out the finished product is the action of the clamping device
1.2.3 Injection Device
Injecting the plastic material into the mould cavity called ‘Injection device’


The following describes the ability of the injection moulding machine, there are three provisions to distinguish the ability of it.
A. Clamping force
When the injection is made, the mould won’t be opened by the maximum clamping force, expressed as the number of TON.
B. Injection volume
The weight of a shot is generally expressed in terms of grams.
C. Plasticizing capacity
A certain amount of time able to melt the amount of resin, this is generally expressed in terms of grams.
The most important part is the clamping force, the area of the moulded article is referring the mould perpendicular to the shadow of the opening and closing direction (basically the moud’s area). The average pressure within the mold added to the projection area is called the clamping force. If the mold “projection area × average pressure” is greater than the “clamping force” then the left and the right side moulds will be pushed out.
Clamping force = projection area × average pressure within the mold In general, the mold can withstand the pressure of 400KGF / Cm2, so base on this figure to calculate the clamping force, but the clamping force often based on the shape of forming materials and the shape of the product’s vary, the difference between the larger parameters such as PE, PP, PS, ABS materials, these raw materials are used to make the shallow box, the parameter is 300KGF / CM2, , if the depth of the box is deeper then the parameter is 400 KGF / CM2, If it is the small but high precision products. The projection area is about 10CM2 or less, its parameters are 600KGF / CM2. The smaller parameters such as PVC, PC, POM, AS materials, these materials are also used to make a shallow box, the parameters of 400KGF / CM2, if it is a deep box of its parameters is 500KGF / CM2, if it is a small and high precision products, projection area of about 10CM2 below, its parameter is 800KGF / CM2.Chinese molding company

To working with Plastic Moulding is not easy, if you have a project that needs plastic molding service you need to find a professional plastic molding company to support you, to reduce your plastic mold and Injection moulding cost, find a Chinese molding company to support you will be one of the best options, plastic mould and moulding parts from China mold company has inexpensive price and short lead time, this is no reason that you do not choose your plastic molding supplier from China, on the world, over 80% or overseas companies that buy products from China, China is the biggest manufacturer country on the world, this is no doubt about this,

Sincere Tech is an injection mold company in China, offer injection mould, plastic moulding service to the world, 90% of our mold and parts are export to American, Europe, and the world, if you want to know more information about service, you are welcome to send us an email, if you need price for your project, please send us your requirement for quotation, we will offer you the best price and service. Hope to work together in the near future.


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.
If you have any question about Plastic Injection Mold Parting please contact our technical department, if you have an injection molding service requirement, you are welcome to send us the requirement for a quotation, you will lose nothing but have our good price and suggestion to help your project, we will never share your data to any others, we can sign an NDA document to avoid any issue.