Injection Mold Life Expectancy: How to Improve

In the realm of manufacturing, particularly in the plastics industry, the durability and longevity of injection molds are pivotal for efficient production.

DENICE are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

Understanding the life expectancy of these molds is not just about numbers; it&#;s about grasping the intricate dance of material, design, and maintenance that dictates their lifespan. This article dives deep into the world of injection molds, shedding light on their average lifespan and the factors influencing it.

What is Injection Mold?

An injection mold, often made from materials like steel or aluminum, is the heart of the injection molding process, shaping everything from everyday items to complex components.

The precision and quality of an injection mold tooling directly affect the quality of the final product, usually made from plastic material, making its design and maintenance a subject of utmost importance.

What is Average Injection Mold Life Expectancy?

An injection mold life expectancy can range from hundreds to over a million cycles.

Understanding the average life expectancy of injection molds in terms of cycles is crucial for manufacturers to anticipate production capabilities and plan for maintenance and replacements.

Average Life Expectancy in Cycles:

• High-End Molds (Class 101): These molds, designed for high volume production and made from materials like hardened steel, can endure over a million cycles. They are the standard-bearers in terms of longevity.
• Mid-Range Molds (Class 102 and 103): These are suitable for medium to high volume production, with life expectancies ranging from 100,000 to 500,000 cycles. Class 102 molds can typically withstand up to half a million cycles, while Class 103 molds are often limited to around 100,000 cycles.
• Lower-End Molds (Class 104 and 105): Used for smaller production runs and prototyping, these molds have a significantly shorter lifespan. Class 104 molds can endure approximately 10,000 to 25,000 cycles, and Class 105 molds are typically limited to under 500 cycles.

How Are Injection Mold Lifespans Measured and Classified?

Injection mold life expectancy is methodically measured and classified, with the Society of the Plastics Industry (SPI) mold classifications serving as a primary benchmark in the industry.

SPI Mold Classifications and Standards:

• Purpose: These classifications provide a standardized framework for categorizing molds based on their durability, material quality, and expected lifespan.
• Impact: This system aids manufacturers in making informed decisions about mold selection, aligning their production needs with the capabilities of different mold classes.
• Influence on Manufacturing: The classification of a mold directly impacts the manufacturing process, affecting factors like production volume, maintenance requirements, and overall cost-effectiveness.

Class 101 Mold

Class 101 molds represent the pinnacle of mold design and durability, catering to high-volume and high-demand manufacturing environments.

Main Specifications and Characteristics:

• Life Expectancy: Designed for longevity, these molds can withstand over a million cycles, making them ideal for continuous, high-speed production.
• Material Quality: Typically constructed from premium-grade, hardened steel, Class 101 molds offer unparalleled strength and resistance to wear and tear. The steel used often undergoes special heat treatments to enhance its durability and performance under extreme conditions.
• Design Complexity: Engineered to handle complex designs and high-stress conditions, these molds are characterized by their intricate and precise tooling. This includes sophisticated cooling systems, specialized ejection mechanisms, and advanced gating techniques to ensure optimal molding.
• Applications: Best suited for large-scale manufacturing where consistent quality and high output are paramount. These molds are often employed in the automotive, aerospace, and medical device industries where precision and reliability are critical.
• Maintenance Protocol: Despite their robustness, they require a comprehensive maintenance regime to ensure optimal performance over their extended lifespan.
• Cost Consideration: While they represent a significant initial investment, their durability and efficiency make them cost-effective for high-volume production scenarios.

Class 102 Mold

Class 102 molds, recognized for striking a balance between longevity and cost-effectiveness, are highly suitable for medium to high volume production cycles. These molds stand as a testament to engineering efficiency, offering a robust solution for a variety of manufacturing scenarios where neither the extreme volume of Class 101 molds nor the lower volumes of Class 103 molds are required.

Main Specifications and Characteristics:

• Life Expectancy: Designed to endure up to 500,000 cycles, Class 102 molds cater to production needs that are demanding yet not as intensive as those requiring Class 101 molds. This makes them a practical choice for manufacturers who need a balance between high durability and economic viability.
• Material Quality: Often constructed from high-grade steel, these molds provide a good balance of durability and cost-efficiency.
• Physical Properties: Class 102 molds are characterized by their sturdy design, capable of tolerating the stresses of medium to high volume production. This includes the ability to withstand various injection pressures and temperatures without significant degradation.
• Usage: These molds are particularly well-suited for industries where production requirements are substantial but do not necessitate the highest level of mold endurance. Examples include consumer electronics, automotive components, and other commercial goods that require consistent quality over numerous production runs.
• Maintenance Requirements: Regular maintenance is essential, though it may not be as intensive as that required for Class 101 molds.

Class 103 Mold

Class 103 molds, designed to cater to lower production volumes, provide a practical and cost-effective solution for less intensive manufacturing processes. These molds are tailored for scenarios where the extreme durability of Class 101 and 102 molds isn&#;t necessary, thereby offering an optimal blend of performance and economy for specific manufacturing needs.

Main Specifications and Characteristics:

• Lifespan: Designed to endure up to 100,000 cycles, making them suitable for moderate production requirements.
• Material Composition: These molds are constructed from quality materials, including less hardened variants of steel, which offer durability and resilience. While they may not match the high-end materials of Class 101 molds, they provide sufficient strength for their intended use-case scenarios.
  Physical Properties: Class 103 molds are designed with simplicity and functionality in mind. They are typically less complex, facilitating easier production of simpler part designs under lower stress conditions.
• Application Suitability: Particularly suitable for smaller production runs or for products that do not require the extreme endurance of higher class molds. They are often the go-to choice for special projects, prototype development, or products with shorter life cycles in the market.
• Maintenance Protocol: Although requiring regular maintenance, the frequency and intensity of care are generally less demanding compared to higher-class molds. This includes standard cleaning, inspection, and occasional repairs or adjustments to ensure consistent mold performance.

Class 104 Mold

Class 104 molds cater to lower production volumes, making them ideal for specific applications such as prototyping or limited-run productions.

Main Specifications and Characteristics:

• Life Expectancy: Designed to deliver a functional life range of approximately 10,000 to 25,000 cycles, Class 104 molds are particularly well-suited for low-volume applications.
• Material Composition: Class 104 molds are typically constructed from softer materials compared to their higher-class counterparts. The use of aluminum or mild steel not only aids in reducing manufacturing costs but also ensures sufficient durability for their intended limited use.
• Design and Use: These molds are engineered with simplicity in mind for less complex part designs. While they may lack the durability of higher-class molds, their cost-effectiveness makes them a valuable choice for short production runs or prototyping, where the intricacy and stress on the mold are comparatively low.
• Physical Properties: Their construction reflects a focus on flexibility and adaptability for varied designs, albeit with reduced longevity.
• Maintenance Needs: Regular maintenance is less stringent than higher-class molds but still crucial for maximizing their lifespan.
• Ideal Applications: Perfect for specialized, low-volume products, prototyping projects, and applications where mold longevity is not the primary concern.

Class 105 Mold

Class 105 molds represent the lowest tier in the SPI mold classification, primarily used for extremely low volume productions or one-off projects.

Main Specifications and Characteristics:

• Lifespan: These molds are designed for less than 500 cycles, making them the least durable in the SPI classification system.
• Material Selection: Constructed from the least expensive materials, like cast metal or epoxy, they are designed for very specific, limited-use cases.
• Design Suitability: Ideal for simple designs and products where the mold is not subjected to intensive use.
• Physical Characteristics: They exhibit basic functionality with minimal complexity in design and structure.
• Maintenance Protocol: Given their limited use and lifespan, these molds require minimal maintenance efforts.
• Application Scope: Suited for one-off projects, experimental designs, or extremely low volume productions where the cost of mold is a significant consideration.

What Factors Influence the Lifespan of Injection Molds?

 

The lifespan of an injection mold is contingent upon multiple factors, each playing a crucial role in determining its durability and efficacy. Understanding these factors is essential for manufacturers to ensure optimal performance and longevity of their molds.

Injection Mold Material Quality

The material from which a mold is made is a key factor influencing its durability. Different materials offer varying degrees of hardness, wear resistance, and capacity to withstand high temperatures and pressures.

Steel Alloys

Steel alloys are commonly used in plastic injection mold making due to their strength and durability. The type of steel alloy chosen can greatly affect injection mold lifespan.

• Characteristics: Steel alloys are prized for their hardness, resistance to abrasion, and ability to withstand high temperatures.
• Applications: Ideal for high-volume production and complex mold designs.
• Varieties: There are several types of steel alloys used, each with unique properties suited to different molding requirements.

P20 (1.)

• Hardness Range: Typically, P20 steel has a hardness range of 28-32 HRC.
• Mold Life Expectancy: P20 is known for its good machinability and can typically last for around 300,000 to 500,000 shots/cycles, making it a popular choice for less strenuous applications.
• Usage: Commonly used in the production of large molds due to its excellent balance between cost and durability.

H13 (1.)

• Hardness Range: H13 steel usually falls within the hardness range of 42-52 HRC.
• Mold Life Expectancy: It is renowned for its high toughness and can endure upwards of one million shots/cycles, especially in high-temperature applications.
• Usage: Frequently utilized for molds subjected to harsher conditions, like those in high-pressure injection molding processes.

S136 (1.)

• Hardness Range: S136 steel exhibits a hardness range of approximately 48-52 HRC.
• Mold Life Expectancy: This type of steel is known for its exceptional corrosion resistance and can sustain hundreds of thousands to a million shots/cycles, especially in aggressive environments.
• Usage: Ideal for molds used in corrosive applications, such as those involving PVC and other abrasive materials.

420 Stainless Steel Material Description:

• Hardness Range: 420 stainless steel typically has a hardness range of 48-52 HRC.
• Mold Life Expectancy: It is known for its impressive corrosion resistance and can last for several hundred thousand shots/cycles, making it suitable for molds used in corrosive environments.
• Usage: This alloy is often chosen for its polishability and corrosion resistance, ideal for molds used in medical devices, food packaging, and other applications where cleanliness and precision are critical.

718 (1.) Material Description:

• Hardness Range: 718 steel, also known as 1., generally has a hardness range of 33-37 HRC after quenching and tempering.
• Mold Life Expectancy: It can sustain up to 500,000 shots/cycles, making it a versatile option for medium to high-volume production.
• Usage: This material is favored for its excellent machinability and uniform hardness, suitable for complex mold designs and detailed tooling components.

ESR (Thru-Hardening Steel) Material Description:

• Hardness Range: ESR steel typically exhibits a hardness of 50-54 HRC.
• Mold Life Expectancy: Known for its high-temperature strength, it can endure over a million cycles, particularly in high-stress and high-temperature molding processes.
• Usage: Ideal for manufacturing robust molds for high-volume production, especially in the automotive and aerospace industries where durability is paramount.

NAK80 (P21) Material Description:

• Hardness Range: NAK80 (P21) steel has a hardness range of 37-43 HRC.
• Mold Life Expectancy: This alloy can last for approximately 300,000 to 500,000 shots/cycles.
• Usage: NAK80 is often used for intricate mold designs due to its excellent polishability and wear resistance, making it suitable for high-precision and aesthetic parts like consumer electronics and automotive components.

Material Description:

• Hardness Range: tool steel is typically hardened to 45-52 HRC.
• Mold Life Expectancy: It is known for its toughness and resistance to wear, offering a lifespan of several hundred thousand cycles.
• Usage: This alloy is particularly used in heavy-duty molds for large parts, where its strength and durability are crucial to withstand prolonged production cycles and mechanical stress.

Aluminum Alloys

Aluminum alloys are increasingly being utilized in the construction of injection molds due to their specific properties that benefit certain manufacturing scenarios. They are particularly favored for their lightweight nature, thermal conductivity, and corrosion resistance.

• Characteristics: Aluminum injection molds are known for their excellent thermal conductivity, which can lead to faster cooling times and shorter cycle times in the injection molding process.
• Applications: They are often used for lower volume production runs or for parts that do not require the extreme hardness and wear resistance of steel.

Aluminum

• Hardness Range: Aluminum alloy typically has a hardness range of 53-63 HRC when properly heat-treated.
• Mold Life Expectancy: This alloy can withstand approximately 100,000 to 150,000 shots/cycles, making it suitable for moderate production runs.
• Usage: Known for its high strength, is often used in aerospace applications and is ideal for molds requiring a higher strength-to-weight ratio.

Aluminum

• Hardness Range: Aluminum generally has a lower hardness range of 40-50 HRC.
• Mold Life Expectancy: It is capable of sustaining about 50,000 to 100,000 shots/cycles, suitable for lower volume production or prototypes.
• Usage: Due to its excellent corrosion resistance and weldability, is commonly used in automotive applications and consumer goods.

List of Other Materials and Injection Mold Lifespan:

1. ABS Plastic: Widely used for its good impact resistance and toughness, ABS plastic injection molds can last for about 100,000 to 300,000 cycles.
2. Polycarbonate: Known for its strength and transparency, polycarbonate molds typically have a lifespan of around 100,000 to 200,000 cycles.
3. Polypropylene: With its resistance to fatigue, polypropylene molds can endure approximately 500,000 to 1,000,000 cycles.
4. Nylon (Polyamide): Durable and resistant to wear and chemicals, nylon molds can sustain about 100,000 to 300,000 cycles.
5. PVC: Due to its versatility and chemical resistance, PVC molds can last from 100,000 to 500,000 cycles, depending on the application.

Mold Design and Structure

The intricacy and precision of a mold&#;s design are fundamental in determining its resilience over time. A well-thought-out design not only ensures efficient production but also significantly extends the mold&#;s lifespan.

• Complexity: Complex molds with intricate details may require more maintenance and are potentially more susceptible to wear.
• Precision: High-precision molds are designed to minimize wear and tear, thereby extending their lifespan.
• Design Quality: The overall quality of the mold design, including the arrangement of its components and thermal balance, plays a crucial role in its durability.

Operating Environment

The conditions under which the mold operates, including aspects like temperature, humidity, and cleanliness, can greatly impact mold structure and its longevity.

• Temperature: Extreme temperatures, either too high or too low, can affect the mold material, potentially leading to faster degradation.
• Humidity: Excessive moisture can cause corrosion, especially in molds made of susceptible injection molding materials.
• Cleanliness: A clean operating environment reduces the risk of mold contamination and damage, thereby prolonging its lifespan.

Production Run Time and Cycle Time

The frequency and duration of mold usage, particularly in high-volume production settings, are critical factors that affect its wear and tear.

• Frequency of Use: Molds used in continuous, high-volume production runs may degrade faster due to the constant stress and thermal cycling.
• Production Cycle Time: Longer cycle times can lead to increased exposure to high temperatures and pressures, accelerating wear.
• Rest Periods: Adequate rest periods between cycles can help in reducing thermal and mechanical stress on the mold.

Maintenance and Surface Treatment

Regular maintenance, including routine cleaning and repairs, is crucial in prolonging the life of injection molds. Surface treatments can also play a significant role in this regard.

Example:

A manufacturer reported that an injection mold treated with a protective anti-corrosion coating and subjected to bi-weekly maintenance schedules lasted approximately 30% longer than untreated counterparts. The coated mold, used for high-density polyethylene (HDPE) products, showed a life expectancy of around 1.2 million cycles, compared to 900,000 cycles for untreated molds.

Injection Molding Machine Conditions

The condition and performance of the injection molding machine, including factors like precision and stability, can directly impact the wear and tear on the mold.

Example:

In a study, molds operated on high-precision injection molding machines with consistent temperature control showed less wear compared to those on older, less precise machinery. Molds on precision machines demonstrated a 20% increase in lifespan, with average life expectancies reaching up to 1.1 million cycles.

Quality of Molded Material

The type of plastic materials or other materials being molded can have a significant effect on the mold. Abrasive or corrosive materials can accelerate mold wear.

Example:

A manufacturing facility using abrasive glass-filled polymers noted a reduced mold lifespan compared to when using standard thermoplastics. Molds used for glass-filled polymers had a life expectancy of about 600,000 cycles, while those used for standard plastics like polypropylene could last up to 1 million cycles.

Injection Parameters

Injection parameters, including pressure, temperature, and speed, can significantly impact the stress endured by a mold, thereby affecting its durability.

Example:

A study in a high-volume automotive parts manufacturer revealed that reducing injection pressure by 10% and moderating temperature controls increased mold lifespan by 15%. The adjusted parameters resulted in an average mold life of 1.15 million cycles, compared to 1 million cycles under previous conditions.

Mold Storage Conditions

The way a mold is stored when not in use, particularly its environmental conditions and protection from elements, is pivotal in preserving its condition.

Example:

An electronics component manufacturer implemented climate-controlled storage for their molds and reported a 20% increase in mold lifespan. Molds stored under controlled conditions had an average life expectancy of 1.2 million cycles, as opposed to 1 million cycles in standard storage.

Mold Handling and Setup Practices

Improper handling or incorrect setup of molds can cause physical damage or misalignments, significantly shortening the mold&#;s operational life.

Example:

A case study in a medical device company showed that improved handling and setup protocols reduced mold damage incidents by 30%. Enhanced practices led to an increase in mold lifespan from 800,000 cycles to over 1 million cycles.

Thermal Expansion and Contraction

Thermal expansion and contraction is a significant factor in the lifespan of injection molds. The cyclic nature of the injection molding process, involving heating and cooling, can induce stress on the mold materials.

Example:

• Scenario: An electronics manufacturer was experiencing frequent mold failures in their production line.
• Investigation: The molds were subjected to rapid temperature changes during the molding process, causing excessive thermal stress.
• Intervention: Introduction of a gradual heating and cooling cycle, to minimize thermal shock.
• Result: The implementation of controlled temperature transitions extended the mold life by about 25%, translating to approximately 200,000 additional cycles before requiring maintenance or replacement.

Use of Mold Release Agents

The type and frequency of mold release agents used can significantly affect the lifespan of injection molds. While necessary for efficient production, these agents can impact the mold surface, especially if not correctly matched with the mold material.

Example:

• Scenario: A company specializing in automotive parts reported decreasing mold performance and surface quality.
• Investigation: Overuse and misapplication of aggressive chemical release agents were identified as the cause of premature mold wear.
• Intervention: A switch to a milder, more compatible release agent and training for staff on proper application techniques.
• Result: This change led to an improvement in mold surface integrity and extended the life of the mold by around 100,000 cycles.

Mold Coatings

The application of specialized coatings to injection molds can significantly enhance their resistance to wear and corrosion. These coatings often provide a protective barrier, reducing direct contact with harsh materials and environmental factors.

Example:

• Background: A high-volume automotive parts manufacturer faced rapid mold degradation due to aggressive use.
• Intervention: The company decided to apply a high-grade PVD (Physical Vapor Deposition) coating on their molds.
• Outcome: The coated molds displayed a 30% increase in lifespan, with improved resistance to abrasive wear and corrosion, leading to fewer production interruptions and maintenance needs.

Frequency of Mold Changes

The frequency of mold changes and setups in the injection molding process can significantly influence mold wear and tear. Frequent changes can lead to physical damage or alignment issues, which reduce the mold&#;s effective lifespan.

Example:

• Scenario: A consumer goods manufacturer frequently changed molds to meet varied product demands.
• Problem: This frequent changing led to increased wear and misalignment issues.
• Solution: Implementing a standardized setup procedure and training staff on careful handling significantly reduced the incidence of damage, improving the mold lifespan by around 20%.

Quality of Water Used in Cooling Channels

The quality of water used in a mold&#;s cooling channels is a critical factor. Impurities or high mineral content in the water can lead to internal corrosion or buildup, affecting mold efficiency and longevity.

Example:

• Situation: A medical device manufacturer noticed a decrease in mold performance.
• Investigation: It was discovered that hard water was being used in the mold cooling channels.
• Resolution: Switching to filtered, softened water and regular maintenance of the cooling system resulted in a marked improvement in mold condition and an extension of its usable life by approximately 25%.

What Are Common Injection Molding Defects and Their Impact on Mold Life?

 

In the realm of injection molding, various defects can arise, affecting both the quality of the produced parts and the lifespan of the molds. Understanding these defects is essential for enhancing mold longevity and ensuring efficient production.

Flow Lines

These are streaks, patterns, or lines that appear on the part&#;s surface, often near the gates or narrow sections.

• Impact on Mold Life: Flow lines may indicate uneven cooling or inappropriate injection speed, leading to stress on certain mold parts, potentially decreasing their lifespan.

Sink Marks

Small depressions or recesses on the part&#;s surface.

• Impact on Mold Life: Sink marks often result from insufficient cooling time or material in certain areas, leading to uneven shrinkage and stress on the mold.

Burn Marks

Black or rust-colored discoloration on the edge or surface of the part.

• Impact on Mold Life: These are often caused by trapped air or excessive heating, which can degrade mold components over time.

Delamination

Surface delamination is when thin layers of material appear separated or flaky on the part&#;s surface.

Impact on Mold Life: Delamination indicates issues with material purity or processing, which can increase wear on the mold surface.

Flash

Excess material that seeps out of the mold cavity, typically along the parting line.

• Impact on Mold Life: Flash often suggests improper clamp force or wear on the mold, potentially leading to further damage if not addressed.

Other Relevant Defects:

• Warping: Injection molded parts distort during cooling. Impact: Stresses the mold during ejection, potentially misaligning mold components.
• Short Shot: Incomplete filling of the mold cavity. Impact: May lead to increased cycles for correction, wearing out the mold faster.
• Jetting: Wavy patterns caused by molten plastic pushing against the mold cavity. Impact: Can lead to erosion or damage to specific mold areas.

How Can Injection Mold Lifespan Be Extended?

Extending the lifespan of injection molds is crucial for maximizing efficiency and minimizing costs in the manufacturing process. Several strategies and technologies can significantly contribute to this goal:

• Regular Maintenance: Timely and thorough maintenance is key. This includes cleaning the mold, checking for wear and tear, and making necessary repairs.
• Optimal Operating Conditions: Ensuring the injection molding machine operates under ideal conditions (appropriate temperature, pressure, and injection speed) reduces stress on the mold.
• Use of Quality Materials: High-grade steel or aluminum molds tend to last longer than those made from less durable materials.
• Coatings and Treatments: Applying protective coatings can shield molds from corrosion and wear.
• Mold Structure Design Improvements: Designing molds with uniform wall thickness and adequate cooling channels can reduce the risk of defects and wear.
• Controlled Environment: Storing molds in a controlled environment prevents rust and degradation.
• Training Personnel: Skilled operators and maintenance staff can significantly extend mold life through proper handling and upkeep.

Best Practices and Common Mistakes in Maintenance affecting Injection Mold Lifespan?

Effective maintenance is pivotal in prolonging the life of injection molds. Below are some best practices and common pitfalls.

• Regular Cleaning: Removing residues and lubricating moving parts can prevent wear and tear.
• Scheduled Inspections: Regularly scheduled checks can identify issues before they become serious.
• Proper Storage: Molds should be stored in a clean and dry environment with proper temperature control
• Avoiding Overuse: Rotating molds and not overusing a single mold can distribute wear evenly.

Common Mistakes:

• Neglecting Regular Maintenance: Infrequent or improper maintenance can accelerate mold degradation.
• Improper Handling: Mishandling during installation or removal can damage mold components.
• Overlooking Minor Issues: Small problems can escalate into major damages if ignored.

What is the schedule for injection mold maintenance?

A well-defined maintenance schedule is critical for injection mold care. Here&#;s an ideal timeline:

• After Every Production Run: Perform basic cleaning and inspection for any visible damage.
• Monthly: Conduct a thorough inspection of all mold components, including ejector pins and cooling channels.
• Annually: Schedule a detailed examination and maintenance session, possibly involving disassembly for deep cleaning and repair.

Conclusion

Extending injection mold tool life is a multifaceted approach that involves meticulous maintenance, optimal operation conditions, use of high-quality materials, and continuous improvement in mold design and handling.

Regular maintenance, both scheduled and predictive, plays a vital role. With the right practices, the life expectancy of molds can be significantly increased, leading to cost savings and enhanced efficiency in the plastics industry.

Share this blog:

For more information, please visit automated Bakelite moulding machine.

Injection molding is a very efficient and widely used plastic manufacturing process for producing parts in large quantities. Mold development is a critical aspect of this process, essential for accurately shaping and forming molten plastic with high precision. The creation of molds, as one of the first steps, demands great precision and accuracy to ensure the quality and consistency of the final products.

There are various ways to classify molds in injection molding, including by plate type, runner type, cavity design and class. Among these classifications, mold cavity design&#;single-cavity, multi-cavity, and family molds&#;plays a pivotal role in determining production efficiency and quality. Single-cavity molds are simpler and offer high-quality parts, ideal for low-volume production and intricate designs. Multi-cavity molds enhance production speed and reduce the cost per part for large volumes, but require precise balancing to avoid defects. Family molds allow for the simultaneous production of different parts, optimizing manufacturing for multi-part products but increasing design complexity and the potential for defects.

Dmitry Romanov

Lead Injection Molding Engineer

When selecting the right mold type, it&#;s important to consider your immediate production needs but also the long-term performance and durability of the mold. Molds are classified based on how long they&#;re expected to last. Class 101 molds can handle over a million cycles, so they&#;re great for really high production levels. On the other hand, Class 105 molds are good for up to 500 cycles, which makes them perfect for prototypes and low-volume production. At Xometry, we typically use molds that last at least 10,000 shots for our injection molding projects.

What Type of Mold Is Used in Injection Molding?

Injection molds can be categorized in several ways, each affecting various aspects of the production process. Here&#;s a detailed look at these categories and their significance:

Plate Type

The plate type influences the mold&#;s cost, the finish of the final product, and overall production efficiency.

• Two-Plate Molds: Consist of two main parts&#;the cavity and the core. They are simpler and less expensive but may have limitations in complex part designs.
• Three-Plate Molds: Include an additional plate for separating parts from the runners, improving part ejection and quality. They are more versatile but also more costly.
• Stacked Plate Molds: Utilize multiple levels of cavities, doubling the output without increasing the footprint. They are ideal for high-volume production but require precise alignment and complex design.

Comparison of injection molds: Three plate mold vs two plate mold (Source: plasticmoulds.net/)

Runner Type

The runner type impacts mold design flexibility, material waste, and the amount of post-processing required.

• Cold-Runner Molds: Use unheated channels to guide the molten plastic into the mold cavities. They are less expensive but require more post-processing to remove the runners from the final product.
• Hot-Runner Molds: Incorporate heated channels, keeping the plastic molten until it reaches the cavities. They reduce waste and post-processing needs but are more complex and expensive.

Mold Cavity Design

The mold cavity design plays a crucial role in production efficiency and part quality, directly influencing the speed, cost, and consistency of the manufacturing process.

• Single-Cavity Molds: Single-cavity molds produce one plastic part per injection cycle. This gives single-cavity models the slowest production times of the three types of molds we are discussing. However, due to their size and relative simplicity, they are quite affordable to produce, making them a good option for small production volumes in which production speed isn&#;t the biggest factor.
• Multi-Cavity Molds: Multi-cavity molds contain multiple cavities, as the name suggests. These molds produce multiple copies of the same plastic product in each production cycle. They are ideal for mass production purposes, with high production speeds and a low price per part at large production volumes. Multi-cavity molds are complex and expensive to design and produce, however this can be offset when working with large production volumes.
• Family Molds: Family molds are injection molds that produce multiple different parts per production cycle. They are useful for manufacturing multi-part products quickly but are very complex to design and more prone to molding defects.

CNC machining can be used to manufacture metal injection molds

Multi-cavity injection mold designed for high-volume production of identical parts

Injection molded parts from a family mold, illustrating the simultaneous production of different components

Additionally, the SPI (Society of the Plastics Industry) classifications provide a standardized method (Class 101 to 105) to evaluate mold life expectancy and suitability for different production volumes.

Comparing Single-cavity, Multi-cavity and Family Molds

The table below compares the three types of injection molding molds:

Property Single-Cavity Mold Multi-Cavity Mold Family Mold Applications

&#; High-quality plastic products (e.g. containers for which aesthetics matter).

&#; Intricate geometries or designs with precise control over material flow and injection pressure.

&#; Prototypes with design changes and new mold iterations.

&#; Low-volume production in which cost is a more significant factor than production speed.

&#; Large production volumes (over 40,000 products per month).

&#; Applications for which price per part is the most important factor.

&#; High-demand products that require short lead times for high volumes (e.g. bottle caps or packaging).

&#; Multi-part products, for which all the parts can be manufactured in a single production cycle.

&#; Prototyping with multiple variations of parts being manufactured simultaneously.

&#; Medium to large production volumes with the same part&#;s material and color.

Cost

Low cost, with the simplest design and tooling requirements.

High, requiring more complex design and tooling.

Highest, due to being the most complex to design.

Complexity

Low, as it doesn&#;t require balancing of pressures between multiple cavities.

High, with complex runner, cooling, and gate systems needed.

Highest, with multiple different cavities requiring careful design to balance injection pressures and uniformity.

Lead Time

Lowest, due to the simpler design process.

High, requiring careful design.

Highest, with a long design and simulation process.

Production Speed

Slowest, limited to one part per injection cycle.

Fastest, multiple copies of a part can be made simultaneously.

Fast, multiple different parts can be made in a single injection cycle.

Surface Quality

Highest, with minimal post-processing needed.

High, with some post-processing needed and risk of defects.

Medium, with the highest risk of unbalanced injection and defects.

Advantages

&#; Lowest risk of molding defects.

&#; The simplest and fastest type of mold to design and manufacture.

&#; Fastest production speed of the three mold cavity types.

&#; One mold can produce multiple different parts.

&#; Fast production speeds, especially for multi-part products.

Disadvantages

&#; Lowest production efficiency (only one part can be produced at a time).

&#; Highest cost per part at large production volumes.

&#; Highly complex to design and manufacture.

&#; Requires higher maintenance than single-cavity molds.

&#; More prone to unbalanced injections and molding defects than single-cavity molds.

&#; Very complex to design and manufacture.

&#; Long lead times for new mold designs, due to design complexity.

&#; More post-processing is required than for single- or multi-cavity molds.

What Are the Components of Injection Molding Molds?

The injection molding mold itself consists of several components, each with its own specific function within the mold.

Detailed structure of a two-plate mold with labeled parts (Source: CustomPartNet)

The components are:

• Mold base: The mold base or mold frame is the foundational infrastructure for the mold assembly, providing rigidity and strength against the internal pressure experienced during injection molding.
• Cavity: The cavity, or cavities, shape the external geometry of the part. The cavity and the core form two halves of the final mold cavity in which the molten plastic is injected.
• Core: The core shapes the internal geometry of the part, and mates with the cavity to form the mold cavity. Multi-cavity and family molds will have multiple pairs of cavities and cores for the multiple parts that they produce.
• Inserts: Inserts are separate components that may be inserted into the mold to create specific geometric features. They are separate from the cavity and core but also help form the internal and external geometries.
• Runner system: The runner system distributes molten plastic throughout the mold cavity to ensure an even distribution of material. They are a network of channels that ultimately end in gates, which are the openings into the mold cavities. Good runner system design is vital for ensuring even material distribution and minimizing defects.
• Nozzle & sprue bushing: The nozzle controls how the molten plastic flows into the mold from the feeding system of the injection molding machine. The sprue bushing is a component of the mold that positions the nozzle to ensure it is centered and aligned.
• Ejector pins: They are used to help eject the part from the mold after it has solidified and the mold has been opened. The part can potentially stick to the mold cavity, and ejector pins are used to automatically provide a force that ejects the part from the mold.
• Cooling system: The cooling system helps maintain the temperature of the mold in order to prevent damage and maintain quality of the finished part. 
• Venting system: The venting system provides a way for air and gases to escape from the mold during the injection process. This system consists of various channels, pins, and grooves that allow air to escape, but are small enough to keep plastic inside.
• Guides: The guides of the mold are a series of bushings, sleeves, and guiding pins on the two halves of the mold that help with alignment and assembly.

What is Injection Mold Life Expectancy?

The life expectancy of an injection mold is determined by the number of molding cycles it can perform, with each cycle consisting of the mold opening and closing. Several factors influence this lifespan, including the mold class, operating conditions, environment, maintenance practices, and the materials used.

The Society of the Plastics Industry (SPI) categorizes injection molds into five distinct classes, which are independent of the mold cavity classification. Each class is characterized by specific criteria defined by the SPI, ensuring standardized evaluation for mold life expectancy and suitability for various production volumes.

The table below compares the 5 injection mold classes:

Mold Class Cycles Production Level Uses Investment

Class 101 Mold

1 million or more

Extremely high

Ideal for high-volume production with fast cycles

Class 101 molds are the most expensive, crafted from top-tier materials

Class 102 Mold

Not exceeding 1 million

Medium to high

Suitable for parts requiring durable plastic materials and tight tolerances

Class 102 molds are quite expensive, made with high-quality materials

Class 103 Mold

Not exceeding 500,000

Medium

Commonly used for low to medium production runs

Class 103 molds are priced moderately, falling within average price ranges

Class 104 Mold

Not exceeding 100,000

Low

Best for limited runs with non-abrasive materials

Class 104 molds are lower in cost, suitable for limited to moderate production runs

Class 105 Mold

Not exceeding 500

Very low

Used primarily for prototyping

Class 105 molds are the least expensive, designed for producing a limited number of prototype parts

Get Injection Molding Services for Your Next Project

Choosing the right mold is just the beginning of the plastic manufacturing process. Once the mold type is selected based on your production needs and SPI classification, the next steps involve finalizing and validating your design. This includes reviewing the CAD file for any necessary adjustments, producing the T1 sample to test and verify the mold&#;s performance, and making any required modifications to ensure optimal part quality.

After validating the mold, you can proceed with full-scale production, ensuring that all parameters are set correctly for consistent, high-quality output. Partnering with experienced manufacturers, like Xometry Europe, provides the injection molding expertise and resources needed for successful and efficient production. Begin your injection molding project confidently by using our Instant Quoting Engine to get a free quote for your next project.

Share Content

Share a link to this page:

If you are looking for more details, kindly visit precision Bakelite injection moulding system.