Injection molding is a widely used manufacturing method, used to plastic or rubber parts how much do you learn about the injection mold tool life? It is not only the most expensive part of manufacturing cost, but also seriously affects production efficiency, quality, and accuracy. However, the injection mold life is not infinite. So it is important to understand the injection mold life. This article will discuss the factors that affect the injection mold tool life and how to extend the injection mold lifespan.
What is an Injection Mold Tool Life?
In the context of manufacturing, the term “injection mold tool life” refers to the duration or operational life expectancy of an injection mold used in the process of injection molding. This lifespan is defined by the number of cycles or shots the mold can produce while maintaining the desired product quality and precision. Once an injection mold reaches the end of its lifespan, it may exhibit signs of wear and tear that can impact product quality and necessitate its replacement or refurbishment.
The injection mold lifespan expectancy can range from hundreds to one million cycles, and it varies significantly depending on several factors, including the classification of mold used.
Mold Classes and Lifespan Expectancy of Mold
Mold classes serve as standardized categories that estimate the number of cycles a mold can undergo before needing significant maintenance or replacement. The Society of Plastics Industry (SPI) employs these classifications to gauge a mold lifespan based on cycle counts. Here are common mold classes and their typical lifespan considerations:
SPI Class 101 Molds – Extremely High Volume
High Production, Over 1 Million Cycles Mold. These molds typically use high-quality materials such as tool steels (e.g., P-20, H-13, S-7). Class 101 molds are the most expensive molds and they are engineered for extensive use, with an expected lifespan exceeding 1 million cycles. They excel in high-volume manufacturing scenarios where durability and precision are essential.
SPI Class 102 Molds – High Volume
Medium Production, 500,000 to 1 Million Cycles. Class 102 molds are designed for medium to high production volumes and typically last between 500,000 and 1 million cycles. They strike a balance between longevity and production volume.
SPI Class 103 Molds – Medium Volume
Low Production, 100,000 to 500,000 Cycles. Intended for lower production volumes, Class 103 molds have a lifespan ranging from 100,000 to 500,000 cycles. They are cost-effective for shorter to medium production runs.
SPI Class 104 Molds – Low volume
Prototype, Up to 100,000 Cycles. Class 104 molds are primarily for prototyping and low-volume production, offering a lifespan of up to 100,000 cycles. They are ideal for initial product testing and small-scale runs.
SPI Class 105 Molds – Prototypes
Experimental, Trial, or Sample Molds. Class 105 molds are experimental and not designed for extended production runs. Their lifespan varies based on their intended use, which includes trial runs, sample production, and experimentation.
Factors Affecting Injection Mold Tool Life
Except for the mold classification, there are several factors affecting injection mold lifespan.
1. Mold Material
The choice of material for constructing the mold itself is a critical factor. High-quality materials, such as tool steels like P-20, H-13, or stainless steel, are commonly used. The compatibility between the mold material and the materials being molded is also crucial. Some plastics, like those with abrasive fillers, can accelerate mold wear.
2. Mold Structure Design
The mold structural design will also affect the injection mold lifespan, such as the complexity of the mold design and the cooling system and Venting system. Complex molds with intricate features may experience more wear and require more maintenance over time. Inadequate cooling can lead to uneven thermal stress, which can reduce mold life. Insufficient venting can result in air traps, leading to damage and reducing mold lifespan.
3. Mold Operating Conditions
The mold operating conditions also affect injection mold lifespan, such as temperature, pressure, and cycle time. Excessive heat can cause thermal fatigue and reduce mold life, while overly low temperatures can result in incomplete mold filling. Excessive pressure can lead to mold deformation or cracking. The cycle time, which includes injection, cooling, and ejection, impacts mold wear and tear. Shorter cycles can lead to higher production rates but may increase stress on the mold.
4. Mold Maintenance
Mold condition and maintenance also affect the lifespan of mold. Proper mold maintenance is necessary. It is better to plan a schedule where inspections are carried out on the mold. All records of the services (cleaning, stripping, etc.) and the repairs done on the mold should be archived, as it may help with detecting possible issues and sources of errors in case defects appear. This bookkeeping can also aid in pinpointing the period in which said defect occurred.
5.Mold Setter Skills
Injection molds are subject to wear and tear. This occurs especially in the ejectors, gates, slides, and other moving parts of the tool, but it is also essential to properly set up the mold in the injection molding machine. Some examples of incorrect setups include overlocking, poor tool alignment, excessive ejector stroke, and overpressurization of the plastic material. These types of bad setups lead to mold wear and tear, which is why mold setup must be handled by an experienced injection molder.
6.Production Run Time Gap
The production cycle generates a lot of heat, and the mold must withstand all the thermal stress. The time interval between 2 production runs allows the mold to cool before the next production run. But if the same mold is subjected to continuous cycles, it may cause mold damage.
7.Production Cycle Time
High-speed production cycles may cause excessive stress on the mold. On the other hand, slower processes result in less stress, so it is important to consider the production cycle time. Slower cycle times extend the life of the injection mold, thereby improving durability. The length of the production cycle time depends largely on design elements such as wall thickness and complexity, dimensional control of the molding process.
8.Mold Surface Treatment
In any injection molding process, the highest stress is during part ejection, so the mold surface plays an integral role in determining the ease with which the plastic part can be ejected. PVD coating deposits an extremely thin but strong layer of metal-based particles on the mold surface and cavity, which aids in the ejection and release of the molded part. Even without PVD coating, the mold surface must be kept clean and smooth to ensure there are no defects.
Why is Aluminum Mold not Suitable for Increasing the Service Life of Injection Molds?
The material from which the mold is made is a key factor affecting its durability. Different materials offer varying degrees of hardness, wear resistance, and the ability to withstand high temperatures and pressures.the following is steel alloys VS aluminium Injection mold tool life:
Steel Alloys
Steel alloys are commonly used in plastic injection mold manufacturing due to their strength and durability. The type of steel alloy selected can greatly affect the life of the injection mold.
Characteristics: Steel alloys are highly regarded for their hardness, wear resistance, 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 suitable for different molding requirements.
P20 steel has a hardness range of 28-32 HRC. Known for its good machinability, P20 can typically last for approximately 300,000 to 500,000 injections/cycles, making it a popular choice for less strenuous applications. It is often used in the production of large molds due to its excellent balance between cost and durability.
H13 steel typically has a hardness between 42-52 HRC. It is known for its high toughness and can withstand over 1 million shots/cycles, especially in high temperature applications. Often used for molds that withstand harsher conditions, such as molds in high pressure injection molding processes.
S136 steel has a hardness range of approximately 48-52 HRC. This type of steel is known for its excellent corrosion resistance and can withstand hundreds of thousands to a million shots/cycles, especially in corrosive environments. Ideal for molds used in corrosive applications, such as those involving PVC and other abrasive materials.
420 stainless steel typically has a hardness range of 48-52 HRC. It is known for its impressive corrosion resistance and can last hundreds of thousands of shots/cycles, making it suitable for molds used in corrosive environments. This alloy is often selected for its polishability and corrosion resistance, making it ideal for molds used in medical devices, food packaging, and other applications where cleanliness and precision are critical.
718 steel, also known as 1.2738, generally has a hardness range of 33-37 HRC after quenching and tempering. It can withstand up to 500,000 shots/cycle, making it a versatile choice for medium to high volume production. This material is favored for its excellent machinability and uniform hardness, making it suitable for complex mold designs and detailed mold components.
2344ESR steel typically has a hardness of 50-54 HRC. It is known for its high temperature strength and can withstand more than 1 million cycles, especially during high stress and high temperature molding processes.
Ideal for making strong molds for high volume production, especially in the automotive and aerospace industries where durability is critical.
NAK80 (P21) steel has a hardness range of 37-43 HRC. Mold Life Expectancy: This alloy can last approximately 300,000 to 500,000 shots/cycles. NAK80 is often used in complex mold designs due to its excellent polishability and wear resistance, making it suitable for high precision and aesthetic parts such as consumer electronics and automotive components.
2767 tool steel is typically hardened to 45-52 HRC. It is known for its toughness and wear resistance, with a service life of hundreds of thousands of cycles. This alloy is particularly used for heavy-duty molds for large parts, where its strength and durability are essential to withstand extended production cycles and mechanical stresses.
Aluminum Alloys
Aluminum alloys are increasingly used in the manufacture of injection molds because their specific characteristics are beneficial to certain manufacturing scenarios. They are particularly favored for their lightweight properties, thermal conductivity, and corrosion resistance.
Properties: Aluminum injection molds are known for their excellent thermal conductivity, which can speed up cooling times and reduce cycle times during the injection molding process.
Applications: They are often used for small-volume production or parts that do not require the extreme hardness and wear resistance of steel.
7075 Aluminum alloys typically have a hardness range of 53-63 HRC if properly heat treated. This alloy can withstand approximately 100,000 to 150,000 injections/cycles, making it suitable for medium-sized production runs. Known for its high strength, 7075 is often used in aerospace applications and is well suited for molds that require a higher strength-to-weight ratio.
6061 aluminum typically has a lower hardness range of 40-50 HRC. It is able to sustain approximately 50,000 to 100,000 shots/cycle, making it suitable for low-volume production or prototypes. Due to its excellent corrosion resistance and weldability, 6061 is often used in automotive applications and consumer products.
8 Ways for Extending the Injection Mold Life
Proper maintenance of plastic molds is more important than mold repair. The more frequently injection molds are repaired, the shorter their lifespan. Conversely, the better the mold is maintained, the longer the injection mold’s service life will be.
Mold Materials Should be Compatible with Injection Molding Materials:Ensure compatibility between the mold material and the plastics being molded. This minimizes chemical reactions that can degrade the mold.
Precise Temperature Control During Process:Maintain precise temperature control during the molding process to prevent excessive heating, which can lead to thermal fatigue.
Setting Proper Injection Speed and Pressure:Operate within recommended injection pressure and speed limits to avoid mold deformation or cracking.
Regular Cleaning:Implement a routine cleaning schedule to remove residues, contaminants, or deposits that can accumulate on the mold surfaces during production.
Regular Inspection and Repair:Conduct scheduled mold inspections to identify signs of wear, damage, or corrosion. Address issues promptly through repairs or refurbishment.
Keep Mold Parts Lubricated:Keep mold’s moving components properly lubricated to reduce friction and wear. Select lubricants compatible with the molding process and materials.
Suitable Mold Storage Environment:When molds are not in use, store them in a controlled environment with proper humidity and temperature conditions to prevent corrosion and damage.
With Proper Surface Treatments:In injection molding, the ejection of the part creates high stress on the mold surface. To make demoulding smoother, experts recommend using PVD coating. However, even without coating, the mold surface should be kept clean and smooth. This is also critical to product quality and extending mold life expectancy.
The Relationship Between Injection Molding Defects and Mold Damage
Injection molding defects are closely related to mold damage. Part defects can cause mold damage, which affects mold lifespan. Mold damage can lead to part defects.
Flow Lines:
Flow lines are visible lines or streaks on the surface of molded parts, typically caused by uneven material flow during injection. Flow lines can be an indicator of improper mold design or cooling. Repeated occurrence of flow lines can accelerate mold wear, particularly in areas where flow lines are concentrated. Adjust injection speed, pressure, and temperature to ensure uniform material flow.
Sink Marks:
Sink marks are depressions or dents on the surface of molded parts, often caused by variations in cooling rates within the part. Frequent occurrence of sink marks may indicate that the mold is not efficiently cooling the material. This can lead to mold wear and deformation over time. Optimizing cooling channels in the mold design, and adjusting packing pressure and time during the molding process will improve the defects.
Burn Marks:
Burn marks are dark or discolored areas on the surface of molded parts, typically caused by excessive heat or overheating of the plastic material. Burn marks can be a sign of poor temperature control within the mold or high injection speeds. These conditions can lead to excessive thermal stress on the mold, potentially shortening its lifespan. Reduce melt temperature, decrease injection speed, and ensure proper cooling to prevent material overheating.
Delamination:
Delamination refers to the separation of layers or laminations within a molded part. That can result from improper molding conditions or material selection. The repeated molding of delaminated parts may introduce contaminants into the mold, leading to surface defects and mold wear. Select appropriate materials, improve material drying processes, and optimize injection parameters to enhance material bonding.
Flash:
Flash is excess material that escapes between mold parting lines during the injection process, forming thin, unwanted extensions on the molded part. Frequent flash occurrences can indicate issues with mold alignment or clamping force. That may experience accelerated mold wear and deformation. Adjust clamping force, maintain proper mold alignment, and review the condition of mold components to longevity the mold lifespan.
Create Injection Mold with Zhongde
If you require expert guidance or services related to injection molding, Zhongde is here to assist. As an experienced on-demand manufacturer, Zhongde not only provides the production of customized parts but also includes mold design, production, and storage services. If you have any questions, please contact us. Zhongde is always ready to provide practical suggestions for your injection mold manufacturing.
