Injection molding is a widely used manufacturing method, and injection molds are a very important part of injection molding. It is not only the most expensive part of manufacturing cost, but also seriously affects production efficiency, quality, and accuracy. However, the injection mold lifespan is not infinite. So it is important to understand the injection mold lifespan. This article will discuss the factors that affect the injection mold lifespan and how to extend the injection mold lifespan.
What is an Injection Mold Lifespan?
In the context of manufacturing, the term “injection mold lifespan” 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
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
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
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
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
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 Lifespan
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.
8 Ways for Extending the Injection Mold Lifespan
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.
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 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 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 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 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 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.
The choice between aluminum and steel for a mold tool depends on your specific production requirements and budget constraints. Aluminum mold is more cost-effective for prototyping and low-volume production. However, steel mold is more cost-effective for high-volume production with a longer lifespan.
Signs of a mold nearing its lifespan include surface imperfections, parting line issues, reduced dimensional accuracy, material residue buildup, increased cycle times, mold deformation, and visible corrosion.