The design and development of your mold is an expensive process which makes it important to get right. Therefore, you should know the plastic injection molding lifespan to get an estimate of how many production cycles your mold can give the best results before being permanently deformed.
This article outlines the different types of molds available, the factors that affect their lifespan, and the defects that may arise and reduce this lifespan.
How Long Do Injection Molds Last?
The Plastics Industry Association, known until 2016 as the Society of Plastics Industry, has devised a classification system of molds for various applications. Consisting of five classes, this standard system guides how many cycles a mold can be expected to run.
As a general rule, the more cycles a mold can undergo, the more expensive it will be to develop. By going through the properties of each class, you can determine which type of mold you should use for your desired application.
Mold Class 101
The Class 101 Mold is considered to be the most long-lasting among the five classes. Running for more than 1,00,000 cycles, this class is usually reserved for extremely high-volume productions and fast cycle times.
You can attribute their robustness to the high-quality materials they are made from. Hence, they are resistant to harsh injection molding conditions and corrosive materials that may damage other mold classes.
These molds have a minimum tool structure hardness of 28 on the Rockwell scale (HRC), which imparts a hardened base. Moreover, hard molding surfaces are a result of cavities and cores having 48 HRC hardness.
It is also recommended that you use wear plates on the sliders to reduce friction. Parting line lock, guided ejection, and temperature control cooling channels are also suggested.
Mold Class 102
Not as costly as Class 101, this class of molds can run for 500,000 to 1,000,000 cycles. This denotes medium to high levels of production.
You usually use it for manufacturing parts that are made from abrasive materials or have tight tolerances. They are also resistant to environmental and corrosive conditions, but not as much as Class 101. However, they do have the same tool structure and cavity hardness as Class 101.
They are not as expensive as Class 101 molds, and wear plates, temperature control channels, parting line lock, and guided ejection are not a must.
Mold Class 103
You can expect this class to run for a maximum of 500,000 cycles, which makes them suitable for medium-volume production. Class 103 is also a popular choice as it falls within affordable cost ranges.
The tool structure and cavity/cores should have a minimum hardness of 18 and 28 HRC, respectively. Other mold requisites are not as strict as the ones in Classes 101 and 102.
Mold Class 104
For production cycles below 100,000, you may use Class 104 molds. They have lower quality than the previous three molds, and so are liable to deform easily.
This makes them suited for non-abrasive materials only. Mild steel and aluminum may be used to make their bases, cavities, and cores. Furthermore, they require many maintenance operations to ensure their operational effectiveness.
Mold Class 105
This is the least expensive mold class and is commonly used for prototyping and low-volume manufacturing. They last for less than 500 cycles and are made from cast metal or epoxy.
Factors That Affect Injection Mold Lifespan
You may wonder whether or not plastic injection molding lifespans are determined only by the designated class.
Here, you should remember that these classes only serve as a guide for the number of expected cycles and production levels and do not promise quality during practical applications.
In general, the life of a mold is determined by how well you maintain it and under which conditions you operate on it. Even a Class 101 mold, considered the most durable and expensive, can deform early if subjected to extreme conditions.
If you allow elements such as dust and debris to accumulate on it, the mold undergoes extra wear, affecting its performance and the quality of the molded part.
Here are several factors that have an impact on your plastic injection mold’s lifespan, and the steps you can take to minimize their effects.
Operating Environment
This is one of the most impactful factors that affect your mold’ performance. The presence of a spotless environment without corrosive elements leads to long mold lifespans.
Environments such as clean rooms are specifically designed to ensure no contaminant affects molding operations.
However, if your environment allows your mold to be exposed to debris, dust, and harsh elements, it can have a negative result on not only your mold life but also on the molded part due to the extra degree of wear caused by them.
Mold Setting Skills
As injection molding involves several moving parts, you may not be surprised to learn that the molds constantly experience wear. Its effects are amplified when the molds are not correctly set in the molding machine.
Overlocking, overpressurizing the material, improper alignment of the tool, and extreme ejector stroke all contribute to additional wear on the mold. Therefore, you should ensure that the mold is correctly set in place by a skilled injection molder.
Time Interval Between Each Production Run
You may already know that injection molding depends on the heating of the plastic material before it is inserted into the mold and its cooling before being ejected. This causes thermal stresses to develop inside the mold.
If there is insufficient time between successive production runs, the mold does not cool down properly and thermal stresses are not kept to minimum levels. After several cycles of rapid heating and cooling, these stresses damage the mold, reducing its lifespan.
Hence, to ensure your mold is not affected by these stresses, it is advisable to let it cool down before starting the next production run.
Production Cycle Time
Manufacturers often want to speed up production to achieve greater output from their injection molding facilities. However, prioritizing faster cycle times can sometimes cause damage to the molds and the molded product.
If you do so, it causes the mold to experience more stresses, and can also cause faults in several moving components involved in the process. Incorrect clamping, the opening of vents before their optimum time, and errors in the decoupling step may occur in fast production cycles.
Materials of Injection Mold Tooling
The lifespan of your mold also depends on the material It is made from. Here, you may need to trade off longer life with greater expenses.
Steel has a greater life than aluminum but is also more costly. You should make such decisions after conducting a proper cost-benefit analysis.
Another vital factor regarding your material selection is its ability to withstand corrosive elements. In this case, aluminum has an advantage over steel since it can form an oxide layer on its surface, enabling it to be unreactive to toxic materials.
Mold Surface Treatment
In almost every injection molding process, maximum stresses are present when the molded part is ejected from the mold. Therefore, the surface of the mold also has a bearing on this process.
Surface treatment techniques such as physical vapor deposition (PVD) coating, also known as thin-film coating, are hence suggested by industry leaders to ensure that these stresses are minimized during ejection.
This thin film is composed of metal-based particles and has a similar effect as the oxide layer aluminum forms on its surface.
If PVD coating is not present, you can still ensure that the mold surface is kept clean by regularly adhering to the regular maintenance procedure. By doing so, you can extend the life of your mold and avoid defects.
Proper Mold Structure Design
Another factor that affects your mold’s life expectancy is its structural design. Mold failure is mainly caused by extra thermal stresses.
Hence, you should ensure your mold contains design elements, such as vents and push guides, that help in reducing these stresses as well as enable smoother part ejection.
Moreover, by making mold parts like plates and cavities from high-grade tool steel, you contribute to a higher degree of wear resistance, which maintains the required structure.
Preventative Maintenance
As with other processes, no matter how much care you take in designing, surface treating, and controlling time intervals between each cycle, these steps become less successful over time.
To ensure your plastic injection mold lasts as long as possible, you need to carry out a proper preventative maintenance program.
A maintenance program that involves regular inspections, cleaning, and repairing helps your expensive investments in your mold, thus saving resources. It is often a good idea to keep track of all services, inspections, and repairs carried out on a mold to help identify potential issues and errors.
Moreover, you can decrease operational errors by following a proper operating protocol. You can also blow leftover water from the water lines when pulling the mold from the press.
Additionally, you must be vigilant and replace or grease noisy parts, and follow the suggested mold safety settings and tool modifications.
Remember that by strictly keeping to your preventive maintenance program, you are ultimately extending your mold’s life in the long run. Thus, you should not shy away from taking your mold out of operation for a day or two to follow these steps.
Defects That Shorten Injection Mold Expectancy
Even if you follow all the steps mentioned above, your mold is still liable to produce defects sometimes. Most of the
Flow Lines
These are patterns that emerge on plastic parts. You can attribute them to contrasting flow rates of the material which result in different cooling and solidification rates. Poor mold design can also cause them.
To fix this issue, you can modify the speed and pressure of injection so that the cavity is filled uniformly. Otherwise, you may need to change the design of your mold.
Sink Marks
Sink marks are another result of uneven cooling of the injected material. They usually occur in plastic parts that have edges or narrow openings.
Caused by overheating or insufficient pressure inside the cavity, you can spot them as small depressions present in the thicker areas of the mold. As a result, your mold is damaged, and molded parts are not ejected smoothly.
Burn Marks
Often experienced during high-speed production, burn marks are caused by overheating specific regions of the mold. You can see them as rust-colored spots on your molded parts. In some cases, both the part and the mold are rendered useless.
Surface Delamination
When a part divides into layers during the injection molding process, delamination occurs. Caused by unintentional contamination with release agents, this creates an abrasive surface which increases wear.
You can overcome this problem by modifying the ejection system so that release agents are not required.
Flash
Flash refers to the extra plastic that escapes the mold via the sides of the parting line. You can see it as extra plastic on the sides of the molded part. It causes the wearing of mold clamps, which may necessitate their replacement.
To prevent this, you may change the speed, pressure, and temperature of the molding process. You can also carry out regular inspections of the extrusion part.
Choosing Between Steel and Aluminum Injection Molds
The specifications of your mold mainly depend on factors such as the applications of your product and your budget. For low-volume prototyping applications, aluminum is preferred as it is cheaper.
Class 105 molds are often made from aluminum. On the other hand, if your objective is high-volume manufacturing, you should use a long-lasting, durable material such as steel. It might be more expensive at the start, but it can last longer.
Create Solid Injection Molds With Kemal
Plastic injection molding can seem daunting at first due to the many factors you need to consider and the decisions you have to make in the planning phase to ensure its durability and repeatability.
However, with an experienced, reliable manufacturer like Kemal, you can rest assured that you will get the best injection molding services at affordable rates.
Kemal uses its 28-year experience across a multitude of industries to ensure that the seemingly difficult process of mold design is executed in minimum time without compromising on its quality.
With the help of our professional experts, we guide you through various facets of mold manufacturing such as the choice of material to the recommended design features.
To embark on your profitable journey with us, you can use our free online quote service to upload your design securely and get an estimate and recommendations from our skilled team of developers and engineers. We look forward to helping you achieve successful results.
Conclusion
To sum up our discussion of plastic injection molding lifespans, it can be said that the life of your mold depends on its designated class, as well as factors such as operating environment, production cycle time, and surface treatment.
However, steps such as preventative maintenance can ensure your mold achieves its designated lifespan without getting damaged early.
Learn more about our manufacturing services through our blog here, or contact us if you have any further queries.
