A higher mold temperature slows down the cooling rate of the melt in the mold. This slower cooling is beneficial in reducing internal stresses caused by rapid and uneven cooling. It allows the material more time to shrink uniformly, thereby reducing internal tension.

Moreover, the uniformity of mold temperature, ensuring consistent cooling speed throughout the product, is equally important. This necessitates a well-designed cooling water circuit and, sometimes, even conformal cooling techniques to achieve uniformity.

There is a close relationship between mold temperature and internal stresses in injection-molded products, mainly manifesting in the following aspects:

Air Cooling: In some cases, if the mold temperature easily reaches the working temperature, or if the product does not require strict temperature control, ambient air can be used for cooling. This method does not require connecting cooling water circuits and heating pipes but is less commonly applied, used only under specific conditions.

Therefore, mold cooling is critical, a vital aspect in the production of most injection-molded products. Proper control of mold temperature not only enhances product quality but also prevents mold damage and ensures smooth production.

For specific types of plastics, material suppliers usually provide detailed temperature recommendations in their material property sheets.

In either case, we are fully capable of quickly assessing whether this mold will fit our equipment, and performing any necessary modifications, which are normally minor.

Insulation Plates: To improve heating efficiency and reduce thermal loss, some molds use insulation plates. This method helps maintain stable mold temperatures while also reducing energy consumption.

Internal stresses can lead to instability in product dimensions, cracking, deformation, or deterioration in performance during subsequent processing. Therefore, minimizing internal stresses through appropriate control of mold temperature is crucial.

Electric Coil Heating: This is a cost-effective heating method, but its drawback is potential uneven heating, which can affect product quality. Therefore, it might not be suitable for productions where uniform heating is crucial.

During the injection molding process, the quality and cycle time of the molded product are directly influenced by the mold temperature. Since different resins have varying glass transition and molding temperatures, setting the appropriate mold temperature is crucial. Let’s delve into the comprehensive understanding of mold temperatures in injection molding production.

The rapid cooling and heating technology is suitable for high-precision products with high surface quality requirements, such as transparent plastic products and high-gloss surface items. This technique demands precise temperature control and an efficient heating and cooling system, setting high standards for mold design and manufacturing.

From ABS to PEEK, each material demands a nuanced approach to temperature control. By adhering to these guidelines and adapting to the specific requirements of each plastic, manufacturers can achieve superior product quality, minimize defects, and optimize cycle times. Remember, the key to successful injection molding lies in the meticulous management of mold temperatures.

To increase the size and stability of the product, lowering the mold temperature is an effective method. A lower temperature can reduce the shrinkage rate of the product, helping to maintain consistency in dimensions.

However, due to its substantial energy consumption during production, its use is limited and typically reserved for special occasions.

Internal stresses primarily arise due to inconsistent thermal shrinkage rates in different parts of the plastic product during the cooling process. This uneven shrinkage generates tension and pressure within the material, leading to internal stresses.

What is a "short run"? Typically, it is a low volume order quantity. Many molders wouldn't even consider this type of business—they are more interested in churning out millions of parts. Klann Plastics, however, is a short run expert, and we have offered this level of service for many years. We have learned how to produce small orders efficiently and cost-effectively, using either your existing molds or, if needed, with new molds. If you have a project that requires a prototype or production mold, along with part volumes in the hundreds or thousands, contact us. We'll find a way to work with you.

Temperature Controller Heating: A common method of heating, using temperature controllers that offer water heating and oil heating options. Water heating is suitable for mold temperatures below 100°C, while oil heating is used for temperatures above 100°C. For some high-temperature plastics requiring mold temperatures even up to 200°C, oil heating becomes especially important.

When the mold temperature is high, the temperature of the plastic product after ejection is also high. This leads to an increased shrinkage rate during cooling, causing the product dimensions to decrease. To compensate for this shrinkage, it is possible to increase the product size by extending the holding time and increasing holding pressure.

At high temperatures, certain mold steels may undergo excessive thermal deformation, leading to mold “locking” or the inability to open the mold properly. This requires the use of special steels with low thermal deformation for molds operating in high-temperature environments.

It’s advised to produce these plastics at mold temperatures close to their crystallization temperature. Doing so ensures that the products are fully crystallized during the injection molding stage, thereby avoiding post-crystallization and shrinkage that might occur in high-temperature environments.

In conclusion, understanding and accurately applying mold temperature settings is pivotal in the realm of injection molding. It not only ensures the integrity and quality of the final product but also significantly influences the efficiency of the production process.

It’s apparent that the lower the mold temperature, the shorter the time required for the product to cool and solidify, thus reducing the injection molding cycle. Generally, the cooling phase of injection molding typically takes about 20-70 seconds, occupying the largest proportion of the entire cycle. Consequently, reducing cooling time plays a key role in enhancing productivity and cutting costs.

Mold rapid cooling and heating, also known as “Rapid Heat Cycle Molding” (RHCM), is a specialized treatment technique for injection molding molds. During this process, the mold is quickly heated to a temperature higher than the melting point of the plastic to facilitate plastic flow and fill the mold. Once the plastic fills the mold, the temperature is rapidly lowered to accelerate the plastic’s cooling and solidification, thereby shortening the molding cycle.

In summary, choosing the appropriate mold temperature is vital for semi-crystalline plastics. It enhances the quality and stability of the products, preventing deformation and quality degradation in high-temperature conditions.

Room Temperature Water Cooling: The most common cooling method involves using cooling tower water to cool the mold, bringing the water temperature close to ambient temperature. This method is economical, practical, and suitable for most standard injection molding operations.

High mold temperatures increase the flowability of the plastic melt, leading to the formation of flash. Flash is the excess thin layer of plastic that spills out over the edges of the mold.

Chilled Water Cooling: When faster cooling is required, a chiller is used. By setting the water temperature generally between 13-17°C, mold temperature can be controlled more precisely, suitable for scenarios where high precision and production efficiency are needed.

This table provides an overview of various plastics along with their recommended mold temperature, melting temperature, injection molding temperature, and decomposition temperature. ​

Uniform mold temperature aids in achieving even cooling throughout the product, subsequently reducing the generation of internal stresses. If some areas of the mold are colder or hotter than others, it will lead to uneven material shrinkage and increase internal stresses.

An overly high mold temperature can make it difficult for the product to form and be ejected from the mold. If the product is ejected at a temperature higher than its heat deflection temperature, it can deform, affecting the quality.

This takes place more often than you might think, and occurs in one of two ways. First, we have several large customers who are also very large plastic injection molders of their own proprietary parts. They are very quality conscious, so we are honored when they trust us with their molds to run production parts for them—at times, up to 20 molds at one time. Second, a customer becomes displeased with his current vendor's performance, which usually is a product quality or on-time delivery issue, and investigates other sources. Klann has often been the beneficiary of this type of situation.

We started business in 1910 and have been actively engaged in plastic injection molding and tooling for more than 60 years.

If the temperature varies across different parts of the mold, it leads to uneven cooling speeds and, consequently, varying shrinkage rates. This not only affects the precision of dimensions but can also cause internal stress and warping of the product.

Different plastic materials react differently to mold temperature. Crystalline and amorphous plastics behave differently during cooling and solidification, so the formation of internal stresses is also affected differently by mold temperature.

Mold temperature control in injection molding is primarily categorized into cooling and heating the mold, detailed as follows:

In conclusion, the proper control of mold temperature is key to ensuring the dimensional accuracy and quality of injection-molded products. Adjusting mold temperature effectively controls the product’s shrinkage rate and dimensional stability, ensuring product quality.

The table below shows the recommended mold temperatures for several commonly used plastics. Although it doesn’t cover a wide range of materials, it provides a general idea of what the mold temperatures should be for typical plastics in injection molding.

When such plastics are injected at lower mold temperatures, their molecular alignment is restricted, preventing further crystallization. Products molded this way are prone to re-align and crystallize when exposed to high temperatures during use or secondary processing, leading to deformation well below their heat deflection temperature (HDT).