The essential for Injection Molding Stability - mold temperature

The third factor that increases flow resistance: the mold temperature is too low.

When the temperature of the mold is lower, the thickening speed of the skin layer is faster, and the increase of flow resistance is also faster. On the contrary, when high mold temperature is used, the flow resistance increases slowly, and the plastic is easier to fill the mold cavity, that is, it is easier to inject.

Generally speaking, the higher the processing temperature of raw materials, or the smaller the processing temperature range, often use high mold temperature for injection, for example, plastic nylon (Nylon) or PC materials, most of them need to use high mold temperature during production; in addition , when the thickness of the product is too thin, in order to reduce the dynamic resistance, high mold temperature is often used for production.

Although high mold temperature is beneficial to injection, the biggest disadvantage of increasing mold temperature is that the production cycle will be longer. It can be seen from the formula that the higher the mold temperature, the longer the cooling time required.

When the product is filled in plastic, the next stage is cooling. There are three types of water used in the injection molding process, namely normal temperature water, mold temperature water and chilled water.

1. Normal temperature water

The so-called room temperature water, as the name suggests, is water close to the current ambient temperature, and the water temperature is about 25-33 degrees C.
Most injection factories, in order to speed up the production cycle, most often use "normal temperature water" as the circulating water for mold cooling. However, normal temperature water is prone to temperature drop due to climatic factors. When the water temperature is unstable, the speed of the skin layer produced by the plastic in the mold will be different, and the flow resistance during injection will also be different, which will ultimately affect the stability of production quality.

 

2. Chilled water

Chilled water refers to water that has been cooled by a freezer, and the water temperature is about 13-17 degrees C.
The advantage of chilled water is that it can help to quickly build up the skin layer during injection and shorten the production cycle, but it is not suitable for products that focus on size and appearance.

 

3. Mold warm water

Mold temperature water refers to the water heated by the mold temperature machine, and the water temperature is about 60-120 degrees C.
As for the timing of using mold warm water, the most important purpose of the injection molding cooling step is to eject the finished product smoothly. Therefore, the surface of the finished product needs to be solidified so that the product will not be deformed during ejection. Generally speaking, the best time for product ejection is when the product cools below the "heat distortion temperature" of the material. Therefore, when using a mold temperature controller, it is best to set the upper limit of the temperature at 10 degrees C below the "heat distortion temperature" of the raw material to avoid ejection deformation or excessive cooling time.

"High mold temperature" is conducive to injection, but the cooling time will be longer. To determine an optimal mold temperature setting, it is necessary to obtain the best among "quality requirements", "material characteristics" and "time cost". balance.

 

Further understanding for the essential for plastic injection molding stability

This is just a partial overview of plastic injection molding. Are they the right knowldge for you? Not sure how to apply them to your

next project? Just contact our technical experts and we can offer helpful advice about how to get the best results from its processes.