Estimate the cooling time of Pet Preform Mould injection molding
Fortunately, the cooling time can be reasonably accurately estimated using an equation and a number called the "effective thermal diffusivity", which depends to a large extent on the thickness of the part. “The thermal diffusivity is a measure of how heat enters and exits a given material. In addition, when considering the thickness of a part, it constitutes most of the measure of cooling time.
The thermal diffusivity can be calculated by dividing the thermal conductivity of the part by its density multiplied by the product of the specific heat (the energy required to increase the temperature by 1 degree). Each of these values ​​can be found on the specification sheet for the material used, or contact the manufacturer. Because cooling time is so important, it's best to get this data from first-hand sources (not third-party websites).
Once you know the thermal diffusivity of the part, you can insert it into the rest of the cooling time equation. First, divide the square of the part thickness by the product: the square of the thermal diffusivity multiplied by 6.28 (or twice the "pi"). Then multiply this number by the logarithmic equation. If you are not an engineer, it may be time to call your engineer.
For the person of interest, the calculated initial quantity is multiplied by the logarithmic function of the melt temperature minus the mold temperature (the material maintains the optimum temperature of the mold profile); divided by the mold release temperature minus the mold temperature; multiplied by four Divide by "π". “Fortunately, there are many calculators on the web that can help you with this equation. Of course, any valuable injection molding partner should be proficient in these numbers.
The importance of the mold in the cooling time
As can be seen from the above, mold cooling plays an important role in the injection molding cooling time. Mold design is also an important factor: cooling channels can and should be designed into the mold as much as possible to help more efficient heat dissipation. When you consider the heat path during cooling, the importance of efficiently cooling the mold from material to mold to the surrounding environment is easy to explain. Effective mold cooling means effective overall cooling.
What happens when the injection molding is not enough?
When the injection molding cooling time is improper or insufficient, the biggest problem you will encounter is defective and unqualified parts. The most common cases are those parts that have not yet been cured enough to retain their shape, which are subsequently damaged by the launch of the ram. Improper or inefficient cooling – including poor mold design – can also lead to part errors such as warpage, shrinkage, sinking, etc. Consistent, well-designed cooling times are one of the biggest steps to improve the quality of finished products and reduce the number of defects.
Another factor to keep in mind is that proper cooling temperature does not mean reaching room temperature, nor does it mean that it is cold to the touch. The part should only be cooled to the extent that it retains its shape and can be safely pushed out of the mold. Any further cooling is ineffective (or almost ineffective) and will only unnecessarily lengthen the cycle time.
Ultimately, mathematically estimating the appropriate cooling time for China Pet Bottle will help to avoid excessive cooling and deficiencies.