Analysis of the Factors Affecting the Dimension Accuracy of Plastic Parts In Mold Design

Many factors influence dimensional accuracy and are quite complex. This makes determining the right size tolerance challenging. Dimensional accuracy is affected by numerous major elements. Next, the factors affecting dimensional accuracy in mold design are introduced in detail.

Different mold types have different effects on plastic product dimensional accuracy and single-cavity molds have more precision than multi-cavity molds. The wear of the mold cavity and core, as well as the grinding and polishing of the cavity surface, accounts for approximately 1/6 of the tolerance of the plastic parts. The precision of the single cavity molding is higher. Each increase in the number of cavities of the mold will reduce the accuracy of the plastic parts by 5%. The size of the plastic part formed by the mold's moving part is less precise. Uneven shrinkage of molded plastic parts will result from improper design of the runner system and cooling system on the mold. The insufficient force of the ejection mechanism will result in distortion of the ejected plastic part and dimensional inaccuracy. All of these factors will have an impact on the quality of the injection parts.

The mould's dimension tolerance is approximately 1/3 of the part's tolerance. If this value is used as the mold tolerance of the standard level, then the tolerance of the precision mould is 1/2 of the standard level, and the tolerance of the rough mould is about 2 times of the standard level.

Precision injection molding

Precision injection molding refers to the high dimensional repetition accuracy of the injection molding products, which is a kind of injection molding method that is difficult to meet the requirements of the general injection molding machine and the conventional injection molding process.

Precision injection molding requires that the dimensional accuracy of plastic parts is generally within 0.01 ~ 0.001mm, and many precision injection molding parts also require injection molding machines to have high injection pressure and injection speed. Moreover, the clamping system of injection molding machine is required to have a large enough rigidity and a high enough clamping accuracy. The so-called clamping accuracy refers to the uniformity, stability and repeatability of the clamping force, and the high precision of the opening and closing position. It is also required that the pressure, flow, temperature, measurement, etc., can be accurately controlled to the corresponding accuracy, and precision injection is used to ensure the repeated accuracy of the molding process conditions and product size.