Hole design and residual stress influence in injection mold processing
Publisher: Administrator Date：2020-07-31
Common holes in the processing of injection molded parts include through holes, blind holes, special-shaped holes (complex shaped holes) and threaded holes, etc. These holes should be set in places that are not easy to weaken the strength of the plastic parts. Between the holes, the holes and There should be sufficient distance between the side walls. The relationship between the two holes of the thermosetting injection molded part and the thermoplastic injection molded part and the relationship between the hole and the side wall can be found in the relevant industry table.
The cores for forming through holes generally have the following installation methods. One end of the core is fixed. This method is simple, but there will be lateral flash that is not easy to repair, and it is easy to bend when the hole is deep or the diameter is small.
Two cores fixed at one end are used for molding, and the radial dimension of one core is 0.5-1mm larger than the other, so that even if there is a slight misalignment, it will not cause difficulties in installation and use. Its characteristic is the core length It has been shortened by half and the stability has been increased. This molding method is suitable for applications with deeper holes and low pore size requirements.
One end of the core is fixed and one end is guided and supported. This method makes the core have good strength and rigidity and can ensure concentricity. It is more commonly used, but the guiding part is worn out due to guiding errors, which will cause rounded longitudinal flash.
Blind holes can only be molded with a core fixed at one end, so their depth should be shallower than through holes. According to experience, when injection molding or injection molding, the hole depth should not exceed 4 times the hole diameter. When forming special-shaped holes, they are often formed by splitting, so as to avoid lateral core pulling.
The holes on the injection molded parts are roughly divided into these three types, so the design of the holes on the injection molded parts should be considered before designing the injection molded parts, so as not to affect the strength and rigidity of the injection molded parts, making the product quality unqualified and reducing production effectiveness.
In the future, the market will still have strong demand for various plastic products, especially the development of the domestic plastic products field, which will still maintain a rapid growth stage, and the plastic injection molded products field, as an important part of the plastic products field, is currently developing It is better, and because of this, the differentiation of plastic injection processing machinery will increase in the future.
The market’s strong demand for plastic injection molded products is destined for the rapid development of plastic injection molding processing machinery. However, there are many homogenized plastic machinery on the market. In the future, consumers’ demand for plastic injection molded products will be personalized. This will make the future plastic injection processing machinery will have differentiated competition to meet the needs of different consumers for products.
Injection molding machinery is one of the high-precision machinery and equipment, and the market prospects are relatively good, which makes injection molding processing a lot of capital markets to enter the field, supporting a group of new injection molding machinery manufacturers, and these companies can obtain the market Xianji will inevitably adopt a differentiated competitive strategy. These factors will lead to a variety of injection molding machinery in the future market to meet the different needs of customers.
In the actual injection molding process, due to the requirements for the productivity of the injection mold, when the filled plastic is cooled and solidified in a short time, the macromolecules can only be loosely piled together according to the shape of the cavity. There is no time for tight arrangement, so there will be greater internal stress in the injection molded part after demolding.
Even if the slow cooling measures in production are adopted, the obtained cooling rate is still very urgent for the deformation and rearrangement of macromolecules. After demolding, the macromolecules will continue to deform and rearrange with the development of time to eliminate At the same time, the internal stress promotes the tightness of the loosely stacked organizational structure. This phenomenon is called stress relaxation, and it is called effective deformation of injection molded parts in production.
Aging often lasts for a long time, sometimes even months or years. Therefore, the size and shape of injection molded parts will change during use or storage after demolding. If appropriate measures are not taken, it cannot be satisfied. Quality requirements for injection molded parts.