In injection molding for the production of high-volume production with excellent quality, mold good qualities, with a very precise processing, and acceptable duration it is indispensable. The two most important steps in the production of a plastic part is the part design and mold design.
The type of mold to choose, for a piece is determined essentially by considerations of its design.
The main task of the injection mold is receiving and distributing the melt to be formed and cooled and then eject the molded plastic part.
When designing the injection mold should take into account the following considerations
* Perfectly Knowing the plane of the part to be molded, establish lines of partition, entrance area, instead of the elevators and mold detail to facilitate their construction.
* Determine the type of molding machine and the effect it can have on the design of the mold.
* From thermoplastic specifications, must take into account its contraction, flow characteristics and abrasion and heating and cooling requirements.
There are many points that should be taken into account for the construction of a mold: materials for construction, mold making methods, design and characteristics of the mold and part manufacturing among others.
Requirements for an injection mold
The main requirements to be covered by a mold are the dimensional accuracy (within the permissible tolerances) and final appearance (finishing).
The main problem that influences the accuracy of the mold is plastic shrinkage. There are many different factors that affect the dimensions due to shrinkage of the molded product (temperature, pressure, cooling time, etc.).
Plastics with low shrinkage (less than 0.6%) usually have no problem, and the mold dimensions can be easily calculated to give the final accuracy of the product dimensions. Plastics with a high shrinkage (more than 0.6%) must be taken other important considerations for the design of the mold.
Building materials molds
In the construction of molds for plastic injection it is necessary to use special steels for working conditions, due to severe they are subjected and because high precision is required in the finished loads. To this we must add that the tolerances are very thin handled.
Within the wide range of existing materials for the construction of molds for plastic injection we can find the steel, casting materials, non-metallic materials and ceramic materials.
Steels, used in injection molds must meet the following characteristics:
* Acceptable conditions for its preparation are as machinability, can be punched cold to be tempered.
* Compressive strength
* Temperature resistance
* Abrasion resistance
* Aptitude for polishing
* Have reduced deformation
* Good thermal conductivity
* Good chemical resistance
* Simple heat treatment.
Within the mold steels we can find hardening steels, nitriding, temperate, subsidized employment in the State of supply or resistant