What are the process requirements of the core bar?
The shape and shape of the core bar are determined according to the design of the core bar.The handle or rear part shall be designed according to the core bar itself.The blowing structure of the core bar can be located at the top or bottom.
Once you know the geometry, quality and materials used, you can calculate them as follows:
Mold length = product length - bottle-bottom recessed depth - stroke
Mandrel length = billet length - base thickness
Total volume of material = total volume of mould blank - total volume of mandrel
The total mass of mold blank is equal to the total product X of the material
The mandrel basically shapes the inner diameter of the neck and the shape of the blank.
In terms of art design, the following requirements must be considered.
(1) the diameter and length of the core bar are the main dimensions of the core bar.According to the molding process requirements, the ratio of the length and diameter shall not exceed 10.If the L/D of the core bar is too large, the core bar is easy to bend and the wall thickness of the formed core bar is not uniform.
(2) the diameter of the blank mandrel at the main part should be slightly smaller than the inner diameter of the mouth and neck of the product, so that the product can be removed from the mandrel.However, the decrease of the diameter of the mandrel will increase the billet swelling ratio, which is not conducive to the uniformity of the wall thickness of the products.Therefore, in the design, the core bar should be kept in a larger diameter without affecting the product demoulding.The core bar is best designed to be tapered. When the billet is blown out, it is easy to pull the billet out.
(3) during the molding process, the billet mandrel shall not only undergo the action of high injection pressure, but also undergo the influence of repeated temperature changes such as heating, cooling and temperature regulation.Therefore, in addition to high quality materials, the core bar is required to have high machining accuracy, and the coaxiality of the core bar should be within 0.05 ~0.08mm.
(4) the position of the compressed air outlet of the core bar can be determined according to the type and model of plastics, the shape of products and the ratio of the length and diameter of the core bar.When L/D>8, the size of the product neck is small. In order to reduce the deformation of the blank mandrel, the mandrel with air outlet at the bottom can be adopted.When L/D is small, the size of the neck of the product increases relatively, or when the shoulder of the mold billet is difficult to blow up, or when the selected resin requires a higher blowing temperature of the mold billet, the mandrel with the air outlet can be adopted, and holes can be added at the outlet, with the maximum aperture of 0.4mm.
(5) in order to avoid uneven wall thickness or melt leakage due to mold mandrel migration, the mandrel should be closely matched with the neck ring of injection mold and blow mold (O~ 0.015mm).
(6) the groove with a depth of 0.10 to 0.25mm should be set up on the part of the core bar close to the neck of the product to prevent the screw shift of the mouth when the billet is turned, or to prevent the leakage of compressed air when the billet is blown out.