When it comes to sealing strips, we will think about the application of sealing strips in car parts, windows, body, seats, sunroofs, engine compartments and trunks, as well as its waterproof, sealed, soundproof, dustproof, antifreeze, shock absorption, etc. As a professional manufacturer of sealing strips, Hangzhou Buruite not only goes deep into every step of mold design, structure manufacturing, processing, assembly, trial molding, trial production, mass production, but also pays great attention to the sealing strip. Mold design, because the sealing strip application is equipped in different parts of the car, has different uses and functions, so the structure of the mold is more complicated.
Rubber sealing strip extrusion characteristics
In order to better understand the knowledge of rubber extrusion dies, let us first familiarize yourself with the characteristics of rubber extrusion.
1) The rubber compound is further kneaded and plasticized by the rotation of the extruder screw to ensure the quality of the extruded semi-finished rubber compound is more dense and uniform;
2) Wide application range, by changing the mouth die, it is possible to extrude rubber profiles of various sectional shapes and preformed semi-finished products for pressing molds;
3) Extrusion products have high speed and high production efficiency, which is conducive to automated production;
4) Extrusion molding is not limited by length, and it is possible to produce an ultra-long product which cannot be molded by molding.
Rubber sealing strip extrusion die structure
At present, rubber extrusion dies can be divided into two types, namely, a single rubber extrusion die and a composite rubber extrusion die, which have both commonality and individuality. The single extrusion die is generally composed of a panel and has a simple structure; the composite extrusion die generally consists of a panel, a flow channel plate, a splitter plate, and a fiber guide, which are relatively complicated, for example, the following.
Single extrusion die
Composite extrusion die
Rubber sealing strip extrusion mold design considerations
Commonly used design software for mold design include Auto CAD, Pro/E, UG, CATIA Solid Works, etc., because the sealing strip extrusion products are not limited by length; and the type of sealing strip not only contains single rubber sealing strips (pure rubber sealing strips), but also Contains composite rubber seals (composite seals for metal support skeletons); in addition, seals exhibit very complex mechanical properties during installation and use, such as material properties, geometric nonlinearities, nonlinear boundary conditions, etc. Therefore, the sealing strip forming process is very precise and complicated, so pay attention to the shrinkage of rubber of different materials, as well as the product layout and internal structure when designing the mold.
1) Single rubber extrusion die design considerations
For any extrusion die, the design point is to ensure the composite design requirements for the cross-sectional size and shape of the extruded product. Therefore, the monomer rubber extrusion die needs to consider the following six factors in the design:
(1) When the rubber is extruded from the extrusion die, different expansion occurs. When the hardness of the rubber is from small to large, the expansion ratio of the extrusion section is from large to small;
(2) When the temperature of the extruder changes from low to high, the expansion ratio of the extruded section increases from small to large;
(3) When the extrusion speed is changed from low to high, the section of the extruded product only grows from small to large;
(4) Different kinds of rubber or different rubber compounding ratio, the expansion ratio of the extruded product section is different;
(5) The expansion ratio of each part of the section of any extruded product is not intended to pass, especially the cross section of the opposite sex;
(6) The different design patterns of the extrusion die will have different effects on the cross section and size of the extruded product.
2) Precautions for design of composite rubber extrusion die
In addition to the design commonality of the single rubber extrusion die, the design of the composite rubber extrusion die has the following special requirements.
(1) It must be ensured that the extrusion speeds of different rubber types (and skeletons) are consistent with each other to ensure that different rubber types (and skeletons) can be well integrated into one whole;
(2) For a composite extrusion die with a skeleton (metal or wire braid), it is necessary to ensure the locking of the composite position between the skeleton introduction die and the extrusion die and to adjust the locking design of the composite gap;
(3) The cavity matching angle of the skeleton introduction die and the composite extrusion die in the composite extrusion die should be appropriate.
Rubber seal strip extrusion mold design is a system design, each new product needs to start from the design mold, the quality of the mold will test the accuracy of the product, so every detail of the design is sloppy.