During the forming process of plastic materials (metal sheets, non-metallic sheets, etc.) in
Display Micro Screws, residual gas (i.e., "gas trapping") easily forms between the mold cavity and the blank. Without an effective exhaust system, this residual gas will compress rapidly in the later stages of stretching, generating significant back pressure. This not only hinders the flow of the blank into the mold cavity, leading to uneven wall thickness and localized cracking, but also causes defects such as gas scars and pitting on the surface of the part. It can even cause the part to adhere tightly to the mold during demolding, damaging the surface. Therefore, the exhaust system is one of the core aspects of Display
Micro Screws design, and its rationality directly determines the quality of the formed part.
The design of the exhaust system must focus on key locations where gas accumulates. Gas often tends to stagnate in the blind spots where the blank and mold adhere in the later stages of stretching: such as the sidewalls of the die in cylindrical parts, the corner cavities of square parts, and the top corners where the punch and blank adhere in deep-drawn parts. The selection of the exhaust structure must balance exhaust efficiency and part precision, avoiding flash or indentations due to excessive structure size. The core design logic is "precise positioning and efficient exhaust."
The commonly used venting structure is the venting groove, which is generally opened at the edge of the working zone of the die and evenly distributed around the cavity. The groove width is controlled between 2 and 10 mm depending on the size of the cavity, and the depth must match the blank thickness: 0.01 to 0.03 mm for thin plates during stretching, and can be appropriately increased to 0.05 to 0.1 mm for thick plates during stretching. The depth must be less than the blank thickness to prevent extrusion flash. One end of the groove leads to the dead corner of the cavity, and the other end extends to the outside of the mold or connects with the mold's venting channel to ensure smooth gas discharge. For deep cavities where venting is difficult, such as the top of the punch or the dead zone in the center of the die, a venting hole structure is used: usually, small holes with a diameter of 0.5 to 2 mm are drilled, and the hole depth is controlled within the cavity contour (to avoid drilling through the mold and causing material leakage). A smooth air guide channel is connected after the hole to lead the gas out of the mold. In addition, for small parts or complex structures, venting can be aided by utilizing the clearance between the die and the die, and between the slider and the die body: the clearance between the punch and die, and between the slider and the die body, is controlled within a range slightly larger than the thickness of the blank. This allows for the venting of gas through minute gaps, simplifying the design and offering strong adaptability.
Three core principles must be considered during the design process: First, the venting distribution should be symmetrical and uniform. For example, circular drawn parts should have 4-6 venting grooves evenly spaced circumferentially to avoid uneven venting on one side, which could lead to part displacement and deformation. Second, the venting channels must be free of dead corners and blockages. The design should avoid locating pins, guide pillars, and other die structures to ensure unobstructed gas paths. Third, parameters should match the material properties. For example, for thin aluminum sheets with good plasticity, the venting depth can be slightly larger to improve efficiency, while for harder steel sheets, the depth should be reduced to prevent indentations or scratches. Deep-drawn parts also require additional auxiliary structures, such as micro-venting holes inside the punch, to enhance the venting effect of high-pressure gas in the later stages of drawing.
In summary, the design of an Display Micro Screws exhaust system must take into account factors such as part shape, material thickness, and stretching depth, and rationally match the exhaust structure and parameters to efficiently discharge residual gas from the cavity, improve part forming quality, and reduce scrap rate. This is a key detail design for improving the overall performance of Display Micro Screws.
