Design points of injection mold for left end cover of vacuum cleaner/Digital diagnostic instrument f
Time：2020-08-10 08:28:05 / Popularity： / Source：
Design points of injection mold for left end cover of vacuum cleaner
Left end cover of vacuum cleaner is an important part of vacuum cleaner housing. Product picture is shown in Figure 1. Maximum size of product is 102.13 mm * 62.36 mm * 26.40 mm, average thickness of plastic part is 1.80 mm, material of plastic part is PC, shrinkage rate is 1.006, weight of plastic part is 90.82 grams. Technical requirements for plastic parts are that there must be no defects such as peaks, uncompleted injection, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, bubbles, etc.
Figure 1 Product picture of left end cover of vacuum cleaner
It can be seen from Figure 1 that plastic part has a semicircular opening shape, with a raised side ear on the side, a through hole on the side ear, and three horizontal bone positions on circumferential edge, which act as reinforcing rib. For through hole of side ear, both sides need to be designed with slider core pulling. There is an undercut in the inner mouth of column in the center of plastic part. Considering that its diameter is only ø11.70 and inner hole diameter is smaller, it is impossible to design a core pulling mechanism.Mold cavity is 2 cavities. Core pulling distance of one side of slider at the side ear through hole of plastic part is small, and two sliding cores on the other side are longer. In mold design layout, a slider with a smaller core pulling distance is designed in the center of mold to reduce size of mold base. Since gating system uses hot runner to inject, and secondary ejection system of rear mold needs to design two layers of ejector plates, mold base is a non-standard mold base 3565. Because size of front and rear mold cores is small, mold base size is relatively large. In order to increase contact area between front and rear molds of mold, 6 pressure-bearing plates are designed on the periphery of front and rear mold cores. A zero-degree positioning block is designed on four sides of mold base to facilitate accurate mold clamping.
Mold casting system adopts EWIKON hot runner, type is HPS III, 230V, EWIKON hot runner is a famous German hot runner system supplier. Its products are widely used all over the world, mainly with hot runner system of smaller plastic parts as representative product. After autonomous nozzle of molten plastic enters splitter plate, it enters parting surface through two hot nozzles respectively, and then inject with a side gate through S-shaped runner. Gate is designed on the straight edge of top edge of plastic part.
Ejector of plastic part adopts a flat ejector pin and a thimble to eject together. Pillar in the center of plastic part is formed by a thimble, and undercut is ground on the center thimble. Center thimble is designed on the bottom thimble board, and remaining flat eject pin and thimble are all designed on upper thimble board. Thimble of cold material well under hot nozzle is also designed on the upper thimble plate. Bottom thimble plate is limited by square iron. A resin shutter is installed between two thimble plates. After mold is opened, ejector pin of injection molding machine pushes upper thimble plate, and lower thimble plate is driven by resin shutter. Flat thimble, thimble and center inverted thimble work together to release plastic part from back mold cavity. After pillar in the center of plastic part is separated from movable model core, it continues to be ejected, and lower thimble plate is restricted by square iron, thimble of center undercut stops moving, remaining flat thimble and thimble separate plastic part from center undercut thimble. The first ejection provides deformation space for forced release of undercut.
Figure 2 Mold diagram of left end cover of vacuum cleaner
Digital diagnostic instrument front and rear shell front mold alignment and rear mold clamping mechanism
Plastic parts of front and rear housings of digital diagnostic instrument are made of ABS, and shrinkage rate is 1.005. Technical requirement of plastic parts is that there must be no defects such as peaking, dissatisfaction in injection molding, flow lines, pores, warping deformation, silver streaks, cold materials, jet lines, etc. Difficulty of mold design lies in special molding structure of plastic part. There are large areas of injection and bone positions on back mold and side. Therefore, slider needs to be designed with a slider eject pin. Another difficulty is that there is a countersunk head that requires design of front mold slider, and insert on slider needs to be inserted into back mold slider. In order to prevent front mold slider from interfering with rear mold slider, two front mold sliders and mold clamping mechanism are adopted to ensure normal use of mold opening and closing. See mold design drawing 1.
Before mold is closed, button is tightly attached to pit on the edge of A plate under action of spring. When mold is closed, small step plane pushes A plate forward until inclined surface of button contacts B plate, and then button is gradually opened. AB board is closed first. Pay attention to distance of each board, 38.4>12.85. This inequality size is size condition to ensure that AB board is closed first.
Figure 1 Die diagram of front and rear shells of digital diagnostic instrument
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