Armrest box accessories injection mold
With different models, there are many kinds of armrest box accessories, all of which are different. This article selects two of them to introduce the key points of its mold design. The two kinds of accessories are called plastic part one and plastic part two, and their product diagrams are shown in Figure 1. The maximum dimension of plastic part one is 83.83 mmX43.92mmX76.66mm, the average wall thickness is 1.52mm, and the mass of plastic part is 26.2 grams. The maximum dimension of plastic part two is 83.93 mmX29.92mmX95.30mm, and the average wall thickness is 1.52mm. The quality of the parts is 23.7 grams. The materials of the two plastic parts are FPP TSOP-AT5HF, and the shrinkage rate is 0.0095. Both plastic parts are appearance parts. The plastic parts themselves must not have weld marks, bubbles, burrs and other injection defects.
The armrest box accessory plastic part is an auto part of Canada GTS company. This article takes plastic part one and plastic part two as examples to introduce the design of the inclined slider and the structure of the mold driven by the cylinder. It can be seen from Figure 1 that both plastic part 1 and plastic part 2 are small plastic parts, with different shapes but not much difference in size. The mold structure of the plastic parts is similar, the shape is smooth, and the sides of the two ends are designed with multiple bones. The position is inclined, see the 3D diagram. The inside of the back mold of the two plastic parts is smooth, without bone and column positions. Since the two plastic parts have a closed shape on all sides, the height of the plastic parts is relatively large, and therefore, the plastic parts have a large tightening force when they are ejected. For this type of plastic part, it is not possible to design a thimble inside when ejecting, because the ejection force is large and the ejection pin area is small, which easily makes the top of the plastic part white. Pieces cause inconvenience. Third, it affects the mold opening stroke and the injection cycle.
The mold design cavity ranking is 1+1, and the two sides of the two plastic parts that need to be designed are designed on the mold operating side and the non-operating side. The two ejection cylinders are respectively designed on the heaven and earth side. The mold design uses a non-standard mold base 26"x31", in which the thickness of the A plate is 190.5mm, the process of melting the plastic is longer, and a single open hot nozzle is designed. The molten plastic enters the runner of the parting surface from the hot nozzle, and then is injected into the bottom of the edge of the plastic part through the horn gate. The horns of water can be cut automatically after the mold is opened without affecting the appearance of the plastic parts, so it is widely used in European and American export molds.
Regarding mold strength, many mold design books have related calculation formulas. Due to the complexity and variability of the structure of the plastic part, the structure of the mold cavity and the stress condition are very complicated. For a specific plastic part, it is necessary to pay attention to the strength of the mold. In the mold of this example, because both sides of the plastic part are designed with sliders and the cavity is open, the strength of the cavity cannot be ignored, as shown in Figure 4. For this reason, the thickness of the bottom of the cavity must be increased to ensure strength. In addition, the four corners of the front mold core are designed to increase the accuracy of positioning and mold clamping. When designing the tiger's mouth, attention must be paid to the direction of the tiger's mouth. The tiger's mouth of the front mold core is recessed so that the rear mold core can lock the front mold core.
The bone positions of the two plastic parts are inclined, so the sliding blocks on both sides are the inclined sliding blocks of the rear mold. All the sliders are driven by the inclined guide post. Because the A plate is very thick, all the inclined guide posts are locked by the pressure plate, and the template has an overhaul hole. The inclined surface and the bottom surface of the inclined slider are all designed with wear plates. The positioning of the slider adopts DME's tiger buckle positioning.
The front and rear molds and sliders are all designed for direct water transport to ensure normal injection molding. All water transportation uses a long throat nozzle directly connected to the mold core to avoid water leakage caused by the use of aprons. When using a long throat, if the throat is exposed on the surface of the mold, care must be taken to protect the throat from collision to avoid breaking the throat. In this set of molds, the throat joint is hidden in the mold base.
Regarding the ejection of plastic parts, the previous article has analyzed the drawbacks of directly ejecting the ejector pin. This set of molds is designed with the structure of straight ejection and push block ejection. Each plastic part uses two straight tops and one push block. This kind of plastic part has a special shape. If the push plate is designed to be ejected, the processing of the push plate will be complicated, and the force will be uneven and easy to wear. The design of the push block is the best choice. When the external space is limited, the push block is simplified to a straight top. The ejector rod of the push block is designed with a guide sleeve to avoid wear. The middle supporting edge of the thimble plate and the B plate are avoided to improve the guiding accuracy.
The ejector plate is driven by an oil cylinder, which is fixed on the B plate by a bracket. The head of the piston rod of the oil cylinder is designed with a joint, which is fixed on the thimble plate. The thimble board is controlled by a travel switch.
ABIS MOLD TECHNOLOGY CO.,LTD
Daisy Wang (Sales Engineering)
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E: daisy@abismold.com
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