Introduction to laminated mold
Laminated mold technology is a mold front technology that is different from ordinary injection mold technology, that is, a plurality of cavities are overlapped in a mold clamping direction in a pair of molds. Such a mold typically has a plurality of parting surfaces, and one or more cavities may be disposed on each parting surface. Simply put, a laminated mold is equivalent to stacking multiple single-layer molds together and mounting them on an injection molding machine for injection molding.
The laminated mold structure is composed of a laminated mold hot runner system, a special mold base system, a load guiding system, a two-way ejection system, a split mold linkage system and the like.
Laminated mold characteristics
The production efficiency of laminated molds is one or more times higher than that of ordinary single-layer molds, which greatly reduces the cost of injection molding. From the structural characteristics, the laminated mold combines multiple pairs of cavities into one pair of molds, which can fully meet the production by utilizing ordinary injection molding equipment. The filling, holding and cooling time of the mold is the same as that of the single-layer mold, which determines that the production efficiency of the laminated mold will be doubled or even multiplied by the ordinary single-layer mold, greatly increasing the output per unit time of the product.
Laminated molds can be mounted on the same injection molding machine as single-layer molds, eliminating the need to invest in additional machines and equipment, saving on the cost of machinery, equipment, plant and new labor.
The manufacturing requirements for laminated molds are basically the same as for ordinary molds. According to statistics, the manufacturing cycle of one double-layer laminated mold is 5% to 10% shorter than the manufacturing cycle of two single-layer molds.
Through production verification, the structure of the laminated injection mold is reasonable and reliable, the product size is consistent, the mold cost is reduced by 30%, and the molding efficiency is doubled or multiplied.
The laminating mold is suitable for mass production of large-sized flat products, small multi-chamber thin products, and the larger the batch size, the lower the production cost of the product.
Generally, when the injection molding machine is used in combination with a conventional mold, its injection amount and mold opening stroke are only used at a rated temperature of 20% to 40%, and the performance of the injection molding machine is not fully utilized. Compared with conventional molds, the clamping force of the multi-layer injection mold is only increased by 5% to 10%, but the output can be increased by 90% to 95%, which greatly improves equipment utilization and productivity, and reduces costs.
Laminated injection molds have been continuously developed as a new type of mold technology, especially in combination with hot runner technology, making it a cutting-edge technology for the development of plastic molds today. Conventional conventional mold design theory has not been applied to laminated injection mold design, so it is urgent to develop a new mold design theory to guide the design of laminated injection molds. The design points of the multi-layer injection mold will be described below.
Maximum injection volume
The stacked injection mold can be a cold runner or a hot runner. When using the cold runner, it is necessary to consider the amount of plastic used to pour the system aggregate; when the hot runner is used, the non-returning aggregate production is realized, and the material in the hot runner plate and the central main nozzle does not affect the required injection amount of the mold. Can be ignored [3]. Therefore, when checking the maximum injection volume of the injection molding machine, it depends on the specific situation.
Injection pressure
The check of the injection pressure is mainly to check whether the injection pressure can meet the needs of molding. For the multi-layer injection mold, most of the thin-walled, large-projection, long-flow plastic parts require higher injection pressure and injection speed during the filling process. The laminated hot runner mold adopts the hot runner technology, and the injection pressure can be better transmitted than the stacked cold runner mold, so the required injection pressure is smaller than the laminated cold runner mold; However, due to the increased flow and increased projected area, the required injection pressure is greater than that of a single-layer cold runner mold. When checking the injection pressure, the injection pressure of the plastic part should be determined according to the injection molding process of various plastics, combined with computer simulation flow analysis, and then compared with the rated injection pressure of the injection molding machine.
Maximum clamping force
The layers of the multi-layer injection mold are arranged in a "back-to-back" manner, and theoretically any number of laminations can be realized on the same injection molding machine without increasing the clamping force. However, since the central main nozzle and the manifold of the multi-layer injection mold increase the flow passage, the projected area of ​​the plastic part plus the gating system on the parting surface is increased; and the flow path is extended due to the lamination The pressure loss is larger than that of the conventional single-layer mold, and the injection pressure is increased correspondingly, resulting in an increase in the cavity pressure, so the clamping force is increased, and the clamping force required for the same single-layer mold is increased by 10% to 15% during the check. It is safer.
Molding stroke
The multi-layer injection mold opens the mold on two or more layers of the parting surface and pushes out the plastic part. When the mold opening stroke is checked, the mold thickness is not considered for the injection molding machine using the hydraulic-mechanical mold clamping mechanism; When a laminated injection mold has a side-splitting core pulling mechanism, the influence of the core distance needs to be considered. If a synchronous mold opening mechanism such as a rack-and-pinion or a toggle connecting device of the same gear ratio is used, the stroke of each layer of the laminated injection mold is not limited by the height of the product, and the mold opening stroke is the largest in the multilayer mold. n times the layer of the mold opening stroke (n is the number of layers of the laminated injection mold).
Main nozzle length
The center main nozzle should not be too long or too short so that the center main nozzle does not exceed the maximum distance the injection molding machine nozzle retreats or advances at the base when the mold is closed. Since the central main nozzle should move together with the middle part of the mold during the parting, it should be ensured that the central main nozzle remains in the fixed part after the mold is opened to prevent the overflow of the central main nozzle head from dripping into the fixed cavity wall. on. (We are using a needle valve thermal system to control the phenomenon of feed overflow)
Gating system
The multi-layer injection mold can be either a common flow path casting system (ie, a cold runner casting system) or a hot runner casting system. Hot runner casting
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