Injection mold automatic hair removal design
Among the plastic parts, many industrial products and civil products have the design of internal and external threads, solving the problem of threaded mold release of plastic parts is the key to such mold design.
In general, there are 2 methods of processing plastic parts, one type of method: one is permitted by plastic parts and resins, using forcibly detached methods; one type is deep thread, high resin strength, high thread accuracy requirements Parts must be taken out by rotation.
It is divided into manual discharge and automatic extraction of 2 types. The manual deprived production is low, but the mold structure is simple, adapted to small batch production; high automatic hair removal efficiency, stability, and adapt to mass production.
In the structure of automatic rotary detachment mold, problems such as reliability, stability and practicality of structural design must be solved. The chain drive automatic deprived mold structure described below, has been used for long periods of use, stable mold structure, high production efficiency, and product achieve utility. This mold structure is now described below.
2. Analysis of plastic parts
Figure 1 shows the lubricant bottle cap, the material is PP, the product is characterized by rectangular threads, anti-counterpart and stop-opening groove design, the product appearance requires high, and the demand is large. In addition, the cap is a rotating cover of the automatic power supply machine, so the product size and threaded precision are high, and the forcibly deprotic mold structure cannot reach the product usage requirement, and the automatic rotary detachment mold structure must be used.
3. mold structure and work process
According to the plastic parts analysis and user production requirements, the mold is designed as a 1 mold 8 cavity, using a hot runner needle valve point gate feed, and the automatic decision motor is completed by the chain transmission, and the mold structure is shown in Figure 2.
Figure 2 Mold structure
1. Small sprocket 2. Motor 4. Motor bracket 5. Limited screw 6. Spring 7. Shed rod 8. Water hole 9. Steel tube 10. Sealing ring 11. Cooling core 12. Template 13. Waste 14. Press Block 15. Big Bank 16. Push Bearing 17. Pushing Board 18. Pushing Board 19. Turbine 20. Threaded Core 21. Covered Core 22. Cushion 23. Pressor 24. Template 25. Positioning Term 27. Main Travel 27. Sports Cushion 28. Heating Mat 29. Heat Nozzle 30. Slave Guide 31. Haf Block 32. Pull Cap 34. Push 35. Screw 36. Tensioner
3.1 Mold Working Process The mold is first divided from the I-I-I-I-plane, while leaning from the oblique column, complete the extraction of the outer concave portion of the plastic parts anti-counterfeiting ring, and leave the plastic parts in the moving mold portion. The motor then starts to rotate, through the sprocket, the chain roses the threaded core, and at the same time, the II-II profile depends on the spring elastic start, and relies on the stop of the stop to prevent the plastic parts and the threaded core. Rotation. When the thread is completely detached, the injection machine is moving out of the mechanism, and the secondary push plate is opened through the top rod, so that the mold is divided from the III-III section, complete the molded parts of the plastic parts, so that the plastic parts from the mold Take out and complete a production cycle. It should be noted that the pressure of the spring when the II-II surface is moderate, and the pressure is too large. It is easy to cause the thread. The pressure is too small, the division surface is not easy to open, and the manufacturing precision of the moving parts can be adjusted. The amount of compression is adjusted.
3.2 Pouring System Design Due to the large amount of production, a hot runner needle valve type gate casting system is used when the quality requirements are high. Because the heat flow path is transported into the mold type cavity by means of heating, insulation and temperature control, the internal pressure loss in the flow path is small, the melt is good, the density is uniform, the stress in the plastic parts is reduced, and the degree of deformation is high. Attenuation, dimensional stability is significantly improved. In addition, there is no running waste of the heat flow path, which greatly reduces the production cost, the needle valve nozzle automatically cuts off the gate, and the production efficiency is improved. In summary, the selection of thermal flow channels is very reasonable for the use of plastic products produced in large quantities.
3.3 Cooling of the mold to increase production efficiency, prevent the deformation of the plastic parts, and prevent the mold parts from being killed due to thermal expansion, the mold cooling system must be fully reliable. Since the threaded core is often in a rotational state, it cannot be directly cooled, so the mold is designed to increase the cooled core at the center portion of the threaded core, and the cooling water is introduced into the core, form a circulation, better completion of the threaded core. cool down. The cooling of the fixed-mold cavity is used in 8 straight water paths, and the outer hose is connected to form a cycle, and the mold cooling is molded.
3.4 Mold Material Selection Since the bottle cover is large, the mold is rotationally movable, and the mold does not have special requirements on polishing, so the mold material should be used with high wear resistance and hardenability.
4. mold transmission part design
Due to no sliding in the chain drive, the transmission size is relatively compact, does not require a large tension force, and the load is small, the efficiency is high, and it is suitable for the transmission of the transfer in the mold, and the chain, sprocket Easy to purchase, no need for special processing, so the chain drive is used in the transmission design.
4.1 Mold cavity center distance and sprocket parameters Determination considers the integrated factor in the mold cavity size and structural size, and the central distance between the cavity should be more reasonable between 150 mm. By designing the chain wheel of the sprocket, the chain pitch P = 15.875, the ram wheel of the teeth is z1 = 23, and the roll of the sprocket is: d = p / sin (180 ° / 23) = 15.875 / SIN (180 ° / 23) ≈117mm can meet the requirements of the mold design center from 150mm. In order to increase the number of meshing teeth of the sprocket, the transmission is more stable, and the two tensioning wheel 36 is added, and the use is good.
4.2 Motor speed and bearing selection If the plastic parts rotate 5 laps, the thread can be taken out, in order to ensure the normal service life of the mold, the speed of the threaded core should not be too fast, so the design is pressed at a time of rotation and demolding each 5S, large The rotational speed of the sprocket should be 60R / min. The gear ratio of the sprocket is: I = N1 / N2 = Z2 / Z1, such as setting the transmission ratio I≈0.5, the small sprocket Z2 ≈ 11, N2≈120R / min, so the speed of the reducing motor should be 120R / MIN left and right.
Since the bearing used by this mold is both a centralized role, it is necessary to withstand the axial push force of the injection pressure on the threaded core, so the bearing must be used at the same time to withstand the radial load and the axial load, due to the center thrust The roller bearing can meet the above conditions simultaneously, so this type of bearing is selected.