Multi-function diagnostic instrument panel injection mold
The panel product of the multi-function diagnostic instrument is shown in Figure 1. The maximum size of the product is 103.53 mm x 104.00mm x 26.35 mm, the average thickness of the plastic part is 3.00 mm, the material of the plastic part is ABS, the shrinkage rate is 1.005, and the quality of the plastic part is 31.47 grams. . The technical requirements for plastic parts are that there must be no defects such as peaks, dissatisfaction with injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc.
It can be seen from Figure 1 that the structure of the plastic part is relatively simple. The plastic part is the panel of Honeywell's multi-function diagnostic instrument. Honeywell is a diversified, high-tech advanced manufacturing company founded in the United States. Now branch companies are spread all over the world. The product pictures of this set of molds are from France, and the technical documents and technical requirements are all in French. Plastic parts require high size, in addition to dimensional tolerances, geometric tolerances are also required.
The former Fourth Ministry of Machinery Industry of my country formulated SJ 1372-78, which has become the industry-recognized guiding standard. On this basis, GB/T 14486-1993 "Engineering Plastic Molded Plastic Parts Dimension Tolerance" was issued in 1993, and it was revised again in 2008, and it was renamed "Molded Parts Dimension Tolerance Table".
Since there are many factors that affect the dimensional accuracy of plastic parts, it is very important to reasonably determine the dimensional tolerances in the design of plastic parts. Generally speaking, under the premise of ensuring the use requirements, the accuracy should be designed to be lower.
At present, there is no uniform dimensional tolerance standard for plastic parts in the world, but various countries have their own specified tolerance standards. For example, the German standard is DIN16901; the Swiss standard is VSM77012; the French standard for plastic parts is NF T58-000; the European general standard is DIN ISO 2768 tolerance table, which can be used as a reference when designing molds for export to Europe.
Due to the different materials and processing methods of the product, the dimensional accuracy of plastic parts is different from that of mechanical products. The size of plastic parts is restricted by plastic materials. At the same time, its accuracy is also affected by fluctuations in material shrinkage, mold manufacturing accuracy, injection technology, and molded parts The wear and tear of the mold parts and the changes in thermal expansion during the assembly and use of the mold parts. Therefore, it is much more difficult to control the accuracy of plastic parts than to control the accuracy of other electromechanical products. It is particularly important to improve the accuracy of plastic parts and control the molding .
The dimensional accuracy of the plastic part is also related to the structure of the plastic part. For example, the difference in accuracy is different in the mold structure design due to whether there is a lateral core pulling mechanism. The unreasonable ejection mechanism will cause ejection deformation. Compared with the open plastic part structure, there is still a difference in shrinkage deformation, and the plastic part itself also has installation elastic deformation.
According to the role of the plastic product in the entire product and the assembly relationship, the size of the plastic product can be divided into: functional size; assembly size; free size.
The geometric tolerance items of plastic parts are basically the same as those of mechanical products. See Figure 3. The geometric tolerance is the shape and position tolerance in the past, which is composed of datum, marking frame guide line and arrow. In Fig. 3, the flatness of the large plane of the plastic part is 0.15; the symmetry of reference A and reference B are respectively 0.05; the tolerance of multiple dimensions is ±0.05 mm.
Strict dimensional tolerances and geometric tolerances have brought technical difficulties to the inspection. The difference between the inspection of plastic parts and mechanical parts is that the rigidity of the plastic parts is poor. Sometimes, when the shape of the plastic part is irregular, it is difficult to straighten the part. Excessive force during testing may also cause plastic parts to deform. Therefore, in view of this situation, plastic parts inspection needs to design inspection fixtures when necessary. The testing fixtures are mostly made of aluminum alloy, which is light and convenient to be placed on the testing table or the surface of the three-coordinate instrument.
The panel plastic parts of the multifunctional diagnostic instrument are small-size precision plastic parts. There are multiple button holes on the top of the plastic part, and the surface is required to be flat. There are 4 places on the side of the plastic part that need to be designed with slider cores. The mold design diagram is shown in Figure 2. The mold base is a standard simplified fine nozzle mold base FCI3550. The simplified nozzle has 4 guide posts less than the standard nozzle. Therefore, the long side of the mold base has a wider space, which is convenient for designing the slider.
A slight modification in the function of the mold can lead to fully automatic injection molding and therefore increase labor productivity. Fully automatic injection molds usually produce better and more stable quality and reduce defective products. In most cases, the life of the mold can also be increased.
Fully automatic operation: The injection molding machine repeatedly completes the entire cycle of the programmed molding function, and only stops when the machine or mold fails or is manually closed. Plastic parts and the runner system of the pouring system will automatically fall down or be removed by a robot.
When the three-platen mold is fully automatic injection molding, the long nozzle material is easily deformed and turned over and loses its original position, which makes it difficult to grasp by the manipulator. Therefore, an anti-rotation column needs to be designed on the aggregate of the gating system, as shown in Figure 2. Another idea is to let the nozzle material of the three-platen mold automatically fall, but if there is a wire drawing phenomenon, the automatic drop will fail, the nozzle material may hang in the air, and the injection molding will fail when the mold is closed again. Therefore, for the fully automatic injection molding of the three-platen mold, the nozzle material should be grasped by a manipulator as much as possible.
ABIS MOLD TECHNOLOGY CO.,LTD
Daisy Wang (Sales Engineering)
M: +86-150 1652 6799
E: daisy@abismold.com
A: Building B#,YingKeli Industrial Part, LongDong Community, LongGang District, Shenzhen, China 518116
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