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Key points for manufacturing precision gear molds [Part 2]

6. Key points of mold making
(1) Tooth processing. Spur gears are precision machined using slow wire cutting, and at least 1 trimmer and 3 knives are used to achieve a smoother tooth surface roughness; helical gears are processed using gear electrode spirals. The precision of making helical electrodes is very high. A company ordered it from a military industrial enterprise in southwest China, and even made the high-precision production and testing of helical electrodes “mysterious”.

(2) Processing of circular tube blocks on the parting surface. The A and B boards are required to be processed slowly at the same time to ensure precise coaxial positioning.

(3) Cylindrical mold meat and inserts. It needs to be processed with an internal and external cylindrical grinder. The mold cavities of plates A and B must be processed with a coordinate grinder. Otherwise, the requirements for cylindricity, roundness, verticality and roughness will not be met, and the product cannot be guaranteed to be “precision”.

(4) General ring gear inserts. After the tooth shape is processed, the thickness of the workpiece is not allowed to be processed by a grinder, otherwise, transverse burrs will occur on the tooth surface and the workpiece will be scrapped. If necessary, EDM processing can only be used.

(5) Save mold. The tooth surface and edges are absolutely not allowed to be molded or polished. The relevant roughness can only be achieved through one-time electrical machining. At the same time, the longer the mold is generally brewed, the smoother the steel tooth surface will be.

7. Mold trial stage

(1) At T1, the water transport must be connected. The gear mold is different from the casing mold. The design structure has determined that the water transport can be made before T1. If water is not transported, the sample will be very different in size and local thermal balance, which directly affects the crystallinity and shrinkage of the plastic material, thus affecting the accuracy and dimensional stability of the product.

(2) At T1, first ensure the gear outer diameter and thickness dimensions, because these two dimensions are generally not repairable or not repairable; secondly, other dimensions. As long as the first two are guaranteed and the molding conditions are stable, other sizes can be temporarily accepted, and then the mold can be repaired and completed a second time. Generally speaking, as long as the outer diameter of the gear is guaranteed, the outline of a single tooth profile will not differ greatly from the theory.

(3) Once the product has two ends or shrinkage in the middle, if the machine adjustment cannot solve the problem, please note that this does not necessarily mean that the sample is NG. In most cases, as long as the gear mesh is acceptable, customers will generally accept it.

8. Gear sample testing

To measure the outer diameter of the gear, you can generally use a digital caliper, but for gears with 3 and 5 multiples of teeth, you need to use a 3-hook micrometer and a 5-hook micrometer. The tooth shape can be profiled by film projection, but precision inspection requires professional gear electronic testing equipment. Install the sample gear with standard teeth, mesh them with each other, and then input the required gear related parameters, and the computer will automatically display the test data, including Gear radial runout and other parameters

9. Mold injection molding and maintenance points

(1) During normal beer production, it is not allowed to spray release agent, otherwise, the product will not be acceptable. The reason is: the lubrication of the release agent affects the meshing and meshing measurement of the teeth; it is not easy to wipe off and is not clean when hidden in the tooth surface; it is easy to stick to dust, affecting the accuracy of the gear.

(2) Mold temperature and barrel temperature are the keys to ensuring dimensional stability of continuous beer molding.

(3) As long as the mold is dropped, or the machine is shut down for more than 1 hour without dropping the mold, the mold must be sprayed with anti-rust agent. Before dropping the mold, check whether it has been sprayed with anti-rust agent. Once the tooth surface of the ring gear insert is severely rusted, there is basically no room for repair because it is a precision mold.

(4) If the sealing rubber ring leaks on the tooth surface, under normal circumstances, it cannot be wiped with a cloth. The better method is to blow it with filtered air, dry it with a gun, spray anti-rust agent and then drop the mold.

(5) Due to the good rigidity and toughness of POM and PA material products, in product packaging, the same kind of tiny gears can be packed together in appropriate amounts in PE bags, and gears with slightly larger shapes can be aligned axially and packed in glue. If the bags are well wrapped, there is no need to worry about product damage, but each box must be separated by cardboard for each layer.

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