Key points and maintenance of mold making

2020/11/30

1. Key points of mold making:

1) Tooth profile processing: Straight teeth are precision processed by slow-moving wire, at least one trimming and 3 cutters are used to achieve a lighter roughness of the tooth profile; the helical gear ring is processed by gear electrode spiral, and the precision of making helical electrode is very high. , A company ordered to a military industry enterprise in southwestern China, it is more "mysterious" for the high-precision production and testing of helical electrodes.

2) The processing of the parting surface circular tube block requires the A and B plates to be processed at the same time with slow wire feeding to ensure precise coaxial positioning.

3) Cylindrical mold meat and inserts need to be processed by internal and external cylindrical grinders, and the mold cavities of A and B plates must be processed by coordinate grinders. Otherwise, the cylindricity, straightness, perpendicularity and roughness cannot meet the requirements. The product cannot be guaranteed "precision".

4) For general gear ring inserts, after the tooth profile is processed, the thickness of the workpiece is not allowed to be processed by a grinder, otherwise it will cause transverse burrs on the tooth surface and the workpiece will be scrapped. When it is really needed, only EDM processing is used to reduce the surface.

5) Mold saving: the tooth profile and edges are absolutely not allowed to save mold or polishing, and the relative roughness can only be achieved by one-time electrical processing. At the same time, the mold usually takes a long time for beer, and the steel tooth surface will be smoother.


2. Model test stage:

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

2) For T1, first ensure the outer diameter and thickness of the gear, because these two dimensions are generally not repaired or not repaired by the mold. Next are other sizes. As long as the first two are guaranteed and the molding conditions are stable, other sizes can be temporarily accepted, and then the mold will be repaired for the second time. Generally speaking, when the outer diameter of the tooth is guaranteed, the contour of a single tooth profile will not differ greatly from the theoretical one.

3) Once the product has both ends and the small head or the middle part shrinks, if the adjustment cannot be solved, please note that this does not necessarily mean that the sample is NG. In most cases, as long as the gear mesh is qualified, customers will generally accept it.


3. Gear sample inspection: To measure the outer diameter of the tooth, a digital caliper can generally be used, but for gears with a number of teeth of 3 and 5 times, a 3-hook micrometer and a 5-hook micrometer are required. The tooth profile can be used for film projection contour lines. However, precision testing must have professional gear electronic testing equipment. The sample gears are equipped with standard teeth to mesh with each other, and then input the required gear related parameters. The computer will automatically display the testing data, including the gear's radial runout and other parameters.


4. mold injection and maintenance points:

1) During normal beer production, it is not allowed to spray release agent, otherwise the product is unacceptable; the reason is that the lubrication of the release agent affects the tooth meshing and meshing measurement; and it is hidden in the tooth surface and is not easy to wipe off or clean; easy to stick Dust will affect the accuracy of gears.

2) Mold temperature and barrel temperature are the keys to ensure the dimensional stability of continuous plastic molding.

3) As long as the mold is dropped, or the mold is stopped for more than 1 hour, the mold must be sprayed with anti-rust agent; before dropping the mold, check whether the anti-rust agent has been sprayed. Once 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, then dry it with a fire gun, and then spray the anti-rust agent to drop the mold.

5) Due to the good rigidity and toughness of POM and PA products, the same kind of small gears can be packed together in the same PE bag in the product packaging, and larger gears can be arranged axially and packed in a plastic bag. , Don’t use but the product is damaged, but each layer of each box must be added with cardboard.