The plastic mold is mainly composed of three parts: the pouring system, the molded parts and the structural parts. The pouring system and the molded parts are the parts that directly contact the plastic and change with the plastic box products. They are the most complex and change the most in plastic molds. They require processing finishes. And the most accurate part.
The plastic mold pouring system refers to the runner part before the plastic enters the cavity from the nozzle, including the main runner, cold slug, runner and gate, etc. Molded parts refer to the various parts that constitute the shape of the product, including movable molds, fixed molds and cavities, cores, molding rods, and vents.
1. Mainstream
It is a passage in the mold that connects the nozzle of the injection machine to the runner or cavity. The top of the main runner is concave in order to connect with the nozzle.
The diameter of the main runner inlet should be slightly larger than the nozzle diameter (0.8mm) to avoid overflow and prevent the two from being blocked due to inaccurate connection.
The diameter of the inlet depends on the size of the product, generally 4-8mm. The diameter of the main runner should be expanded inward at an angle of 3° to 5° to facilitate the demolding of the runner.
2.cold material hole
It is a cavity at the end of the main runner to trap the cold material generated between two injections at the end of the nozzle to prevent the clogging of the runner or gate. Once the cold material is mixed into the cavity, internal stress is likely to occur in the manufactured product.
The diameter of the cold material cavity is about 8-l0mm, and the depth is 6mm. In order to facilitate demolding, the bottom is often borne by the demolding rod. The top of the stripping rod should be designed in a zigzag hook shape or set with a recessed groove, so that the sprue can be pulled out smoothly during demolding.
3. the runner
It is the channel connecting the main runner and each cavity in the multi-slot mold. In order to make the melt fill the cavities at the same speed, the arrangement of the runners on the mold should be symmetrical and equidistant. The shape and size of the cross-section of the runner have an impact on the flow of the plastic melt, the demoulding of the product and the difficulty of mold manufacturing.
If the flow of the same amount of material is used, the flow path resistance of the circular cross section is the least. However, because the specific surface of the cylindrical runner is small, it is unfavorable for the cooling of the runner redundant, and the runner must be opened on the two mold halves, which is laborious and easy to align.
Post time: Sep-27-2021