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What is an injection mold? Today I will explain it thoroughly to you. Thousands of products are produced by him.(Part 2)

Automatic unthreading injection mold For plastic parts with threads, when automatic demoulding is required, a rotatable thread core or ring can be set on the mold, using the mold opening action or the rotation mechanism of the injection molding machine, or setting up a special The transmission device drives the threaded core or threaded ring to rotate to release the plastic part.

Runnerless Injection Mold Runnerless injection mold refers to the method of adiabatic heating of the runner to keep the plastic between the nozzle and the cavity of the injection molding machine in a molten state, so that there is no condensation in the gating system when the mold is opened and the plastic part is taken out. The former is called an insulated runner injection mold, and the latter is called a hot runner injection mold.

Right-angle injection mold Right-angle injection mold is only suitable for angle-type injection molding machines. What is completely different from other injection molds is that the feeding direction of this type of mold during molding is perpendicular to the direction of opening and closing the mold. Its main flow channel is located on both sides of the movable and fixed mold parting surfaces, and its cross-sectional area is usually constant. This is different from the molds used in other injection molding machines. The end of the main flow channel, in order to prevent the injection molding machine from For wear and deformation of the nozzle and the inlet end of the main flow channel, replaceable flow channel inserts can be installed.

In most injection molds where the demoulding mechanism is on the fixed mold, the demoulding device is installed on the side of the movable mold, which is beneficial to the work of the ejection device in the mold opening and closing system of the injection molding machine. In actual production, due to the shape restrictions of some plastic parts, it is better to leave the plastic parts on the fixed mold side for molding. In order to make the plastic parts come out of the mold, a demoulding device must be installed on the fixed mold side. mechanism

The injection mold consists of two parts: a movable mold and a fixed mold. The movable mold is installed on the movable template of the injection molding machine, and the fixed mold is installed on the fixed template of the injection molding machine. During injection molding, the movable mold and the fixed mold are closed to form the pouring system and cavity. When the mold is opened, the movable mold and the fixed mold are separated to facilitate removal of plastic products. In order to reduce the heavy workload of mold design and manufacturing, most injection molds use standard mold bases.

Gating system
The gating system refers to the runner part before the plastic enters the cavity from the nozzle, including the main channel, cold material cavity, runner and gate, etc.

The pouring system is also called the runner system. It is a set of feed channels that guide the plastic melt from the injection machine nozzle to the mold cavity. It usually consists of a main channel, a runner, a gate and a cold material cavity. It is directly related to the molding quality and production efficiency of plastic products.

main channel
It is a passage in the mold that connects the nozzle of the injection molding machine to the runner or cavity. The top of the main flow channel is concave to connect with the nozzle. The diameter of the main channel inlet should be slightly larger than the diameter of the nozzle (0.8mm) to avoid overflow and to prevent the two from being blocked due to inaccurate connection. The inlet diameter depends on the size of the product, generally 4-8mm. The main channel diameter should be expanded inward at an angle of 3° to 5° to facilitate the demoulding of the runner excess.

cold material hole
It is a cavity located at the end of the main channel to capture the cold material generated between two injections at the end of the nozzle, thereby preventing the runner or gate from being blocked. If cold material is mixed into the mold cavity, internal stress will easily occur in the manufactured product. The diameter of the cold material cavity is about 8-10mm and the depth is 6mm. In order to facilitate demoulding, the bottom is often borne by a demoulding rod. The top of the demoulding rod should be designed in a zigzag hook shape or have a sunken groove so that the main channel debris can be pulled out smoothly during demoulding.

shunt
It is the channel connecting the main channel and each cavity in the multi-slot mold. In order for the molten material to fill each cavity at a constant speed, the runner arrangement on the mold should be symmetrical and equidistantly distributed. The shape and size of the runner cross section have an impact on the flow of plastic melt, product demoulding and the ease of mold manufacturing.

If we consider the flow of equal amounts of material, the flow channel with circular cross-section has the smallest resistance. However, because the specific surface of the cylindrical runner is small, it is unfavorable for the cooling of the runner extensions, and the runner must be opened on the two halves of the mold, which is labor-intensive and difficult to align.

Therefore, a trapezoidal or semicircular cross-section runner is often used, and is opened on half of the mold with a demoulding rod. The runner surface must be polished to reduce flow resistance and provide faster mold filling speed. The size of the runner depends on the type of plastic, the size and thickness of the product. For most thermoplastics, the cross-sectional width of the shunt is no more than 8m, the extra large can reach 10-12m, and the extra small can reach 2-3m. On the premise of meeting the needs, the cross-sectional area should be reduced as much as possible to increase the redundancy of the shunt and extend the cooling time.

Chris

Greetings! I’m Chris, deeply fascinated by mechanical parts and engineering. Let’s embark on a journey through design, functionality, and innovation in the hardware world.

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