Which are the injection mold composed of？
Injection Mould
Although the structure of the mold will change because of the change of the plastic variety and performance.plastic products shape and structure ,the type of injection molding machine. But the basic structure is the same.Mold is mainly composed of gating system, temperature control system, molded parts and structural parts. The gating system and molded parts are in direct contact with the plastic and they will change with plastic and products.They are the parts which are the most complex ,the greatest change, the most demanding machining finish and highest precision in the mold.
Injection Mould
Injection mould is a tool for producing plastic products, and it is also a tool for giving plastic products complete structure and precise size. Injection moulding is a processing method used in mass production of some complex parts. Specifically, melted plastics are injected into the cavity by high-pressure injection moulding machine. After cooling and solidification, the formed products are obtained.
Gating system
Gating system refers to the channel section that the plastic from the nozzle enters into the front of the mold cavity, including main sprue, cold-slug, runner and gate, etc.
Gating system is also called as the runner system. It is a group of feed channels that lead plastic melt from injection machine nozzle to cavity.It is composed of sprue, runner, gate and cold slug well. It is directly related to the quality of plastic products molding and productivity.
Sprue
It is a part of the channel in the mold that connects the injection nozzle and the runner or the cavity . The top of the spure is concave in order to connect with the nozzle. The sprue inlet diameter should be slightly larger than the diameter of the nozzle (0.8mm) to avoid overflowing, and prevent the interception because of cohesion atypia. Inlet diameter is according to the size of the product,generally 4-8mm. The sprue diameter should be enlarged inward 3 degrees to 5 degrees, so that the flow superfluous material strip.
Cold slug
It is a hole that locates at the end of spure to trap cold material between the two injection of the nozzle end. In order to prevent the blockage of the runner or the gate. If cold material once mixes in the cavity,then products are easy to produce internal stress.Cold slug diameter is about 8-10mm,and depth is 6mm.For ease of stripping, the bottom is usually borne by a release lever.The top of the release bar should be designed as zigzag hook-shaped or sunken grooves, in order to pull the sprue superfluous successfully when the release.
Shunt
It is a channel in the multi-slot die that connects main channel to each cavity.In order to make melt with velocity fill the cavities.The shunt channel in the mold should be be symmetrical arranged and equally spaced.The shape and size of the shunt flow cross-section have influence on the plastic melt flowing, products releasing and difficulty of mold manufacturing.
If by the the flowing of equal quantity, the flowing channel resistance of circular cross section is least.But the surface area of cylindrical flow path is small which is negative for cooling of shunt warts.And this shunt must be installed on the two mold halves what are both labor intensive and difficult to align.
Therefore we often use trapezoidal or semi-circular cross-section shunt which are installed on the half mold with release lever.The runner surface must be polished to reduce the flow resistance and to provide a faster mold filling speed. The size of the flow channel is determined by the plastic variety, size and thickness of products.For most thermoplastics,the section width of the split channel does not exceed 8m,especially large up to 10-12m, especially small 2-3m. In the premise of meeting the needs,cross-sectional area should be minimized in order to increase the shunt warts and extend the cooling time.
Runner
It is a channel that connects the main road (or shunt) to the cavity.Sectional area of the channel is equal to the main channel (or shunt),but are usually reduced. So it is the smallest part in the whole cross-sectional area of the flow path system.Gate shape and size have a great impact on the product quality.
The role of the runner ：
A.control material flowing rate
B.In the injection,because melt curdles early to prevent backflowing.
C.Make melt rise temperature because of strong shear, thereby reduce the apparent viscosity to improve liquidity.
D.It is convenient for separate products and runner system.The gate shape, size and position are depend on the nature of plastic, size and structure of the products. Cross-sectional shape of the gate is generally rectangular or circular.Cross-sectional area area should be small and the length should be short.This is not only based on the above-mentioned role, but also it is easy for small gate to enlarge.The position of gate generally should not affect the appearance and thickness of product.
Gate size should be designed to consider the nature of the plastic melt.Cavity is space to mold plastic products.Molded parts are component to constitute the cavity.
Each molded parts often have special names.Die is molded parts to constitute the articles. Core or punch constitutes internal shape of the product. Design molded parts should according to performance of plastic,the geometry of the article, dimensional tolerances and requirements to sure the overall structure of the cavity.
To ensure the surface smooth of plastic products,and ease of stripping,the surface where be contact with the plastic must ensure the roughness more than 0.32um and resistant to corrosion.Molded parts generally use heat treatment to increase the hardness and select corrosion-resistant steel.
Temperature regulation system
In order to meet the injection molding process,there needs Temperature regulation system to adjust the temperature of the mold.For thermoplastics,cooling system is mainly designed to make mold cool.The common method of cooling mold is setting cooling water passage to take the heat of the mold.In order to heat mold,we can install electric heating elements inside and around the mold.
Molded parts
