Hot runner system is an important part of plastic mold production equipment. Hot runner system generally consists of a hot nozzle, a manifold, a temperature control box and accessories. Hot runner system whose mold performance meets requirements must be based on correct design and installation of hot runner. Following will introduce common installation methods of hot runner system.
There are many types of hot runner system installation methods. According to the most widely used hot runner systems on market, hot runner system installation methods can be roughly divided into following 4 types.

 

Figure 1 Integral installation
Figure 1 shows integral installation, which is installation method in which hot runner is installed together and then guided by panel guide post into mold. Advantage is that it is convenient to install, original hot runner is not frequently loaded and unloaded, it is not easy to be damaged, and can protect entire hot runner system; disadvantage is that hot runner fixing plate is thicker, four guide posts are added, and cost is relatively high.

 

Figure 2 Split installation
Figure 2 shows split installation, which is installation method of installing hot runner fixing plate, hot nozzle, hot runner plate, and panel in order. Advantage is that it is thinner than integral fixed plate, and there are no four guide posts, which saves costs; disadvantage is that installation and unloading time is long, it is easy to cause problems such as damage to thermocouple and heating wire.

 

Figure 3 Embedded installation
Figure 3 shows embedded installation, which reduces hot runner fixing plate and sinks hot runner plate into A plate. This assembly method is generally suitable for case where A plate and molded parts are inlaid. If A plate and molded parts are integrated, hot runner fixing plate must be added, unless mold is too thick to be installed on specified plastic injection machine.

 

Figure 4 Simplified installation
Figure 4 shows a simplified installation. By reducing hot runner fixing plate and panel, sinking hot runner plate into A plate, locking hot runner plate in A plate with screws, and pressing hot runner by injection molding machine mounting plate to complete installation method of injection molding production. This assembly method is mainly used in soft molds and has low cost, but it is necessary to note that hot runner system is shared with hard mold of mold.

In order to improve performance of mold, many manufacturers will properly process their molds. Mold processing refers to processing of forming and blanking tools. In addition, it also includes shearing molds and die-cutting molds. However, in many cases, molds are processed. It will also reflect processing defects, resulting in a decline in mold performance. How to build mold processing defects? Following seven measures can build mold processing defects.
1. Reasonably select and dress grinding wheel. White corundum grinding wheel is better. Its performance is hard and brittle, it is easy to produce new cutting edges. Therefore, cutting force is small, grinding heat is small, medium grain size is used, such as 46～60 mesh is better. Medium soft and soft (ZR1, ZR2 and R1, R2) are used in hardness of grinding wheel, that is, coarse-grained, low-hardness grinding wheels. Good self-excitation can reduce cutting heat.
It is very important to choose an appropriate grinding wheel for fine grinding. For high vanadium and high molybdenum condition of mold steel, GD single crystal corundum grinding wheel is more suitable. When processing hard alloys and materials with high quenching hardness, organic binder diamond grinding wheel is preferred. Organic binder grinding wheel has good self-grindability, and roughness of the ground workpiece can reach Ra0.2μm.
In recent years, with application of new materials, CBN (cubic boron nitride) grinding wheels have shown very good processing results. Finishing on CNC forming grinders, coordinate grinders, CNC internal and external cylindrical grinders has better results than other types of grinding wheels.
In grinding process, attention should be paid to dressing grinding wheel in time to keep grinding wheel sharp. When grinding wheel is passivated, it will rub and squeeze on the surface of workpiece, causing burns on the surface of workpiece and reducing its strength.
2. Reasonably use cooling lubricating fluid, play three roles of cooling, washing and lubrication, keep cooling and lubrication clean, so as to control grinding heat within allowable range to prevent thermal deformation of workpiece. Improve cooling conditions during grinding, such as using oil-immersed grinding wheels or internal cooling grinding wheels. Introduce cutting fluid into center of grinding wheel, cutting fluid can directly enter grinding area, play an effective cooling role, and prevent burns on the surface of workpiece.
3. Reduce quenching stress after heat treatment to a minimum, because quenching stress and net-like carbonized structure will easily cause cracks in the workpiece due to phase change of structure under action of grinding force. For high-precision molds, in order to eliminate residual stress of grinding, low temperature aging treatment should be carried out after grinding to improve toughness.

 

4. To eliminate grinding stress, mold can be immersed in a salt bath at 260～315℃ for 1.5 min, and then cooled in 30℃ oil, so that hardness can be reduced by 1HRC and residual stress can be reduced by 40%-65%.
5. For precision grinding of precision molds with dimensional tolerances within 0.01 mm, attention should be paid to influence of ambient temperature and constant temperature grinding is required. From calculation, it can be seen that for a 300mm long steel, when temperature difference is 3℃, material will have a change of about 10.8μm (10.8=1.2*3*3, deformation per 100mm is 1.2μm/℃), and each finishing process needs to be fully consider influence of this factor.
6. Electrolytic grinding is used to improve mold manufacturing accuracy and surface quality. During electrolytic grinding, grinding wheel scrapes off oxide film: instead of grinding metal, grinding force is small, grinding heat is also small, and there will be no grinding burrs, cracks, burns, etc. General surface roughness can be better than Ra0 .16μm;
In addition, wear of grinding wheel is small. For example, when grinding cemented carbide, wear amount of silicon carbide grinding wheel is about 400% to 600% of weight of ground cemented carbide. When electrolytic grinding is used, wear amount of grinding wheel is only only 50% to 100% of amount of carbide grinding.
7. Reasonably choose amount of grinding, use fine grinding method with small radial feed or even fine grinding. For example, appropriately reduce radial feed and speed of grinding wheel, increase axial feed, so that contact area between grinding wheel and workpiece is reduced, heat dissipation conditions are improved, thereby effectively controlling increase in surface temperature.