Application Occasions for Hot Runner System

Working Principle
Mould of hot runner is a new-type constitution which is capable of replacing the traditional mold or three plate mold runner with heating runners of constant temperature, so it is no need to take runner out after each molding finishes.

About the Differences in the Respect of Structure
• Molding for oversized products
Only by using hot runner can flow of plastics be balanced, such as car lining plate, balance bar. And runner flows should be processed concurrently.
• Side direction flow with deviation the center of injection molding
The flow of hot runner way can make the structure of mold as simple, molding as easy, and accelerate the molding speed and reduce molding stub bars. That indeed serves several purposes.

Weakness of Three Plate Mold
• During each injection in three plate way, heavy mother model must glide on the guide pin, which is even under use during new launch period. The life time of moulds can not last long.
• During each ejection in three plate way, the movement amount of hot runner material taken out of moulds is more than that of necessary models taken from dies.

Application of a Long Vertical Hot Runner during the Flow into Side of Ejection
Problems resulting from too long stub bars can be eliminated: reducing mould route, saving amount of stub bar residue, making easy molding, no shrink and flow mark.

Application to Products of Large Scale or Injecting Plastics by the Center
• Hot runner may replace three plate mold to avoid unnecessary motion of molding machine templates.
• Mother template should be moved to take out stub bar during the use of three plate mold. By using hot runner molding, mould opening movement can shorten the necessary movement of unloading stub bar, thus the mould thickness could be increased. For the traditional application with large scale molding machine, it is possible to use small scale machine by means of hot runner system.

Application to Complicated Molding
Hot runner system can solve problems like high viscosity, low viscosity and high molding temperature. Specific cases include injection of metal powder, injection of ceramic powder, injection of plastic magnet, injection of plastic bearing and thermoplastic rubber (TPE), etc.

Coordination with Three Plate Mold to Reduce Stroke of Picking Stub Bar
Below are advantages of applying hot runner to three plate mold:
• Easy to pick out stub bar and reduce the route
• An even material flow during injection, controlling operating conditions of injection points to make smooth injection
• Saving in material and costs

Saving in Material, Costs and Expense of Labor
Saving in material
• Costing of cold stub bar (interest loss)
For instance, if cold stub bar takes the rate of 68% in waste, then 320g product would be produced among 1 kilogram of material but the rest is 680g for cold stub bars.
• Although cold stub bar is recyclable, there always stores of stub bars to maintain the normal machine operation due to personnel factors and the proportion mixture of recyclable material. Finally, it causes the problem of funds retaining.
If material costs 100 RMB per kilogram with its total amount stockpile of wastes for 500 kilograms, then the accumulated funds per day will be up to 500 multiplies by 0.68 by 100 equaling to 34,000 RMB. Thus the calculated interest loss per day will be 200 RMB. The coordination with three plate mold would save a great amount for a long term.

Application to High Speed Injection Molding
High speed injection not just aims to raise molding efficiency, but also control thickness for such products as cup or container.

Application to Stack Mold
As to injection molding of thin products with great number like CD shell, granule goods, 15% clamping force should be added with the same injection time to advance 80% output of production.

About Pro-environment and Efficiency
Producing no junk, hot runner systems seldom handle problems about junk.
And the accurate meaning of junk refers to:
• Waste of resources: the process of analyzing plastic injection molding
• Taking little storage space of stub bar. Without the noise of mincing and metamorphic problem.

Hot Runner and Mould Industry
The development of times advances constantly and fast, setting forward with harsh competitions. That is why costs of mould industry, which mainly relies on manpower, soar and talents in job-hunting market are hard to find. What a frustrating situation it is! Thus the priority lay before us is how to increase profits of mould goods to cope with the increasing costs with limited human resources. Enhancing degree of precision or automatic molding is feasible fashion, though, a great sun of funds needs go to purchase equipments and train employees. Considering this situation, nothing could be more straightforward and direct than a fully understanding towards application of hot runner.

Introduction to Features of Plastic Material
Injection molding refers to the projects including melt, flow, molding and solidification plus crystallization. The project render features of plastics vitally important, thereby attention should be paid to the solution temperature, pressure, viscosity and specific heat and so on. Plastic research field is so profound that more thorough introduction is unreachable. Inside, explanations about the general knowledge will be elaborated.

Selection of Plastic Material
At the beginning of designing products, proper plastic material should be selected. However, most designers fail to take mould into account. If possible, the material selected should be able to make mold manufacture simple.
Dimensional accuracy of materials with small injection contractibility rate like PS, ABS and PC, is achievable; Dimensional accuracy of materials with large injection contractibility rate like PP, PE and POM, is hard to achieve. (Mould tolerance is one sixth as that of molding goods)
Solution of material like ABS with strong viscosity flows into gap difficultly; solution of material like PA and POM with slight viscosity flows into gap easily, even with narrow gaps.
Material like PS with low temperature during molding is easy to be molded with quick molding cycle while the one with high temperature like PC get molded slowly.
Material like PS, PE and PP etc, hardly to be deteriorated or resolved quality is hard to produce rejects which affect quality in mass production; material of easily being deteriorated or resolved can not put into mass production if the molding conditions are free of strict control. (Mould is capable of controlling molding conditions accurately). And the situations above are particularly apparent with hot runner application.