After the read, you will learn the 8 advantages and disadvantages of hot runner mold, and what types of injection molds should use hot runner systems.
What is a cold runner?
A cold runner is a part between the mold inlet and the product gate. The plastic is kept flowing in the runner by the injection pressure and its own heat. The runner is used as part of the molded material but is not part of the product.
Therefore, when we design the mold, we have to consider both the filling effect and how to save material by shortening and narrowing the runner, which is ideal, but in practice, it is difficult to achieve the best of both worlds.
What is a hot runner?
Hot runner is also called no runner means that the plastic in the runner does not solidify after each injection, so it is not necessary to take the water outlet out of the runner when the plastic product is demolded. Since the plastic in the runner does not solidify, the runner is still open for the next injection.
In short, the hot runner is an extension of the injection molding machine nozzle.
Hot runner molds are used extensively in all industrial countries and regions of the world today. This is mainly because hot runner mold has the following significant features.
What are the advantages and disadvantages of hot runner mold?
Hot runner mold feature 1: shorten the molding cycle of the parts
Since there is no limitation of cooling time in the sprue system, the parts can be ejected in time after molding and curing. Many thin-walled parts produced with hot runner molds can be molded in less than 5 seconds.
Hot runner mold feature 2: Save plastic material
In a pure hot runner mold, there is no production cost because there is no cold sprue. This is especially significant for applications where plastics are expensive.
In fact, the major international hot runner manufacturers have grown rapidly during the years when oil and plastic materials were expensive in the world. Because hot runner technology is an effective way to reduce the cost of materials.
Hot runner mold feature 3: reduce the cost of products, improve product quality
During the hot runner molding process, the temperature of the plastic melt is accurately controlled in the runner system.
The plastic can flow more uniformly into each cavity, resulting in consistent quality parts. Hot runner molded parts have good gate quality, low residual stress after demolding, and low part deformation. Therefore, many high-quality products in the market are produced by hot runner molds.
Hot runner mold feature 4: Eliminate subsequent processes, conducive to production automation
The finished product is formed by the hot runner mold, so there is no need to trim the gate and recycle the cold sprue. It is conducive to production automation.
Many foreign product manufacturers have combined hot runner with automation to greatly improve production efficiency.
Hot runner mold feature 5: expand the application of the injection molding process
Many advanced plastic molding processes are based on the development of hot runner technology. Such as PET preform production, multi-color co-injection in the mold, multi-material co-injection process, etc.
Although hot runner molds have many significant advantages over cold runner molds, mold users also need to understand the disadvantages of hot runner molds. To summarize, there are the following points.
Hot runner mold disadvantage 1: mold cost increase
Hot runner components are more expensive and the cost of hot runner molds can increase significantly. If the part output is small, the mold tooling cost ratio is high and economically not cost-effective.
For many mold users in developing countries, the high price of hot runner systems is one of the main problems affecting the widespread use of hot runner molds.
Hot runner mold disadvantage 2: hot runner mold production process equipment requirements are high
Hot runner molds need precision processing machinery for guarantee. Hot runner system and mold integration and cooperation requirements are extremely strict, otherwise, the mold in the production process will have many serious problems.
Such as poor plastic sealing leads to plastic overflow damage hot runner components interrupt production, nozzle inserts, and gate relative position is not good to lead to a serious decline in product quality, etc.
Hot runner mold disadvantage 3: complicated operation and maintenance
Compared with cold runner molds, hot runner molds are complicated to operate and maintain. If the use of improper operation is very easy to damage the hot runner parts so that production cannot be carried out, resulting in huge economic losses. For new users of hot runner system injection molding, it takes a long time to accumulate experience using them.
Besides the 8 Advantages and disadvantages of Hot Runner Mold article, you may also be interested in the below.
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