Generally speaking, it is referred to as a cold runner injection mold for thermoplastic injection molds. The main or branch channels, cold material wells, and gates that are injected into the injection mold are demolded together with the products in the mold cavity after solidification. The injection mold is called a hot runner injection mold, which uses heating or insulation methods to keep the plastic melt in the flow channel in a molten state. The molten plastic in the flow channel is poured into the closed mold cavity through a certain injection pressure and rate. Only the products in the mold cavity are cured and demolded.

Advantages of thermoplastic hot runner injection molding over cold runner injection molding:

1. There is no solidified nozzle material, reducing labor and production costs.

2. The cavity is filled quickly, the product forming cycle is shortened, and the degree of automation is high.

3. Can reduce injection pressure, improve product shrinkage, water lines, burrs, filling difficulties, and deformation issues.

4. There is no need to use a three plate mold, and using a point gate method can improve the service life of the mold.

5. For thin meat and large products that require multi gate injection molding, it can better demonstrate superiority.

6. With valve gate, products with different specifications and sizes of multiple cavities can be injected into the same mold step by step.

7. It is possible to make STACKMOLD laminated cavity molds using valve gates.

So when designing and manufacturing thermoplastic injection molds, what factors should be considered when choosing hot runner injection instead of cold runner injection?

1. Actual cost accounting: Whether the production of plastic products formed by a single set of molds is equivalent, whether it can give advantages to saved raw materials and improved injection processes, and whether it can offset investment in equipment such as hot runner injection molds, labor, and peripheral equipment.

2. The hot runner technology has the following drawbacks: plastic melt stays in the long path hot runner for a long time, especially with a long injection cycle, and thermosensitive plastics are prone to overheating damage.

3. The accuracy of mold design and manufacturing, and whether the injection process can be standardized, not only require high requirements for hot runner technology and equipment, but also for the quality and level of operators.

4. Temperature control errors can cause temperature differences in the melt material, resulting in non-uniform filling of the mold cavity with plastic melt.

5. The use of hot runners has choices and limitations on plastic varieties. Different plastic varieties and additives use different thermal nozzles, and there are special restrictions on color change requirements.

6. Thermosensitive plastics, shear sensitive plastics, flame retardants, and fiber reinforced plastics may pose a risk of overheating.

7. Mixing mechanical impurities in raw materials can cause gate blockage.

8. The thickness of the mold will increase, which may exceed the maximum allowable size of the injection machine.

9. To fully leverage the advantages of continuous production with hot runner injection molding, it is necessary not to shut down or interrupt production as a last resort.

10. Mold manufacturers and injection molding personnel need to have certain operational experience, such as how to avoid plastic melt leakage, gate salivation, and cleaning of hot runners.

11. Accurate temperature control should be carried out in different zones for the main flow channel and the long flow diversion channel within the hot runner to avoid temperature errors and require professional operation by skilled personnel.

12. It is not only necessary to consider the production quality of the product, but also to weigh the level of production management, considering technical conditions such as molds and injection machines, such as the selection of product injection points, heating methods, runner paths, gate styles, etc.

Hot runner equipment belongs to fixed assets investment. It is a trend of plastic injection mold development to master the use rules, improve efficiency and save energy.

Another explanation is the difference between two different properties of plastic injection molding: plastics are divided into thermoplastic and thermosetting plastics based on their different properties after heating. The hot working process of thermoplastic is a physical change process, which is prone to softening or melting during heating, solidifying and hardening after cooling, and can be repeatedly heated and melted, and solidified after cooling, with no change in its properties; The hot working process of thermosetting plastics is a chemical transformation process. When heated for the first time, it can soften and flow, and when heated to a certain temperature, it undergoes chemical reaction and solidification. When reheated, it no longer softens or changes its appearance. This formed plastic cannot be repeatedly heated or recycled for use. We refer to both types of injection mold injection systems as thermoplastic hot runner injection molding and thermosetting cold runner injection molding, which can release the solidified material without a nozzle.

Thermosetting cold runner injection molding is a method of maintaining a constant temperature for the pouring system inside the injection mold, so that the plastic melt does not solidify in the pouring channel of the mold, maintaining its flowable state. After a certain pressure or adding a small amount of curing agent, it is poured into the mold cavity that is heated and closed at a high temperature of 150-200C ° C to solidify and form thermosetting products. If the pouring system cannot achieve low temperature constant temperature, the heat transfer from the mold cavity temperature to the pouring system will cause the flow channel to solidify and generate nozzle waste. So it is very important to properly insulate the pouring system and mold by using cold runner equipment. At the same time, using a needle valve type automatic locking gate will make the production of water free waste and can be automated and continuous.