Hot runner mold design 10 errors that should be avoided

Use the method of heating or insulating the runner. To keep the plastic from the injection molding machine nozzle to the cavity gate molten. In each injection cycle, only the plastic parts are ejected and have not runner scrap.

Hot runner molds have many advantages. But its cost is also expensive. Therefore, we should be more cautious in the mold design and manufacturing process. Avoiding errors is the best cost savings.
There have 10 error points in the design. This will help, get it quickly.

The molten material is molded into the respective cavities and reaches a pressure equilibrium state. The number of hot runner gates is typically a multiple of 2 or 3. Then determine the location of the gate and the number of nozzles. In order to make the quality of the product meet the requirements of customers.

There are many nozzle types in the hot runner. Type selection is based on the actual conditions of the plastic parts and molds.

The cost is lower. Feed directly on the surface of the product. Suitable for plastic parts with textured surfaces.

When the plastic parts are engineering plastic parts. Open nozzles should be used. Prevent nozzle clogging.

This type of hot runner system has an additional cylinder mechanism. Under the action of the cylinder, the valve needle is lifted up during injection. Seal the glue port at the end of the filling. It can effectively prevent flow marks.

The hot runner system is contact with the mold plate in a large area and requires a good thermal insulation effect. The insulation of the hot runner plates, nozzles and mold plate is mostly insulated by air. The structural parts should reduce the contact area with the plate. And there must be enough space.

If the hot runner plate is designed as a whole with the pressure ring. It will make the hot runner heat insulation effect worse and cost increase.

The nozzles size of the nozzle is easy to adjust.Set enough cooling waterway near the nozzle. Avoid hot runner near gate halo.

If there is a dead angle in the runner. The will cause residual material to accumulate in the runner. There will be chromatic aberration in the plastic parts.

The hot runner nozzle will elongate due to the expansion dimension after heating. So in the design to calculate the expansion size of the nozzle. The size of the elongation after the nozzle is heated is processed. Otherwise it will damage the cavity and the hot runner. The tolerances required for the assembly are to be marked in the assembly drawing.

The hot runner plate temperature is 200 °C. The cavity temperature is 60 °C. There is a difference in thermal expansion between the two.

There must be enough space between the nozzle and the template. Correct the position of the hot runner touching the mouth. The correction amount is the amount of thermal expansion of the flow path plate. Ensure that the center of the nozzle hole and the center of the gate hole do not deviate.

The nozzle is made of high elasticity steel or high tension nickel bronze or beryllium bronze.

A screw structure cannot be used between the two.
As follows. If it is fixed directly with screws. The direction of thermal expansion of the runner plate is limited. Will cause the runner plate to tilt up.
As show picture B. Use stepped screws. L1 is 0.05 mm higher than L. The runner plate has enough space to expand and contract.

As show blow. The locating sleeve is used to support the end face of the bolt. This solves the problem of the bending of the locating bolt.

The injection mold adopts a hot runner structure and is selected according to the properties of the plastic. See Table for details.

The surface roughness of the runner holes is consistent with the surface of the cavity. Avoid rough runner holes as much as possible.

The electric power calculation is calculated in 1 kg mass corresponding to 1-1.2 kw. Currently, hot runner systems are standard or custom made. It has been supplied by the hot runner manufacturer.

Prevent cooling water from wetting the wires. Caused a leakage accident.

The flow plate and the 2-stage nozzle are separately temperature control. Minimize the temperature difference between the runner plate and the class 2 nozzle. Thermocouples are usually placed in the highest temperature areas. Between the runner and the hottest part of the heater.

The power cord should be fixed and protected from friction with the components. At the same time, used wax tube to protect the wires.

This is the basic 10 point suggestion. Maybe it will help you recall more details. If you still have questions, please feel free to contact us.