Requirements for injection machines and moulds for thin - wall injection molding

The need to produce small food container injection molds, lightweight parts has made thin-wall injection the most important performance increase for injection molding machines."Thin wall" is usually defined by the wall thickness of less than 1mm of portable electronic products.For large automotive parts, the "thin wall" can be 2mm.In short, thin-walled products require changes in processing technology: higher pressure and speed, shorter cooling time, changes in the ejector and gate arrangement.The following are the requirements of thin-wall injection molding for injection machines and molds.

Injection Molding Machine

Standard injection machines can be used to produce a variety of thin-walled products.The performance of the new injectors is much better than it was 10 years ago.Advances in materials, gate technology and design have further expanded the capability of standard injection machines to fill mold for thin-walled parts.However, as the wall thickness is decreasing, a more special injection machine with high speed and high pressure performance is needed.

For example, it is normal for an electronic part with a thickness of less than 1mm to be filled for less than 0.5 seconds and with injection pressure exceeding 210MPa.The hydraulic injection machine used for thin wall injection molding is designed with a pressure storage device, which can frequently drive injection molding and die.Fully electric injectors and electric/hydraulic injectors with high speed and high pressure properties are also available.To withstand the high pressure of the new injection machine, the minimum clamping force must be 5 ~ 7 tons/inch (projected area).

In addition, large templates help reduce bending when wall thickness reduces injection pressure increase.For thin-walled products, the tie bar of the injector has a 2:1 or lower ratio to the thickness of the template.In the production of thin-wall products, the endless cycle control of injection speed and pressure and other processing parameters is helpful to control the filling and pressure retention at high pressure and high speed.

As for the injection volume, the large diameter of the barrel is often too large, the recommended injection volume for the barrel capacity of 40% ~ 70%, thin-wall products total molding cycle is greatly shortened, it is possible to reduce the minimum injection volume to the barrel capacity of 20% ~ 30%.Users must be very careful when using injection molding, because for materials, a small injection volume means that the material will remain in the cylinder for a longer time, which will lead to a degradation of product performance.

Plastic Injection Mold

Speed is one of the key factors for the success of thin-wall injection molding.Rapid mold filling and high pressure can inject molten thermoplastic material into the mold cavity at high speed, thus preventing gate cooling.If a standard piece is filled in less than two seconds, the die thickness is reduced by 25%, potentially reducing the filling time by 50%, just one second.

One of the advantages of thin-wall injection molding is that less material is needed to cool down when the thickness is reduced.As the thickness decreases, the molding cycle can be shortened by half.The proper setting of melt conveyer ensures that the hot runner and runner will not hinder the shortening of forming cycle.The use of hot runner and runner bushing helps to minimize the forming cycle.In addition, should also consider the mold with wood.

P20 steel is widely used in traditional products, but because of the higher pressure of thin-wall injection, the molds must be made very strong.H-13 and other hard steels add additional safety features to thin-walled molds.However, the cost of a solid mold can be 30 to 40 percent higher than a standard mold.But the increased cost is usually offset by improved production performance.