Essentials of Design and Processing of Blow Molds

The design and manufacture of blow molds with fast cycle and long life are required by the development of Dongguan blow molding products industry. The factors that determine mold efficiency are:

1) materials;

2) cooling;

3) Cutting blank mouth design;

4) Exhaust.

 

 The material used to make the mold must have high thermal conductivity and sufficient cutting edge strength. Aluminium 70/75 is currently an advanced alloy used to make most molds. Due to the good machinability of this metal, the cavity is usually machine cut. The copper alloy mold also has high heat transfer and good corrosion resistance. However, its cost is high and its price is high, and its specific gravity is three times that of aluminum, which may cause severe wear on the molding machine. The steel alloy mold is easy to repair by welding or setting.

 

The thermal conductivity of the cast aluminum mold is worse than that of the cut aluminum mold. The cut opening of the mold cavity usually needs to be broken with copper alloy or stainless steel, because the strength and hardness of cast aluminum cannot meet the requirements of the cutting edge of the cut opening.

 

Kirk alloy (zinc) castings can be made on steel masters. The cavity and the base plate are cast to a certain size. Because the Kirk alloy is not strong enough to cut plastic, the operating hole and shoulder area are inlaid with copper alloy or stainless steel. The bottom and neck are also inlaid with these two metals. The casting mold can also be made of a cast copper alloy. It is easier to cast the steel mold cavity because it is cast by pressure or gravity. These cavities have many fine parts produced by steel master or ceramic molds.

 

Cooling is challenging and important in mold design. Drilled cooling lines are installed where cooling is most needed. For better production control, most molds are designed with several independent cooling zones. The neck and bottom need to dissipate the most heat, and therefore require the most effective cooling.

 

Cut the blank. The design depth of the blank cut area may become a significant factor in the yield and quality of the part. The blank cut area is where excessive plastic enters the part during the blow molding process in Dongguan. The type and shape of the cut mouth may determine the welding of a part.

 

For harder resins, steel or copper alloys need to be used as cutting material. Sometimes the cutting area of ​​the blank is blown with air to accelerate the cooling of the plastic, remove excess material, and prevent distortion of the part.

 

exhaust. In order to allow the gas to escape quickly when the parts are blown in Dongguan, the mold must be vented. The most common and economical method of venting is surface venting. Deep blasting or texturing the cavity can also help with venting. Another important reason to vent (for those parts where plastic must be blown into tight, narrow spaces) is to show detail.