When making plastic molds, three main materials can be used: steel, aluminum, or beryllium copper alloy. Each of these materials has advantages and disadvantages. Steel molds are heavier and less durable, and aluminum molds are less expensive. Beryllium copper molds offer the advantages of steel and aluminum without the disadvantages. Aluminum is also less wear-resistant than steel and can produce thousands of parts per mold. However, this material is also softer than steel, which can result in excessive downtime and unexpected repair costs.
The most common use of aluminum and beryllium copper is for molds that require high strength and durability. These metals are used in aerospace, automotive, and energy industries. They are also used in musical instruments and are excellent for producing consistent tones. Another advantage of beryllium copper is that it resists corrosion in the factory environment. In addition, beryllium copper is not susceptible to rusting, which means mold cooling channels do not become clogged with corrosion products. Because of these properties, beryllium copper is ideal for mold applications that require corrosive plastics.
Beryllium copper is also a great option for molds because of its superior strength and thermal conductivity. It can also be used in manifold designs for improved cycle times and mold life.
In addition to this, aluminum molds are prone to damage and require additional maintenance procedures. Its high thermal conductivity and strength can prevent thermal cracking.
Aluminum has great thermal properties, but poor mechanical properties, which can result in warping or distortion. Tungsten carbide is another candidate for heat-resistant plastic molds, but its use is limited by size limits.
It can also result in excessive mold sweating, which can lead to distortion. Aluminum-bronze copper alloys are also becoming a common choice for mold making. Copper alloys have a unique property of reducing warpage and improving assembly.
The plastic used for a mold should be a high-quality material with high thermal stability. It must be resistant to oxidation because the molten plastic will be in contact with oxygen while it is inside the mold.
The pnext ste in the process is cooling the mold. This can be done with a fan. The temperature in the mold should be controlled for tens of minutes. Then, the part can be removed manually.
Ideally, the resin source must be placed below the mold cavity. This way, the resin flow rate will be proportional to the resin column’s hydrostatic pressure. For instance, a 10-meter liquid column generates 1000mbar of pressure force. A 1.5-meter height differential has a similar effect. Depending on the type of resin used, this differential may be reduced. However, it is advisable to experiment with different materials before attempting to apply the process to larger parts.