High Pressure Die Casting

Transcription

1 High Pressure Die Casting High pressure die casting is the worldwide most commonly used casting technique for light metal alloys such as aluminum, zinc and magnesium. Therefore almost 80% of our products are manufactured by the high pressure die casting technique. Using the die casting process the molten metal is pushed into the mould under high pressure. This production process is also suitable for a high level of automation, rendering it very efficient. High pressure die casting can reach the highest tolerances among metal castings and realizes high surface quality levels and levels of automation. Die casting is especially suitable for medium to mass production series starting from batch quantities of 2500 up to several millions of pieces. Information on implementation Degree of Complexity Tolerances Process Cores Inserts Part weights Batch quantity Heating treatment Mechanical treatment Surface treatments Cast investment high highest level of metal casting semi-automatic with high degree of automation 20g 10000g from 2500 pieces up not suitable CNC machine powder coating, wet paint, E-coating, polishing, nickel electro plating, technical chrome anodization, aesthetic anodization limited high

2 Cold-chamber die casting In cold-chamber die casting the molten charge (more material than is requires to fill the casting) is ladled from the crucible into a shot sleeve, where a hydraulically operated plunger pushes the metal into the die. The extra material is used to force additional metal into the die cavity to supplement the shrinkage that takes place during solidification. The principle components of a cold-chamber die casting machine are shown below. Injection pressures over 10,000 psi or 70,000 KPa can be obtained from this type of machine. Operating Sequence of the Cold-Chamber Die Casting Process 1. The die is closed and the molten metal is ladled into the cold chamber shot sleeve.

3 2. The plunger pushes the molten metal into the die cavity where it is held under pressure until solidification. CC Die Casting 3. The die opens and the plunger advances, to ensure that the casting remains in the ejector die. Cores, if any, retract. 4. Ejector pins push the casting out of the ejector die and the plunger returns to its original position. Hot-chamber Die Casting The hot-chamber process is the only used for zinc and other low melting-point alloys that do not readily attack and erode metal pots, cylinders and plungers. Development of this technology, through the use

4 of advanced materials, allows this process to be used for some magnesium alloys. The basic components of a hot chamber die casting machine and die are illustrated below. In this process, the plunger and cylinder, which constitute the injection mechanism, are submerged in the molten metal in the crucible (or pot), which is integral to the machine. The operation sequence for the hot-chamber cycle is illustrated below. Operating Sequence of the Hot-Chamber Die Casting Process 1. The die is closed and the piston rises, opening the port and allowing molten metal to fill the cylinder.

5 2. The plunger moves down and seals the port pushing the molten metal through the gooseneck and nozzle into the die cavity, where it is held under pressure until it solidifies. 3. The die opens and the cores, if any, retract. The casting remains in only on die half, the ejector side. The plunger returns, allowing residual molten metal to flow back through the nozzle and gooseneck. 4. Ejector pins push the casting out of the ejector die. As the plunger uncovers the filling hole, molten metal flows through the inlet to refill the gooseneck, as in step 1.

6 Multi-slide tooling Multi-slide tooling is designed to use 4 perpendicular slides in the tool to enable very complex and accurate castings to be produced. In some cases, up to 6 slides can be used, which may be at angles other than 90 degrees. The process is used principally for small zinc components but also Alumess has developed a multi-slide machine for die casting magnesium parts. Multi-slide die casting process: The multi-slide tool is made up of the die block, sliders, crosshead and cover plate. Each die block has either a cavity and/or cores on its face, which together form the complete cavity and runner profile into which the molten metal is injected. These die blocks are mounted onto sliders, which fit precisely into a crosshead, ensuring repeatable opening and closing operations. A cover plate, bolted onto the top of the tool, holds all these components together. Each slide is managed by our PC controller, and moves independently of the other, both during the closing and opening sequences. This provides tremendous flexibility, which ensures part integrity and prevents damage to the tool. Ejection of the parts is achieved with an airblast, which blows the shot clear of the cavity and into a padded collection mechanism. The machines themselves cycle at speeds of up to 75 cycles per minute (4,500 shots per hour). This is achieved by using pneumatics, rather than slower hydraulics, to operate the different parts of the machine. Mechanical toggle mechanisms and hydraulic thrusters supplement the weaker locking force available with pneumatics, ensuring that the die casting tool is held together securely during the injection process. Alumess had also developed fully hydraulic multi-side machines, allowing us to further match the process to the part. BENEFITS OF ALUMESS PRECISION DIE CASTING High volume cost-effective production with consistent quality Value engineered parts save money by eliminating costly post-casting operations Easily manufacture complex net shaped parts with tight tolerances Lower tool cost and longer tool life Lowest total acquisition cost