High Pressure Die Casted parts, commonly utilizing aluminum, but sometimes also other non-ferrous metals such as copper and magnesium, are found in most modern products to include automotive components, and high-tech devices such as PCs, laptops, and smart phones.
In a high pressure die casting machine, non-ferrous metals are melted at elevated temperatures to convert into a flowable liquid. Aluminum as an example, needs to be heated at approximately 660 o C to take the form of a liquid, which is subsequently injected by plunger action at high pressures, into a die cavity. As the molten metal cools and solidifies, it takes the form of the die cavity and forms the desired part. It is ejected, and trimmed, and may undergo succeeding processes such as painting or assembly.
The process by which such parts are formed, high pressure die casting, provides significant challenges lubrication wise, owing to the pressures, and higher temperatures that lubricants are subjected to. The critical lubricants for a high pressure die cast machine include the following,
1.) Hydraulic Oils, which are required to generate sufficient pressure to ensure that the two (2) halves of the die (mold) are clamped tight, and able to resist the force generated by the injected molten metal flowing into the die cavities.
2.) Die Release Agents, which are water-based fluids that are sprayed onto the die cavity surface prior to each injection of liquid metal, require significant strength to resist the effects of the high temperatures. Die release agents are needed in the process to ensure that that casted parts are released from the die without distortion or defects, and is a important component also for the purposes of lengthening or optimizing die life.
3.) Plunger Lubricants, high viscosity oils, both compounded and un-compounded, as well as dry solids and water based fluids, are utilized to reduce the friction and wear that occurs on the interface between the plunger tip that injects the aluminum and other similar metals, and the plunger sleeve that holds the liquid metal. The injection process occurs on a boundary lubrication regimes, and pressures of up to 10,000 psi are not uncommon, placing stress on the lubricant.
In the succeeding discussions, we shall tackle the lubricants individually, identify the challenges, and propose solutions.