Search:

CD Replication Company

CD moulding machines are specifically designed high temperature polycarbonate injection moulders. They have an average throughput of 550-900 discs per hour, per moulding line. Clear polycarbonate pellets are first dried at around 130 degrees Celsius for nominally three hours (dependent on which optical grade resin is in use) and are fed via vacuum transport into the one end of the injection moulder's barrel (the feed throat) and are transported to the injection chamber via a large screw inside the barrel. The barrel, wrapped with heater bands ranging in temperature from circa 210 to 320 degrees Celsius melts the polycarbonate. When the mould is closed the screw moves forward to inject molten plastic into the mould cavity. When the mould is full, cool water running through mould halves, outside the cavity, cools the plastic so it solidifies somewhat. The entire process from the mould closing, injection and opening again takes approximately 3 to 5 seconds.

The moulded "disc" (referred to as a 'green' disc, i.e. unprocessed) is removed from the mould by vacuum high-speed robots with vacuum suction caps and moved onto the infeed conveyor or cooling station of the finishing line before metallisation. At this point the discs are clear and contains all the digital information however it cannot be played because there is no reflective layer.

The discs then pass, one at a time into the metaliser, a small chamber operating at approximately 10E-3 Torr vacuum. This process is called 'sputtering'. The metaliser contains a metal "target" made of an alloy of mostly aluminium and some small amounts of other metals. There is a system of a load-lock (like an airlock so that the process chamber can maintain high vacuum as the discs are exchanged. When the disc is rotated into the processing position by the swivel arm in the vacuum chamber, a small dose of argon gas is injected into the process chamber and a 700 Volt DC electrical current at up to 20 kW is applied to the target. This results in a plasma igniting and the aluminium target evaporates onto the disc (anode - cathode reaction). The metal coats the information side of the disc (upper surface) and covers the pits. This metal layer is the reflective surface that can be seen on the reverse of a CD. This thin layer of metal is unstable and will oxidise if it is not protected by a lacquer.

After metalisation the discs pass onto a spin-coater, where UV curable lacquer is dispensed on to the metal layer and spun rapidly to coat the entire disc in a very thin layer (circa 70 nm). After the lacquer is applied it passes under a high intensity UV lamp which cures the lacquer. The lacquer also provides a surface for the screen printing or offset printing ink to adhere to.

http://www.solarcd.com

Article Source: http://www.uberarticles.com/articles

www.solarcd.com

This article is licensed under a Creative Commons Attribution-No Derivative Works 3.0 Unported License, which means you may freely reprint it, in its entiretly, provided you include the author's resource box along with LIVE links (without "nofollow" tags).