Production of records

Production of records – from the master program to the pressing die

The industrial pressing of records is a multi-stage process that enables the production of large quantities. First, the master program is cut into the lacquer of a coated film using a heated cutting stylus. The sound components are modulated in accordance with a standardized characteristic curve in order to ensure the frequency response during playback. playback optimized. This lacquer plate is coated with silver to make it electrically conductive and then electroplated with copper or nickel to produce an approximately 0.5 mm thick negative, the “father”. Several positives, the “mothers”, are then taken from this “father”, which are read to check the recording and reworked if necessary. The actual press dies, the “sons”, are in turn produced from the mother plates using an electroplating process and then chrome-plated to increase their durability. This process must be repeated for both sides of the plate.

In order to avoid the intermediate step via “fathers” and “mothers”, the DMM process (“Direct Metal Mastering”) was developed in the early 1980s. This involves cutting directly into a copper layer on a stainless steel plate, from which the “sons” are then produced directly. Although this process is less susceptible to distortion, it has the disadvantage that the groove depth and deflection are smaller.

Polyvinyl chloride (PVC) is the raw material for pressed sheets, to which around 20 % polyvinyl acetate (PVAc) and other additives are added. The raw material can be colored and no longer contains carbon black. For so-called audiophile pressings, only pure, fresh PVC raw material (“virgin vinyl”) is used, as paper residues cannot be completely removed during recycling and can lead to quality problems.

The pressing process takes approx. 30 seconds. A metered quantity (150 – 180 g) of raw material is placed between the pressing dies together with the labels and pressed under a pressure of approx. ^8-106 Pa (approx. 80 kg/cm²) and a temperature of approx. 150 °C. After opening the press, the disk is placed on the cutting plate with the help of a holding ring and a punching plate. This creates a vacuum to hold it in place and is then set in rotation. A knife attached to the outer edge of the cutting plate cuts off the crushing burr created during the pressing process. The slice is then removed from the plate using a transport arm and temporarily stored on a spindle until it is packaged, during which time the slice is cooled by the ambient air for approx. 10 seconds. During this time, the extruder produces a press cake again and the process begins anew.