A record press is a machine for manufacturing vinyl records. It is essentially a hydraulic press with a closing force of 100 tons and is fitted with moulds. Labels and a vinyl pattie (pre-heated vinyl blob) are placed in the mould cavity while the moulds are being steam-heated with an ideal steam pressure of 140-170psi. Stampers (metal plates, one for each of Side A and Side B) for each title to be pressed are fitted to the moulds. The stamper contains a negative image of the grooves. The moulds close and through the process of compression moulding the vinyl fills the cavity and takes the form of the finished record, complete with grooves courtesy of the thin metal "stamper".
Water at a pressure equal to the steam pressure is then admitted to the moulds which both expels the steam and cools the moulds down. The press opens and the record is removed from the moulds. The overflow vinyl at the edges is trimmed and the records stacked and allowed to cool. Cycle time for a 7" record is about 15 seconds and for a 12" record about 25 seconds.
The last record presses ever made are said to be those built and supplied by Alpha Toolex to Melodiya Records (USSR) in the mid 80s. Most presses in use today were made in the 60s and 70s.
All of the above brands except for Philips, and Tracy-Val are still in use in some 43 record-pressing plants around the world in 2011.