Nowadays, the success of the manufacturing industry is largely determined by its ability to respond to the rapidly changing market and customer needs. This has resulted in an increasing deployment of automated manufacturing equipment and systems that provide the agility to cope with these new demands. Flexible Manufacturing Systems (FMS) are the most widely used technology to cover these needs. Of course, these FMS must be studied in a formal frame, but the complexity and the dimension of real FMS has prevented from developing efficient control techniques and several challenges are still left. We face up these challenges and present a language that is able to specify nearly any type of real FMS. We use a timed process algebra called BTC (for Bounded True Concurrency) that we have developed from CSP and which takes into account that the available resources in a system have to be shared by all the processes. It is able to consider heterogeneous resources of any type (preemptable and non-preemptable) which makes it suitable for specifying FMS. We show by means of an example that the specifications obtained suit the real systems quite well and are straightforward. To the best of our knowledge, this is the first attempt to do this with process algebras, and we think that it is a good way, mainly, because we are able to split up the system into subsystems which will be easier analyzed.