1. Decomposition of a manufacturing line

A machine is a fundamental component of a manufacturing system. Following ANSI/ISA-88 standard it can be placed in the physical hierarchy as presented in Figure 1. A manufacturing line is an arrangement in a factory in which a product passes through a linear sequence of mechanical or manual operations. These operations are performed at workstations which are here called machines. Each machine performs at least one distinguishable operation using its modules. For example a labeler may consist of product separator, conveyor, front and rear labelling modules, as well as quality control camera or scanner. Every module can be further decomposed into actuators or sensors e.g. capping unit may consist of rotary servodrive, torque meter and vertical servodrive with linear transmission. Signals and alarms registered over time can be linked to any level of the hierarchy, but they are usually caused by the operation, or failure of actuators or sensors due to internal or external reasons. 

Open

In addition to the above hierarchy, we define the classes of machines depending on the number of input and output material streams. A simplest machine class is a processor which consumes and produces a single material stream, e.g. a bottle feeder or dynamic scales (fig 2a). A machine which merges two or more separate streams is called a combiner (fig. 2b). A good example is a labeler which can stick front and back labels on a plastic jar or bottle. A filling machine also combines bulk (e.g. perfume, cream or lotion) and primary packaging (e.g. jar or bottle). The opposite class is a separator in which a single input stream is split into multiple outputs (fig. 2c). Each of the output can be further processed (cutter splits a packaging foil reel into tapes), returned in a subcycle (depaxer) or can exit the process (depalletizer in which pallets are transferred to the warehouse, while packaging is fed to the subsequent machine). A separate machine class is a transportation unit (e.g. conveyor or elevator) as it interconnects the machines in the line. The transportation units can also serve as a natural buffer improving the material flow and reducing the efficiency losses due to machine failures. Please note that the conveyor can also be a part of a machine in which its primary function is to transport objects between its modules.

Open

Machines can also be classified based on the characteristics of process they perform, e.g.: sorter, filler, capper, labeler, cartoner, casepacker, cello, foiler, palletizer, depalletizer or their combinations. Each process is usually done by one or more modules which, in principle, are similar for each sector like cosmetics, pharma or food industry. For example you can fill lotion in a bottle or cream in a jar using same kind of servodriven nozzles with dosage controlled via flowmeter. Since there is a vastness of machine providers and design approaches, some modules can be sold as separate machines, while the others are combined within one entity (filler and capper). In other cases, for the same process, different number of modules can be installed in parallel (number of nozzles or capping units) to increase the production rate. In addition, some modules can be driven by a single drive (transmitted via a long shaft, gears, belts, chains, etc.) to ensure maintaining the production cycle, while, in other designs, same kind of modules are driven by independent servos, electronically coupled with each other. That is why considering the modules in the hierarchy is critical to achieve  the flexibility in creating a machine library and to reflect to the real manufacturing world. 

An example of the decomposition of a cosmetics manufacturing line (Futureproof 120) on machines, modules and actuators/sensors is shown in Figure 3. Main stream is always associated with primary packaging (bottles in this case). Looking at the lowest hierarchy level, certain objects are repetitive, e.g. vacuum pump, AC motor with reducer, servo, robot, level meter etc. Although they may differ in terms of the output power, torque or sensitivity they serve the same function. This translates into similarity of signals and alarms which can be collected from them. For example, information about current and revolutions per minute (real and/or set) can be most probably retrieved from any kind of servodrive used in any module, or any kind of electric heater should allow registration of temperature.  Actual signals and alarms coming from real machines can be mapped to a predefined list of signals and alarms created for particular module type during the implementation.

Open