Function diagram
The function diagram is a graphic method of clearly showing the “functional sequences” of machines. It was described in the VDI guideline VDI 3260 of July 1977 and was replaced in 1992 by the function plan of DIN 40719-6. DIN 40719-6 was temporarily valid until April 1, 2005 and has since been replaced by DIN EN 60848.
In this respect, the function diagram is an old and - measured against standards and guidelines - invalid tool. However, it is still used in mechanical engineering , pneumatics and hydraulics, and especially in training. It is also so easy to use for small function sequences and so clear in its presentation that it is worth knowing and using the function diagram.
idea
The function diagram enables a simple graphic representation of the functional sequences of sequence controls .
The sequences are listed horizontally in steps (path-step diagram / "path diagram") or time units (path-time diagram / "state diagram").
regulate
A table is developed in the function diagram. The columns correspond to the names (first column) and steps / times (further columns). The lines correspond to the signals, first and foremost the actions / actuators / "drive elements".
Each step or time unit is given a consecutive number in the columns, which is written at the beginning of the step / time unit.
In the left column the actuators / "drive elements" are written one below the other.
Then a “thick line” is used to indicate how the work elements have to move. If switching on or off is assumed, the line is displayed vertically (a motor is switched on or off, only if the acceleration / braking of the motor has a special meaning in the display, the display is made as with a linear drive). In contrast, a linear drive, usually a hydraulic or pneumatic cylinder, is shown diagonally to make it clear that such a drive needs time to move from start to finish.
A production process almost always has to work in a loop - after all, many parts should be produced. Therefore, the process - in the representation as a distance-step diagram at the end of the process must have the same position of the drives as at the beginning or in an initial step. To identify this loop (or this jump) the step number is z. B. entered as 7 = 1. This means that after the end of step 6, the system is back in the starting position and a new process can begin.
editor
An editor for function diagrams is included in Fluiddraw (Festo AG) and Fluidsim (Festo Didactic), as well as in the software package sovis (socon GmbH).
Note
All graphics in this article were created with the Function Diagram Editor from Fluidsim. The diagrams that can be drawn with it are simpler than provided in the VD 3260. However, since today's standardized planning with Grafcet is much easier and easier to handle for complex processes , this simple representation and use of the function diagram is sensible and justified.
The original names are enclosed in quotation marks in order to distinguish them from common terms, e.g. B. Path-step diagram / "Path diagram".
literature
- VDI 3260, July 1977