Tasks and Complexities
When designing automation, flexibility in the system should be built into the framework of the automation concept, so that new predictable part variants made up of existing parts can be processed with no or little intervention.
A machine assembling watches can build the following types of watch,
- A mens watch, in gold, with a leather strap and roman numerals, sold in a blue box.
- A ladies' watch, in silver, with a fabric strap and dot numerals, sold in a red box.
- A child's watch, in plastic, with a cartoon strap and numeric numerals, sold in a green box.
Each of the constituent parts of the product (the watch) is made from known bounds of the designed tasks, called complexities.
Thus, each of the products can be described as having multiple tasks in their recipe, which is first selected from a predetermined file and then processed by the machine to assemble the required parts.
| Complexity Number | Frame Colour | Strap Material | numerals | packaging |
|---|---|---|---|---|
| 1 | gold | leather | roman | blue box |
| 2 | silver | fabric | dot | red box |
| 3 | plastic | cartoon | numeric | green box |
A machine with 4 stations, each using one task, assembles the watch to its given recipe stored on its hard drive. Each station performs 1 task, however the machine can assemble multiple products in a FIFO basis, as it is undesirable to run the assembly in batches.
- Station 1 assembles and paints the frame, gold or silver with no paint for plastic
- Station 2 picks a strap and presses to the watch body
- Station 3 is a laser marker that marks the numbers to the watch face
- Station 4 is a packaging station that puts the product in a box
The recipe file on the PLC stores the recipe data and its breakdown of complexities.
In order for the machine and its stations to perform a task, e.g. send program number to a feeder, press program, pick to light location, engraving program, etc, it must know the contents of the above table
With the part loaded and its RFID tag read, the complexities are loaded when the part arrives in the station. The task's complexity number is outputted in the function block FB_Task
The output pin of qComplexity can be moved to elsewhere in the program to perform the correct task, e.g. move pouStation1.task1.qComplexity to profinet memory of a laser marker.
The file is stored in
C:\PLC\Complexity
The contents of the file is ASCII text that describes what each complexity is given for a specified task in relation to the recipe table (above)
Men's watch complexity (part type 1)
Ladies' watch complexity (part type 2)
Child's watch complexity (part type 3)
Using this method, it is possible for the machine to create new products based on a modular product design and known processes.
For example, if a new product can be selected from existing complexities, then the machine can create the new product, without re-tooling the machine. A new product consisting of a gold frame, with a fabric strap, with numeric numerals in a green box can be defined;
| Complexity Number | Frame Colour | Strap Material | numerals | packaging |
|---|---|---|---|---|
| 1 | gold | leather | roman | blue box |
| 2 | silver | fabric | dot | red box |
| 3 | plastic | cartoon | numeric | green box |
| 4 | gold | fabric | numeric | blue box |
The new file will look as below:
This file is then sent to the C:\PLC\Complexity folder of the PLC's hard drive.
If a new platen with an RFID tag part type of "4" exists and is inserted into the machine, the machine will then create a watch using the sum of the existing part types