This chapter is concerned with the selection, application and implementation of the microprocessor element in the control system.
The first task was to choose a microprocessor suitable for controlling the flow-turning process. Also in this chapter, some of the application areas are highlighted to illustrate how the microprocessor has become an essential ingredient in almost all sectors of life. Microprocessor-aided flow-turning is contrasted with other manufacturing techniques in terms of efficiency, initial cost and degree of accuracy after which it was decided to adopt the new technology as an alternative to the existing methods. The choice of microprocessor was carefully considered in this research in view of
availability and associated expertise.
Some of the tools used in developing the flow-turning process software are described briefly to demonstrate how considerable time and cost can be saved. Also, the language used (PL/M 80) was underlined and explained in some detail.
The use of a microprocessor may in itself promote a change in present manufacturing techniques for this process or it may pave the way for other further research. This research was directed towards implementation of a microprocessor in the flow-turning process.
2.2 - Examples of common microprocessor uses
There are many current application areas for microprocessor, and to some extent these indicate the likely course of future developments. It is useful for manufacturers and users to know in what fields investment will be fruitful and what are the practical application
opportunities. Major areas in which microprocessors were likely to make an impact are listed
1- production monitoring / recording 2- automatic warehousing
3- distribution
4- retail trade (point of sale / stock recording) 5- banking transactions
6- tickets /reservations / passenger movements 7- hotel / restaurant booking
8- hospitals (patient records / monitoring/ analysis) 9- road control (traffic lights / hazards)
10- building control (heat / light / lifts / fires) 11- office systems (word processing / automatic filing)
There are many processes and phases in industrial activity from the handling of basic raw materials, through the design and manufacture of products. All the associated tasks, processes and production control lend themselves to computerisation.
As far as the engineering industry is concerned, processes such as flow-turning, metal-spinning and tube-bending are amenable to microprocessor control. Micros can also help to optimise forging, cold-forming and extrusion operations(lA).
2.3 - Using the microprocessor as an alternative method of tool movement control
As mentioned earlier in chapter 1 section 1.3, there are various well-known methods of controlling tool movement which can be used satisfactorily and efficiently. The techniques use specialised
flow-turning machines (with their supporting hardware and software) which are usually expensive. Some of these techniques involved using a medi computer or a CNC lathe to store the tool movements, as mentioned
previously in section 1.4.
In this research, a lathe was converted to accommodate the flow-turning process and can also perform spinning. Certain modifications were carried out, which included the hardware (which is elaborated on in chapters 3 and 4) and software (as explicated in chapter 5).
In this study, a controller was conceived, fabricated and installed on the lathe to perform the flow-turning process. A single board microcomputer system (SDK-85) was utilized with the necessary interface to communicate with the designed rig. A program was written to enable the roller to follow the required shape(s) (conical or parabolic).
The rig design was simplified by using a single hydraulic cylinder to actuate the tool (in the y-axis) while employing the screw threads on the lathe to move in the x-axis. In this way, the added features can be implemented on a second hand lathe of appropriate size and cost, thus keeping the overheads to a minimum. The price of the added features was around £1300 in total and, assuming an estimated lathe value of £8000, thus the sum total is £9300 which is probably less than 1/7 the cost of a new flow-turning machine.
2.4 - Selection of the microprocessor
The microprocessor selected should be able to perform the following
1- Fulfil the arithematic manipulations which involve addition, subtraction, multiplication and division with adequate accuracy (whether it is 8 or 16 bit processor).
2- Possess adequate speed to process data which include input/output operations (the input of transducer movement i.e ADC, the shaft encoder input, which is the roller tool position, and the output of digital values to the DAC)•
3- Meet good language facilities, with floating point variables if possible•
The two possible available models are the SDK-85 or the SDK-86 microcomputer boards.
On the one hand, the SDK-85 board has the 8085 as a CPU, which is an 8-bit general-purpose microcomputer that is very cost-effective in small systems because it has a low hardware overhead requirement. At the same time it is capable of accessing up to 64K bytes of memory and has status lines for controlling large systems. The SDK-85 microcomputer is used mainly is small control applications. It has enough I/O ports, yet has some language limitations (there are no floating point variables, only integers, which limits the accuracy).
On the other hand, the SDK-86 board has a newer, more powerful 16-bit processor with good language facilities (floating point variables). However the supporting hardware and software were not available to the researcher within the Mechanical and Production Department of Sheffield Polytechnic.
The microprocessor to be selected must fulfil the three requirements mentioned above for the flow-turning process. In addition, other factors have to be considered, such as expertise. Both the SDK-85 microcomputer systems satisfy the three criteria. However, because the former has been accessible for several years, expertise is already obtainable, an important incentive when undertaking such research. Moreover, all the difficulties associated with using the
hardware and software are well known. Thus the SDK-85 was chosen as the most suitable device.
Some of the development aids available were
1- Intellec series II microcomputer development system. 2- In-circuit emulator (ICE-85).
3- PL/M 80 programming language. 4- Universal PROM programmer.
5- ISIS-II diskette operating system.
These aids are discussed in the following section
2.4.1 - Intellec series II microcomputer development system
The Intellec series (model iMDX 225) is a complete microcomputer development system integrated in one compact package. It includes a CPU with 64K of RAM memory, 4K bytes of ROM memory, a 2000 character CRT, detachable full ASCII keyboard with cursor controls and upper/lower case capability, an integrated 250K byte disk drive, plus an iMDX 721 dual disk drive system. Plate 2.1 shows the Intellec development system.
2.4.2 - In-circuit emulator (ICE-85)
This is a debugging device which is available with the development system. It is invaluable because of its ability to test software without 1 blowing’ an EPROM. This works by allowing a program that exists in object code on a disk file, to be loaded and run in the development system’s CPU, under the control of ICE. The ICE software