SFDC Whilst wholesale implementation of a new shop floor data collection system can cause chaos and confusion, there are other ways of going about it. Roger Bardell argues for a modular approach. DIVIDED WE STAND I T he derivation of management information, via shop floor data collection, is now an es- tablished progress discipline, and considered essential for the main- tenance of production efficiency. The principle behind strict monitor- ing of the manufacturing progress, en- abling rapid management decisions to be made as soon as variances from norms are detected, is equally applic- able to the control of a single progress function (such as finished product weighing) as it is in full plant control. Naturally, the more comprehens- ive the control system, the more effi- cient will be production, with the asso- ciated cost savings. Management func- tions which can be improved through at-line data collection include: • Achieving quality attributes • Maintaining consistent product specification • Ensuring compliance with manu- facturing and product legislation • Maximising product efficiency • Improve record traceability. However, severe cost and disrup- tion implications tend to prohibit the introduction of complete process- wide control systems at a single stroke. Gradual development of the principle is more practical, which is where the modular approach is ideal. Simplicity of design By definition, modular-based data collection systems have the ability to be extended in line with plant expan- sion or progressive development to- wards increased control. In addition, the individual module, at the heart of any system, has the flexibility and the functional capacity to collect and man- ipulate data appropriate to the appli- cation. Most modular control systems, whether large or small, are based around networks of industrial termi- nals linked to on-line measuring de- vices. Located at each significant stage of production, the industrial terminals collect procedural data, either via operator entry or by direct interface with the measuring device, and are networked to management PCs (and to the company mainframe where ap- propriate) from which application spe- cific management information is ac- cessed. The whole system may be linked via a network. Applications Modules, whether stand-alone or within a network, are interfaced di- rectly to the relevant measuring trans- ducer for the application. Any measuring device (checkweigher, weigh-counters, temperature probes etc) can be interfaced into the system, making production control developed on this principle suitable for all forms of manufacture. Module design Modules usually have functional capacities comparable to that of stand- ard PCs enabling them to operate as truly stand-alone units or to be net- worked into complex systems. Hence, it is evident that the industrial terminal and application software governing the entire system represent the heart and brains of the operation. Nova Sys- tems Ltd has developed a terminal which has several exceptional features enabling it to perform expertly as a stand-alone, yet making it ideal for networking. Fully networked control system To expand beyond single process control with stand-alone units, mo- dules have the facilities to be linked via standard Ethernet network. Thus the extent of the modular network is at the designer's discretion and can be ex- tended to include additional functions at any time. Various processes are co- ordinated by the inclusion of con- trol/management PCs, and master files can be downloaded from the com- pany mainframe onto the local area network. The comprehensive control will be driven by application software, dictat- ing the collection and the manipula- Computerised Manufacturing February 1992
Transcript
SFDC
Whilst wholesaleimplementation of anew shop floor data
collection system cancause chaos and
confusion, there areother ways of going
about it. Roger Bardellargues for a modular
approach.
DIVIDEDWESTAND
I
The derivation of managementinformation, via shop floordata collection, is now an es-tablished progress discipline,
and considered essential for the main-tenance of production efficiency.
The principle behind strict monitor-ing of the manufacturing progress, en-abling rapid management decisions tobe made as soon as variances fromnorms are detected, is equally applic-able to the control of a single progressfunction (such as finished productweighing) as it is in full plant control.
Naturally, the more comprehens-ive the control system, the more effi-cient will be production, with the asso-ciated cost savings. Management func-tions which can be improved throughat-line data collection include:
facturing and product legislation• Maximising product efficiency• Improve record traceability.
However, severe cost and disrup-tion implications tend to prohibit theintroduction of complete process-wide control systems at a single stroke.Gradual development of the principleis more practical, which is where themodular approach is ideal.
Simplicity of designBy definition, modular-based data
collection systems have the ability tobe extended in line with plant expan-sion or progressive development to-wards increased control. In addition,the individual module, at the heart ofany system, has the flexibility and thefunctional capacity to collect and man-ipulate data appropriate to the appli-cation.
Most modular control systems,whether large or small, are basedaround networks of industrial termi-nals linked to on-line measuring de-vices. Located at each significant stageof production, the industrial terminalscollect procedural data, either viaoperator entry or by direct interfacewith the measuring device, and arenetworked to management PCs (andto the company mainframe where ap-propriate) from which application spe-cific management information is ac-cessed. The whole system may belinked via a network.
ApplicationsModules, whether stand-alone or
within a network, are interfaced di-rectly to the relevant measuring trans-ducer for the application. Anymeasuring device (checkweigher,weigh-counters, temperature probesetc) can be interfaced into the system,making production control developed
on this principle suitable for all formsof manufacture.
Module designModules usually have functional
capacities comparable to that of stand-ard PCs enabling them to operate astruly stand-alone units or to be net-worked into complex systems. Hence,it is evident that the industrial terminaland application software governingthe entire system represent the heartand brains of the operation. Nova Sys-tems Ltd has developed a terminalwhich has several exceptional featuresenabling it to perform expertly as astand-alone, yet making it ideal fornetworking.
Fully networked control systemTo expand beyond single process
control with stand-alone units, mo-dules have the facilities to be linked viastandard Ethernet network. Thus theextent of the modular network is at thedesigner's discretion and can be ex-tended to include additional functionsat any time. Various processes are co-ordinated by the inclusion of con-trol/management PCs, and masterfiles can be downloaded from the com-pany mainframe onto the local areanetwork.
The comprehensive control will bedriven by application software, dictat-ing the collection and the manipula-
Computerised Manufacturing February 1992
SFDC
tions of shop floor data into meaning-ful management information, the rele-vant details of which can be accessedby managers at-line. A system pre-viously comprising independent mo-dules now operates as an inter-linkingnetwork, from which product ionplans can be derived, estimated com-pletion times calculated, quality effi-ciencies continuously monitored at-line, and immediate revisions madewherever variances detected or pro-duction schedules fall foul.
Benefits of modular process controlThe advantages of taking the modu-
lar approach to data collection andcontrol can be summarised as follows:
1. Cost benefits include:(i) Spreading capital costs incurred byintroducing the complete system overan extended period of time,(ii) Savings made by using the initialstages of development as pilotschemes in which to understand thesystems potential. Further, becausemodular systems are designed for ex-pansion, the pilot will be integrated asthe system is enlarged, as opposed tobeing replaced.
2. Establishing an effective micro system,on which to build the macro design
Ensuring the initial stages of pro-cess control are successful provides asolid foundation on which to developthe system.
3. Retaining localised intelligenceThe system's intelligence is held in
the terminal at each workstation,which merely draw data from a file-saver as necessary as opposed to oper-ating as a dumb unit replicating infor-mation derived from the mainframe.This means that in the event of failurein the mainframe or LAN, individualterminals continue operating as nor-mal.
4. Helping personnel to grow with the sys-tems
Introducing sophisticated controlmechanisms can be an unwelcome
surprise to operators who often regardsuch developments with suspicion. Byprogressively installing the systemstaff are given time to understand theprinciples of its use, and the BigBrother fear is avoided.
5. Software developmentThe modular system has the benefit
of software design anticipating devel-opment, enabling many of the refine-ments which are made with pro-gressive control to be performed off-line, thereby minimising disruption.
6. Planning and installation benefitsStrategic planning of the control
system is eased, and made more effec-tive, by the progressive approach.Further, gradual installation over aperiod of time reduces disruption toproduction output.
7. Progressive introduction of data man-ipulation and integration of information of
various linesIt is not necessary to immediately
network parallel manufacturing linesto achieve cumulat ive data. Forexample, three identical process linesmay be operating. To accumulate totaldata for the three operations, detailscan be drawn from the intelligent ter-minals onto a lap-top which then per-forms the data analysis or in turn feedsthe control PC for this function thusgenerating the statistical managementinformation required.
In due course networking the linesenables this function to be performedautomatically, providing managerswith information even more rapidlyfor instant decision making. A similarapproach can be taken to programm-ing control data and instructions intothe terminals. 3J3For more information enter ME39
Roger Bardell is with Nova SystemsLimited.
The NovaIT191 terminal
stores manyhundreds ofparameters
and operatorinstructions re-
lating to theprocess at any
particularstage of pro-
duction
Jt
J
Computerised Manufacturing February 1992
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