ENX300 Manufacturing Systems Design. 2014 REVISION Module Leader: Ken Robson, St Peters Campus. Module Aim. The module equips students with knowledge and skills relevant to the current thinking associated with manufacturing systems design and analysis. It focuses on three key areas :
ENX300Manufacturing Systems Design 2014 REVISION Module Leader: Ken Robson, St Peters Campus
Module Aim The module equips students with knowledge and skills relevant to the current thinking associated with manufacturing systems design and analysis. It focuses on three key areas : 1. ‘JIT/Lean operations’, 2. ‘Maintenance’ 3. ‘Tools of analysis and improvement’. My website for powerpoints,exam papers etc. http://www.cet.sunderland.ac.uk/~cs0kro
Lesson 1 Lean & JIT Philsophy
The lean philosophy of operations Involve everyone Continuous improvement Eliminate waste JIT as a set of techniques for managing operations JIT as a method of planning and control Basic working practices Design for manufacture Operations focus Small, simple machines Flow layout TPM Set-up reduction Total people involvement Visibility JIT supply Pull scheduling Kanban control Levelled scheduling Mixed modelling Synchronization The lean philosophy of operations is the basis for JIT techniques that include JIT methods of planning and control
Lean Philosophy Eliminate waste – in all its forms Waste is any activity that does not add value to the final product. Objectives are to remove NVA and enhance VA activities.
Lean Philosophy Involve everyone A total system; therefore needs guidelines which cover both people and process. All staff are involved and the culture of the company is important. Requires teamwork in problem solving, job rotation, mutli-skilling etc. Intention to give high degree of personal responsibility and ownership of the job. There are criticisms of the approach as it is patronising - what are your thoughts on this issue.
Lean Philosophy Continuous Improvement Believe that, with appropriate effort, the ‘ideal’ can become nearer to over time. The ideals it sets out to achieve may not be (or can not be) reached, but they act as a motivation to achieving it. The Japanese term is kaizen and we will consider this in detail later in the module.
JIT Techniques Nine Areas Flow Layout The basic working practices of JIT Design for Ease of Processing Emphasize Operations Focus Small Machines Total productive maintenance (TPM) Reduction of Set-Up Times Ensure Visibility JIT purchasing
The Seven Wastes Overproduction Waiting time Transport Process Inventory Motion Defective goods JIT seeks to reduce all these wastes
Lesson 3 Layout & Flow
Volume & Variety Layout and flow cannot be discussed without first considering : The product volume and variety The type of process to be employed These factors are inextricably linked
Volume & Variety Product volume – quantity of units produced Product Variety – is the variation in products (SKU’s) Product volume and variety is affected by the type of business and the market demand for products
Volume-Variety Dilemma Low VOLUME High High Not possible? VARIETY Accepted continuum for processes Not viable? Low
Volume & Variety Process types in manufacturing are generally considered as: Project Processes Jobbing Processes Batch Processes Mass Processes Continuous Processes The volume/variety position points to the most appropriate process
Layout Product volume and variety dictate the process type selected. Areas of overlap exist where more than one type could be applicable – in this case operational objectives are used to make decision: cost, flexibility, known future areas of growth etc. There are four broad layouts Fixed position Process Cell Product
Fixed Position Transformed resources do not move Equipment and resources move to the product which is stationery. Normally because product is too large, i.e. shipbuilding, aero-engine, power generators. Or too delicate or fragile – heart transplant patient Main problems associated with this type of operations are space and scheduling issues: Adequate space for groups to work without interference Storage for materials and equipment Scheduling of material and people is key to FP success
Process Layout Resource types dominate layout decision Similar process are located together – for convenience or utilisation Parts are routed through the operation based upon their requirements Flow patterns are different and complex Control and visibility is also an issue Example of use – production of aero-engine parts – many different processes involved.
Cellular Layout Where all the required resources are available in one area to meet the processing needs. Can be of the product or process layout type. After completion the product may be finished or go to another cell. Cells attempt to bring order to the product flow
Process Layout Cellular Layout
Product Layout Each product follows the same route Can also be known as flow-line Flow is clear predictable and therefore offers visibility and ease of control. Products produced are standardised (although small variations are possible) – but flow route is the same. Examples – car assembly, electronic goods etc.
Advantages and disadvantages Fixed Process Cell Product position layout layout layout layout Very high product High product and Can give good and mix flexibility. mix flexibility. compromise. Low unit costs for high volume. Product/customer Relatively robust Fast throughput. A dvantages not moved. in the case of Opportunities for disruptions. Group work can specialization of High variety of result in good equipment. tasks for staff. Easy to supervise. motivation. Can have low mix Very high unit Low utilization. Can be costly to flexibility. costs. rearrange existing Can have very layout. Not very robust to Disadvantages Scheduling space high WIP. disruption. and activities can Can need more be difficult. Complex flow. plant. Work can be very repetitive.
Lesson 4 Layout Design Techniques: Line Balancing
Product Layout Transforming resources located for the convenience of the transformed resources Product/customer/information follow a pre-arranged route Sequence of activities matches the sequence in which process’s have been located
Detailed Design - Product Layout Key decisions are concerned with ‘what to place where’ – in terms of what to allocate to each of the workstations. This is termed line balancing Other key questions are: What cycle time is needed? How many stages are needed? How should the layout be balanced? How should the stages be arranged?
Some definitions – (ch4 Slack) Cycle time – the average time for units of output to emerge from the process Throughput time – the time for a ‘unit’ to move through the process Work Content – the total amount of work required to produce a unit of output WIP – work in progress
Detailed Design - Product Layout Cycle time = time available No.of units to be processed Number of stages req. = work content required cycle time
Calculation of Balancing Loss An ideal ‘balance’ where work is allocated equally between the stages But if work is not equally allocated the cycle time will increase and ‘balancing losses’ will occur 3 Cycle time = 2.5 mins Cycle time = 3.0 mins 3.5 2.5 3 3.0 2.5 2 2.5 Load 2.3 2.5 2.2 2.2 3.0 2.3 2 Load 1.5 1.5 1 1 0.5 0.5 0 0 1 2 3 4 1 2 3 4 Stage Stage Work allocated to stage Calculating balancing loss: Idle time every cycle =(3.0 - 2.3) + (3.0 - 2.5) + (3.0 - 2.2) = 2.0 mins Balancing loss = 2.0 4 x 3.0 = 0.1667 = 16.67% Idle time
Line Balancing Exercise A manufacturer wishes to create a flow line which will produce 2000 products / day (24hours). The assembly information for the product is outlined in Table 1 below. Calculate the maximum cycle time.(2) Calculate the minimum number of work stations. (2) Produce the precedence diagram. (6) Produce the line design which achieves the required cycle time. (6) Calculate the idle time/cycle based upon the longest station time and comment upon the result. (4) Draw the balance-loss diagram for your design showing the work allocated to each stage and its idle time. Explain which station you would improve first, and why? (5)
Line Balancing Exercise
Line Balancing Exercise a) Max cycle time = total time available /No of units to be processed = (24x60x60)/2000 = 43.2 sec = 43 sec (44 secs is not a correct answer as the min. of 2000 units would not be produced) b) Theoretical min. number of work stationstotal work content/ max cycle time = 206/43 = 4.7 Therefore 5 workstations
Line Balancing Exercise
Line Balancing Exercise
Line Balancing Exercise e) Idle time per cycle = Total idle time No of stages x longest stage time = (52/(5*43))*100 = 24.19 % A reasonably well designed solution but we still have two stations which are a considerable way from the required cycle time
Product Flow Analysis ADVANTAGES; Quick and simple to perform Low cost method as no specialist equipment or training is needed. No need for resource or product technical expertise DISADVANTAGES It does not consider the number of resources available - separate capacity calculation have to be carried out to determine the number of each resource type needed in each cell. It does not consider the geometry / features of parts – this may prove problematic when material handling devices and transport systems are considered. Resource and routing data has to be verified or the output for the process is meaningless.
Lesson 5 Production Flow Analysis
Product Flow AnalysisTutorial Example - SEPT 2008
Product Flow AnalysisTutorial Example
Product Flow AnalysisTutorial Example - ROWS SORTED
Product Flow AnalysisTutorial Example
Product Flow AnalysisTutorial Example – COLUMNS SORTED
Product Flow AnalysisTutorial Example (3)
Product Flow AnalysisTutorial Example We can now see that this matrix is fully sorted as two distinct groupings have become visible and further sorts would not change this arrangement. This operation has now exposed two likely cells; Cell 1 contains product families A,E,C and resource types 1,2,3,4,5,6,7 and Cell 2 contains product families D,F,B and resource types 8,9,10,11,12,13,14
JIT Planning and Control Lessons 6
JIT Planning and Control There are many approaches to the planning and control of products through a process. The main issue is to ensure inventory timing is predictable. (parts arrive on time) without excessive build up of inventory The following methods will be considered: ‘Push’ and ‘Pull’ systems – the two main approaches to planning and control. (Chapter 10 – p347 (309)gives a useful account of these two systems). Will also consider the elements of ‘Theory of constraints’ proposed by Eli Goldratt (1984) Levelled scheduling
Push philosophy of planning and control PUSH CONTROL FORECAST CENTRAL OPS. PLANNING AND CONTROL SYSTEM OR Instruction on what to make and where to send it Work centre Work centre Work centre Work centre DEMAND Activities are scheduled centrally There are always errors in the forecast – Why? Each work-centre produces work irrespective of whether the next centre needs it or not This inevitably leads to queues and inventory build up
Pull philosophy of planning and control PULL CONTROL Request Request Request Request Work centre Work centre Work centre Work centre DEMAND Delivery Delivery Delivery Delivery The customer determines what is produced at what frequency The customer’s request pulls work through the system. Can be used to link both suppliers and customers into an organisation’s control system. Less likely to allow inventory build-up. JIT uses the pull system
Drum, Buffer, Rope Concept It is not necessary for processes before the bottleneck to run at full capacity Some form of feedback is necessary from the bottleneck to the input of the process to ensure earlier activities do not overproduce This is called the ‘rope’. The whole system can be represented in a diagram as follows
Drum, Buffer, Rope Concept Eli Goldratt (1984) used this idea in his book ‘The Goal’ He suggested that the control should be placed around the ‘bottleneck’ Remember the bottleneck ‘constrains’ the whole process so therefore it is important to keep this part of the process running The bottleneck is known as the ‘drum’ or the heartbeat of the process. Because it does not have sufficient capacity Goldrattsuggested it should always have a ‘buffer’ of stock in front of it
Bufferof inventory Activity A Activity B Activity C Activity D Activity E Bottleneck drum sets the beat Communicationropecontrols prior activities The drum, buffer, rope, concept
Reduce the level of inventory (water) to reveal the operations’ problems to managers (the ship) WIP productivity problems Scrap Rework Downtime WIP productivity problems Scrap Rework Downtime The problem with inventory WIP,Downtime Rework,unstable demand,scrap.poor floor layout,untrained operators
JIT Planning and Control Kanban Control A key method used to implement a pull-based planning and control system. Kanban – Japanese word for card or signal Card used by customer to inform supplier to send more material or product. There are different types: Move – the signal to transfer inventory to a specific destination. Production – the signal to a process that it can start producing a part. Vendor – signal to external suppliers to send material
JIT Planning and Control Kanban Control Principle is the same irrespective of what type is used – ‘Receipt of a kanban triggers the movement, production or supply of one unit or a standard container of units’. Kanban squares can also be used to trigger production.
Example -Single Card Kanban Key benefits are: Simple method to control production based upon demand. Limits the amount of inventory. Inventory reduced by reducing the number of kanbans.
KANBANS Formula to determine the number of kanbans (N) required in a system: N = (R*T*(1+X))/C Where: R is the utilisation rate for the components (units/hr) T is the delay in receiving a container (production, transfer and waiting time) (hr) C is the capacity of the container, i.e. number of units X is the variation in the operation expressed as %
KANBANS – MAY 2011 exam b) Calculate the number of Kanbans a company requires for the following situation and the relative inventory level. (5) Utilisation rate = 850/hr Delay time = 60 mins Capacity = 50 units Operation Variation = 12% c) The following options have been proposed to reduce the inventory level for the situation outlined in (b). Which option would you choose and why? (12) Option A: Variation rate becomes 6% Option B: The delay time is halved Option C: The capacity is increased to 250 units. The calculations for each option must be shown.
Unit 2:Lesson 9Maintenance Strategies
Maintenance There are three basic approaches to maintenance: Run to Breakdown (RTB) Preventive Maintenance (PM) Condition Based Monitoring (CBM)
Run to Breakdown Allow the equipment to run until it fails. Maintenance work performed only when failure has taken place Can be used when failure is not critical, but is often used as the main maintenance approach in a lot of organisations, particular SMEs. Examples of equipment that might be allowed to ‘Run to breakdown’ Telephone, lightbulb, non-critical pump or motor
Preventive Maintenance Attempts to reduce the chance of failure by servicing the equipment at pre-planned intervals. Servicing can include cleaning, lubricating, replacing and checking. Examples include, regular cleaning and lubricating of machine tools. Often managed using a computerised maintenance management system (CMMS) Based prescribed examination procedures/checklists Equipment generally needs to be out of service whilst inspections and work is carried out
Condition based monitoring Attempts to identify when maintenance on the equipment is needed. Achieved through measuring the ‘condition’ of the machine This could be simple measurements, temperature, pressure, current, voltage etc. or more sophisticated techniques such as: Vibration analysis Thermography Oil analysis The results of these approaches would be analysed to determine whether any maintenance action was required.
Unit 2: Lesson 10 Maintenance Strategies
Total Productive Maintenance (TPM) Definition: ‘the productive maintenance carried out by all employees through small group activities’ Where productive maintenance is ‘ maintenance management which recognises the importance of reliability, maintenance and economic efficiency in plant design.’ Originated in Japan , seen as natural extension in the evolution from PTB to PM.
Total Productive Maintenance (TPM) Includes the following elements: Team working Empowerment Continuous Improvement Views maintenance as a company wide activity
Total Productive Maintenance (TPM) Five Pillars: Improve Equipment effectiveness: Examines all the losses associated with equipment and facilities. Down –time losses, speed losses and defect losses. OEE is a tool used to quantify this figure. Benefit - Allows the real cost of maintenance to be considered before action is taken Achieve Autonomous Maintenance Requires the operators of equipment to take some responsibility for some maintenance tasks. Benefit - Frees up maintenance personnel to do more higher- level tasks such as developing planned maintenance regimes. Three levels of involvement: Repair level Prevention level Improvement level.
Total Productive Maintenance (TPM) Plan Maintenance – Develop a maintenance strategy for all equipment. Outline the required levels of PM, where CBM is to be applied and clear responsibilities for all staff. Benefit - Decreases breakdowns due to the development and implementation of an appropriate maintenance strategy
Total Productive Maintenance (TPM) Train all staff in relevant maintenance skills – TPM requires a appropriate and continuous training programme. Benefit - other staff, in addition to maintenance are involved in the maintenance function Achieve early equipment management. Stresses maintenance prevention by early consideration of maintenance issues in machine tool design Benefit - equipment is more robust and reliable as a result of maintenance being considered during the design phase
OEE – Worked Example May 2008 a) Explain the problems that might occur when trying to use and compare OEE data between similar manufacturing plants. (5) b) Data has been collected for a machine over a number of weeks and is contained in Table 3 below. Calculate the OEE value for this resource. (15) c) Discuss the results you obtain and suggest the areas where any improvement effort should be focused. (5)
OEE – Worked Example May 2008
Process Improvement Slack et al, Operations Management; Chapter 18
Actual performance improvement with breakthrough improvement Performance Actual improvement Time
Improvement Approaches Continuous Improvement Assumes much smaller incremental improvement steps are needed. Small improvement follows small improvement. Also called kaizen. It is not the rate of improvement which is important rather the commitment to continuous improvement, i.e. ongoing.
Performance improvement with continuous improvement Performance Standardize and maintain Improvement “Continuous” improvement Time
Continuous Improvement Key concept is one of never ending questions concerning detailed operation of an activity or service. This concept is best represented by the improvement cycle. Many exist - most famous is the Deming PDCA model.
A four-step approach to problem solving Observe the test results (CHECK) Recognise the opportunity (PLAN) Test the theory to achieve the opportunity (DO) Act on the opportunity (ACTION) The Deming (Shewart) Cycle
Improvement Approaches Differences between the two approaches: Breakthrough – requires creative solutions, free thinking, clean sheet of paper, ignore constraints. CI – less ambitious in short term Not radical Builds upon experience of people who operate in existing system. Sprint v Marathon analogy
Often combine continuous/breakthrough improvement Breakthrough improvement Cumulative improvement Continuous improvement Time Combination is often preferred choice to hold the gains.
Breakthrough Most well known approach is BPR: Business Process Reengineering. BPR in its original form emerged in early 1990s in the USA, devised by Hammer & Champy (1993). BPR has a number of key concepts at its heart: JIT concepts (removal of waste), process flow, customer focused operations.
BPR Defined by Hammer & Champy as: “The fundamental rethinking radical design of business processes to achieve dramatic improvements in critical, contemporary measures of performance, such as cost, quality, service and speed.”
BPR Key belief of BPR is that operations should be organised around the total process, rather than functions. (see earlier work on process organisations)
Business process re-engineering Process structure Functional structure Process 1 Function 2 Function 3 Function 1 Customers Customers Process 2 Suppliers Suppliers Process 3
BPR Key Principles include: Business process should be cross-functional and organised around the nature of flow. Achieve dramatic improvements by radical redesign. Have those who use the output perform the process. [this means forming into a process grouping all those who contribute to the output of the process] Decision points where the work is performed. See example on pg 659-660
BPR Benefits A reduction in interface errors resulting from the reduction or removal of hand-overs between departments. A reduction in miscommunication A reduction in lead-time resulting from the reduction in the above. Clear and unambiguous process scope – so every process knows what exactly they are expected to do and what others are expected to do. One point of contact with external bodies such as customers and suppliers Each process has a process owner who has complete authority over the process and makes decisions without consulting others. Clear responsibility and ownership of the process by the process owner and their team.
BPR Literature Al-Mashari et al (2000) have provided a comprehensive literature review of BPR, which includes: BPR is best defined by: It’s focus on business processes It’s radicalness It’s use of IT as a ‘tool’ and ‘enabler’ It’s resulting need for organisational change
Key differences between CI and BPR Approach- CI small projects – little impact, BPR one big project, big impact. CI is largely a group effort where change is gradual and constant, BPR is intermittent and non –incremental and is based on individualism and effort. Risk - BPR: High, as major changes to organisation as it radically changes what the organisation does and how it does it. High financial cost. CI: low risk and spread over many projects, each being low investment and impact on organisation. Cost - BPR: high due to cost of change and cost of team, CI: low as little investment needed as small scale.
Key differences between CI and BPR If there is only a small gap to be made up in performance, i.e. 2-3 % in a particular area, then CI is the most suitable On the other hand, if the gap is very large, say upwards of 50%, then BPR will most probably be needed to make up this performance gap in a short space of time.