Note : Answer all the questions and submit this assignment on or before April 30, 2012, to the coordinator of your study center.
Q1.Discuss GT, FMS and OPT and their importance for improving the performance of production system.
Solution: GT importance for improving the performance of production system.FMS
Group Technology (GT) based production system should form an important strategy for developing countries like India presently characterised by poor performance and declining profitability of a number of public sector enterprises. If workers as well as managers have no sense of belonging to a social unit and adopt an attitude of confrontation with each other and the capacity utilisation of these enterprises is unsatisfactory, these are to be seen in the light of their working in systems which are most inappropriate and inefficient. Group Technology represents a major breakthrough in the economic management through a more efficient utilisation of the country's available capacity, resources, capital, services and production facilities. The hope to achieve a higher growth rate lies in this vital system of production particularly for the developing nations which cannot afford the capital intensive machining centres. The paper gives a brief account of Group Technology applications in India and highlights the potential beenfits of its introduction in a multiproduct engineering industry.
FMS importance for improving the performance of production system.
The flexible automation is applicable to a variety of manufacturing operations. According to Yang, et al (2002), FMS technology is most widely applied in machining operations. FMS technology combines the capabilities of the transfer lines for high volume low variety work on the one hand and stands alone CNC machines for mid to low volume high variety production on the other.
Following are the derived benefits of FMS
Reduction of inventories
Reduction of lead times
Improved machine utilization
Reduction of labor times
Quick and uncompleted reaction to engineering and design changes
Increased management control over the entire manufacturing process.
Reduced equipment cost
Reduced floor space
High product quality
OPT importance for improving the performance of production system.
OPT's is to simultaneously raise throughput while reducing inventory and operating costs, and achieve a smooth, continuous flow of work in process. OPT build a production system capable of producing 27 million backlight units per month by the end of the present fiscal year. Going forward, the aim is to increase the monthly capacity to 55 million units by the end of fiscal 2012. Once accomplished, this system will enable OPT to establish a leading position in its industry. Based on this well-established position, OPT will continue to respond to robust market demand, promoting growth and further expanding its business.
The benefits claimed for OPT are that it will schedule finite resources in order to achieve maximum factory effectiveness.
The scheduling system:
1.Addresses the key problem of bottlenecks.
2.Improves profitability by simultaneously increasing throughput.
3.Reduces inventory and operating expenses.
Q2.How does a quantitative forecasting differ from a qualitative forecasting? How do we measure the forecasting error?
Solution: Quantitative forecasting methods are used when historical data on variables of interest are available—these methods are based on an analysis of historical data concerning the time series of the specific variable of interest and possibly other related time series. There are two major categories of quantitative forecasting methods. The first type uses the past trend of a particular variable to base the future forecast of the variable. As this category of forecasting methods simply uses time series on past data of the variable that is being forecasted, these techniques are called time series methods.The second category of quantitative forecasting techniques also uses historical data. But in forecasting future values of a variable, the forecaster examines the cause-and-effect relationships of the variable with other relevant variables such as the level of consumer confidence, changes in consumers' disposable incomes, the interest rate at which consumers can finance their spending through borrowing, and the state of the economy represented by such variables as the unemployment rate. Thus, this category of forecasting techniques uses past time series on many relevant variables to produce the forecast for the variable of interest. Forecasting techniques falling under this category are called causal methods, as the basis of such forecasting is the cause-and-effect relationship between the variable forecasted and other time series selected to help in generating the forecasts.
Qualitative forecasting techniques generally employ the judgment of experts in the appropriate field to generate forecasts. A key advantage of these procedures is that they can be applied in situations where historical data are simply not available. Moreover, even when historical data are available, significant changes in environmental conditions affecting the relevant time series may make the use of past data irrelevant and questionable in forecasting future values of the time series. Consider, for example, that historical data on gasoline sales are available. If the government then implemented a gasoline rationing program, changing the way gasoline is sold, one would have to question the validity of a gasoline sales forecast based on the past data. Qualitative forecasting methods offer a way to generate forecasts in such cases. Three important qualitative forecasting methods are: the Delphi technique, scenario writing, and the subject approach.
Q3.Discuss the relationship exists between Layout decisions, capacity decision and scheduling.
Solution: Layout decisions refer to studying various options in term of plant and machinery layout that enables smooth flow materials for smooth production.
Capacity decisions Deals with the issues pertaining to planning the capacity for the plant that enables cost competitive production even with certain degree of fluctuations in the required volumes. Capacity planning Capacity is the measure of ability to produce goods and services or it may be called as rate of output. Its seen that full capacity is never used due to certain constraints e.g. production the different constraints can be input, market demand, government.
Scheduling Organizing Work study Also known as time and motion study that aims at improving the cycle time required for producing a product.Scheduling of activities It simply means sequencing of different activities according to these importance and resources which are available.
HRM It start for recruitment, selection of employees and see that various task are being performed in the best way. Statistics and mathematics The data is collected, analyzed and interpreted as per our requirement. And its later on used to solve the problem in best possible manner. Decision area of production and operation management On the basis of function on the basis of level Technology selection and allocation strategic decisions Capacity management tactical decisions Scheduling operational decisions System maintenance On the basis of function Technology selection and management The very first decision which has to be taken in production and operation management is regarding the type of technology because in this hi-tech world it keeps on changing everyday and decisions regarding how the management has to perform its functions are taken. Capacity management The decisions has to be taken regarding the capacity as full capacity is never being used due to certain constraints and because of it they have to decide maximum capacity which can be used and how it can be managed. Scheduling or time allocation Here, as we know that a proper sequence is followed so time is divided among these activities. Time is allocated so that no activity which could be completed in les time is taking excessively more time. System maintenance Its concerned with controlling aspect. The overall maintenance of complete system is also important because any fault in one subsystem can cause a great problem in the overall result. On the basis of level Strategic decision These decision are taken at top level. Alternative manufacturing approaches and alternative approaches to automation are used. Example product selection and design, facility design, process selection and planning, capacity planning, facilities layout and material handling. Tactical decision Decision which are taken by middle level. To cope with the decisions level and also relating to factors which are out of control how to control and manage them. Example summary reports which compare overall planned or standard performance for such classification as cost per unit and labour used. Operational decisions Reports comparing actual performance to production schedule and highlighting areas where bottlenecks occur. Example production planning, production control, inventory control, method study, cost reduction control and quality control. Such decisions are taken by bottom level.
Q4.Compare and contrast PUSH type of production system with PULL type of production system and justify which one is better.
Solution: A conservation agricultural approach known as `Push-Pull' technology has been developed for integrated management of stemborers, striga weed and soil fertility. Push-pull was developed by a scientific team led by Prof. Zeyaur Khan at the International Centre of Insect Physiology and Ecology (icipe), Kenya in collaboration with Rothamsted Research, in the United Kingdom and national partners. The technology is appropriate and economical to the resource-poor smallholder farmers in the region as it is based on locally available plants, not expensive external inputs, and fits well with traditional mixed cropping systems in Africa. To date it has been adopted by over 46,000 smallholder farmers in East Africa where maize yields have increased from about 1 t/ha to 3.5 t/ha, achieved with minimal inputs.
The approach relies on a combination of companion crops to be planted around and among maize or sorghum. Both domestic and wild grasses can help to protect the crops by attracting and trapping the stemborers. The grasses are planted in the border around the maize and sorghum fields where invading adult moths become attracted to chemicals emitted by the grasses themselves. Instead of landing on the maize or sorghum plants, the insects head for what appears to be a tastier meal. These grasses provide the "pull" in the "push–pull" strategy. They also serve as a haven for the borers' natural enemies. Good trap crops include well-known grasses such as Napier grass (Pennisetum purpureum) and Sudan grass (Sorghum vulgare sudanense). Napier grass has a particularly effective way of defending itself against the pests: once attacked by a borer larva, it secrets a sticky substance which physically traps the pest and limits its damage.
The "push" in the intercropping scheme is provided by the plants that emit chemicals (kairomones) which repel stemborer moths and drive them away from the main crop (maize or sorghum). The best candidates discovered so far with the repellent properties are members of leguminous genus Desmodium spp. Desmodium is planted in between the rows of maize or sorghum. Being a low-growing plant it does not interfere with the crops' growth and, furthermore, has the advantage of maintaining soil stability, improving soil fertility through enhanced soil organic matter content and nitrogen-fixation. It also serves as a highly nutritious animal feed and effectively suppresses striga weeds. Another plant showing good repellent properties is molasses grass (Melinis minutiflora), a nutritious animal feed with tick-repelling and stemborer larval parasitoid attractive properties.
PUSH type of production system is better as it has advantage of maintaining soil stability, improving soil fertility through enhanced soil organic matter content and nitrogen-fixation
Q5.Explain the role of Master Production Schedule (MPS) in the context of overall planning and scheduling of manufacturing.
Solution: The MPS (Master Production Schedule) is the schedule program aimed at defining precisely the required quantity per period for each finished product to sell. It is the main part of the manufacturing production plan to make the supply chain work.
The bucket is usually the week and the time horizon up to 3-6 months or a least twice the longest product leadtime.The aggregate master production schedule (MPS) at product level should match with the S&OP defined at product family level and the deviation should be under 3-5% maximum to be consistent accross the supply chain.The master production schedule (MPS) is the reference for the customer service that needs to satisfy its customers, and also for the manufacturing that should plan accordingly taking into account the constraints from the entire supply chain.The Master production schedule (MPS) is established from firm customer orders, Sales forecasts and finished good stock levels and is aimed at:
Anticipate the customer demand per product (forecast)
Explode S&OP families into part numbers for each period
Input quantity to produce and deadlines for each product
Follow current Sales versus forecasts
Insure the required customer service level while maintaining a low stock level
Inform the customer service on the available-to-promise (ATP) quantity for a given product
According to the bill of material, the master production schedule (MPS) could be at different level. The idea is to define the MPS level where there are fewer components:
Low finished products variety but lots of components: MPS at finished product level
High finished products variety but few components: MPS at component level
But there can be a finished goods variety due to intensive customer personalization or customization, but a fewer components to assemble and high raw material variety.
In this case we have multiple MPS levels:
Finished goods MPS
Planned BOM with probability by components (or component types) in order to forecast the sub-assembly items to launch per period
Percentage or ratios are used to plan for components on a make-to-stock mode. Here we see that the finished good sales forecasts will be at 80% with option B1 and at 60% with module M2 but in all cases the component A is always required.
The ATP represents the products manufactured on stock and available for customer orders. This encompasses all what can be sold without modifying the MPS and allow quick responses by the supply chain organisation.
The available to promise (ATP) is a tool for the customer service to accept or not an order and to give a firm promise to the customer.
MPS time horizon
As stated before the minimum time horizon in the master production schedule (MPS) is twice the manufacturing leadtime in order to be able to plan. In most cases, planning is done for a full quarter.
But this horizon is split into 2 areas: firm and planned zone.
The firm zone corresponds to firm customer orders, usually not negotiable or modifiable. Only the manufacturing manager is allowed to accept or not any change.
We also called it the frozen horizon where all orders are frozen, in term of start date or quantity.The goal of this firm horizon is to prevent any bullwhip effect or chaotic variability that will disorganize the production lines and lower its efficiency.
The MRP-2 states that the firm horizon should be equal to twice the longest manufacturing leadtime, as when we’re getting close to the manufacturing leadtime, any change is critical since it screwed up all shop floor scheduling.
Over the frozen horizon, the orders can still be modified, or at least are negotiable. Change of customer orders is also still possible (options or customization), but subject also to manufacturing manager.
Let’s build an MPS for 8 weeks, fed with forecasts and firm orders.
Batch size = 50 units
Manufacturing Leadtime = 1 period
Safety Stock = 20 units
The first 2 weeks is the frozen horizon.
Let’s do it:
In Firm horizon:
- Inventory and ATP are calculated from sales orders only
- Inventory[P] = Inventory[P-1] + MPS_due_date[P] – sales_orders[P]
- The ATP is calculated between 2 consecutive MPS_due_date not null, intial value is equal to the initial inventory one
In Forecast horizon:
- Inventory is calculated from max(sales_orders,forecasts) in order to take into account the forecasts
- Inventory[P] = Inventory[P-1] + MPS_due_date[P] – Max(sales_orders[P];forecast[P])
- The ATP is calculated from sales orders only! (otherwise no ATP concept)
- The ATP is calculated between 2 consecutive MPS_due_date not null
ATP[next MPS>0] = ATP[last_value] + Sum(MPS_due_date)- Sum(sales_orders)
Q6.Explain the six big losses in maintenance. Suggest the methods to reduce/eliminate these losses.
Solution: Now that we know what the Six Big Losses are and some of the events that contribute to these losses, we can focus on ways to monitor and correct them. Categorizing data makes loss analysis much easier, and a key goal should be fast and efficient data collection, with data put to use throughout the day and in real-time.
Eliminating unplanned Down Time is critical to improving OEE. Other OEE Factors cannot be addressed if the process is down. It is not only important to know how much Down Time your process is experiencing (and when) but also to be able to attribute the lost time to the specific source or reason for the loss (tabulated through Reason Codes). With Down Time and Reason Code data tabulated, Root Cause Analysis is applied starting with the most severe loss categories.
Setup and Adjustments
Setup and Adjustment time is generally measured as the time between the last good part produced before Setup to the first consistent good parts produced after Setup. This often includes substantial adjustment and/or warm-up time in order to consistently produce parts that meet quality standards.Tracking Setup Time is critical to reducing this loss, together with an active program to reduce this time (such as an SMED - Single Minute Exchange of Dies program).Many companies use creative methods of reducing Setup Time including assembling changeover carts with all tools and supplies necessary for the changeover in one place, pinned or marked settings so that coarse adjustments are no longer necessary, and use of prefabricated setup gauges.
Small Stops and Reduced Speed
Small Stops and Reduced Speed are the most difficult of the Six Big Losses to monitor and record. Cycle Time Analysis should be utilized to pinpoint these loss types. In most processes recording data for Cycle Time Analysis needs to be automated since cycles are quick and repetitive events that do not leave adequate time for manual data-logging.By comparing all completed cycles to the Ideal Cycle Time and filtering the data through a Small Stop Threshold and Reduced Speed Threshold the errant cycles can be automatically categorized for analysis. The reason for analyzing Small Stops separately from Reduced Speed is that the root causes are typically very different, as can be seen from the Event Examples in the previous table.
Startup Rejects and Production Rejects
Startup Rejects and Production Rejects are differentiated, since often the root causes are different between startup and steady-state production. Parts that require rework of any kind should be considered rejects. Tracking when rejects occur during a shift and/or job run can help pinpoint potential causes, and in many cases patterns will be discovered.
The Methods to Eliminate These Losses.
First, identify all components that are candidates for proactive maintenance:
Identify and document all components that undergo wear (these should have been established as inspection points in Step Two). Consider replacing wear components with low-wear or no-wear versions.
Identify and document all components that are known to regularly fail.
Consider utilizing thermography and/or vibration analysis to provide additional insights as to equipment stress points.
Next, establish initial proactive maintenance intervals:
For wear components, establish the current wear level and a baseline replacement interval (in some cases replacement may be triggered early by an Autonomous Maintenance inspection as established in Step Two).
For failure-prone components, establish a baseline (predicted) failure interval.
Create a baseline Planned Maintenance Schedule that schedules proactive replacement of all wear and failure-prone components. Consider using “Run Time” rather than “Calendar Time” as the interval time base. Create a standard process for generating Work Orders based on the Planned Maintenance Schedule.
Next, create a feedback system for optimizing the maintenance intervals:
Create a Component Log sheet for each wear and failure-prone component. Record every instance of replacement, along with information about the component condition at the time of replacement (e.g. wear amount, “component failed”, “no observable issues”, etc.).
Perform a monthly Planned Maintenance audit: a) verify that the Planned Maintenance Schedule is being followed, b) verify that the Component Log sheets are being maintained, and c) review all new entries in the Component Log and adjust maintenance intervals where appropriate. Keep audits positive and motivational (treat them as a training exercise).
Anytime there is an unscheduled component replacement, consider adjusting the maintenance interval. If the component is not on the Planned Maintenance Schedule, consider adding it.
Consider plotting data over time from thermography and vibration analysis to expose emerging problems and issues.