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Thursday, November 13, 2008
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BENEFITS OF PRODUCTION SCHEDULING
BENEFITS OF PRODUCTION SCHEDULING
There are some goals and benefits of production scheduling:
- A production schedule can determine whether delivery promises can be met and identify time periods available for preventive maintenance.
- A production schedule gives shop floor personnel an explicit statement of what should be done so that supervisors and managers can measure their performance.
- Minimize WIP inventory
- Minimize average flow time through the system
- Maximize machine and/or worker utilization
- Minimize setup times
- A production schedule can identify resource conflicts, control the release of jobs to the shop, and ensure that required raw materials are ordered in time.
- Better coordination to increase productivity and minimizing operating costs.
ORDER MANAGEMENT AND SCHEDULING
Order management is a vital issue on make-to-order systems. Pinedo [5] illustrated the way and how an order is processed via capacity planning, scheduling, and dispatching activities to shop floor management.
Key decisions in different stages of order management, production planning, andoperations scheduling (OMPPOS) process(From Kemppainen [9] which based on Pinedo [5])
Order management is closely related with production capacity, current production utilization level, customer priority, and due date based prizing. Some of the customers may have an agreement with the company then we can give high priority according to this agreement. Utilization of resources is done by considering these factors [5]. While accepting an order it is possible to give range of prizes based on time and current state of the production level.
THE GAP BETWEEN THEORY AND PRACTICE
Application of computer based schedules are very scarce. Pinedo[6]
In spite of the fact that during this last decade many companies have made large investments in the development as well as in the implementation of scheduling systems, not that many systems appear to be used on a regular basis. Systems, after being implemented, often remain in use for only a limited amount of time; after a while they often are, for one reason or another, ignored altogether. (p. 2151).
Real world is somehow different than idealized computer models so there are some fuzzy constraints, lack of accurate information and, sudden changes. Berlung [7] stated in their paper: “Outcome of the scheduling process is influenced by the scheduler adding human capabilities that cannot be automated, problem-solving when the technical system fails, and negotiating between groups of employees to handle incompatible goals. Technology influences by limitations in the scheduled production system as well as the scheduling tools available. The organization, finally, influences the outcome through degree of proximity between employees, meeting structures, the schedulers’ position in hierarchy and their work role interconnecting activities of different organizational parts.” Also, Wiers [8] presented applicability of operations research and artificial intelligence techniques and their shortcomings in practice:
1. Robustness. Robustness refers to the extent to which a schedule will remain unchanged when the information on which a schedule is based changes. Robustness avoids nervousness in scheduling in situations with uncertainty. Most authors recognize that nervousness should be avoided as much as possible.
2. Complexity. Complexity is an oft used construct, and can be defined in many ways. In this context, complexity refers to the number of real world elements that are relevant for the scheduling problem, and the relationships between these elements. Some of the issues mentioned in this chapter are linked to the complexity of the problem, such as: oversimplification, and knowledge of the problem domain.
3. Performance measurement. The optimization criteria of many scheduling techniques do not meet the criteria used in practice. In practice, performance is often a matter of judgment by the human scheduler, and can be subject to negotiation.
4. Fixed vs. changeable input. Most scheduling techniques assume that information input is a given and cannot be changed. However, in practice, the situation is often not taken for granted: inputs, such as available capacity, might be changed if judged necessary.
5. Organizational embedding. The relationship of scheduling decision making to other parts of an organization is generally not considered in scheduling techniques.
6. Availability and accuracy of data. The scheduling process predominantly depends on the availability of accurate data. If this condition is not met, the schedule will be incorrect and cannot be executed properly.
7. Interaction with human scheduler. It is recognized by many authors that the human scheduler will remain an indispensable factor in the scheduling process. However, many techniques do not account for interaction with the human scheduler.
8. Learning from experience (artificial intelligence techniques). The intelligence that is built into artificial intelligence scheduling techniques is often not stable in practice. Therefore, these systems should learn from experience to keep their intelligence base up to date. However, most artificial intelligence scheduling techniques are not able to learn from experience, and therefore may become outdated.
9. Availability and reliability of human experts (artificial intelligence techniques). The intelligence of AI based scheduling systems sometimes comprises expertise that must be elicited from human experts. However, in many cases, this expertise cannot be adequately acquired.
[1] Bitran G. R., (1983),A Simulation Model for Job Shop Modeling, A. P. Sloan School of Management Massachusetts Institute of Technology
[2] Hermann, J., W., (2006) Improving Production Scheduling: Integrating Organizational, Decision-Making, and Problem-Solving Perspectives, Industrial Engineering Research Conference, Orlando, Florida
[3] Bayındır, Z., P., (2005) EIN 4333 Production and Distribution Systems class notes.
[4] Barták, R., (1999), On the Boundary of Planning and Scheduling: A Study, Proceedings of Eighteenth Workshop of the UK Planning and Scheduling Special Interest Group (PLANSIG99)Workshop,
[5] Pinedo, M. (1995), Scheduling: theory, algorithms, and systems, Prentice-Hall, Englewood Cliffs, New Jersey.
[6] Pinedo, M. (1992). Scheduling. In G. Salvendy (Ed.), Handbook of Industrial Engineering (2ndedition). Chichester: Wiley.Interscience.
[7] Berlung, B., Karltun, J.,(2005), Human, Technological and Organizational Aspects Influencing the Production Scheduling Process, 18th International Conference on Production Research
[8]Wiers,V., (1997) ,Human-computer interaction in production scheduling-Analysis and design of decision support systems for production scheduling tasks ,Eindhoven, The Netherlands: Eindhoven University of Technology Press, Ph.D. Thesis.
[9] Kemppainen, K.,(2005) Priority Scheduling Revisited –Dominant Rules, Open Protocols, And Integrated Order Management
WHAT IS PRODUCTION SCHEDULING?
WHAT IS PRODUCTION SCHEDULING?
Scheduling concerns the allocation of limited resources to tasks over time. Bitran [1]explained “Production scheduling is concerned with the allocation of resources and the sequencing of tasks to produce goods and services. Although allocation and sequencing decisions are closely related, it is very difficult to model mathematically the interaction between them. However, by using a hierarchical approach, the allocation and the sequencing problems can be solved separately. The allocation problem is solved first and its results are supplied as inputs to the sequencing problem. The resource allocation problem can sometimes be solved using aggregate production planning techniques. To specify completely the input to the sequencing problem, the resulting detailed or item plan (also referred to as the master schedule) has to be disaggregated. A breakdown by component parts can be obtained in a straightforward way by using Material Requirements Planning (MRP) systems. Although MRP continues to be popular in practice, many issues still need to be resolved to make it an effective production planning tool.”
Because of complexity of production scheduling there are different views of it [2].
Problem Solving Perspective views the scheduling as an optimization problem. It is the formulation of scheduling as a combinatorial optimization problem isolated form the manufacturing planning and control system place.
Decision making Perspective is the view that scheduling is a decision that a human must make. Schedulers perform a variety of tasks and use both formal and informal information to accomplish these. Schedulers must address uncertainty, manage bottlenecks, and anticipate the problems that people cause
Organizational Perspective: is a systems-level view that scheduling is part of the complex flow of information and decision-making that forms the manufacturing planning and control system. Such systems are typically divided into modules that perform different functions such as aggregate planning and material requirements planning
Production scheduling can be classified according to the following criteria [3]:
1. Flow patterns
(a) Flow shop: All the jobs have identical process flows and require the same sequence of
operations.
(b) Job shop: Jobs have different process flows, and may require significantly different sequence
of operations.
2. Processing mode
(a) Unit processing: Jobs are processed one by one.
(b) Batch processing: A number of jobs are processed together as a batch.
3. Job release pattern (job release time is the earliest time at which processing can start)
(a) Static: Jobs are (or assumed to be) released to the shop floor at time zero.
(b) Dynamic: Jobs are (or assumed to be) released to the shop floor over time.
4. Work center configuration
(a) Single machine
(b) Identical parallel machines:
(c) Uniform parallel machines:
(d) Unrelated parallel machines:
DIFFERENCE BETWEEN PRODUCTION PLANNING AND PRODUCTION SCHEDULING
Barták[4] stated that “the main difference is in the resolution of the resulting plan or schedule. While the industrial planning deals with the task of finding “rough” plans for longer period of time where activities are assigned to departments etc., the industrial scheduling deals with the task of finding detail schedules for individual machines for shorter period of time. From this point of view, scheduling can be seen as a high-resolution short-term planning.”
Planning and scheduling in industry
Hierarchical Planning
Barták[4] also defines a new mixed planning and scheduling approach in his paper.
Wednesday, November 12, 2008
Sniffly Surfing: Google Unveils Flu-Bug Tracker
Sniffly Surfing: Google Unveils Flu-Bug Tracker
By ROBERT A. GUTH
http://online.wsj.com/article/SB122644309498518615.html
You can Google to get a hotel, find a flight and buy a book. Now you may be able to use Google to avoid the flu.
One month into flu season, Google Inc. on Tuesday opened a free Web service that the Internet company says can show if the number of influenza cases is increasing in areas around the U.S., earlier than many existing methods.
![[Google Unveils Flu-Bug Tracker]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_uK2n8l6c107pcr4DZdxuJnaLO8YyIhMbN9fBjTBegNbFVgrKLPfAGptGf8RX7s6BMdg6kyrhBQqd9G7cMkbOUAb6oLh6INPV3ADeVXPkuBtpc7xM60IRUUynpXwiZGF7NbqGUJAQ0PyDy1LMr4QIoI1A=s0-d)
A screen shot from Google's Flu Trends site.
The service, called Flu Trends (www.google.org/flutrends), uses computers to crunch millions of Internet searches people make for keywords that might be related to the flu -- for instance "cough," or "fever." It displays the results on a map of the U.S. and shows a chart of changes in flu activity around the country. The data is meaningful because the Google arm that created Flu Trends found a strong correlation between the number of Internet searches related to the flu and the number of people reporting flu symptoms.
Google built the service with the guidance of the Centers for Disease Control and Prevention, the U.S. government's public-health watchdog that runs a range of flu-surveillance systems. Flu Trends can be a complement to those tools, health officials say.
Flu Trends "maps very closely to the influenza-like trends that we see in the U.S.," says Lyn Finelli, lead of the influenza surveillance team at CDC's headquarters in Atlanta.
The service adds Google to a growing number of Web sites that are trolling, culling and crunching Internet data in ways to better pinpoint and predict where diseases are hitting around the world. The sites use varying degrees of human and computer methods for detecting outbreaks and many have historically been aimed at doctors and health-care professionals. Google executives say their service could also appeal to consumers.
In any given year, between 5% and 20% of Americans can catch the flu, depending upon the strength of a particular flu virus and other factors, the CDC says. Around 145 million doses of flu vaccines will be available this flu season, which generally runs from October to May and typically peaks in February.
Finding a new tool to stave off infection is important to Maureen Rinehart, a 28-year-old kindergarten teacher in San Francisco. Ms. Rinehart says daily contact with her kids means she gets sick about once a month. She got a flu shot about two weeks ago and is armed with hand sanitizer in the classroom.
"They're really snotty and they want to hold hands with you; you know how it is with the little guys," says Ms. Rinehart. So if the Google service shows flu cases are rising, she says, "you could bulk up on vitamins and wash your hands more -- all the necessary things you should do."
The Google service is the brainchild of Google.org, a three-year-old group at the Mountain View, Calif., company that works on areas for the public good -- such as renewable energy -- that may or may not have a direct financial benefit to Google. The company won't use advertising on the Flu Trends site.
The Google group examined flu-related keywords over five years, noting times when searches of those terms surged. It then compared those times to CDC records and found a strong correlation between when people searched flu keywords and when people have had flu-like symptoms. It spent the past year testing new search results against data from the CDC, tweaking its software to make its results more accurate, Google executives said.
The Flu Trends site displays results of its analysis in a five-tier scale of flu activity ranging from "minimal" to "intense," with a middle point of "moderate." The site includes CDC flu prevention messages, a flu vaccination locator and links to flu-related news items.
"It's still quite experimental," says Jeremy Ginsberg, Google's lead engineer on Flu Trends. "We feel it's an interesting, unique way to track disease outbreaks."
In 2003, the Canadian government and other organizations used versions of these data-collection and health sites to detect early signs of the SARS virus in China. The Canadian service -- the Global Public Health Intelligence Network -- automatically scans Web sites and news sources in seven languages for information on disease outbreaks, contaminated food and water, natural disasters and other health risks around the world. It charges a fee based on the type of organization that accesses it and its usage.
At Harvard Medical School's Children's Hospital Boston, a site called HealthMap crawls through 24,000 Web sites looking for disease-related terms. Results appear on a world map, which has colored markers for dengue fever, avian flu and other diseases.
Google.org last month started funding HealthMap to find ways to collaborate with ProMED, a site that uses people to gather clues about diseases from the Web and from other sources.
The Web-based services have shortcomings. The most accurate way to measure a disease outbreak is by the number of actual cases confirmed by a laboratory. By tracking keywords in news stories and search results, the Web sites can't guarantee that they are finding actual outbreaks.
But what they lose in accuracy, the sites may make up in speed. Getting accurate data on real disease cases requires people to be tested for a disease and that data to be collected by public-health organizations. While the CDC and other organizations do this kind of research, it takes time.
Reducing that time is crucial for combating influenza, which can manifest itself one to three days after a person comes into contact with the virus. "If you get data that's not very timely one or two weeks old it's possible that the outbreak has already peaked," the CDC's Ms. Finelli says.
Still, some consumers question how helpful the new Google health service will be for them. Tony Deen, a 22-year-old recent college grad in San Francisco, says he hasn't had the flu since he was a kid and uses health Web sites only when he has a medical problem. "It's not like I can flee the city if the flu is coming," Mr. Deen says. But "it might convince me to get a flu shot if people are getting sick."
Write to Robert A. Guth at rob.guth@wsj.com
A screen shot from Google's Flu Trends site.
GM: The Threat of Bankruptcy
November 12, 2008, 12:01AM EST
GM: The Threat of Bankruptcy
GM's senior management, business experts, and some members of Congress think letting the automaker go Chapter 11 would be a disaster
GM Chairman and CEO G. Richard Wagoner Jr. Getty Images
Over the past several days, whileGeneral Motors (GM) Chairman and Chief Executive G. Richard Wagoner Jr. has repeated his mantra that "bankruptcy is not an option," the specter of a Chapter 11 reorganization is circling GM's downtown Detroit headquarters like vultures.
When it reported its third-quarter earnings on Nov. 7, GM said that it may face cash reserve levels(BusinessWeek.com, 11/7/08) by the New Year that would put it at the threshold needed just to meet payroll and continue some level of normal operations.
It has already suspended most of its future product programs. It has stepped up the pressure on the White House and Congress, especially the Michigan caucus, to find a way to get government help. "The third-quarter results made it clear that, without government intervention, GM is headed for bankruptcy," Gimme Credit auto analyst Shelly Lombard said.
CIRCUIT CITY ISN'T A MODEL
Bankruptcy lawyers say the automaker could benefit from a prepackaged bankruptcy, which would be a reorganization that is worked out among the automaker's creditors before the case ever gets to a bankruptcy court judge. "It would be messy but ultimately could help the company restructure itself a lot faster," says Mark Bane, a partner at New York law firm Ropes & Gray.
The biggest obstacle to any bankruptcy is the lack of availability of debtor-in-possession (DIP) financing, which is liquidity normally provided by banks and private equity firms that a company in bankruptcy needs to reorganize itself. Indeed, the question of bankruptcy has been on the minds of GM's top executives. On Nov. 6, GM North America President Troy Clarke told a gathering of auto suppliers that obtaining DIP financing would be "practically impossible" given the state of the credit markets and the size of GM's obligations. "But that's where the government could come in," says attorney Bane, "providing the liquidity GM would need to massively reorganize under Chapter 11."
The worst-case scenario for GM, say most experts, is a spontaneous Chapter 11, like the one filed by electronics retailer Circuit City (CCTYQ.PK) on Nov. 10. But a prepackaged filing could be set up to make sure that the vast majority of auto suppliers would continue to get paid on time.
HOPING FOR LIQUIDITY
Others disagree. Kimberly Rodriguez, a partner at Grant Thornton, an accounting and management consulting firm that works with auto companies and suppliers, says bankruptcy is a "last resort." Rodriguez says that in better times GM and Ford (F) have provided liquidity to its biggest suppliers who would have otherwise been forced into Chapter 11, which is very messy and destructive. "The government could play that same role for GM, and it will be a lot more orderly," says Rodriguez.
Aides to House Speaker Nancy Pelosi (D-Calif.) said on Tuesday, Nov. 11, that the Speaker, whose congressional district is in San Francisco, is working up a bill with House leadership that would help automakers and suppliers with liquidity to avoid bankruptcy. President-elect Barack Obama's transition chief, John Podesta, told reporters Tuesday that he is in favor of helping the auto companies "remain independent."
Robert Reich, former Labor Secretary under President Bill Clinton and a member of Obama's economic transition team, said Tuesday: "The question [about bailing out the U.S. automakers] is what kind of conditions do you put on that bailout?" In an interview on MSNBC, Reich said that those conditions will likely center on job protections and commitments to green technology. A congressional staffer with knowledge of negotiations on Capitol Hill said limits on executive compensation at the automakers is "probably going to be a condition as well."
"BUY" RECOMMENDATION ON BONDS
After a few days of dire Wall Street warnings about GM and forecasts of possible bankruptcy that drove GM stock down 33% from Friday to Tuesday's close, JPMorgan Chase (JPM) issued a "buy" recommendation on GM's bonds, not its stock, and spotlighted different sources of liquidity it can tap.
"We believe GM has several sources of liquidity it can access to bridge the company to 2010 when it realizes considerable cost cuts," JPMorgan Chase analysts Eric Selle and Atiba Edwards said in a report issued Tuesday. "These include an overfunded pension plan, possible asset sales, capital market transactions, equity injections, cost-cutting, and government loans," they said. Participation by the government could help free up an additional $10 billion, said one source at GM, from banks and equity holders who are sitting on the sidelines waiting for the government to act. GM executives believe they must have $10 billion to $15 billion in government loans to get through 2010 if auto industry sales in 2009 are below the 13 million forecast by some firms.
Certainly, there is a history of companies operating under Chapter 11, and emerging. United Airlines and LTV Steel—now known as Cliffs Erie are examples. But there are several reasons why GM is avoiding the option.
BANKRUPTCY WOULD KILL SALES
Chief among them is GM's belief that customers who own GM vehicles, as well as those who might consider them in the near future, would flee the companies' brands if it were in bankruptcy. In the past, when GM has been associated with the specter of a bankruptcy filing, showroom traffic drops off. During an interview with Fox Business News on Nov. 7, Wagoner said that GM's research shows that 80% of those surveyed said they wouldn't buy a car from a bankrupt car company. "If your revenue line falls, you would not be talking about a reorganization, you would be talking about a liquidation."
Some experts agree with Wagoner's assessment. Eric Dezenhall, a crisis management consultant, says the consumer doesn't always act rationally even after he has all the information. "Even though bankruptcy doesn't necessarily mean obliteration, these decisions aren't entirely rational…In the minds of many, bankruptcy equals oblivion," he said.
Still, it's tempting to find out if a coordinated communication effort between GM, Congress, and the White House could persuade consumers that GM would remain in business. Under Chapter 11, the company could renegotiate contracts with the United Auto Workers and more rapidly realign and kill superfluous brands without worry about lawsuits from its dealers. "I can envision a very efficient GM operating Chevrolet, Cadillac, and a third sales channel that sells GMC and Saturn," says independent marketing consultant Dennis Keene. "The aim of GM should be to get to the structure it would choose if it was starting with a clean sheet of paper, and that doesn't, I would think, include Saab, Pontiac, Buick, and Hummer."
NEGATIVE STOCKHOLDER EQUITY
GM spokesman Tony Cervone says that kind of speculation is simplistic. He notes that GM has already made huge gains in cost reductions with labor that will start paying off in 2010. "Our cost of sales will be 25%, and that is better than Toyota is today," said Cervone.
GM, in the most recent quarter, has a negative $58 million in stockholder equity on its balance sheet. That's how much the liabilities exceed its assets. That compares with negative $42 billion it reported a year ago.
The aspect of a GM bankruptcy that worries some analysts and legislators is the ripple effect that would impact Ford and Chrysler as well as numerous auto suppliers. Grant Thornton's Rodriguez says that Ford and Chrysler, in the event of a GM bankruptcy, would also be quickly driven to bankruptcy court because their costs would be so much higher than GM's, "they'd quickly find themselves uncompetitive." Too, there could be such a disruption to auto suppliers that the auto companies' production of vehicles would be interrupted as if their workers were on strike. Seventy percent of GM's suppliers also supply critical parts to Ford and Chrysler, and there is no new credit or loans for those companies outside of the government.
A LITTLE BREATHING ROOM
The best-case scenario, says Rodriguez, is for government loans that give GM the time and space it needs to work through the recession, the way a bankruptcy court gives relief from creditors.
"The Detroit automakers have, in essence, been pursuing an out-of-court restructuring over the past three years. These efforts have produced a competitive labor contract with the UAW, a viable solution to reduce retiree health-care expense, and a substantial downsizing of capacity and headcount," analyst Kid Penniman of independent research firm KDP Advisors wrote in a report. "Incremental gains achieved through bankruptcy would be minimal in comparison and would likely result in an even further deterioration of enterprise values as consumers would be far less likely to purchase an expensive vehicle from a bankrupt manufacturer, with or without government guarantees," he added.
Kiley is a senior correspondent in BusinessWeek's Detroit bureau.
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