Chapter 17 – Page 2 – The OM Blog by Heizer, Render, & Munson

Guest Post: Safety and Maintenance at the DC Metro

Professor Howard Weiss, creator of our Excel OM and POM for Windows software, provides his monthly guest post.

The Maintenance chapter of your Heizer/Render/Munson text points out that “poor maintenance can be disruptive, inconvenient, wasteful and expensive in dollars and even in lives”. The Washington DC metro is a prime example of this situation. Last month, a DC Metro train derailed. Fortunately, only one of the 187 passengers was hospitalized. The derailment was caused because the original specifications for manufacturing the wheels for the most recently purchased cars, the 7000 series, were not correct. The new cars went into service in 2015 and have been received in batches since then.

The Metro agency had received approximately 470 7000-series railcars by the end of 2017, 610 by the end of 2018, around 730 by the end of 2019, and all 748 delivered by the end of 2020. Correspondingly, as more 7000 series cars entered the system, the failure rate on the axles has increased from .01% in 2017 to 1.3% in 2021. Typically, about 150 cars are in maintenance on any day but due to the derailment, all 748 of the newest cars were pulled from service causing the Metro to operate with only 22% of its fleet.

Your text notes that to improve reliability individual components should be improved. This was the case with the cars in that the specifications improved for the most recent batch of cars that were delivered. The book also notes that improving preventive maintenance is useful. This is what the Metro is now doing for the 748 cars removed from service.

Classroom discussion questions:

How might the Metro increase its car capacity during this inspection time.
What are the repercussions of the fleet being reduced to 22% of normal?

OM in the News: The Exploding Tesla

The San Francisco home burns after 2 Tesla Model S sedans erupted in flames in the garage.

Automakers face numerous challenges as they race to get electric vehicles to consumers ahead of regulatory and company deadlines for shifting production away from gas-powered vehicles. They face skepticism about the availability of charging stations, concerns about vehicle range and apprehensions over cost. Fires have drawn attention because of the high-profile recalls and blazes that followed product rollouts, writes The Washington Post (Aug. 4, 2021), further complicating the automakers’ calculations.

In San Francisco, a Tesla Model S (the expensive one) blew up in the owner’s garage, set fire to their second Tesla, and destroyed the million dollar home. “Gasoline driven cars don’t catch fire in the garage when they’re sitting there. And that’s the difference,” said the owner who has since witched brands. “I don’t worry about my Audi catching fire downstairs when it’s not running.”

The fire is one in a string of recent examples showing what can happen when electric cars are left parked in garages to charge overnight. The issue is causing mounting concern as a number of EV makers have warned owners not to leave the cars charging unattended in certain circumstances, or sitting fully charged in garages. “Battery fires can take up to 24 hours to extinguish,” Tesla’s website says. “Consider allowing the battery to burn while protecting exposures.”

Automakers including GM, Audi and Hyundai have recalled EVs over fire risks in recent years and have warned of the associated dangers. Chevrolet advised owners not to charge their vehicles overnight or keep their fully charged vehicles in garages. It recalled more than 60,000 of its Bolt EVs over concerns about the cars spontaneously combusting while parked with full batteries or charging, after reports of 5 fires. Hyundai advised owners to lower the maximum state of charge in their vehicles to 80%, and park outside until the state of charge is lowered. Battery-powered vehicles have not been shown to catch fire at rates higher than gasoline cars, but when fires do erupt, they burn longer and hotter, propelled by lithium-ion batteries that supercharge the blazes.

Classroom discussion questions:

Will incidents like this impact the transition to EVs?
How is this an issue for operations managers?

Guest Post: The Tesla Recall

Prof. Howard Weiss, recently retired from Temple U., shares his stimulating insights monthly on our blog.

Tesla is about to recall 135,000 automobiles, reports The Wall Street Journal (Feb. 2, 2021). Recalls occur after delivery of an item to a customer and as noted in Chapter 6’s “Cost of Quality” section in your textbook, their external failure costs can be extremely expensive. In particular, this recall means that the direct costs to Tesla will include the “cumbersome physical repair” (according to Tesla); the cost of the computer chip that needs to be replaced; the cost of reimbursement for the 23,000 owners who paid out of pocket for the repair prior to the recall; and the cost of informing Tesla’s service centers and owners about the recall. Your text also notes that there may also be a loss of goodwill or possibly liability costs.

The Tesla recall has to do with the touch screen control. Its failure can impact many different features, including backup cameras, defog and defrost controls, turn signals, heat and air-conditioning. Tesla claims that the touch screen should last 5-6 years. This is analogous to the Mean Time Between Failures (MTBF) in Chapter 17’s discussion of Reliability. But the National Highway Traffic Safety Administration (NHTSA) expects the touchscreen to last “at least the useful life of the vehicle.”

Tesla, of course, is not the only automobile manufacturer to experience recalls. According to NHTSA, from 2000 to 2019 there have been 14,791 vehicle recalls in the U.S. affecting roughly 680,000,000 vehicles. Over 90% of the recalls were for safety reasons whereas the other recalls were for non-compliance with federal standards. Manufacturers voluntarily initiated 80% of these recalls, while the remainder were instigated by the NHTSA.

Classroom discussion questions:

Have you been affected by the recall of any product?
What will be the major cost to Tesla for this recall?

OM in the News: The Boeing 737 MAX and Reliability

The troubled (and grounded) Boeing 737 MAX, as widely reported, included a new system (MCAS) that automatically deployed when a single sensor detected the danger of a stall. MCAS strongly pushed the nose of the plane down, and pilots could not successfully countermand the activation unless they turned MCAS off. Astoundingly, writes MIT Prof. Arnold Barnett in OR/MS Today (Oct., 2019), “Boeing told airlines nothing about the existence of MCAS, let alone about the procedure to disable it.” Put bluntly, says Barnett, “MCAS was directly responsible for two fatal crashes, Lion Air Flight 610 in Indonesia and Ethiopian Airlines Flight 302.”

Why did Boeing initially say nothing about MCAS? The dependence on one sensor violates the principle of redundancy, under which no single failure can cause the loss of the aircraft. Boeing argued that redundancy did exist: the pilots (who were not even told of the existence of MCAS) were the backup system that would disable an improperly deployed MCAS.

There were actually 2 angle-of-attack sensors on the MAX, one of which did not affect MCAS. Boeing devised a cockpit warning light that would come on if the 2 sensors gave highly divergent readings. But a production error meant that the light that was supposedly a standard feature of the MAX could never come on, except when the airline customer bought some optional equipment. Boeing discovered the error in 2017 but did not mention it to airlines until after the first MAX crash a year later.

Now Boeing is fixing the problems with MCAS, with 2 sensors. If one detects a dangerous tilt while the other does not, MCAS will not deploy. But what if the erroneous sensor is the one that says things are normal? More prudent is the policy followed by Airbus, which uses 3 sensors and goes with the majority when there is disagreement. “Given that the feature is standard on Airbus planes,” writes Barnett, “it is far from obvious that having 3 sensors is infeasible or prohibitively expensive.”

Classroom discussion questions:

Which formula in Ch. 17 (Maintenance and Reliability) applies to this issue?
What impact on airline scheduling is the MAX grounding having?

OM in the News: Using AI to Keep Trucks on the Road

“In the trucking industry, few things will sour a manager’s mood like a mechanical failure disabling an 18-wheel rig in the middle of a big delivery,” writes The Wall Street Journal (March 12, 2019). But if mechanics can predict when a pump or cable or other component is about to fail, they can avoid having a truck stuck on the side of the road.

NFI Industries Inc., a $2 billion N.J.-based company, is using artificial intelligence to anticipate when the truck components in its 2,200 tractors and 9,700 trailers need adjusting or replacing. By predicting maintenance and reducing malfunctions, NFI expects to reduce truck maintenance and repair costs by 7%, or $1.5-$2 million a year.

NFI’s data is taken from truck sensors, odometers, speedometers, repair logs, temperature logs and other sources. The information collected includes truck ages, route distances, payload weights, weather conditions, driving conditions, and even the braking and accelerating styles of individual drivers. That data is analyzed by Noodle.ai, a San Francisco startup that pushes the information through a supercomputer nicknamed The Beast. Noodle.ai’s machine learning technology synthesizes the disparate bits of data to determine when a $100,000 rig needs an oil change, a filter replacement, a brake adjustment or a new set of tires.

As a result, NFI is jettisoning a sacrosanct industry ritual: regular truck maintenance and mandatory oil changes every 30,000 miles. Instead, the company is switching to less frequent tuneups, as prescribed by AI, that are based on a truck’s age, wear, driving conditions and a host of other factors. NFI’s trucks break down about twice a year, on average. The company expects predictive maintenance to reduce those mishaps to 1.5 breakdowns a year per truck. Among the surprising insights AI has produced: NFI had been procuring a truck model from a manufacturer that offered a $10,000 purchase incentive per truck. But over a lifespan of five to six years, that truck model was costing NFI about $25,000 more in maintenance and repair than other trucks.

Classroom discussion questions:

What is the difference between predictive and preventive maintenance?
What is the role of AI at NFI?

OM in the News: Using Machine Learning to Keep the Beer Flowing

Anheuser-Busch uses this sensor to pick up ultrasonic sounds coming off conveyor belt and motors.

The world’s largest beer maker is using low-cost sensors and machine learning to predict when motors at a Colorado brewery might malfunction, reports The Wall Street Journal (Jan. 24, 2019). The Anheuser-Busch plant was the first among the company’s 350 beer facilities to test whether wireless sensors that can detect ultrasonic sounds—beyond the grasp of the human ear—can be analyzed to predict when machines need maintenance. “You can start hearing days in advance that something will go wrong, and you’ll know within hours when it’ll fail. It’s really, for us, very practical,” said the VP.

The installation at the brewery cost just $20,000. Since the system was deployed, it has predicted pending equipment failures and prevented unscheduled production-line halts, and more than $200,000 in product loss. (The Colorado plant employs 580 people and ships 225 truckloads of Budweiser, Bud Light and other beer brands each day).

Sensors have been used for predictive maintenance in the past, but they were unable to transmit information in real time. Advances in processing data at the edge of the network, referred to as edge computing, enable companies to collect and analyze real-time sensor data from machines. Machine learning refers to the subset of AI that allows computers to act “intelligently” without being explicitly programmed. Algorithms can increase the accuracy of predictions based on large amounts of historical and real-time sensor data.

Organizations that own wind turbines or jet engines are expected to save about $1 trillion a year as a result of predictive maintenance techniques. Sound-based predictive maintenance is becoming more important for companies, as there has been a wave of retirements among workers who were tasked with listening to machines to identify potential breakdowns. The price of internet-of-things sensors is expected to fall to 26 cents on average by 2024, from 46 cents in 2018.

Classroom discussion questions:

What is predictive maintenance?
How does this differ from “breakdown maintenance?”

OM in the News: A Primer on Predictive Maintenance

“Nearly everyone in manufacturing, from equipment manufacturers to processing plants, commonly face the challenge of keeping their fleet, machinery, and other assets working efficiently, while also reducing the cost of maintenance and time-sensitive repairs,” writes Industry Week (Dec. 6, 2018). So it is crucial to identify the cause of potential faults or failures before they have an opportunity to occur. Emerging technologies such as the Industrial Internet of Things, data analytics, and cloud data storage are enabling more vehicles, industrial equipment, and assembly robots to send condition-based data to a centralized server, making fault detection easier, more practical, and more direct. By proactively identifying potential issues, companies can deploy their maintenance services more effectively and improve equipment up-time.

Using AI to identify anomalous behavior, the information derived from the equipment sensors can be turned into meaningful and actionable insights for proactive maintenance of assets, thereby preventing incidents that result in asset downtime or accidents. Known as predictive maintenance (a topic we have added to Chapter 17 in our new edition, due out Jan. 1st), this added intelligence enables organizations to forecast when or if functional equipment will fail so that its maintenance and repair can be scheduled before the failure occurs. As industrial customers become increasingly aware of the growing maintenance costs and downtime caused by the unexpected machinery failures, predictive maintenance solutions are gaining even more traction.

Predictive maintenance is also a step ahead of preventive maintenance. As maintenance work is scheduled at preset intervals, maintenance technicians are informed of the likelihood of parts and components failing during the next work cycle and can take action to minimize downtime. In addition to the advantages of controlling repair costs, avoiding warranty costs for failure recovery, reducing unplanned downtime and eliminating the causes of failure, predictive maintenance employs non-intrusive testing techniques to evaluate and compute asset performance trends.

Classroom discussion questions:

How do preventive maintenance and predictive maintenance differ?
What technologies are allowing predictive maintenance to spread?

OM in the News: Hurricanes, F-22 Fighter Jets, and Chapter 17

We are well aware that Chapter 17, Maintenance and Reliability, is not reached by semester end in many syllabi. But we would suggest that it is an important topic, especially when we consider the terrible impact of Hurricane Michael in Florida 2 weeks ago. About $2 billion in fighter jets were trapped on the ground because of maintenance issues and forced to ride out the Category 4 hurricane.

As many as 17 of Tyndall Air Force base’s 55 F-22s sustained damage or have been destroyed during the storm. (Considering the level of destruction, all of them could be damaged). One F-22 jet costs about $139 million. The aircraft were unable to escape with the rest of the base’s F-22 fleet to Wright Patterson Air Force Base, Ohio. The jets left behind were parked inside hangars as officials hoped for the best.

But why can’t F-22 jet fighters, of all things, escape a storm? Answer: They lack the parts to be operational. “Welcome to a fighting force damaged by bad political decisions and misguided priorities”, writes The Wall Street Journal (Oct. 17, 2018). Of the Air Force’s 186 F-22s, only about 80 are “mission capable,” meaning less than half are flyable at any given time.

Part of the F-22 problem is upkeep on a coating that helps the planes evade radar. Another issue is the supply chain for parts now that the U.S. no longer produces the airplane, and some original manufacturers no longer make the parts or are completely out of business. Air Force officials say that a simple wiring harness requires a 30-week lead time for finding a new contractor and producing the part. Ripping out parts from planes that work, or “cannibalizing,” is now common practice in military aviation.

Classroom discussion questions:

What OM policies could the Air Force implement to deal with this issue?
Which graph in Figure 17.4 provides a better representation of the F-22 costs?

OM in the News: 787 Dreamliners Facing More Rolls-Royce Engine Flaws

Rolls Royce engine of a Boeing 787 Dreamliner

Faulty Rolls-Royce engine blades are deteriorating faster than expected, prompting additional groundings of Boeing Co.’s 787 jetliners for early repairs, reports Businessweek (Sept. 27, 2018). The discovery affects about 120 Trent 1000 turbines, 8% of the global fleet, and has frustrated efforts to reduce the number of idled planes after a series of engine issues.

Rolls-Royce uncovered the part’s shorter life-span in December, when Air New Zealand Dreamliners suffered in-flight turbine damage on successive days. The flaws add to Rolls-Royce’s struggle with design faults to the engines, which have already prompted the company to record $1.5 billion in charges. The engine maker also faces a blow to its image because the faults involve the high-profile 787, Boeing’s most advanced model, leaving airlines rushing to find replacement aircraft for long-haul routes. Air New Zealand said it will cost the airline $26 million this year. With as many as five of its 13 Dreamliners grounded at any given time, the carrier has had to lease three aircraft to make up for the shortage.

The intermediate pressure turbine blades — which had already been flagged for replacement — aren’t lasting long enough to meet the previously set maintenance schedule. Engine makers like Rolls-Royce typically foot the bill — including for the leasing of replacement aircraft — when design or production issues delay deliveries or force airlines to idle jets that are already in service. The U.K. manufacturer has gone on a fence-mending campaign as customers for the engine — including British Airways, Virgin Atlantic, and Norwegian Air — have been forced to hire jets this summer as turbines go in for repairs.

Classroom discussion questions:

Why are flights being grounded?
What is the cost to Boeing? To customers? To Rolls-Royce?

OM in the News: Read this Blog Before You Fly!

Last month, 2 people with measles flew into O’Hare Airport

Is there anything air travelers despise more than a flight delay? Perhaps sitting in a dirty airplane or next to someone who is coughing, sneezing or worse. Passengers have experienced all kinds of affronts to personal health and hygiene in the tight quarters of an airline cabin.

Now, imagine the complex choreography involved in cleaning a Boeing 737 with more than 160 seats in just the few minutes between the plane’s arrival at the gate and its departure, writes The New York Times (Feb. 6, 2018). It’s a grueling task, and the stakes are high.

A passenger’s greatest health risk on an airplane may come from exposure to fellow travelers. And the risk of spreading diseases increases if surfaces in cabins and bathrooms are not adequately cleaned. Airlines typically hire outside companies to perform “quick turns” (the cleaning between flights) and overnight cleaning, as well as deep cleaning, which occurs about once a month.

But cabin cleaners describe a work environment where pay is at or near the minimum wage, morale is low and turnover is high. “To clean, we need 10 to 15 minutes, but they give us 6 or 7, or even less time for quick turns,” says one crew chief. A 2015 GAO report states: “the U.S. lacks a comprehensive plan aimed at preventing and containing the spread of diseases through air travel.” Part of the problem is that airlines have created an incredible disincentive for travelers to alter their travel plans when they are sick by charging high change fees, so people who are sick fly. The CDC says “the greatest risk for the spread of infectious disease on airplanes was from passengers.”

What can you do? Take cleaning matters into your own hands. Buy medical-grade hand sanitizers and carry a travel package of disinfectant wipes to wipe down the seat and surfaces that you touch.

Classroom discussion questions:
1. How is this an OM issue?

2. What suggestions do you have for improving the quick turn process?

OM in the News: NASA’s “Failed Mission” Probabilities

NASA is working with Elon Musk’s SpaceX to redesign part of the fuel system for the company’s Falcon 9 rockets and then will demand at least 7 successful unmanned flights before allowing astronauts on board. With routine flights ferrying U.S. astronauts to the orbiting international space station slated to begin in fall of 2019, the agency has raised new questions about potential hazards and longstanding NASA safety standards, writes The Wall Street Journal (Jan.18, 2018). Ending current U.S. reliance on Russian capsules for crew transportation may “require decisions to accept a higher risk” on next-generation U.S. systems than anticipated, says NASA.

NASA’s statistical limit for a “failed mission” remains 1 in 55 launches, despite several years of intense development, NASA expenditures of about $5 billion and significant additional investment by the two companies bidding for contracts–Boeing and SpaceX. That limit applies to mission failures in which the vehicle doesn’t reach the space station but the crew uses emergency procedures to survive.

NASA’s statistical standard for crew fatalities is no greater than one in 270 flights, though neither Boeing nor SpaceX is on track to meet that precise mandatory benchmark. By contrast, the global airline industry has achieved fatal accident rates for jetliners of 1 crash for several million flights.

System reliability is an old, but crucial issue at NASA. During the long era of the Space Shuttle, which I was proud to be a part of, mission reliability was set at 98%. This meant a critical failure was anticipated every 50 flights. And indeed, the first Shuttle exploded on flight no. 25 (Challenger), and the 2nd loss on flight 113 (Columbia) . The Shuttle program ended with flight no. 135, as a 3rd crash was viewed as unsustainable.

Classroom discussion questions:

Is 1 in 55 (reliability = .982) acceptable? Why?
Why is NASA seeking this alternative to Russia’s Soyuz ferrying rockets?

OM in the News: Autonomous Cars May Not Need a Driver, But They Still Need a Good Mechanic

One of the cars being used by Waymo in the Phoenix area to test driverless technology

Waymo, one of the leading forces in self-driving technology, is enlisting the largest auto retailer in the U.S., AutoNation, to maintain and repair the growing number of driverless vehicles Waymo is testing around the country. Waymo — a unit of Google’s parent, Alphabet — is moving a step closer to putting driverless vehicles into ride-hailing fleets that would serve the general public, not just its own employees. Maintaining expensive and technology-packed self-driving vehicles is a main challenge for using them in moneymaking businesses, like ride-hailing fleets, writes The New York Times (Nov. 3, 2017).

Says AutoNation’s CEO. “In most cases, driverless vehicles in such fleets will have to be on the road almost around the clock to offset the cost of the sensors, computer chips, software and other systems that allow them to drive safely and reach their destinations without human operators. These vehicles need to be in service for hundreds of thousands of miles, much more than personal-use vehicles, to make them economically viable. To do that, you have to do much more proactive, preventative maintenance than what a normal person would do on a car.”

Because the vehicles are intended to operate without drivers, breakdowns have to be avoided and parts replaced when signs of wear first appear, not when they fail or when a warning light comes on. They need to work not 99% of the time, but 100% of the time.

Auto dealers, like AutoNation, sell cars, but a big chunk of their profits comes from servicing vehicles. They are looking for ways to become more relevant if car usage becomes more of a shared service.

Classroom discussion questions:

How is this an OM decision by Waymo?
How will the auto industry be impacted by driverless cars?

OM in the News: Reliabilty and Maintenance Secrets of the Airlines

“Airlines are pouring lots of time and money into understanding fleet reliability,” reports The Wall Street Journal (Oct. 12, 2017). Delta put together a team of mechanics, engineers and data geeks to find ways to make specific types of planes less prone to breakdowns. American has renewed efforts to schedule flights so each type of plane performs better.

“It’s not necessarily the airplane itself. It’s how we’re operating it,” says American’s VP. If no planes are reserved as spares, fleets become less reliable. Small fleets spread out among multiple hub airports often suffer higher cancellation rates because there aren’t opportunities to swap planes. Time scheduled for routine maintenance can get crimped if the planes get to mechanics late day after day. In 2016 American had 6 different kinds of wide-body jets flying international trips from Chicago. Reliability suffered. When glitches hit, the airline had little ability to swap planes.

Summer reliability is critical for airlines. Among the worst-performing planes were United 747s, which arrived on-time an average 63% of flights during the past 2 summers. United says it has worked the last several years on improving the reliability of the wide-bodies to achieve better on-time performance. Wide-body cancellations are down 60% since 2014.

Delta’s technical data team can not only predict which parts are liable to break, but also redesign some parts to make them more reliable and add monitors to track the health of parts on older jets. Suspect parts get replaced proactively ahead of manufacturers’ recommended replacement schedules, dramatically cutting cancellations. In 2010, Delta had 5,600 flights canceled by maintenance problems. Last year breakdowns caused only 303 cancellations, and the airline has suffered only 70 so far in 2017. Delta also loads seven 40-foot trailers each summer and sends mechanics out with the equipment to small cities to create temporary maintenance bases for specific types of planes. Last summer they were positioned in 7 spoke cities to do preventive maintenance on planes parked overnight there.

Classroom discussion questions:

Why do reliability figures differ dramatically among airlines and plane models?
What is the “secret” to picking an on-time flight?

OM in the News: Samsung’s Battery Fix Gets a C Grade

To figure out what caused its Note 7 to catch on fire, Samsung put 200,000 phones through several different tests — To figure out what caused its Note 7 to catch on fire, Samsung put 200,000 phones through different tests

“After four months of testing over 200,000 phones,” writes The Wall Street Journal (Jan. 23, 2017), “what did Samsung determine caused its flagship Note 7 to catch fire?” The answer: Bad batteries. Two separate sets of bad batteries made by two different companies.

But what Samsung is still missing is its Tylenol moment. In 1982, Johnson & Johnson issued a massive recall after 7 people died from taking Tylenol products laced with cyanide. It led the company, and then the rest of the industry, to rethink pill packaging. Consumers saw the new seals as a mark of safety and protection. Samsung’s work on a seal that consumers can understand is still incomplete.

A quick recap: Note 7’s with 2 different versions of the battery–Samsung calls them A and B–were released last August. Soon after, some of the phones with Battery A started to burn up. Samsung recalled the phones, quickly replacing them with just Battery B models. Some of these phones started to burn up also, compelling Samsung to yank the phone altogether.

After erecting labs with 700 staff to test 30,000 batteries, Samsung has concluded that neither its hardware nor software was to blame. Instead, Samsung says the battery had issues.

Battery A had a design issue: There wasn’t enough room inside the battery for routine expansion of its component electrodes. Battery B had a welding issue caused by a manufacturing defect, which didn’t appear until production ramped up after Battery A was pulled from the market. (The resulting microscopic burrs poked through barriers inside the battery).

The core of the problem was that Samsung didn’t have the quality controls needed to identify the battery problems before they reached consumers.

Classroom discussion questions:

What responsibility might Samsung share in setting the specifications and requirements for the Note 7 batteries?
How can a phone maker prevent this kind of problem in the future?

OM in the News: Maintenance, Reliability and the McFlurry

Employees often just say the machine is down rather than reassembling it. Here an employee spills ice cream mix all over herself while trying to fill the machine.

Why is the McDonald’s McFlurry ice cream machine down again? “The interruption in ice cream, milkshake and McFlurry service is so widespread that it has spawned an avalanche of social-media complaints in the U.S. and abroad—and conspiracy theories,” writes The Wall Street Journal (Jan. 20, 2017).

“I’m convinced there’s no way an ice cream machine would be down all the time with no replacement or repair of the machine,” says one NY college student. After experiencing downed machines numerous times, another student had a meltdown, which she captured on Facebook. The video rant received 1 million views and 5,000 comments, many of which came from customers with the same complaint.

Fans say they love the texture of the McFlurry’s hard, crunchy candy and smooth, creamy, vanilla soft serve. (A 16-ounce McFlurry contains 930 calories and 128 grams of sugar, more than three 12-ounce cans of Coke, by the way.)

In the years since the McFlurry made its debut on the menu in 1998, it has garnered a cult following. And the cravings for it often come on suddenly and late at night. That may be part of the problem.

McDonald’s requires the machines to undergo a nightly automated heat cleaning cycle of up to 4 hours to destroy any bacteria in them. Getting the machines ready for the cleaning cycle is an 11-step process that involves combining a sanitizing mix with warm water, removing and rinsing 7 parts, brushing clean 2 fixed parts for 60 seconds and wiping down the machine with a sanitized towel. Once the heat cycle begins, it can’t be interrupted because the product is hot and under extreme pressure.

One survey found 25% of the restaurants weren’t serving ice cream because the machines were reported not to be functional. Downed ice cream machines is now the most common service-related complaint among McDonald’s customers.

Classroom discussion questions:

What are the OM issues here?
Have students had similar complaints? Suggestions?