quality control – The OM Blog by Heizer, Render, & Munson

Guest Post: Martin Guitars and Operations

Prof. Howard Weiss, retired from Temple U., illustrates his wide range of interests.

Martin is a guitar manufacturer that began operations in 1833. Martin specializes in acoustic guitars which account for about half as many guitars as electric guitars in the global guitar market. It is one of the most popular brands along with Fender, Gibson, Yamaha, Ibanez and Taylor.

Location: Martin began its operation in Manhattan. In 1839 Martin opened a plant in Nazareth PA, 90 miles due west of its NYC plant. In 1989 Martin opened a plant in Sonora, Mexico in order to make guitars that were more affordable. It is worth noting that two of Martin’s competitors, Fender and Taylor guitars also have plants in Mexico. These guitars are commonly referred to as MIM (Made in Mexico). See Ch.8.

Capacity: Martin has made over 3 million guitars since its inception, including one million since 2016. It currently produces a total of 500 guitars per day, 6 days per week, at the two plants. (See Supp. 7)

Forecasting: Clearly demand has been increasing. Martin’s forecasting needs to consider historical and causal analysis (see Ch. 4) since certain events can spike or drop the sales. For example, sales increased more than usual during the folk music craze and also when MTV was running its Unplugged series (featuring acoustic guitars). At first, COVID caused a decline in sales due to cancelled concerts and closed stores. But then there was an increase in demand, especially for beginner guitars since people were looking for activities while at home and could order guitars online.

Supply Chain: The supply chain (Ch. 11) begins in the forest and at the lumber facilities both in the U.S. and India.

Layout: Martin uses process layout–see Ch.7. Most of the work is done by hand but there are robots in the factory.

Safety: With all of the woodwork that is being performed the major safety concern is that of sawdust.

Quality Control: The incoming wood is inspected by humans because machines cannot pick up defects in the wood. Each guitar is checked for tone. The guitar gets put in a case, but then sits for 4 days and then undergoes rigorous testing to make certain the guitar parts, e.g. neck, bridge, tuning pegs, still work. (See Ch. 6).

Classroom Discussion Questions

How could Martin use the Quality Control techniques discussed in Ch. 6 of your text book?
What are some possible reasons Martin relocated from Manhattan to Nazareth, PA?

Guest Post: Food Processing Ingredients

Prof. Howard Weiss shares his insights monthly. Howard created the Excel OM and POM software that we provide free with our book.

A recent Philadelphia Inquirer article (February 19, 2026) reports that “The grandson of the inventor of Reese’s Peanut Butter Cups has lashed out at the Hershey Co., accusing the candy company of hurting the Reese’s brand by shifting to cheaper ingredients in many products.”

In prior years consumers expressed dissatisfaction when Nutella reduced the amount of cocoa in its product. One reason for the change in the recipes for these two products is the high cost of cocoa. Clearly, a change in a recipe will affect inventory, material (ingredient) costs, and the supply chain.

The most infamous recipe change is probably “New Coke” which was introduced in 1985. Consumer backlash forced Coke to revert to its original recipe. Recently, Coke announced it will add a new product made with cane sugar rather than corn syrup.

Food taste and recipes can vary for a number of legitimate reasons. The recipe for Twinkies was changed in order to extend its shelf life from 25 days to 45 days. Butterfinger took an alternative approach and double-wrapped its candy. Several food processors have changed recipes in order to eliminate certain food dyes or additives or reduce sodium, including Kraft Macaroni and Cheese and Turkey Hill ice cream.

The same product may have a different recipe for sales at bulk stores rather than supermarkets. Colas may have a different amount of corn syrup in bulk stores.

Sometimes recipe changes are inadvertent. In one case consumers complained about the taste of meals they cooked using 4C Italian Bread Crumbs. 4C investigated and found that trace amounts of cinnamon were in the bread crumbs and should not have been. There are many examples of bacteria being in processed food which would affect the health of the person eating the food. This is different. There is a processing problem but it will NOT cause health issues just taste issues.

The repercussions of food quality are different than the repercussions of food safety. Food safety problems can lead to recalls, liabilities, brand damage and penalties. Failure to maintain taste can result in brand damage and product returns.

Classroom discussion questions:
1. Identify other products in which change resulted in complaints or safety issues.

2. What are the main changes these days to food products?

Guest Post: Reliability of Bridges

Retired Temple U. Prof. Howard Weiss is the developer of the POM and Excel OM software that we provide free with our text.

On March 26, 2024 the container ship Dali crashed into the Francis Scott Key Bridge that spans Baltimore harbor. Ships had crashed into major bridges previously but in this case the damage was far worse than usual. The bridge collapsed into the harbor, 6 died, and, of course, travel across the harbor was affected.

The Dali was not even that large, with a capacity of 10,000 containers. (The largest container ships have a capacity of 24,000 containers). The obvious operational problem is that the bridge, which carried over 30,000 vehicles daily could not be used and the vehicles had to take either alternative routes. Reconstruction of the bridge began in January, 2025 but the detours will be needed until Fall, 2028.

The NTSB reported that Maryland did not conduct a test that would have identified structural risks for the bridge. After this incident, the NTSB indicated that 68 bridges that have commercial traffic in the U.S. needed to be inspected.

A recent study provided a list of the 20 bridges with the highest probability of having major damage due to being hit by a ship. The results of the top and bottom five in that list are displayed below along with reliability calculations in the shaded area.

operations management blog The table performs these computations for each of the 20 bridges for a 1- year period, a 10-year period and a 100-year period.

The single year reliability is simply = # of years minus 1 divided by # of years. For example, for the Huey P. Long Bridge, reliability is 16/17 = .9412. That is, there is roughly a 6% chance of an accident in any given year. From your Heizer/Render/Munson textbook (Ch. 17), the 10 year reliability is given by

Rs=R 1 ×R 2 ×R 3 ×…× R 10

And since the reliability each year is the same this is identical to R 1 ^10. Thus, there is roughly a 50% chance that in 10 years the Huey P. Long bridge will have an incident. The safest of the 20 bridges, the John Blatnik has a less than 1% chance of a major accident over 10 years. Similar computations are given for a 100 year period.

Classroom Discussion Questions
1. What actions can be taken to reduce the chance of a major accident?
2. If the number of years between collisions can be increased by 10% (rounded up) how does that affect the 10 year reliability for the Long and Blatnik bridges?

Guest Post: The Natural Gas Supply Chain

Prof. Howard Weiss shares his insights with our readers monthly.

Natural Gas is a resource with several uses and, in fact, almost 50% of U.S. homes use it for heating. This figure shows the supply chain for natural gas.

Resource location Natural gas is extracted from rock formations, wells and coalbeds.

Pareto Principle Natural gas is produced in varying amounts in 95 countries. The U.S., Russia, Iran, and Qatar produce half of the natural gas worldwide. Five states, Texas, Pennsylvania, Louisiana, W. Virginia and New Mexico, produce over 60% of the total natural gas in the US. Thus, both U.S. and worldwide production follow the Pareto principle as explained in the quality chapter (Ch. 6).

Transportation The supply chain chapter (Ch.11) lists six major means of distribution – trucking, railroads, airfreight, waterways, multimodal and pipelines. Unlike oil, before natural gas is processed it can only be transported through pipelines.

Project Management. Building the pipeline is a project with two major parts. The pipeline company does not own the land where the pipeline is, but rather needs to get legal access to the properties. The second part is the construction of the pipeline itself. This involves digging and bending pipes to fit the planned route of the pipeline. Companies install about one mile of pipe per day. The U.S. has more than 300,000 miles of main pipelines, while Russia has more than 100,000.

Quality control After construction the pipeline is testing using water piped at a higher pressure than the gas will be transported.

Processing The gas goes to a compressor station (where impurities are removed) and then is pressurized to move it post-processing.

Post Processing Transportation The gas is then moved at 25 miles per hour through pipelines. Some gas is liquefied by chilling it to -263 degrees Fahrenheit so it can be shipped by special tanker ships and rail cars. Natural Gas is 600 times more in volume than liquefied natural gas. LNG can also be shipped to places that do not have pipelines.

Storage Currently there are 400 storage sites for natural gas in the U.S.

Classroom Discussion Questions:
1. Does your residence use natural gas? If so, what are its uses?
2. Some natural gas that is discovered is not sold but rather is burnt off at the site where it is found. Why do you think the gas is wasted rather than being sold?

Guest Post: Food Safety and the E. coli Outbreak at McDonald’s

Temple U. Prof. Misty Blessley raises a timely topic that has broad interest for those of us who are fast-food consumers.

Your Heizer/Render/Munson textbook highlights several examples of McDonald’s operations and supply chain practices. In Chapter 6, poka-yoke methods like the aluminum scoop and fry container ensure portion accuracy. Chapter 11 highlights how the company mitigates supply risks by working with multiple vendors and establishing robust contracts. Chapter 9 discusses how McDonald’s balances production flow in its hamburger assembly lines.

However, the recent E. coli outbreak prompted McDonald’s to reevaluate parts of its supply chain to maintain food safety standards. At least 75 people have been infected across 13 states—most reporting they ate a Quarter Pounder before falling ill. The states include Colorado, Montana, Nebraska, and others throughout the Midwest and West.

After tests confirmed that its beef patties were not linked to the E. coli outbreak, McDonald’s has reintroduced Quarter Pounders in several restaurants. Although the Food and Drug Administration (FDA) initially examined both the beef and slivered onions, it ruled out the patties. Early evidence indicates the onions are the likely source, but the FDA’s investigation is ongoing.

Taylor Farms, based in Salinas, California, recently issued a voluntary recall of four onion products due to possible E. coli contamination. McDonald’s identified Taylor Farms as the onion supplier for all locations connected to the outbreak and confirmed its decision to halt orders and deliveries from this supplier.

McDonald’s chief supply chain officer for North America, reassured the public that the outbreak was limited to a specific ingredient and region. He expressed confidence that all contaminated products had been removed from their supply chain and are no longer present in any McDonald’s restaurants.

This outbreak highlights the importance of quick and efficient food traceability for high-risk foods like cut onions. The Food Safety Modernization Act (FSMA) focuses on shifting the FDA’s approach from reactive to proactive. A key part is the FSMA 204 Food Traceability Rule, which requires more detailed recordkeeping for high-risk foods. The rule, discussed in OM Podcast #18: An Inside Look at the U.S. Food Supply Chain, goes into effect in 2026.

Classroom discussion questions:
1. What are the challenges associated with traceability of cut food items from farm to fork?
2. How do slivered onions present different food safety challenges than cooked beef patties for McDonald’s?

Guest Post: Quality, Marketing and Cross Contamination

Professor Howard Weiss shares his thoughts about a variety of unusual OM topics with us monthly.

People with food allergies typically check the ingredients of a food product very carefully to ensure that the product does not contain an ingredient to which they are allergic. The top 8 allergens in food production are soy, wheat, milk, peanuts, tree nuts, fish, and shellfish.

Bimbo Bakeries, headquartered in Mexico with bakeries in 35 countries including the U.S., has taken a unique approach to listing allergens on some of its products. U.S. inspectors reported that Bimbo Bakeries USA — which includes brands such as Sara Lee, Oroweat, Thomas, Entenmanns and Ball Park buns and rolls —”listed ingredients such as sesame or tree nuts on labels even when they weren’t in the foods.” (Bimbo claims to be the largest bakery in this country).

The reason a company might purposely list ingredients that are not in its products is that it may be concerned about cross-contamination in a bakery plant and wants to ensure it will not be legally responsible in the event of cross contamination. In other words, rather than trying to introduce quality control procedures to prevent cross-contamination in its plant, the company is willing to be untruthful when listing ingredients to minimize the chance and or cost of a law suit.

It may be very expensive or difficult to prevent cross-contamination from one part of plant to another or from one machine to another. So to stay within the letter of the law some companies have deliberately added small amounts of allergens to products that previously did not contain these allergens. This helps the company avoid liability and legal costs.

Cross contamination can occur in several different ways:
 primary food production — from plants and animals on farms
 during harvest or slaughter
 secondary food production — including food processing and manufacturing
 transportation of food
 storage of food
 distribution of food — grocery stores, farmer’s markets, and more
 food preparation and serving — at home, restaurants, and other foodservice operations

There are strategies available to minimize the chance of cross-contamination. The best way is for food manufacturers to process products that contain allergens in a separate facility. If this is not possible then scheduling the production of products that contain allergens at a different time than other products may help. Cleaning procedures can be used to minimize the chance of cross contamination.

OM in the News: How Boeing’s Troubles are Affecting its Suppliers

Boeing’s troubles are bleeding out to its supply chain, where uncertainty over production rates has suppliers guessing at how many parts to make to avoid the cost of holding too much inventory, reports Financial Times (May 29, 2024) . It has slowed manufacturing of its workhorse jet, the 737 Max, as it tries to improve production quality following a recent door panel blowout on a flight. And it is facing an FAA deadline to deliver a plan that addresses a “flawed safety culture”.

The production slowdown is testing the resilience of a brittle aerospace supply chain that already has faced years of price cuts and choppy production thanks to Covid-19 and two fatal crashes that grounded the Max worldwide. Without a well-oiled supply chain, Boeing will struggle to deliver jets to airlines clamoring for them, and could destabilize labor in an industry that employs hundreds of thousands of workers.

The FAA has capped Boeing’s production of the Max at 38 per month. (The company is currently building even less). That affects the operations and finances for suppliers. The ones that do a lot of business with Boeing were “feeling the pain at the moment. Everybody was expecting a ramp-up in the production of the 737 and 787. They may have invested in people or capacity to meet that ramp- up, and when they get pushed back, it’s a problem,” said one industry consultant.

Spirit Aerospace, which produces the 737 fuselages, has had its own struggles with quality and has been the most high-profile casualty of the slowdown on the Max. Boeing stopped accepting those fuselages that do not meet specifications in an effort to reduce rework at its own Washington state factory, where rework performed increases the likelihood of manufacturing errors.

Spirit is far from alone. Howmet Aerospace, Triumph Group, Hexcel, Senior and ATI all have been affected by the slowdown on the 737. Triumph, for example, supplies $300,000 worth of equipment on each 737 Max and $1 million worth on each 787. It has slowed ordering materials from its own suppliers. Howmet is now assuming Boeing will produce 20 Maxes a month for the rest of the year, down from a previous assumption of 34. It is planning to deliver lower volumes “to prevent the case where we get caught with a lot of inventory.”

Classroom discussion questions:

What are Boeing’s OM options?
What can its suppliers do?

OM in the News: Tesla Recalls its Cybertrucks Over a Soap Issue

Tesla is recalling every Cybertruck built thus far to fix a defective pedal pad that could cause accelerator pedals to get stuck in the depressed position, raising the risk of a crash, reports USA Today (April 22, 2024). Specifically, when someone stomps on the accelerator, the pad can come off and get trapped in a bit of trim.

Cybertrucks are lined up at the Tesla Giga Factory in Texas this month

That would leave the accelerator stuck in the “on” position — something that has happened at least twice. When a driver hits the brake pedal, the truck will stop even if the accelerator is depressed. No injuries or crashes have been reported.

The problem, as Tesla reported to the National Highway Transportation Safety Administration, originated on production lines with soap. “An unapproved change introduced soap to aid in the component assembly,” the report says. Evidently, workers used soap to help get the pad into place on the pedal. Traces of that slippery soap remained, hence the problem.

The recall involves all 3,878 of the aesthetically-divisive angular trucks that have been sold so far. While some Tesla recalls are for software fixes that can be issued over-the-air, meaning a vehicle downloads an update without a trip to a mechanic, this one is a physical defect. It requires a physical repair.

This is the second soap-related manufacturing process to make headlines this month. A Boeing supplier recently defended the use of Dawn dish soap as lubricant in assembling door seals in manufacturing jets like the one that lost a door mid-flight.

Meanwhile, the Tesla Cybertruck, a vehicle with an extremely unusual manufacturing process, has also faced complaints since its launch about problems with rust and potentially finger-pinching trunks.

Classroom discussion questions:

Is this a quality issue–or a design issue?
What are the strengths and weaknesses of Cybertrucks, according to early reviews in auto magazines?

OM in the News: Boeing’s Outsourcing Strategy That Went Too Far

It appears that Boeing is about to acquire Spirit AeroSystems , the troubled jet-fuselage supplier that has been at the center of quality issues affecting 737 MAX jets, reports The Wall Street Journal (March 2, 2024). Spirit, which makes 737 and 787 fuselages and other major components, was created when Boeing decided to outsource and sold some of its factories 2 decades ago. Boeing now accounts for nearly 2/3 of Spirit’s sales, and cannot afford to have Spirit fail.

But Boeing engineers warned back in 2001 that the company risked losing control of its manufacturing processes and hollowing out its internal capabilities. The move to reacquire Spirit comes after a long series of quality problems with the fuselage sections it supplies. Spirit parts frequently arrive at the factory with defects. Those caused repeated delivery pauses at Boeing’s final assembly plants.

The move concedes that the strategy went much too far and has damaged Boeing. Last year, Boeing sent “armies of people,” its CEO stated, to Wichita to help Spirit get its manufacturing processes under control. When asked about Boeing’s outsourcing strategy, he recently told CNBC, “Did it go too far? Yeah, it probably did. But now it’s here and now. And now, I’ve got to deal with it.”

A deal would be a strategic reversal. Boeing sold the Wichita plant in a push to focus on final assembly. Acquiring Spirit would leave Boeing with the task of cleaning up its operations at the same time that Boeing’s own quality-control systems have been questioned by regulators. The FAA has just given Boeing 90 days to come up with a quality-improvement plan.

Boeing in the past few years had done everything short of acquiring Spirit to gain control over the supplier. Spirit has lost an average of more than $1 million per airplane on the nearly 1,200 fuselage sections it built for the 787, a cumulative loss totaling $1.4 billion.

Chapter 2 in your Heizer/Render/Munson text discusses the Theory of Competitive Advantage and the risks of outsourcing on pages 44-47.

Classroom discussion questions:

Describe the risks of outsourcing in general, and then the particular risks Boeing faced.
What are the risks Boeing faces as it reacquires Spirit?

Guest Post: Peanuts, Peanut Butter, and Byproducts

Dr. Howard Weiss shares his thoughts with our readers monthly. Howard is a retired Temple U. professor.

Skippy Foods is recalling thousands of pounds of Skippy peanut butter because of stainless steel fragments possibly contaminating “a limited number of jars.” Clearly, the quality control department did not find the fragments in the jars that they inspected. While this is unfortunate, your Statistical Process Control chapter (Supplement 6) indicates that this can happen and describes the failure as a Type II error where a bad lot passes inspection but is accepted.

Of course, placing the peanut butter in jars is only one step in the peanut butter supply chain. The supply chain for peanut butter is very similar to the supply chain for soft drinks described in Figure 1.2 of your Heizer/Render/Munson textbook.

Farmer: Peanuts are planted in spring, 4 to 5 months later are delivered to warehouses for cleaning, shelled, graded for size, shipped to peanut butter manufacturers

Producer: Peanuts are dry roasted, removed from heat, skins are removed. Nuts are screened and inspected. Peanuts are ground and converted to peanut butter

Packaging: Peanut butter is packed

Distribution: Peanut butter goes to distributor

Sales: Peanut butter goes to retail outlets

Quality control is a part of each of the steps listed above. The peanut butter must meet standards maintained by the U.S. Department of Agriculture and the Food and Drug Administration and the peanut butter is graded by the USDA as Grade A or Fancy, Grade B or Choice or substandard. The grade is a weighted average of color, consistency, absence of defects and flavor and aromas

As is the case with many production operations, the processes yield byproducts. While peanuts are grown mainly as food or for their oil, after harvesting there are leaves, stalks, vines and pods that remain in the field. This residue has high nutritional value and is used as animal feed for assorted livestock. The peanut shells that are a byproduct of the shelling plant are used in the manufacturing of several products and also can be used as compost, mulch, kitty litter or used in fireplaces. Peanut shells can also be used in place of salt on icy sidewalks. And, of course, real peanut shells can be used as packing material in lieu of styrofoam peanut shells.

Classroom Discussion Questions:

Cite another product that produces byproducts during production.
What other nuts are commonly turned into nut butter?

OM in the News: When a Company Fails at Quality Control

In the late 1990s, GM got an unexpected and enticing offer. A little-known Japanese supplier, Takata, had designed a much cheaper automotive airbag. So GM turned to its airbag supplier, Autoliv, and asked it to match the cheaper design or risk losing the automaker’s business. But when Autoliv’s scientists studied the Takata airbag, they found that it relied on a dangerously volatile compound in its inflater, a critical part that causes the airbag to expand. In spite of the report GM chose the Takata product.

The result of failed quality control: Takata, behind the biggest safety recall in automotive history, is filing for bankruptcy, says Industry Week (June 15, 2017). Its liabilities exceed $9 billion. Takata’s faulty air bag inflators have been linked to at least 17 deaths worldwide. Mounting liabilities from having to replace an estimated more than 100 million air bags force Takata to seek an acquirer that could get it through the costly restructuring process.

Honda, a Takata shareholder and the auto-parts maker’s largest customer, first started recalling Accord and Civic models in 2008. The supplier’s air bag inflators use a propellant that can be rendered unstable after long-term exposure to heat and humidity, leading them to rupture and spray deadly metal shards at vehicle occupants.

More than a dozen automakers have recalled vehicles since, include VW, Toyota and GM. Takata in January agreed to pay $1 billion to U.S. regulators, consumers and carmakers. The settlement includes a $25 million criminal fine, $125 million in victim compensation and $850 million to compensate automakers who have suffered losses from massive recalls.

Classroom discussion questions:

Should automakers assume some of the blame for this supply chain problem?
Compare this to other recent auto industry quality and ethical blunders.

OM in the News: Need a Poka Yoke at San Francisco’s Baseball Stadium?

$99 batter's box template — $99 batter’s box template

Though it doesn’t take long for them to get destroyed and disappear, the batter’s boxes originally drawn in for this week’s Reds-Giants baseball game at San Francisco’s AT&T Park “may be the most crooked and awkward looking we’ve ever seen,” reports Yahoo Sports (July 25, 2013).

Of course that also means they were not up to Major League Baseball standards — or sandlot ball standards, for that matter — but no one on the field seemed to notice or care — most notably home plate umpire Chris Guccione — as the game started and carried on without the lines being corrected. The umpires collectively missed it or ignored it.

Most hitters, like Miguel Cabrera, can sense when a line is an inch too long or too close to the pitcher’s mound. A lot of that is based on routine. A lot of that is based on instincts. But, in this case the errors weren’t even marginal. Both sides were angled so noticeably. The cure is a poka yoke like the one shown here, available for less than $100 on-line. (For more on poka yoke, see Chapter 6, Managing Quality).

Discussion questions:

1. Why does the crooked batter’s box make a difference?

2. Name some other popular poka yokes.

OM in the News: The Meningitis Scare and Acceptance Sampling

My family has been closely following the news of the recent meningitis outbreak caused by a contaminated steroid Methylprednisolone. The drug is injected for the treatment of acute back and leg pain. The Centers for Disease Control (CDC) reports 21 deaths and 257 people infected in 16 states from the steroid. Some 14,000 patients, including my sister-in-law, have received such contaminated injections and are in danger of contracting meningitis during the coming months.The specialty pharmacy, New England Compounding Center (NECC), had the products tested at an independent lab, which in May stated that samples from a batch of steroids were “sterile.”

But The Wall Street Journal (Oct.25, 2012) reports that the sample size that was tested was too small to be meaningful and didn’t comply with industry guidelines. The Oklahoma City testing lab had examined just two 5-milliliter vials of the NECC drug, and found them to be both sterile. The vials came from a batch of 6,528 implicated by the CDC.

Drug makers and compounding pharmacies routinely have their drugs tested by labs as a quality-control measure. Industry experts say such testing can never completely rule out contamination unless every vial in a batch is tested, which is economically impractical. In the case of the NECC steroids tainted with fungi, the size of the testing sample—two vials—is much smaller than the industry standard for the test; for a batch of more than 6,000 vials, the lab should have tested at least 20. And one drug-testing laboratory quoted in The Journal typically asks for double the number of samples called for in the US standards. “If they’re only testing two vials out of a batch of 6,000, the chances of finding a contaminated vial are very small. Half the batch could be contaminated, and you’d never find it,” says the firm.

For a test to detect contamination with 95% confidence, 18% of the batch would have to be tested, adds a Bristol-Myers executive. “You cannot test quality into a product. You’ve got to manufacture a product in a controlled way and only then does the testing mean anything”.

Discussion questions

1. Ask your students to read Supplement 6’s discussion of Acceptance Sampling and comment on NECC’s approach to quality.

2. Why can’t every vial be tested?