Harnswell Sewing Machine Company
Phase 1: For more than 40 years, the HarnswellSewing Machine Company has manufactured industrial sewing machines.The company specializes in automated machines called patterntackers that sew repetitive patterns on such mass-produced productsas shoes, garments, and seat belts. Aside from the sales ofmachines, the company sells machine parts. Because the company’sproducts have a reputation for being superior, Harnswell is able tocommand a price premium for its product line.
Recently, the operations manager, Natalie York, purchasedseveral books related to quality. After reading them, sheconsidered the feasibility of beginning a quality program at thecompany. At the current time, the company has no formal qualityprogram. Parts are 100% inspected at the time of shipping to acustomer or installation in a machine, yet Natalie has alwayswondered why inventory of certain parts (in particular, thehalf-inch cam rollers) invariably falls short before a full yearlapses, even though 7,000 pieces have been produced for a demand of5,000 pieces per year.
After a great deal of reflection and with some apprehension,Natalie has decided that she will approach John Harnswell, theowner of the company, about the possibility of beginning a programto improve quality in the company, starting with a trial project inthe machine parts area. As she is walking to Mr. Harnswell’s officefor the meeting, she has second thoughts about whether this is sucha good idea. After all, just last month, Mr. Harnswell told her,“Why do you need to go to graduate school for your master’s degreein business? That is a waste of your time and will not be of anyvalue to the Harnswell Company. All those professors are just up intheir ivory towers and don’t know a thing about running a business,like I do.”
As she enters his office, Mr. Harnswell invites Natalie to sitdown across from him. “Well, what do you have on your mind thismorning?” Mr. Harnswell asks her in an inquisitive tone. She beginsby starting to talk about the books that she has just completedreading and about how she has some interesting ideas for makingproduction even better than it is now and improving profits. Beforeshe can finish, Mr. Harnswell has started to answer: “Look,everything has been fine since I started this company in 1968. Ihave built this company up from nothing to one that employs morethan 100 people. Why do you want to make waves? Remember, if itain’t broke, don’t fix it.” With that, he ushers her from hisoffice with the admonishment of, “What am I going to do with you ifyou keep coming up with these ridiculous ideas?”
a. Based on what you have read, which of Deming’s 14 points ofmanagement are most lacking at the Harnswell Sewing MachineCompany? Explain.
b. What changes, if any, do you think that Natalie York might beable to institute in the company? Explain.
Phase 2: Natalie slowly walks down the hallafter leaving Mr. Harnswell’s office, feeling rather downcast. Hejust won’t listen to anyone, she thinks. As she walks, Jim Murante,the shop foreman, comes up beside her. “So,” he says, “did youreally think that he would listen to you? I’ve been here more than25 years. The only way he listens is if he is shown something thatworked after it has already been done. Let’s see what we can plantogether.”
Natalie and Jim decide to begin by investigating the productionof the cam rollers, which are precision-ground parts. The last partof the production process involves the grinding of the outerdiameter. After grinding, the part mates with the cam groove of theparticular sewing pattern. The half-inch rollers technically havean engineering specification for the outer diameter of the rollerof 0.5075 inch (the specifications are actually metric, but infactory floor jargon, they are referred to as half-inch), plus atolerable error of 0.0003 inch on the lower side. Thus, the outerdiameter is allowed to be between 0.5072 and 0.5075 inch. Anythinglarger is reclassified into a different and less costly category,and anything smaller is unusable for anything other than scrap.
The grinding of the cam roller is done on a single machine witha single tool setup and no change in the grinding wheel afterinitial setup. The operation is done by Dave Martin, the headmachinist, who has 30 years of experience in the trade and specificexperience producing the cam roller part. Because production occursin batches, Natalie and Jim sample five parts produced from eachbatch. Table below presents data collected over 30 batches (storedin Harnswell).
a. Is the process in control? Why?
b. What recommendations do you have for improving theprocess?
Phase 3: Natalie examines the X and R chartsdeveloped from the data stored in Harnswell.xls from Phase 2. The Rchart indicates that the process is in control, but the chart X treveals that the mean for batch 17 is outside the LCL. Thisimmediately gives her cause for concern because low values for theroller diameter could mean that parts have to be scrapped. Nataliegoes to see Jim Murante, the shop foreman, to try to find out whathad happened to batch 17. Jim looks up the production records todetermine when this batch was produced. “Aha!” he exclaims. “Ithink I’ve got the answer! This batch was produced on thatreally-cold morning we had last month. I’ve been after Mr.Harnswell for a long time to let us install an automatic thermostathere in the shop so that the place doesn’t feel so cold when we gethere in the morning. All he ever tells me is that people aren’t astough as they used to be.”
Natalie is almost in shock. She realizes that what happened isthat, rather than standing idle until the environment and theequipment warmed to acceptable temperatures, the machinist opted tomanufacture parts that might have to be scrapped. In fact, Natalierecalls that a major problem occurred on that same day, whenseveral other expensive parts had to be scrapped. Natalie says toJim, “We just have to do something. We can’t let this go on nowthat we know what problems it is potentially causing.” Natalie andJim decide to take enough money out of petty cash to get thethermostat without having to fill out a requisition requiring Mr.Harnswell’s signature. They install the thermostat and set theheating control so that the heat turns on a half hour before theshop opens each morning.
a. What should Natalie do now concerning the cam roller data?Explain.
b. Explain how the actions of Natalie and Jim to avoid thisparticular problem in the future have resulted in qualityimprovement.
PHASE 4: Because corrective action was taken toeliminate the special cause of variation, Natalie removes the datafor batch 17 from the analysis. The control charts for theremaining days indicate a stable system, with only common causes ofvariation operating on the system. Then, Natalie and Jim sit downwith Dave Martin and several other machinists to try to determineall the possible causes for the existence of oversized and scrappedrollers. Natalie is still troubled by the data. After all, shewants to find out whether the process is giving oversizes (whichare downgraded) and undersizes (which are scrapped). She thinksabout which tables and charts might be most helpful.
a. Construct a frequency distribution and a stem-and-leafdisplay of the cam roller diameters. Which do you prefer in thissituation?
b. Based on your results in (a), construct all appropriatecharts of the cam roller diameters.
c. Write a report, expressing your conclusions concerning thecam roller diameters. Be sure to discuss the diameters as theyrelate to the specifications.
PHASE 5: Natalie notices immediately that theoverall mean diameter with batch 17 eliminated is 0.507527, whichis higher than the specification value. Thus, the mean diameter ofthe rollers produced is so high that many will be downgraded invalue. In fact, 55 of the 150 rollers sampled (36.67%) are abovethe specification value. If this percentage is extrapolated to thefull year’s production, 36.67% of the 7,000 pieces manufactured, or2,567, could not be sold as half-inch rollers, leaving only 4,433available for sale. “No wonder we often have shortages that requirecostly emergency runs,” she thinks. She also notes that not onediameter is below the lower specification of 0.5072, so not one ofthe rollers had to be scrapped.
Natalie realizes that there has to be a reason for all this.Along with Jim Murante, she decides to show the results to DaveMartin, the head machinist. Dave says that the results don’tsurprise him that much. “You know,” he says, “there is only 0.0003inch variation in diameter that I’m allowed. If I aim for exactlyhalfway between 0.5072 and 0.5075, I’m afraid that I’ll make a lotof short pieces that will have to be scrapped. I know from way backwhen I first started here that Mr. Harnswell and everybody elsewill come down on my head if they start seeing too many of thosescraps. I figure that if I aim at 0.5075, the worst thing that willhappen will be a bunch of downgrades, but I won’t make any piecesthat have to be scrapped.”
a. What approach do you think the machinist should take in termsof the diameter he should aim for? Explain.
b. What do you think that Natalie should do next? Explain.
