Design for Stamping: Identifying Pedagogically Effective Components in Multimedia Tutors and the...

July 2003 Journal of Engineering Education 227

CORRADO POLIMechanical and Industrial Engineering DepartmentUniversity of Massachusetts Amherst

DONALD FISHERMechanical and Industrial Engineering DepartmentUniversity of Massachusetts Amherst

ALEXANDER POLLATSEKPsychology DepartmentUniversity of Massachusetts Amherst

BEVERLY PARK WOOLFComputer Science DepartmentUniversity of Massachusetts Amherst

ABSTRACT

Multimedia tutors have been developed for a number of differentareas in manufacturing—including forging, die casting, andinjection molding. Typically, students using these tutors performbetter than students receiving traditional classroom instruction.However, the strengths and weaknesses of the tutors have notbeen isolated in any of the reports to date. This paper presents theresults of experiments designed to isolate the most effectivecomponents used to teach design for stamping. The experimentscompared classroom instruction with software tutorials. Theresults of these experiments indicate that the use of softwaretutorials when combined with feedback on graded homeworkassignments is as effective as traditional lectures that also makeuse of graded homework assignments

I. INTRODUCTION

In an effort to better educate students about manufacturing, stu-dents and faculty at the University of Massachusetts Amherst(UMass) have been developing interactive multimedia software tu-torials for teaching design for manufacturing (DFM). The overallgoals and objectives of the software tutorials (tutors) have been toenable students to identify difficult to create (expensive) features ofa part, to assist them in visualizing the tooling required to create thepart, and to provide them with the material that they need in orderto learn with understanding. These tutors contain slowed down an-imations of the most important manufacturing processes used inthe production of consumer products. They are designed to helpstudents overcome some of the inherent difficulties encountered

when viewing various manufacturing processes caused by the highspeed of the processing equipment (stamping) and/or OSHA safe-ty requirements.

To date four manufacturing software tutorials have been devel-oped, namely, one each for design for injection molding [1–3], design for forging [2, 3], design for stamping [2, 3], and design fordie casting. Formal and preliminary evaluative testing of the injectionmolding and forging tutors reveals that the tutors are approximatelyas effective as traditional lecture instruction. Numerous other com-parisons have now been made of tutors and classroom instruction, al-most all showing that tutors are generally more effective than class-room instruction [4–7]. However, the comparisons of various formsof tutor and classroom instruction that have been undertaken to datehave failed to identify those factors that make instruction via onemodality superior to instruction in other modalities. The overall goalof this research was to isolate the factors that made instruction instamping most effective, both when that instruction was delivered inthe classroom and when it was delivered using a multimedia tutor.

II. WHY MULTIMEDIA?

Multimedia tutoring systems have been shown to be highly effective with students [4–7]. Properly designed computer-based tu-tors have achieved the one-sigma effect [8], which is the same im-provement in learning that results from one-on-one human tutoringover classroom instruction. That is, on average, students who learnusing either computer-based tutors or one-on-one human tutoringperform at a level one standard deviation above the mean of studentswho learn using more traditional methods. Several success storieshave described students learning in one-third to one-half the time ittakes for a control group to learn the same material [9]. For example,undergraduate students using a Lisp tutor at Carnegie Mellon Uni-versity [10] completed programming exercises in 30 percent less timethan those receiving traditional classroom instruction did and scored43 percent higher on the final exam. In another study, students work-ing with an Air Force electronics troubleshooting tutor for only 20hours gained a proficiency equivalent to that of trainees with 40months (almost four years) of on-the-job training [6]. In a thirdstudy, students learned general scientific inquiry skills and principlesof basic economics in one-half the time required by students in aclassroom setting [9].

III. THE STAMPING TUTOR DEVELOPMENT TEAM

According to Bransford, Brown and Cocking [11], development of a successful tutor requires that the tutors:

Design for Stamping: IdentifyingPedagogically Effective Components inMultimedia Tutors and the Classroom

� be based on an organized knowledge domain as an expertwould organize it,

� be developed using an interdisciplinary software develop-ment team,

� contain a friendly and useable user interface,� include clearly identifiable learning objectives, and� have an introduction and a workshop.To meet these requirements, the UMass team formed contained

domain experts from engineering, and software and animation ex-perts from computer science. The domain experts provided clearlyidentifiable learning objectives while the software experts were responsible for the development of a friendly and useable interface.

A. The Team’s Domain ExpertiseWhen asked to provide a cost estimate for the production of a

special purpose part, a manufacturing vendor studies the drawing ofthe part and uses knowledge based on his or her extensive experi-ence (i.e., what we will refer to here as conditionalized knowledge) toretrieve the practical information needed to provide the estimate. Inthe case of a stamped sheet metal part, the expert visualizes the tool-ing required to produce the part and the potential difficulties pre-sented by the choice of part material and sheet thickness.

In an effort to emulate the vendor’s conditionalized knowledge, aknowledge acquisition phase was undertaken prior to developmentof the tutor. The approach used to acquire this domain expertise isdescribed in [12]. The goal of the knowledge acquisition phase wasto develop a group-technology based methodology [12] that couldemulate the ability of an expert vendor to visualize the tooling re-quired to produce the part and the potential difficulties presented bythe choice of part geometry, part material and part thickness.

The methodologies developed and outlined in [12] and described in greater detail in, [13], among other places, formed theorganized knowledge basis for the UMass tutors.

B. The Interdisciplinary TeamIn addition to the engineering domain experts, who wrote the

script and directed the production of the stamping tutor, animationand software experts were also part of the team. These experts wereprimarily faculty and students from the Computer Science Depart-ment. Their role was to produce high quality visually effective animations to illustrate the relationship between part geometry andthe required tooling.

C. User InterfaceThe software domain experts on the tutor development team

ensured that good color schemes and an agreeable layout with but-tons and drop down menus were used and properly located. Com-ments provided by users of the various manufacturing tutors [1–3]indicate that a pleasant and easily navigable interface was used oneach of the tutors.

D. Learning ObjectivesThe learning objectives of the UMass stamping tutor were to en-able users to:

a) identify costly to produce parts,b) suggest less costly to produce alternative designs,c) visualize the tooling needed to produce these geometries,

andd) learn with understanding.

E. Introduction and WorkshopThe stamping tutor has both an introductory module and a

workshop module. The introductory module provides the knowl-edge needed to understand the basic stamping process for individu-als, such as students who may have no previous knowledge of thesubject matter. The workshop module provides an opportunity forstudents to assess how well they have learned the elementary con-cepts explained in the introductory module. The tutor is designedso that one can go directly to the workshop module.

IV. THE SOFTWARE TUTORIAL

The actual design for stamping tutor, and in particular the intro-ductory module and workshop module, need to be explained inmore detail at this point in order to understand the evaluations ofthe tutor that we want to describe later in this paper.

A. Introductory ModuleIn the introductory module, the user is introduced to stamping via

a series of screens that contain text, animations, and voice-overs. Theemphasis in this module is to make the user aware of the relationshipbetween the shape of a part (part geometry) and the ease or difficulty ofconstructing the dies (tooling) required to produce the part.

The module begins with a short video clip of the stampingprocess (Figure 1), followed by an overview of the process using ani-mations, and a description of the equipment used. Students are alsointroduced to the various features found in stamped parts (holes,ribs, etc.) A more detailed discussion of the relationship betweenthe geometry of the part and the difficulty of producing the requiredtooling the follows. A combination of text, graphics (still and ani-mated), and voice are used. The final portion of the introductionsummarizes the various design for manufacturing (DFM) issues forstamping, namely: a) the number of distinct features, b) whether thefeatures are closely spaced or not, c) whether narrow cutouts andprojections are present, and d) the number of stages required tobend the part. The topics covered in the introduction are presentedin a sequential order to encourage the user to learn in an organizedmanner.

After viewing the video clip, the user is shown an animation ofthe stamping process. In this case, the animation shows a sectionalview of a simplified version of a progressive die used in creating aflat link (Figure 2). This stripped down, slowed down version ispresented so that the user can grasp and comprehend what is occur-ring over time as the die creates the part. It should be noted that theuser is not given an opportunity at this point (or at any other pointin the introductory module) to alter the sequence of steps in theprocess.

Figure 3 shows a snapshot version of one of the animations usedto illustrate the creation of a more complex bent part. The imageshown here was captured as the punches complete their downwardstroke. As seen in Figure 3, the die is divided into six sections or sta-tions that include five active stations and one idle station. The firstactive station consists of a punch creating a pilot hole for use in lo-cating the strip as it moves from station to station. Although twopilot holes are generally used, only one pilot hole is shown here tosimplify the instruction. The second active station consists of twonotching punches used to create the peripheral shape of the partprior to bending. There are two bending punches, one directly

228 Journal of Engineering Education July 2003

behind the other, at each bending station. At bending station 1, thefront punch bends plate 1 (see corresponding number in Figure 3)while the rear punch bends plate 2. At bending station 2, the frontpunch bends plate 3 while the rear punch bends plate 4. The last ac-tive station consists of a punch used to separate the part from the strip.The top view of the strip is referred to as a process plan or strip layout.

B. The Active Learning Workshop ModuleThe workshop module provides users with the opportunity to de-

termine how well they have mastered the concepts presented in theintroductory module. In this module, users are allowed to design and‘build’ a part from a restricted family of part geometries and to obtaina design evaluation of the part tooling similar to the one illustrated in the Evaluate window shown in Figure 4. If users haveunderstood the concepts presented in the introduction, it was hopedthat they would be able to visualize the tooling required to producethe part. That is, it was hoped that they would be able to recognizewhether or not the part designed or selected is easy to produce and, ifnot, they would know how to alter the design to reduce costs. What

follows is a description of a small portion of one of the workshopmodules found in the stamping tutor. It deals with the effect of usingdistinct features on the number of stations required to produce thepart.

As seen in Figure 4, this particular workshop consists of threewindows, a Design window, a Tooling window and an Evaluatewindow. A fourth window, not shown here, is a Help window thatexplains to the user how to design a part and obtain the resultingtooling for that design.

A part is created in the Design window by clicking on one of thefeatures (hole, rib, emboss, or extruded hole) and dragging it ontothe metal strip. In this illustration four distinct features have alreadybeen dragged onto the strip. The Tooling window contains an ani-mated version of the five-station tool required to stamp the flat stripshown in the Design window. If the user recalls the Design ForManufacturing results summarized in the introduction, he or shewill realize that five stations will be required to produce the part.The user can verify that five stations are necessary by clicking on the�show tooling and evaluate� button. Evaluations of the design,the relative tooling cost for this design (not shown here), and a re-design suggestion, are contained in the Evaluate window. The re-design suggestion made in this case is attempting to get the user torecall that one of the design for manufacturing rules presented inthe introductory portion of the tutor stated that the number of dis-tinct features should be minimized. In this case, the user might de-cide for the particular project he or she had in mind that, say, thattwo extruded holes could take the place of the separate hole and ex-truded hole, thus potentially reducing by one the number of differ-ent punches need to create the part.

V. DID THE STAMPING SOFTWARE TUTORIALACHIEVE ITS LEARNING OBJECTIVES?

To determine whether or not the stamping tutor met its learningobjectives an evaluation of the tutor was carried out during theSpring 1999 semester. Twenty-two undergraduate mechanical en-gineering students at UMass, none of whom had ever had previous


Figure 1. One frame from the video clip showing a sheet-metal strip being fed through a progressive die as it creates a part (inset picture onright) from a flat metal strip. Because of the speed of the mechanical press (about 1 cycle/second) it is difficult for the user to watch the video clipand see what is actually occurring.

Figure 2. A snapshot of the animation showing a progressive diecreating a simple flat link. The sheet metal strip in the animationmoves from right to left.

exposure to stamping, spent about one hour each using the tutorand were then asked to take a quantitative evaluation test. Studentswere permitted to access the tutor during the post-test. Concur-rently with this, seventeen graduate students in the Department ofDecision Sciences and Engineering Systems at Rensselaer Poly-technic Institute (RPI) were introduced to stamping via a fairlystandard lecture approach in which only black and white engineer-ing drawings were used to illustrate the stamping process. Follow-ing this one-hour lecture they were then asked to take the samepost-test as the UMass students. These students, although moreadvanced, also had no prior knowledge of stamping. They were per-mitted access to their lecture notes during the post-test.

The overall results of the post-test are presented in Table 1. Thestudents who used the tutor outperformed the students given astandard lecture, t(37) � 2.29, p � 0.05. Similar to evaluations of


Figure 4. A snapshot from one of the workshop modules for flat parts available in the stamping tutor.

Table 1. Post-test results of the design for stamping tutor.

Figure 3. A snapshot of the animation showing a progressive die creating a bent part. There were no labels in the actual tutorial; the labels inthis figure were provided to aid the exposition of the module.

other tutors, there is close to a one standard deviation improvementin the performance of students who are exposed to a tutor as op-posed to a standard classroom lecture.

In order to understand better the reason for the improvement, itis useful to consider in more detail the sections of the test that wereused to evaluate overall performance. The test consisted of threesections. In the first section, students were presented with isometricdrawings of four parts and asked to indicate whether or not theparts could be stamped, and, if so, to list those active stations re-quired to create the part. They were also required to make redesignsuggestions in order to reduce tooling costs. The results indicatethat both the tutor and lecture students were able to identify fea-tures costly to produce and to make redesign suggestions that wouldreduce tooling costs. What the test also seemed to indicate was that,for bent parts at least, unless students are first shown the toolingand/or strip layout for the part, they have difficulty identifying thesequence of operations that should occur as a part is being formed.In particular, they had difficulty comprehending that before bend-ing can take place, notching is needed in order to provide the partwith its proper peripheral shape. This indicates that a key conceptwas not learned, for either the tutor group or the lecture group.Problems with notching occurred for over 80% of the students inboth groups.

In the second section of the test, students were shown a part anda viable strip layout (top view of the sheet metal strip) for producingthe part. They were then asked to indicate on the strip layout wherenotching and bending occurred. The students who used the tutordid reasonably well on this portion of the test whereas the studentswho were exposed to a traditional lecture had difficulty. This is notsurprising since both strip layouts and animations were used in thetutor while neither was used in the lecture. In the animations theycould actually see what was happening at each station to the striplayout and, as a result, processed that information more deeply thanstudents who were not presented an animated version.

In the final section of the test, students were shown a part andthe tooling required to produce it. They were asked to label the vari-ous portions of the tool. Both students exposed and not exposed tothe tutor did well. Thus, if given the strip layout and/or the toolingneeded to produce the part, students realized that notching wasrequired first. However, when not given the tooling, as in the firstportion of the test, the students failed to realize that notching isrequired.

These test results indicate that the students using the stampingtutor performed almost one standard deviation better than studentsexposed to the standard lecture. Moreover, it looks like the locus ofimprovement is exactly where we expected it to be, on that portionof the material where animation would help. However, it also ap-pears that as currently structured neither the multimedia tutor northe traditional lecture approaches completely enabled learning withunderstanding. The failure of students to realize that notching is re-quired before bending and that, more generally, a part must begiven its external shape on a strip before any bending can occur, in-dicates a deeper problem that students are having in visualizing theentire stamping process. The deeper problem could appear as a fail-ure to master one of two skills. The first is that students must beable to visualize both the unfolding of a part required to generatethe strip layout and the folding required of the strip layout to regen-erate the part. The second is that students must be able to visualizethe sequence of operations required to give a part its external shape

before any folding takes place. The next section discusses some ofthe experiments carried out to determine whether unfolding andfolding is a major visualization.

A. Visualization Tests (Unfolding and Folding)In most cases, the first step in designing a bent thin-walled sheet

metal part is to create a solid model version of the part using soft-ware such as ProE or Inventor. Following the creation of the solidmodel version of the part, the software is then used to unfold or flat-ten the part in order to determine whether or not the part can in factbe formed from a flat sheet metal strip. Once it is ascertained thatthe part can be formed from a flat sheet of metal, a series of shearingand bending (folding) operations are required to convert the flatsheet into the final part. With this in mind, a two-part visualizationtest was created which focused on part unfolding (Part I) and partfolding (Part II).

In Part I of the test, students were shown pictorial views of vari-ous thin-walled parts. The purpose of this test was to determinewhether students could visualize how these parts with bends wouldappear when unfolded so that they could ascertain whether or notthe parts could in fact be created from a single sheet of paper ormetal. For those parts that could be created from a single sheet ofpaper, students were asked to create a drawing of this same part as itwould appear after it is unfolded. For those parts that could not becreated from a single sheet of paper, the students were asked to ex-plain why they could not. Figures 5 and 6 show two of the drawingsof parts that appeared on the test. Figure 5 is a drawing of a part thatcan be formed from a single sheet of paper, hence is stampable,while Figure 6 shows a part that is not stampable since sides A andB would overlap when unfolded.


Figure 6. Example of a non-stampable part.

Figure 5. Example of a stampable part.

Part II of the test, taken a month later by the same students, con-sisted of showing students pictorial views of various bent parts alongwith three flat patterns (Figure 7). Students were asked to pick thepattern, which when folded, would produce the part shown in thepictorial view.

The same forty first-year students in Mechanical and IndustrialEngineering at the University of Massachusetts, Amherst, tookPart I and Part II of this test during the fall 2001 semester. Thefreshman course in which the students were enrolled dealt with en-gineering communications skills and emphasized drawing, oral andwritten communications, and teamwork. A semester long designfor assembly project was used as a catalyst to teach communicationsskills. At the time the tests were taken, the students had not yetbeen introduced to the manufacturing process of stamping.

Table 2 shows a summary of the test results. On average, students answered 84.6% of the Part I questions correctly and97.2% of the Part II questions correctly. Students performance onPart I differed significantly from their performance on Part II,t(38) � 6.47, p � 0.001, indicating that they were significantly bet-ter at folding a part than they were at unfolding a part. The relative-ly poor performance of students when asked to unfold an isometricview of a part is consistent with the results from the evaluation ofthe stamping tutor and, therefore, may explain some of the difficul-ties that students had with the test. In particular, recall that the stu-dents had difficulty answering those questions on the stampingtutor which asked them to identify the active stations required tostamp a part shown in such a view. In order to identify these activestations the students needed to unfold the part, which requiresthem to imagine a flat, uncut strip being cut so that after one ormore operations the peripheral shape of the part appears on thestrip. If they are having difficulty unfolding a part and giving thatpart its unfolded peripheral shape, then they may forget that theyneed to notch the part prior to folding (bending).

Based on the unfolding and folding test results, it may make senseto give students practice unfolding an object presented in an isometricview. However, it is not likely that improvement in students’ unfold-ing skills would eliminate the various problems that students had onthe stamping tutor, and in particular, the problems that they had onthe first part of the evaluation of that tutor. This follows because theobjects that students were given on the first part of the stamping tutorwere generally more simple (had fewer features) than the objects thatstudents were given on the unfolding test. Thus, there is still reason tobelieve that some students had difficulty sequencing the operationsthat are designed to give a part its peripheral geometric shape.

VI. STRIP LAYOUT INSTRUCTION

As all parts in stamping begin as a flat sheet of metal, one mustfirst determine (visualize) the sequence of operations required togive a part its proper peripheral geometry (outside contour or shape)prior to bending or folding the part to provide it with its final shape.The ability to visualize this sequence of operations typically requiresyears of experience in the field, and the results from Experiment 1demonstrate that students have difficulty with this visualization.However, we believed that it was possible to reduce the time re-quired to learn how to visualize the requisite sequencing throughappropriate instruction. Because we were not sure just how exten-sive instruction would need to be, we developed three differentforms of the traditional classroom lecture instruction as well as twoforms of multimedia software tutorial instruction.

A. Objectives of Classroom InstructionOur development of the three modes of classroom instruction

was based on the following logic. If students are having troublevisualizing the sequence of operations, then students who both sat


Figure 7. Sample part from the folding portion of the visualization test. Dashed lines are used to indicate bend lines. The correct answer is (b).

Table 2. Results of the unfolding and folding tests.

through a classroom lecture and were given access to the source ma-terial upon which the lecture was based (containing additionalworked out examples) should do better on a test of their strip layoutknowledge than students who just sat through the lecture. More-over, giving students feedback on their homework problems in ad-dition to having access to the source material and sitting throughthe lecture should improve their performance further. In short, wehad three forms of classroom instruction: lecture only (VideoGroup A), lecture plus source material (Video Group B), lectureplus source material and feedback on homework problems (Tradi-tional Classroom). In order to make the comparison between thegroups more diagnostic, we did not allow students to ask questionsduring the presentation in Video Groups A and B, but did allowthem to ask questions in the Traditional Classroom Group. We willelaborate on this in the discussion.

B. Objectives of the Strip Layout Tutor1

In addition to comparing students’ performance on differentmodes of classroom instruction, we wanted to evaluate students’performance on a tutor. Typically, as we saw in Experiment 1, stu-dents perform at least one standard deviation better when using asoftware tutorial than they do when exposed only to a traditionalclassroom lecture. However, students’ performance on a tutor isusually compared with just one type of classroom instruction. Herewe could determine whether students using the software performedbetter than students exposed to the most effective classroom in-struction or, instead, their performance was better than only somemodes of classroom instruction. Thus, we can hopefully isolate thefactors that are leading to relative advantages of the two modes ofinstruction. We now describe the details of the Strip Layout Tutor.Like the classroom instruction, the goal of the strip layout tutor wasto provide students with a structured methodology for determiningthe proper sequence of operations (i.e., the strip layout) needed toproduce a sheet metal part by use of a progressive die. A critical de-sign feature of both the tutor and classroom instruction was to min-imize those visualization requirements that depend heavily on theconditioned knowledge possessed only by stamping experts. In par-ticular, an attempt was made to give the students a procedure for se-quencing the bending and notching operations that reduced greatly

their reliance on visual short term memory and the need mentally torotate, translate and transform objects in that memory.

C. Introductory ModuleThe Strip Layout Tutor includes several knowledge-centered

sections which focus on communicating the necessary backgroundinformation needed to be able to develop a strip layout or processplan. The introductory module begins with a review of some of thebasic concepts presented in the Stamping Tutor. Lessons dealingwith the unfolding of parts and schemes for arranging an unfoldedpart on a flat metal strip follow this introductory module. We willrefer to this as the structured approach because the student first laysout the structure (peripheral shape) of the unfolded part on the flat sheet of metal. Figure 8 shows two alternative layouts taken fromthe Strip Layout Tutor for a part similar to the one shown in Figure 7.The purpose of showing these layouts is to indicate to the user thesize and shape of those areas around the periphery that must benotched prior to folding or bending the part. Following the presen-tation of these layouts, a detailed station by station process plan orstrip layout is presented illustrating to the user how to go from thelayouts shown in Figure 8 to the final plan presented in Figure 9.

D. Workshop ModuleUpon completion of the knowledge-centered portion of the

tutor, the user moves into the workshop. The workshop consists offive active learning modules where the user has the opportunity to


1The Strip Layout software was developed by Maria Benson and Nick Steglichof the University of Massachusetts Amherst.

Figure 8(a). One potential layout for the unfolded part shown inFigure 7.

Figure 8(b). Another potential layout for the unfolded partshown in Figure 7.

Figure 9. Final process plan for the layout shown in Figure 8(a).

practice developing a strip layout for five different parts. Since mul-tiple possible layouts exist for a part, the user is asked to create theprocess plan or strip layout for a specified layout.

The workshop is structured so that the user develops a strip layoutby selecting the specific operation required at each die station fromamong multiple choices provided by the software. Figure 10 showsthe layout to be used for the part shown in Figure 11, while Figure 11shows a screen capture taken from Workshop 3. Figure 12 shows thefeedback obtained if the user selects B as the choice for station 2. Insome cases, as shown in Figure 11, more than one possible “correct”choice exists. If the student chooses a correct choice that is not opti-mal, there is feedback that indicates that while this choice is not in-correct, a better choice exists (Figure 12). If the user selects the best

choice first, then feedback to the student explains why this is the bestof all possible choices, and why the other choices are less favorable.

E. HypothesesBased on the results from Experiment 1, we expected that stu-

dents exposed to the tutor would perform better than students ex-posed to a classroom lecture who were not given access to the sourcematerial. We had no a priori hypotheses about the relative perfor-mance of students using the tutor compared to those of students exposed to the two other types of classroom instruction.

F. MethodThe different types of instruction were evaluated using five dif-

ferent groups of third year mechanical and industrial engineeringstudents at the University of Massachusetts Amherst. The com-plete details of the procedure are given in the bullets below.

Each of the five groups was initially exposed to some form of thestrip layout instruction. Those learning in the classroom were thengiven homework problems to complete. Those exposed to only thetutor had the opportunity as they worked their way through the lesson to solve problems similar to the ones that were assigned sepa-rately to students receiving classroom instruction. The post-test con-tained isometric drawings of five parts including one that could notbe stamped. The parts varied in complexity (number of features) andwe hypothesized that this complexity would have an effect on per-formance. Students were asked to create a process plan or strip layout


Figure 10. Sketch of part layout to be used to develop the processplan for creating the part.

Figure 11. Creation of station 2 during the strip layout devel opment for Workshop 3. Station 1 is used for creating a pilot hole.

Figure 12. Feedback obtained when the user selects B in Figure 11. The correct selection is C.

for any part that could be stamped. Figure 5 is a drawing of one ofthe parts that appeared on the post-test. All lectures, both taped andlive, were given by the lead author of this paper. In addition, the soft-ware tutor was principally based on Chapter 8 of [15].

a) Software Tutor Only Group (Fall 2000). This group was in-troduced to strip layout development by use of the Strip LayoutTutor and was permitted use of the software during the post-test.Note that although this group did not have homework questionsper se, they did get the opportunity to practice the same generaltypes of questions on the tutor that were used as homework for thetraditional classroom lecture described below.

b) Video Lecture Group A (Fall 2000). This group was intro-duced to strip layout development by viewing a videotaped PowerPoint lecture that followed the Strip Layout Tutor closely. Thisgroup was given a copy of the Power Point slides and had access tothese slides during the post-test. However, since this was not a livelecture, the students were not able to ask questions.

c) Video Lecture Group B (Spring 2001). This group was alsointroduced to strip layout development by viewing the same video-taped, Power Point lecture used by Group A. This group was givena copy of the Power Point slides and had access to these slides dur-ing the post-test. This group was also given a copy of Chapter 8from Ref. [15] that formed the basis for both the software and thevideo-taped lecture. This group was permitted access to Chapter 8during the post-test. Once again, since this was a taped lecture, stu-dents were unable to ask any questions.

d) Traditional Lecture Group (Fall 2001). This group receiveda live lecture based on Chapter 8 of [15]. Since the lecture was live,questions were permitted. In addition, this group was given ahomework assignment dealing with strip layout development. Aswith other homework assignments in the course, these homeworkproblems were to be turned in, graded, and discussed in class. Manyquestions were asked and many of the student’s muddy points (i.e.,concepts students failed to understand) were cleared up when thehomework was discussed in class. This group was permitted accessto Chapter 8 during the post-test.

e) Software Tutor Plus Homework Group (Fall 2002). Thisgroup was introduced to strip layout development by use of theStrip Layout Tutor, and was given the same homework assignmentas the Traditional Lecture Group. This homework was turned in,graded and discussed in class. This group was not permitted use ofthe software during the post-test.

G. Evaluating the Different Modalities of Strip Layout InstructionTable 3 shows a summary of the post-test results. Interestingly,

there was no effect of part type (complexity) (1–5), but a large andsignificant effect of group, F(3,101) � 15.65, p � 0.001.

Post-hoc comparisons indicated that students in the traditionallecture group and the software tutor plus homework group whowere allowed to ask questions about their homework exercises performed better than students in any of the other three non-homework discussion groups (all p values were less than 0.05). Inaddition, students in the two software tutor groups performed sig-nificantly better than students in the video lecture group that wasnot given access to source material (video lecture group A;p � 0.01). However, there was clearly no difference in the perfor-mance of students learning with the tutor only and students in thevideo lecture group who were allowed access to source material(video lecture group B). There was also no difference in the perfor-mance of students learning with the tutor plus homework and stu-dents in the traditional lecture group.

Before discussing the results of the post-test it is necessary to re-call from the earlier section “Does the Stamping Tutor Achieve ItsLearning Objectives?,” that: a) prior to the development of eitherthe strip layout tutor or a lecture students had difficulty in just list-ing the sequence of operations needed to produce a bent part, and b) problems with notching occurred for over 80% of the students.The results in Table 3 show, however, that by using either the soft-ware or lecture versions of the strip layout tutor the students’ abilityto develop process plans for stamped parts improved dramatically.Here, they are answering at least 50% of the questions correctly.This was particularly true when students were permitted access toreference material, such as software or Chapter 8 of [15] during thepost-test.

Most of the post-test errors occurred when students rejected theuse of the structured approach outlined in both the lecture and soft-ware versions of the tutor. That is, students who used a structuredapproach would explicitly draw the peripheral shape of the unfoldedpart on the strip layout and then create the notching and bendingstations with the peripheral shape externally represented. Studentsusing an unstructured approach would have needed to visualize theperipheral shape without actually drawing it, much as experts cando. However, unlike experts, they do not have available the neces-sary conditioned knowledge and experience which would enablethem to create the process plan in this manner. Since studentslacked the experience needed to use such a more visual approach,the layouts produced consisted of somewhat random spacing be-tween stations, incorrect peripheral shapes, and inconsistent and/orincorrect sequence of operations between stations. Similarly, mostof the errors found on the homework assignment also appeared tobe primarily caused when students discarded the use of the struc-tured approach.

Perhaps the most striking aspect of the results is the finding ofwhat we will call a reverse one sigma effect. Specifically, students ex-posed to the traditional lecture, who were able to discuss questionsthat they had about their homework, performed on average onestandard deviation better than students who were exposed to eitherthe software tutor alone or the traditional lecture alone (video) withsource material. This begs the question: when stamping is the focusof the instruction, why do students exposed to the stamping soft-ware tutorial alone perform one standard deviation better than stu-dents exposed to the traditional lecture, but when strip layout is thefocus of instruction, they perform one standard deviation worse?We believe that the answer is a simple one. When students weretaught how to lay out a strip using the traditional lecture method, adiscussion of the major sources of errors found on the homework


Table 3. Results of the Strip Layout Tutor evaluations.

took place prior to the post-test. This discussion was used todemonstrate that most of the errors could be eliminated by use ofthe more structured dependent approach to process planning.However, when students were taught about the operation of stamp-ing using the traditional lecture method, there was no discussion ofthe major sources of errors found on the homework. Thus, wewould argue that, as a result, the traditional lecture students and thesoftware plus homework student achieved the highest post-testscores on each and every post-test problem for the strip layout unit.

VII. SUMMARY

We have shown that an intelligent, multimedia tutor can achievethe standard one sigma effect that has been reported widely in theliterature. Specifically, in the stamping unit, the students using thetutor performed one standard deviation better on average than stu-dents exposed to traditional lectures. We have argued that themajor difference between stamping as taught by a tutor and stamp-ing as taught in the classroom is the inclusion in the tutor of the ani-mation of manufacturing operations that are difficult to view whenseen in real time. Until recently, output from PCs was not easilyprojected on a screen large enough for an entire class to view. Thus,the delivery of instruction that included the animation had largelyto occur on PCs (i.e., tutors). However, now with much better pro-jection capabilities and much less expensive equipment to realizethese capabilities, the advantage of the tutors could potentially beachieved in the classroom via projection of the animated sections ofa lecture. Thus, what we may need is a blend of instructional tech-nologies.

Somewhat surprisingly, we have also found that students exposedto traditional instruction can outperform students using only a soft-ware tutorial, again by as much as one standard deviation. Specifical-ly, in the strip layout unit, the students exposed to a traditional class-room lecture that included feedback on assigned homeworkproblems performed one standard deviation better than studentsusing a tutor without the benefit of feedback on homework. Howev-er, when the benefits of feedback on homework are included withthe use of a software tutorial these students performed at least as wellas those exposed to a traditional lecture. This tells us that studentswho attempt problems and get directed feedback on their perfor-mance do profit from that feedback by some considerable amount.Unfortunately, it may not be easy to develop a tutor that would givethis kind of instruction, as it would likely require a more precisemodel of the students’ difficulties than we have at present. Thus, fornow, a blend of instructional modalities may produce the largestgains in student performance. Finally, we looked at the failures of thevarious types of instruction, as well as their successes. We found thatperformance, both on the tutors and in the classroom, were less thanperfect. We have argued that the less than perfect performance canbe traced to difficulties that students have visualizing both the un-folding of an isometric view of a part and the sequencing of thenotching operations needed to cut the strip in ways that generate theperipheral shape of the part (leaving it attached to the carrier strip allthe while). Thus, we have been able to identify not only how instruc-tion in one or the other modality might be improved, but how in-struction in both modalities needs to be improved.

Our findings, while holding true for stamping, may not easilygeneralize to other topics in manufacturing and more broadly in

engineering, science and mathematics. Clearly more research needsto be done. Our methodology may also be limited in its generality.Still, we see much to be gained by a more microscopic analysis ofthe evaluations of the performance of students exposed to differenttypes of instruction. In this way the best parts of each can be isolatedand then recombined in ways that make for the most effective andleast costly instructional alternative for a given situation.

ACKNOWLEDGMENTS

Portions of this research were supported by a grant from the Gen-eral Electric Fund and the National Science Foundation Knowledgeand Distributed Intelligence Initiative to Donald L. Fisher

REFERENCES

[1] Riggs, Brian, Corrado Poli, and Beverly Woolf, “A MultimediaApplication for Teaching Design for Manufacturing,” Journal of Engineer-ing Education, Vol. 87, No. 1, Jan. 1998.

[2] Poli, Corrado, and Beverly Woolf, “Design for Manufacturing Tutorial—A Multimedia Approach,” Proceedings of the 1999 American Society of Engineering Education annual Conference and Exposition, Charlotte, NC, June 1999.

[3] Poli, Corrado, Ian Grosse, and Beverly Woolf, “Multimedia-BasedActive Tutors—A New Approach to Teaching Design for Manufactur-ing,” Proceedings of the 4th ASME Design for Manufacturing Conference, LasVegas, Sept. 1999.

[4] Anderson, J.R., C.F. Boyle, and G. Yost, “The Geometry Tutor,”Proceedings of the Ninth IJCAI, Los Angeles, Morgan Kaufmann: SanMateo, CA, 1985.

[5] Katz, S., A. Lesgold, G. Eggan, and M. Gordin, “Modeling theStudent in Sherlock II,” Journal of AI and Education, Vol. 3, No. 4, 1992.

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[7] Woolf, B., “AI in Education,” Encyclopedia of Artificial Intelligence,Second Edition, John Wiley & Sons: New York, NY, 1992, pp. 434–444.

[8] Bloom, B.S., “The 2-Sigma Problem: The Search for Methods ofGroup Instruction as Effective as One-to-One Tutoring,” Educational Researcher, Vol. 13, 1984, pp. 4–16.

[9] Shute, V.J., and R. Glaser, “A Large-scale Evaluation of an Intelli-gent Discovery World: Smithtown,” Interactive Learning Environments,Vol. 1, 1990, pp. 51–77.

[10] Anderson, J.R., “Analysis of Student Performance with the Lisptutor,” Diagnostic Monitoring of Skill and Knowledge Acquisition, LawrenceErlbaum, Hillsdale, NY, 1990.

[11] Bransford, John D., Ann L. Brown, and Rodney R. Cocking (editors), “How People Learn—Brain, Mind, Experience, and School,”National Academy Press, Washington, D.C., 1999 (available on line at�http://www.nap.edu�)

[12] Poli, Corrado, Pratip Dastidar, and Robert Graves, “DesignKnowledge Acquisition for DFM Methodologies,” Research in EngineeringDesign, Vol. 4, pp. 121–145, 1992.

[13] Poli, Corrado, P. Dastidar, and P. Mahajan, “Design forStamping—Analysis of Part Attributes that impact Die ConstructionCosts for Metal Stampings,” Journal of Mechanical Design, Vol. 115,pp. 735–743, Dec. 1993.


[14] Narayanan, N.H., and M. Hegarty, “Designing ComprehensibleInteractive Hypermedia Manuals,” International Journal Human-ComputerStudies, Vol. 48, pp. 267–301, 1998.

[15] Poli, Corrado, Design for Manufacturing—A Structured Approach, Butterworth-Heinemann, Woburn, MA, 2001

[16] Romoser, M.R.E., and D. L. Fisher, “Maintaining KinematicConstraints when Performing Mental Rotations About a Fixed Axis: Im-plications for Instruction and Displays, “Proceedings of the Annual Meetingsof the Human Factors and Ergonomics Society, Minneapolis, Minnesota, October, 2001.

AUTHORS’ BIOGRAPHIES

Corrado Poli is a professor in the Department of Mechanical andIndustrial Engineering. He has been involved in several NSF-funded research projects dealing with assembly, forging, injectionmolding, die casting and stamping. His research publications include some 90 papers, four text books, including two on Designfor Manufacture and two handbooks. Dr. Poli has been pivotal tothe creation and funding of the Engineering Academy of SouthernNew England, which focused on reform of the engineering curricu-lum. He has designed new courses and led the movement towardsusing software tutors in the classroom.

Address: Department of Mechanical and Industrial EngineeringDepartment Engineering Lab Building, Box 32210, University ofMassachusetts Amherst, Amherst, MA, 01003-2210; telephone:413-545-0212; e-mail: [email protected].

Donald Fisher is a professor in the Department of Mechanicaland Industrial Engineering. He is a member of the Human FactorsCommittee of the National Academy of Sciences and serves on several editorial boards, including Human Factors and the Journal ofExperimental Psychology: Applied. He has published over 100 techni-cal papers. His research in the general areas of transportationhuman factors, visualization and spatial reasoning, and assistive

technologies is funded by grants from the National Science Foundation, the General Electric Fund, the Link Foundation forSimulation and Training, the Massachusetts Highway Depart-ment, and the National Cooperative Highway Research Project.He is director of the Human Performance Laboratory which hous-es one of the most advanced driving simulation facilities in thecountry.

Address: Department of Mechanical and Industrial Engineering,University of Massachusetts, Amherst, MA, 01003; telephone 413-545-1657, e-mail: [email protected].

Alexander Pollatsek is a professor emeritus in the Department ofPsychology. In addition to having a Ph.D. in psychology, he has anM.S. in chemistry and an M.S. in mathematics. His research hasbeen continuously funded for 20 years from grants from NIH andNSF. His research interests are varied, involving using eye move-ments to study reading and scene perception, examining difficultiesof students in statistical and scientific reasoning and mathematicallymodeling various psychological processes. His research publicationsinclude some 130 papers, and two textbooks. He served for manyyears on a grant panel for NIH and is a consulting editor for severaljournals.

Beverly Woolf has both a Ph.D. in Computer Science and an Ed.D. in Education. She teaches both in the Department ofComputer Science and the School of Education. Her work focuses on development of advisory, explanatory, and tutoring systems for a wide range of pedagogical domains. She is an acknowledged leader in the area of computer science and educationand currently leads four NSF or Department of Education sponsored projects to develop educational multimedia systems. Shehas published more than eighty articles on educational software andhas presented her work in dozens of foreign countries.

Address: Computer Science Department, Computer Science Building, University of Massachusetts Amherst, Amherst,MA, 01003; telephone 413-545-4625; e-mail: [email protected].


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