**6.2 MDSU-based construction of 3D objects by means of wire bending**

A set of questions were applied after the students executed the second experiment. There were almost the same questions that in the first experiment. These set of questions will help to us detect the impact of our methodology which is inspired in TRIZ principles. In this section first we will present the questions that are unique to this experiment then in the following section we will present the comparison between the first and second experiments.

The MDSU methodology was executed twice. With respect to the question about the unfolding the options for both executions are: separate the base and sectioned walls, keep the base with sectioned walls, base and walls sectioned, keep some section of the based together to the walls and other. In the first intend, 42% of the novice students chosen the second option while 42% of the advanced students chosen the first option. In the second intend both types of students exchange their choices. In general the first two options were chosen by both types of students. We think that students did not explore other potential possibilities because time restrictions on the experiments. We also asked to the students if the unfolding stage was confused and why. The results showed to us that almost half of the students consider confuse the unfolding stage. The most important reason why they consider that the unfolding is confused is that was difficult to imagine the unfolding.

TRIZ-Based Design of Rapid 3D Modelling Techniques with Formative Manufacturing Processes 185

Two final important questions were compared. The first was about the complexity of the experiment. At 100%, both group of students considered that the MDSU methodology is less complex than the freeform methodology. Advanced students feel that MDSU methodology reduces the complexity more than the novice students do. The other important question is more related to cognitive processes, specially the creativity. At 100% and 75% (more at 75%) feel that the MDSU methodology reduces the generation of ideas to improve the process.

**6.4 Automated machine for rapid 3D physical modeling based on wire bending** 

the contrary novice students have not used so much software as advanced students.

conditions.

The next series of questions were about the criteria to be considered in the design of a machine that automate the MDSU process. The list of criteria is: design, functionality, manufacturability, execution times, precision, size, feasibility, sustainability, security, easy machine user interaction. For the novice students, the functionality criteria was the most important among all the criteria, followed by manufacturability, execution time, security, then by the design and machine user interaction. For the advanced students the security criteria was the most important followed by the machine user interaction and then by the functionality criteria. Another series of questions were about the criteria students will consider to select if the machine already existed. Novice students selected the precision as the most important factor followed by material optimization and mesh structure. Advanced students selected the precision as well as the most important factor followed by material optimization and mesh structure. The size of the machine was the less important factor. Another important question was about the students' opinion if the machine will be dedicated to prototypes or final products. 90% of both types of students believe that the machine will serve for prototypes. The last series of questions we asked to the students were about their appreciation of the MDSU-based machine on: reducing complexity, reducing creativity, reducing manufacturing time, and improves work conditions. 49% and 47% of novice and advanced students respectively believe that the MDSU-based machine reduce the complexity of manufacturing 3D Wireframing objects. 49% and 24% of novice and advanced students respectively believe at 100% that the MDSU-based machine will reduce the creativity. This criteria has a more uniform distribution from the 25% to 100%. 75% and 66% of novice and advanced students respectively believe at 100% that the MDSU-based machine will reduce the manufacturing time. Among the set of criteria evaluated in this last series of questions this is with the more believability. The last criterion in this series is about the improvement of work conditions. 60% and 66% of novice and advanced students respectively believe at 100% that the MDSU-based machine will improve the work

The first question of this experiment was about the credibility of both groups of students about the feasibility of automating the MDSU process. 96% and 97% of the novice and advanced students respectively thought that the MDSU process can be automated. Students that do not believe in the automation of the MDSU process justified their answer by stating that such process is not really necessary. We believe that such answers were because they are young and do not foresee potentialities in automating such methodology. From the question that the MDSU process will need a software, 82% and 97% of the novice and advanced students respectively believe that the MDSU process will need a software. Our interpretation of the difference in results is that advanced students have used more software than novice students and therefore they do not see the MDSU process without software. On

Another question was related to the complexity of the union sub-process in the MDSU methodology. 29% and 42% of novice and advanced students respectively considered the union sub-process as complex.

In a later section we will compare the first experiment with the second experiment in this parameter. We will also present a comparison of some criteria students took into consideration to select their proposals. Here we present some of the criteria that are not comparable and belong only to the MDSU methodology. Students were asked if once the object was unfolded sectioning was easy. 32% of both type of students considered at 100% that the model was easy to section. Students were asked about other criteria considered to decide their proposals. But they are less relevant for the objective of this study and therefore we will not present them here. Students were also asked about difficulties on the MDSU and related processes but the results will be presented in the following section.

#### **6.3 Comparison between the first and the second experiment**

The first compared question is about the geometrical form used in the meshing sub-process (finite element). According to our statistics, most of the geometrical forms used were mix. Both types of students mix more the geometrical figures during the second experiment. In novice students increased 20% while in the advanced students the increase was about 32%. Therefore, there is some evidence that the MDSU methodology help to increase the variability of geometrical forms used in the meshing sub-process. The use of mix forms was superior in the advanced students that in the novice students. The basic form with significant more use after the mix was the circle. This form was reduced about 24% in novice students and 15% in advanced students from the first to the second experiment. The use of triangle was not significantly changed as well as the square. Another important change was perceived in the spiral form; it was reduced about 7% in novice and advanced students. Other forms used where polygon. As we can appreciate the MDSU methodology impact positively the variation of forms more in the advanced students that in the novice. This may be due to the freedom feeling experienced by the advanced students. The triangle is the most suggested form used in finite element theory and according to our statistics it was not changed significantly. This is a positive result because the MDSU does not affect the percentage of use in this form.

When comparing the design criteria for choosing the proposals. The MDSU methodology impacts positively advanced students. For such group of students and at 100%, the criteria is increased by 8% while for novice students the increase is about 7% On the other side, when comparing the easy to build criteria a significant increase is perceived in novice students from 50% to 75%, the increase at 75% is about 29%. At 100%, both groups of students showed an increase when using the MDSU methodology. 15% in novice students and 9% in advanced students. With respect to material optimization criteria, the behavior is of the same kind but at different percentages. The increase at 100% was about 6% in novice students while 8% in advanced students.

The experimentation time had a positive impact also. The more significant increase was shown between 0 and 15 minutes for novice students. By using the MDSU methodology they increase 14% their experiment time. The timeframe between 15 and 30 minutes have had also a positive impact by decreasing less than 10% percentage. Timeframes above 30 minutes had a reduction. These results shown that the MDSU methodology reduces the timeframe spent in the experiment.

Another question was related to the complexity of the union sub-process in the MDSU methodology. 29% and 42% of novice and advanced students respectively considered the

In a later section we will compare the first experiment with the second experiment in this parameter. We will also present a comparison of some criteria students took into consideration to select their proposals. Here we present some of the criteria that are not comparable and belong only to the MDSU methodology. Students were asked if once the object was unfolded sectioning was easy. 32% of both type of students considered at 100% that the model was easy to section. Students were asked about other criteria considered to decide their proposals. But they are less relevant for the objective of this study and therefore we will not present them here. Students were also asked about difficulties on the MDSU and

The first compared question is about the geometrical form used in the meshing sub-process (finite element). According to our statistics, most of the geometrical forms used were mix. Both types of students mix more the geometrical figures during the second experiment. In novice students increased 20% while in the advanced students the increase was about 32%. Therefore, there is some evidence that the MDSU methodology help to increase the variability of geometrical forms used in the meshing sub-process. The use of mix forms was superior in the advanced students that in the novice students. The basic form with significant more use after the mix was the circle. This form was reduced about 24% in novice students and 15% in advanced students from the first to the second experiment. The use of triangle was not significantly changed as well as the square. Another important change was perceived in the spiral form; it was reduced about 7% in novice and advanced students. Other forms used where polygon. As we can appreciate the MDSU methodology impact positively the variation of forms more in the advanced students that in the novice. This may be due to the freedom feeling experienced by the advanced students. The triangle is the most suggested form used in finite element theory and according to our statistics it was not changed significantly. This is a positive result because the MDSU does not affect the

When comparing the design criteria for choosing the proposals. The MDSU methodology impacts positively advanced students. For such group of students and at 100%, the criteria is increased by 8% while for novice students the increase is about 7% On the other side, when comparing the easy to build criteria a significant increase is perceived in novice students from 50% to 75%, the increase at 75% is about 29%. At 100%, both groups of students showed an increase when using the MDSU methodology. 15% in novice students and 9% in advanced students. With respect to material optimization criteria, the behavior is of the same kind but at different percentages. The increase at 100% was about 6% in novice

The experimentation time had a positive impact also. The more significant increase was shown between 0 and 15 minutes for novice students. By using the MDSU methodology they increase 14% their experiment time. The timeframe between 15 and 30 minutes have had also a positive impact by decreasing less than 10% percentage. Timeframes above 30 minutes had a reduction. These results shown that the MDSU methodology reduces the

related processes but the results will be presented in the following section.

**6.3 Comparison between the first and the second experiment** 

union sub-process as complex.

percentage of use in this form.

students while 8% in advanced students.

timeframe spent in the experiment.

Two final important questions were compared. The first was about the complexity of the experiment. At 100%, both group of students considered that the MDSU methodology is less complex than the freeform methodology. Advanced students feel that MDSU methodology reduces the complexity more than the novice students do. The other important question is more related to cognitive processes, specially the creativity. At 100% and 75% (more at 75%) feel that the MDSU methodology reduces the generation of ideas to improve the process.
