Coming into this class, I brought 5 years of laboratory work experience from Prof. Wooldridge’s Lab. During my time there, I have dealt with several of the topics covered in this class. For 3 years, I worked on assembling a single cylinder optical engine from just a head donated from ford and helped perform HCCI experiments. My intuition has taken me very far, but I have gotten to a point in my education that I must fully understand the theory to understand the big picture and not just know what works and what doesn’t. Realizing that the class is targeted for students with almost no experience in this topic, I was worried that I wouldn’t find the class engaging enough. I must say that I was pleasantly surprised with the vast range of topics covered and particularly with the depth and complexity that they were covered in. Often, I found myself asking weather it was too much for kids that were seeing this for the first time, but I selfishly indulged in extending my education. This class properly develops fundamental concepts and creates a good foundation for future design and manufacturing classes to come.

This class has definitely a lot of work associated with it. It is very easy to lose track of how much time you have spent in a design project. This can cause potential problems for the student in other classes. One way to fix this problem is by setting guidelines and expectations ahead of time. It is not easy to quantify how much work one must do in a design class to get an A. Since we are not building the perfect slot bot to enter into a million dollar competition, it would have been nice to know where the shortcuts could have been taken. My biggest issue with the class was the lack of knowledge ahead of time, specifically grading rubrics and expectations. I am sure that things are going to be much smoother the second time around that this class gets taught.

It is very interesting to consider how many different concepts and equations were covered in lecture, but were never explicitly applied in assignment and deliverables. I was actually disappointed in a way. I do not believe the examination in this class was what it should have been. I felt that our exam was not necessarily hard, but extremely long. I would have expected a single design problem with multiple parts within the design problem that would force the student to utilize motor, projectile motion, and friction equations (etc.). Essentially keep part I of the exam and incorporate part II within the design problem. Instead of writing a manufacturing plan for a nut, how about pick a component from the machine you just designed in part I. I wanted the exam to test the innovative and critical thinking abilities of a student.

I believe that this class should be subdivided into two classes. There should almost be an ME 150 that freshmen can take…perhaps in replacement to ENG 100? The proposed ME 150 class would feature a more involved shop-training program with carefully chosen manufacturing projects as homework assignments. This would certify that students actually know how to use a manufacturing machine and are able to better design components once they know the manufacturing processes and their limitations. This can only come through experience. ME 150 should focus on more fundamental concept like the design principles we learned and hand sketching and a good solid introduction to CAD. Then ME 250 students can hit the ground running. Harder equations and tougher design criteria will be able to be incorporated. Engineering analysis can be more inclusive. Design standards can be raised. Having a slot bot competition and trying to cram essentially this ME150 class and ME250 class made it so weaker students never really got fully involved because they felt this class was in over their head.

In summary, I come out with positive experiences from this class. It is the closest thing to a robotics building class I have taken to date and thus it was very exciting.

-Dimitris Assanis

Final Reflection

For me this class was not as useful as it may have been to most other members of the class. I am on the Formula SAE team here at the Michigan, and have been designing and building parts/machines for 2 years. Almost everything that we are required to have learned by the end of this class, I have already learned and had experience with, from CAD to manufacturing. I did learn a descent amount about teamwork and time management. We had one of the more complex machines to put together, which required a lot of time to machine and even more time to assemble. Our team ended up pushing a lot of the work off towards the end of the semester where a number of issues were discovered in our design. This caused us to spend literally day and night finishing up the manufacturing of our machine to be ready for both the deadlines and the competition. On the teamwork side, I learned that a lot more time than I previously thought needs to be put into planning and carefully laying out what each person needs to do and when they need to have it done. I understand that this course was recently redesigned and this semester was in part a test, but there are a number of things that need to be improved if this course is going to stay the way it was this semester. The rules for the competition, and the construction of the arena (or similar) must be completed prior to the start of class or during the first couple of weeks. I felt that a lot of time was wasted during the design portion of the class designing possible machines that were completely irrelevant to the final arena design and final rules of the competition. Since this is a design class, I believe that there should be more requirements on proving your design (using math) to the staff, and the student should be graded more heavily on this. Otherwise the class will become one where a student can throw together a machine with no thought behind it and perform decently in the. I did think that the idea of having a competition at the end of the class was a good idea, but it would have helped if the competition was a part of our grade (even if it was a small part). This gives more of an incentive to put some work into the class. Earlier on in the class I also felt that some of the written homework assignments were busy work instead of being helpful or applicable to the class. Questions such as coming up with a story describing a picture seems unimportant to me (hmwk 1). If the goal is to improve creativity I would suggest creating assignments that are aimed at expanding a students creativity rather than just seeing if they can be creative or not. Another issue I saw in the class was the midterm exam. I felt that this exam was much to long to the amount of time we were given to complete it. It seems to me as though it was designed so that the person that could go through and finish the most would get the best grade. It could have been better if the questions were made harder (require more thought) instead of giving twice as many of them. To improve my own performance in this course, I would have created a slightly better (more simple) design so that we could spend more time on the design of our project and less time on the manufacturing. I would have also organized my time better so that the assembly process could go smoother and we could have time to figure out issues that pop up.

Final Reflection on Course

In the past semester ME250 has taught me many valuable lessons about the design process, team project work and manufacturing processes. My favorite part of the course was my work on designing the machine in CAD and with my teammates. I had a lot of experience with CAD before coming to UM, but I had no experience with solid works as my high school concentrated on Auto Cad and its applications. I enjoyed learning new software and its various features. At first it was very frustrating for me because I was very used to the Auto Cad format, but I eventually became used to Solid Works. Mainly it was frustrating because this literacy came with very little help from the teaching staff. I attended all CAD sections but I thought that it was very hard to understand the GSI and how he was trying to teach the software at such a fast pace. Little explanation was given in section and it was even hard to ask questions, because everyone was very confused as the GSI flew through the material. I had to spend countless hours learning the software for myself with the tutorials that rarely answered my questions. I think that if there was one thing that needs to be improved upon in this course it would be the teaching of cad. We generally wasted a lot of section time while the GSI had to check all the teams’ assignments when this time could have been used for teaching CAD and the manufacturing processes.
I did enjoy almost all other aspects of the course though. It was a rewarding experience to design and build our own machine for the competition. We learned that it was impossible to design something that wouldn’t need corrections later, because of flaws or needed modifications to the initial design. Many of the subjects in class were very useful to our design process. Learning about gears linkages and various other mechanical components was key to our concepts and eventually our final design. I do think that it was kind of unproductive to not let us form into our groups earlier in the semester. We wasted a lot of time coming up with ideas that we knew would never work or be used in the teams design. I think that the course should be changed so that the groups are formed early so that groups are allowed more time to finalize their projects and begin manufacturing.
I learned a lot this semester about time management and at times it was hard to complete milestones and assignments due to the teams varying schedules, but I believe that we worked around it well so that everything was completed in a timely manner. I also feel that a lot of the homework early in the semester was busy work that I did not learn much from. Then at the end of the semester it seemed like we were very rushed to do all of the manufacturing in a short period of time. I think that this final part of the semester was far more important to my education and professional development, but it was neglected with the percentage of time the course allocated to it.
The final exam in this class also seemed like it fit the class material very well and I believe that was how it was designed to be. The only problem with the exam was that though it could have tested my knowledge of the course material very well, it did not because of the lack of time given for completion. Most of the students in the class described the exam as pretty much a writing contest that really did not test their knowledge.
On the whole I was very happy with my experience in ME250, because it was a fun and interesting class. It taught me a lot about the design and manufacturing processes, but there were various things about the class that could have been improved upon. I tried to list as many as I could above. A large amount of work was required outside of the classroom but I felt that this was the most valuable. Overall, I believe that I did very well in the class and my group did very well in the competition. We would have most likely made it to the finals if one of our plastic motors hadn’t failed in the semis. Again it was a very enjoyable class and I made some good friends in the process.

Reflection

This past semester in ME250 was a lot of work where a lot was also learned. The first few weeks of the semester spent on the project were dedicated to brainstorming and designing the machine. The first noticeable thing I learned from these few weeks was the ability to use CAD. I had never used a CAD program before this class and I think my skills improved drastically. The labs were helpful as well as the homework, and the work load was challenging but defiantly doable. Looking back though, another important thing I learned was the procedures of the actual design process. The amount of repetition, critique and failure that goes with the design process is huge. I learned it is almost impossible to design something from scratch without having problems or flaws with the initial design.

Moving into the lectures and next part of the semester, I learned a lot about ways to utilize and manufacture parts of a machine. For example, learning about different types of gears, linkages, etc. paid off for our team. Our machine used bevel gears as a key component making our machine quit durable. Also, creating a bill of materials and manufacturing plan was something I had never done before. Finally, moving into the manufacturing phase of the project, I learned a lot. The obvious being, learning how to use the lathe and mill as well as how to fit and use tolerances properly. The manufacturing in my opinion, despite having a short period of time, was the most intriguing part of the class.

I learned all of the things listed above, but another key thing I learned this semester was how to meet deadlines. Our team was often pushed to meet deadlines that seemed impossible. Several of our team members were often up late nights completing work that still had to be completed. Contributing your own time on your own schedule was important because our group could not meet all together several times a week. Our group had to assign individuals tasks over week long periods and trust that they were going to get done.

Overall the ME250 course was very challenging. I feel that this idea and purpose of the course is very on target, fun and interesting. I do, however, think there should be some things done differently in the course. The initial design and repetition of design, with the addition of homework and CAD assignments was too much. Some of the homework and design homework’s seemed like busy work that wasn’t necessary. The large amount of time for this process also reduced manufacturing time which fell right around midterm exam times. There should be more time laid out for manufacturing the machine. Also, when it came to scoring some of the homework and assignments, I think there should be a more clear and precise rubric for the students to look at to know how they are being scored. Finally, there was too much work outside of the classroom that was necessary. The recitation sections were helpful, but was almost as if I had another class to attend. The motor and bike labs required our group to meet outside of class as well when it was very difficult as is to meet all together as a group. I don’t think the work outside the classroom should be neglected, however, more time slots should be available.

I think I did fairly well in the course. At the beginning of the semester and during midterm exam times, I became very stressed and had other courses to worry about as well so I think I could have done better on the homework and design milestones had I been more prepared. I began to use smaller periods of time during the day to complete the work little by little and improved my scores. Overall, I think I did decently well in the class and enjoyed it.

- Adam Hall

Weekly Update: Competition and Final Update

Figure1: View Of Cad of Final Machine



Figure 2: Our Machine In Competition

Our final machine ended up placing fourth overall in the “slot-bots” competition this past Thursday. For those that could not see our machine, it involves a cart module allowing us to drive back and forth, with an arm that travels vertically via acetal gear and nylon rack allowing us to reach the hard to get ping pong balls. The end of our arm, there was a rotating scoop driven by a motor in the cart that turned a stainless steel shaft with bevel gears rotating the scoop. On the front of our cart module we had our defensive module which was a wall that helped constrain the vertically moving arm. As the arm travelled downwards a switch on our wall released the wall flaps made from delrin and mesh, where two torsion springs expanded our wall outwards. The final rear defensive module was a very basic wall made from wood, used to protect our rear container.

Figure 3: CAD Model of Machine Showing Shaft Module

During the competition, out team decided not to use the wall flaps (zip tied together) or the rear defensive module, so that we could have a larger initial offensive move without violating the rules of the competition (No defensive moves first). We used a large amount of aluminum on our cart and welded a significant portion of our machine while using very high torque motors. This combination allowed us to push nearly every machine out of our way to score ping pong balls. Despite having technical trouble (A stripped Set screw in the motor) during the first round of competition, we came back and achieved a fourth place finish.



Our final design of our machine did not vary a great deal from our initial design. The biggest variation was the attachment of the torsion springs to the wall. In our CAD model, our torsion springs were just sitting between the wall and wall flaps. During the final week, we determined how to attach the torsion springs using extended hinge rod, and turned out to be successful. One other component we had trouble with was the timing belt we used as treads. The timing belts turned out to be very taught, and we had to manufacture new, offset bushings for the rear axle to accommodate the timing belt properly. It worked out well for us, providing extra traction on the arena.

Figure 4: CAD Model Showing Hiden Lines (Shows Timing Belt Pulleys, shafts, Acetal Gears)

The wall module seen below was modified slightly in the manufacturing process as well. Originally made from aluminum, we decided to save weight, and not make our cart as front heavy, so used a combination of delrin, acrylic and mesh. Finally, the last modification we made, that has been talked about in previous posts was the bushings. Originally planning on using delrin bushing, we sought something with less friction to use, and turned to Teflon. The Teflon bushing worked very well for our purposes letting our shafts turn well and being very low friction.

Figure 5: Wall Module Made from Delrin, Mesh and Acrylic

Overall, the competition was fun and we are happy with our finish. Despite some big and small problems arising throughout the semester, we pushed through and had a working machine for the competition, pulling out a top five finish.

Figure 6: Read Defensive Module that was not used in Competition

Video Update

(Music: TNT by AC/DC)

Weekly Update: Completing the Machine

This past week was spent completing our machine and preparing it for testing on the arena. Due to exams and assignments, our group was really only able to meet from the middle of the week until the end of the week during nights. All of the modules had to be completed, and assembled.

Figure 1: Cart Module Being Assembled After Welding

The rear defensive module had been finished with the exception of being painted, as well as the shaft module (most critical module). A significant protion of time during the late week was spent manufacturing and assembling the wall module. One problem we ran into was the motion of the torsion springs could not be held by simply epoxying them onto our wall. We decided to extend our hinges on the module to house the torsion springs as well. You can see this in Figure 2 below of our wall module.

Figure 2: Wall Module Complete (Torsion Springs Below Hinges)

The weekend team meetings were spent assembling the cart and making sure eerything would work when the motors were attached. Some bushings had to be remanufactured because of problems fitting the shaft. While waiting for the cart to be welded together, our team decided to paint our rear defensive module as shown below.

Figure 3: Rear Defensive Module Painted withName Team

While we still have some work to do on the cart module, most of our remaining work is assembling the entire machine. There are a lot of small pieces that still need to be incorporated into our machine that will take a lot of time. The machine should be completely assembled by the end of the night, and ready for testing in the morning.

Figure 4: Pieces of Last Motor Waiting to be Assembled