Julien Cohen's Reflection

I think that, overall, ME250 this semester was a fantastic learning experience, imparting real-world applicable knowledge and the theory behind it. Many aspects of the design, machining, and manufacturing of simple mechanical machines were covered. This course did a great job of building the students up to the point where building our final machines was actually feasible-- I imagine that, had I zero experience with machining and mechanical design, I would still have been able to produce a working machine for my final project (although I doubt it would have won).

What the course taught us about teamwork and time management was equally important as the actual coursework. The system of early milestones (MS1-MS5), where each group member is responsible for bringing their own designs and ideas to discuss and integrate into the final machine design, was successful in forcing a certain degree of communication and involvement. The entire team aspect is so important because it is how real-world engineering works. If I'm not a team player, no sane engineering company will be hiring me.

I was bothered, along with some of my friends in the course, by some of the lecture material, and especially the CAD labs. The bottom line is that it was far to simplistic for the knowledge base and skill level of many of the students in the course. On the flip side, I also know of many students for whom the CAD labs started off at a perfect level and progressed them through basic computer modeling. I understand that no course can be expected to teach to every single skill level present, but you also have to take into account that this is a required core engineering course, at the University of Michigan. If we are actually “the best and the brightest”, and every one of us will pass through this course, shouldn’t we be able to demonstrate our mastery of this facet of the course beforehand? Perhaps allow students to test out of it at the beginning of the course? I’m not sure of the answer to this conundrum, but I do feel that students who haven’t had any experience with CAD should be taught it.

I do think that there were some issues with the course. My most top-level problem is the amount of time spent on lectures and early milestones vs. the actual engineering and building of our final project. In my opinion, spending two to four more weeks on the final project, and condensing the information in the lectures and labs, would benefit future students in the course. The way it is structured right now, most teams barely finished their robot by the final week. With another month, every team would be able to go through at least one design iteration, something that is so incredibly important to the design process. Allowing students to make mistakes is great, but making a mistake does not teach one anything. If you then force students to evaluate those problems, devise solutions, and then deploy those solutions, they will take away lessons from this course that are applicable in every walk of life.

Our performance could have been improved by another week or two of design and problem solving on our machine. With three other courses, homework, and the extremely tight machining schedule we were forced to adapt to in the ME Machine Shop, our team struggled to finish our machine in time. We chose from the start of our project to attempt to build a machine that was both novel and high scoring. I think that our ideas were fantastic, but the execution did not live up to the original plan. Frankly, we may have bit off more than we could chew.


Whatever hardships we went through and disagreements we had, I can truly say I am happy and proud to have been a part of this team. Each one of us brought something different to the table-- Miguel's experience, Mark's dogged determination, Haipei's numerical skills and total dominance of the class schedule. I couldn't have asked for a better GSI in David, he was instrumental in helping every team in his section succeed, and, in a turn of events I did not expect, I believe I will be keeping in touch with one of my GSIs.


Thank you Mike and Albert for a great start to the MEx50 series of classes, I look forward to the rest.


Thanks for the great experience.

Julien Cohen

Reflection of Wenqian Ma

I am a transfer student. When I was notified that the ME 250 was successfully transferred to U of M at the beginning of this semester, I did not choose to drop this course; instead, I chose to insist on learning this course again because I previewed this course is going to be worth the time. And it does!

The four parts of this course—lecture, CAD lab, engineering labs, and the ball tower projected taught me different knowledge at various aspects of mechanical engineering and showed me a broader view of what mechanical engineering really is.

From the lecture I gained a series of knowledge including of all kinds of concepts, engineering principle and engineering drawing, which I can apply to the real calculation. Both of professor Shih and Michael are great instructors. The most important thing from the lecture in my point of view is the engineering drawing. After that, I can understand a lot of drawings including clocks, model cars, and so forth. And then I am even able to design a real clock based on the knowledge from CAD and the gear knowledge taught in class.

The CAD drawing is also a lot of fun. Although there were only six sections for the CAD drawing, we were able to learn the basic skills for a computer-based drawing tool, which on the other hand, added another experience to our resume.

The series of engineering labs, including the motor lab, bike lab, etc., are bridge connecting the engineering concept and knowledge to the real world. I was really impressed by the bike lab. I was not aware of how the bike is really working. After the bike, although it was just 1 hour, I totally understand the mechanism of a bike and I did fixed my own bike at home!

The most fun part is the ball tower project which is also the most time consuming part I have to acknowledge. However, from this exciting project, I learned how to cooperate with my team mates—Haipei, Julien, and Miguel. They are great guys who did great jobs. I learned a lot from them. I also learned how to manage time for a project in order not to do everything just the day before the due date. The experience I gained from the machine shop is especially valuable for the engineering career, which is another skill that can enrich my resume. I must specially thank Bob and Mark for helping me with the milling machine, they are great guys! David, our GSI, is the man who fully supported us throughout this semester. He is always happy to help us with the design and manufacturing and gave us a lot of valuable suggestions.

Overall I think this course is excellent; however, there is no perfection in this world, something I think is needed for improvement of this course. First, I think there should be more homework for the CAD drawing for us to practice and be well prepared for designing the project machine. Second, it is better for us to have for time for manufacturing of our machine in order to perform well on the competition.

Again, thank you all for letting me have such a great course! I'm gonna miss you all!

ME-250 Reflection - 3 Projects

I still remember how the team was formed. Three of us, did not follow the announcement that David Hiemstra made before our first lab, and we ended up in a completely different room and different building… Remember? Many things have happened since then, not only at school but also at work and in the personal side. It is ironic that this assignment asks for a reflection about the project, as it is only one of the three that I had going on this semester.

At work, since January I have been working on the analysis of a data base that has already brought more than $3M to the company and I am currently working on the next one. At home I have painted all the interior walls, replace kitchen vinyl flooring with tile, all carpet with hardwood, including 17 highly time consuming stairs, all kitchen backsplash and replace most of the lighting…how long? About 500 hours of work. And finally ME-250

Even though I have some manufacturing and engineering experience, participating in ME-250 has leaved many enriching experiences and lessons learned, mainly from my team mates that did an excellent job, keeping up with all the assignment dates and distributing load evenly at all times. From the beginning, I really wanted to be the leader of the group, but two things stopped me from even proposing it to my team. The first and most obvious was the extra time that I had to commit to it, and secondly, I believed that my team mates would have a greater benefit if they did it.

The class overall has given me exposure to software that I was not familiar with as perhaps SolidWorks and CES not to mention laser and watercut equipment. But this is only an small part of the learning as I truly believe that most of it came from Haipei, Julien and Wenquian.

Both Wenquian and Haipei are from China, Julien from California and me from Spain, and from the beginning we knew that communication was going to be key for success as even we all speak (to some degree) English, the meaning in our conversations always had slight differences that we had to be aware off because it actually brought some controllable delays to the project, but each of us had an area of expertise fundamental for the final product.

Haipei Zhu, very disciplined, always on time, always on top of everything and every due date. Lives in Duderstadt Center….3^rd floor. Any question about the project? Ask him

Wenquian Ma, bright guy, always calm and also aware of every date, look at the simple side of things and execute them on time.

Julien Cohen, hands on, designer, give him it’s own space and let him develop, good ideas creator, official English communicator of the team, as the rest of us only try.

Me….I will let that to my team.

About some constructive ideas here are three simple ones that I think will benefit next generations of ME-250:

1.     Start working in the shop a little earlier

2.     Set up goals as Mechanical and Electrical

a.      100% Mechanical completion is only 75% worth. Defined Due date

b.     100% Electrical completion is the remaining 25%. One week later so all teams will work on the electrical system for at least one week.

3.     Announce from the beginning of the semester the price involved and invite companies to attend the competition. I am sure that the interest will increase within the students.

Overall ME-250 has been a fun and positive experience, the start of the 50’s series!.. and although I would have liked some more time to enjoy it more, I am satisfied with the results. We demonstrated the potential of the car and the unique and creative idea that we were able to bring to reality.

Finally I would also like to take the opportunity to thank David Hiemstra, Prof. Mike Umbriac and Prof Albert Shih for their fantastic dedication and attention to the students. It isn’t easy to attend so many people and not lose site and/or patience.

To all, Thanks, I have really enjoyed the experience.

….see you sometime soon!!

Miguel Vidal

Haipei Zhu’s Individual Reflection

Haipei Zhu’s Individual Reflection

ME 250 is named after Design and Manufacturing and I did learn a lot about them from this course. Basically, there are three parts of this class, taking lectures, doing HW 1 to 4, and working on our ball tower project.

The lecture is just like a guideline of the whole class. I like the way both professor Shih and Michal give us those lectures. We are not only introduced the new stuff about mechanics like bearings, bushings, gears and so on but also shown some really cool concept, like over constrain and something like that. I do learn a lot mechanical things from lectures. Those lecture also act as reminders for upcoming events, like milestone due or Design review and so on.

Well for the HW 1 to 4, I sharpen my skill of software like Solidworks, CES Edupack to build 3d models and find suitable materials for certain utility. Those software saved our life more than once! From homework 3, I feel like I was repairing a bike. I feel excited as I have never done that before. I am pretty sure that I can repair my bike right since this lab. Motor lab helps me to know better of the torque-angular velocity curve and the quality of gear box. That is essential for choosing the right motor for our project later this semester.

The last part: Ball tower project is the one that I really want to talk about in this reflection. From the basic idea: lifting the arm to get balls from the plateau to finishing the cad work, we are doing design work all as a team. As we separate the work to each person, I am in charge of the motor choosing, calculation of torque and gear box choosing. I did not realize how complicated the calculation is before I really start doing that. There are so many things that need to be taken into consideration, like friction, the mass of the every little thing. And there is also something that you cannot even calculate, like the sum of error, like the dynamics torque. I had a hard time to balance the turning speed and torque the gear box can provide.

For the Manufacturing, I learnt a lot from my teammate Miguel, who is a consultant with a lot of experience. He knew how manufacturing works better in ME shop and mechanical world. That is amazing to me. He showed me how to use arbor press the first time I use it and he also teach me how to use bending and cutting machine. I enjoyed the time working in machine shop doing cool stuff while listening to radio music, which makes me proud of being a Mechanical Engineer. Band saw and milling machine are what we use all the time and I do appreciate the chance getting familiar to those fundamental manufacturing machines from this class.

Although we argue about some topics seriously, Julient, Miguel, Mark and I enjoy our time being a team in ME250. We work well together: Captain Julient is in charge of Cad modeling, Miguel is good at manufacturing and giving fresh concepts, I am good at calculation and connecting between team members and Mark is in charge of writing some report and data reduction. We did well in time management and we finish our car successfully. I appreciate each member’s work and I hope maybe we can work together in ME 350 or ME450.

Last but not the least, I show my gratitude to our GSI: David. He helps me to answer our question patiently and gave us a lot valuable suggestions about improving our design. Apart from that, he grades our milestone fairly to each team with detailed notation beside where we lose points. I appreciate his help and also this course! It makes my life much harder when approaching to the end of the semester but it provides me tons of fun at the same time. I think the only thing that can be improved is hiring more nice GSIs like David!

Haipei Zhu

Team Pangaea

Me 250 2012 Winter

Final Team Documentation

Our final machine is essentially the same as our initial design.

We utilized the double gear motor for mobility, and this drives the back two wheels of our machine (pictured under the aluminum strip). Our two front wheels are separately mobile for turning ability. The front of our machine has two arm-towers that support a Polulo metal gear motor attached through gearing to the axle of our swing arm. On the end of the swing arm is our MCM, what we call the ball-grabber. It allows us to pick up balls by lowering the ball-grabber on top of sand-filled squash balls on top of the wave tower, allowing the ball to slide through the beaded elastic bands, and then roll back down the swing arm into the waiting ball hopper, basically just a hole in the middle of our robot.

We standardized as much as possible with our machine. All support structure is based on a single ,achined aluminum angle-bracket piece, we use twelve of these to support both the arm-towers and the ball hopper walls (in white delrin). All of the bolts, except for those restricted by size or other constraint, are 1/4"-20 threaded hex bolts. This standardization allows us a measure of replaceability and ease of fixing.

Our final bill of materials:

• 1/4" Acrylic plate, green 
• 1/8" Delrin plate
• Aluminum plate, 1/16" thick
• Aluminum Square Tube Stock - 1"x1", 1/8" Wall
• Architectural Aluminum Tube (Alloy 6063) Square, 2" X 1", 1/8" Wall
• Aluminum 90 Degree Angle Stock - 1"x1"x6', 1/4" thick
• (10) Flanged brass bushing - 1/4" ID, 3/8" OD
• (6) E-Clip retaining rings - 1/4" Dia.
• (2) 48 D.P.,48 Teeth, 20° Pressure Angle, Acetal/No insert spur gear
• (4) Polypropylene wheels, 3" diameter, 1/4" bore
• Tamiya 70168 Double Gearbox Kit (includes 2 motors)
• Pololu 1576 99:1 Metal Gearmotor 25D x 54L mm HP
• Adhesive Velcro, 1.2 pull-apart, 200 cycles, 1" wide 0.188" thick
• Cable ties
• 2-Part Epoxy
• Assorted standard wiring
• (32) 1/4"-20 bolts and requisite nuts
• (4) strips adhesive backed grip tape
• Pololu metal gearmotor mount
• 1/4" OD aluminum rod
• (6) clear elastic bands - $4.99
• Blue beads (en masse) - $6.99

Now that  is what I call production value. I like to think I'm like a modern day Orson Welles. Here is our bio video, explaining a little about how our machine works and introducing ourselves.

Today was a whirlwind day of machining and assembly and final testing in preparation for MS10. We had to lathe down the axle for the swing arm because it was sticking-- it ended up that we were a couple thou off of our design parameters. The gears that we are interfacing between the metal gear motor and the swing arm axle may not work as well as we though they would. Larger teeth, and possibly multiple gears in a herringbone pattern, would definitely help the strength of said interface.

Other than that, assembly goes well. Everything fits tightly as per the design, although using through-bolts instead of threading the plexiglass is an annoyance.

It's interesting to be able to look at the different revisions we've done of different critical components. This is our MCM and baseplate shaping up for milestone number 9, alongside their previous iterations. You can see in the first picture the paper model fo our MCM, then our first iteration which was made out of a single aluminum waterjet-cut plate, and then our final version constructed of multiple waterjet cut pieces and hand-cut aluminum pieces. What we found during our initial iteration was that actually folding the aluminum proved trying because of all of the different angles and bends involved. We ended up cracking the aluminum and having to start over. Our final iteration uses a flat watercut base with two bends, and the walls are separately cut and bent aluminum pieces that we riveted onto the base.

Furthermore, you can see the two baseplate iterations. The first, in clear plexiglass, was cut incorrectly, and we also noticed a couple of features that could be improved upon. We ended up recutting the entire baseplate using the laser cutter in green plexiglass.