Individual Reflection: Ronald Deang

Being an EECS major, I learned a great deal from ME250 and also found the same things I had learned from my EECS classes to hold true. I haven’t taken any classes in manufacturing since my Tech Ed classes in middle school, so being able to get back into the machine shop was a great experience. I learned how to use SolidWorks and learned that the new CAD programs today are very powerful and sophisticated. I learned how to use a number of different machines, including the mill and the lathe. As for the design process, I found that it is much more complex and structural than I had imagined, with there being many tools in aiding this process, such as the FRDPARRC diagram. This class also helped to reaffirm the idea that teamwork in a design is very important. Gathering different people together allows for the melding of different thought processes and ultimately a greater design. Being able to bounce ideas back and forth allowed us to create our final machine. I also found again that time management is very important. If  we had not been in the shop on a regular basis, we would not have finished our project on time, as it seems Murphy’s Law of “anything that can go wrong, will” seemed to hold true as well.

I feel like the course has its strengths and weaknesses. Learning the tools needed for design is very important, such as CAD modeling and mechanical concepts, as you will need to apply them later for your project. However, I feel that there is still room for improvement. As I said learning mechanical tools and concepts is important, but lectures could get a bit dry sometimes. I feel like the shop tutorials were too quick and too early in the semester to retain anything for someone who is a first-time user of these machines. The first time we actually learned to use many of the machines was from asking for help in the shop from the instructors. So if you did not end up using a machine for your final project, there is a good chance you never learned to use it.

There are many things I could have done to improve my performance in this class. As I said earlier, I am an EECS major, and so I haven’t taken a class on mechanics since Physics 140 in my freshmen year of college. So for the homeworks which were heavy on this material, I did not do so well. I should have started them earlier and gone to office hours for help. As for the exam, I neglected studying for it as much as I should have, and consequently did not do well. Again, beginning to study earlier and office hours would have helped a great deal, especially for someone whose background is not in mechanics. If given the chance to redo this course, I would make sure to do this differently and not take the resources available for granted.

Bill of Materials and Trade Log

Trade Log: http://bit.ly/7MK8qt

Bill of Materials: http://bit.ly/7QyVqa

Individual Reflecion: Will Stewart

For me, ME 250 was much more difficult then I originally intended. Coming into the class I already had some basic design and manufacturing experience, being that I took Energy Technology, Introduction to Automation and Robotics, and was involved in the Physics/Engineering Club in high school. Still, this class was definitely challenging for me.

At the beginning of the semester, the homework was much more time consuming than I originally expected. Three assignments due per week seemed a little excessive, and I wish they were spaced out a little more. The Solidworks assignments were difficult but that’s to be expected when you’re learning a new program. For the Design Reviews I wish there was more time in class to collaborate with classmates, as the peer reviews seemed more to really be more “let’s get this done quickly” than “let’s bounce ideas off each other.” However, the homework assignments seemed to be more much more geared towards physics than towards design and manufacturing. I feel like I would have rather had assignments that gives you a problem and materials and asks you to design something than some kinematics problems.

As for the actual project, I liked the idea of the arena. It was a project that none of us had ever had any experience with, and therefore allowed for some creative ideas. I would say from a manufacturing standpoint, we did a pretty good job with the design of our machine. The major flaw we had was constraining the worm gear. In our original design we did not account for this to be a problem, but in hindsight we definitely should have considered it, being that we were entrusting an aluminum couple with a 1/8” diameter to hold up the radial force being brought by a 36” long steel arm. We realized this flaw with only a couple days left before the competition, as when we finally put our project all together the worm deflected back instead of driving the motor. Because of the limited time left, we pretty much just threw together several constraints to hold it steady, but these ended up binding the worm because the constraints were actually misaligned. We didn’t figure this out until between rounds of the competition (our first run was a 0-0 tie), and we were extremely disappointed in the fact our machine wasn’t working properly when it was being graded, especially since all we had to do was take a misaligned constraint out. One possible way we could have avoided this in the design was to put a spur gear on a fixed axle behind the worm gear. The worm gear could then not deflect back because it’s being constrained by that axle. There would also be no energy lost (aside from the negligible moment of inertia of the gear), so there would be minimal lost power in the motor. A problem with this, however, is that we would have had to purchase a gear that was the same pitch as the worm and gear, and this probably would have put us dangerously close to the $100 limit, as we had already needed to purchase a lot. This can definitely be viewed as a positive, though, in that now I can guarantee I will never leave a motor couple under or over constrained ever again.

Overall I feel that the project was a good design project. However, the work at the beginning of the semester definitely seemed much too packed together. Time management was definitely difficult at the beginning, but I began enjoying the course much more once the project got underway. I definitely think this was a helpful course, and I definitely feel more experienced in Design and Manufacturing.

Team: Final Documentation

Our final machine was quite similar to the original design, but it had some definite differences. One such was the sliding method of the long arm. Initially, we planned on using a sliding dovetail bearing, but in the end we milled a channel in a steel arm and slid the arm along bolts. The Rack and pinion used to drive the extension remained the same.

The Worm Gear drive didn’t change until it was too late. The worm was under-constrained and we had some deflection issues, where the arm’s force caused the worm gear to deflect the worm out of the threads, causing stripping. We finally constrained it properly, but our intermediate constraint was poorly made and misaligned due to time limitations (we ignored this problem for far too long) and caused binding issues. This made our worm gear, which we relied on for a great deal of torque, to be seemingly weak and unable to lift any balls at all. At the very least it still prevented back-driving…

Our baseplate, mounts, and uprights were essentially identical to the original design. These parts were simply manufactured and used as initially intended. If the original design had been better, the need to add more in addition to the planned mounts and constraints would not have been needed. However, we were forced to add more stuff as the manufacturing went on, and we ended up with an over-constrained worm and a poorly constrained pinion drive.

The machine’s performance was poor, as earlier stated. The setscrews in the pinion stripped completely, and the worm was rendered near-useless by the binding issues. We believe that our concept was sound, and that if the design for the constraints were better, the machine would have performed extremely well and been very competitive in the arena competition.

Individual reflection: Gyungcheol Shin

Since I just transferred this fall semester from another college, this ME 250 class was my first class that I took here at the University of Michigan. At first, I did not expect to make any machines made out of any metal things in this class. I just thought I would design a machine by cad programming and make simple thing. Honestly, when I went to the ME training shop, I was not familiar with any kinds of machines there and I felt like ‘Wow, this class should be much harder than I thought.’ However, I did not have the choice. Therefore, when I first came to the lecture and heard that students are supposed to design a machine that will move the balls to the opposite side, I wondered if I could successfully complete this course.

I cannot forget many nights that I struggled with homework and cad assignments. I had never used cad program before, so it was hard for me even though I was living with the cad tutorials. At the end, however, I learned a lot about using cad designing from lectures and GSI’s help. I enjoyed doing modeling little bit. I now feel quite experienced with SolidWorks. The cad assignments helped me a lot.

Another main problem was making the real machine. It seemed impossible at first. However, as the professor, GSIs and machine shop directors taught each step of the designing process, we could slowly design our machine and manufacture it. The idea that we planed about our machine was just perfect. However, unexpected error and problem happens all the time. At the same time, however, making process was the best time for me even though I could not participate on it many times. I had some problem about my international student status and it made me panic that time so I really appreciate to my teammate’s efforts. Anyway, it was really fun to make things on my own and it made me go back to the lecture slides and learn the contents. I gain much motivation about materials covered in lecture to complete our machine. In other words, making a machine gave me the basic reason to study.

Finally, I learned the importance of teamwork and distribution. While in ME 250 class, we were assigned a lot of assignments. To finish all that assignments correctly and on time, we better divide the work to each teammate. By distributing all the work, we could have finished the assignments quickly. Our teammates did really good job that I was not able to finish sometimes. If there were no help from them, I would not have finished the assignments. I am sure that everyone who passes this class will know that the importance of the group work.

I definitely will take things from ME250 that will help me in my future. I am sure that will be very helpful especially whenever I am working with other people. Although we could not win in the contest, I am proud of the final product we built and appreciate to my all teammates.

Individual reflection: Peter Gibbs

In this course, I learned quite a bit about design and manufacturing. I had limited manufacturing experience in the past, so this course was a good opportunity to familiarize myself with the equipment used in the shop. This course was also a good opportunity for me to learn about the design process and to design something from start to finish.

For teamwork, I learned that not everyone needs to be an expert in the material to be a good team member, or be a credit to the team. I also learned how if one team member puts forth a poor effort, the whole team suffers greatly.

On time management, I learned that working in small chunks along the way is better than doing everything all at once, especially in the shop. In CAD, it’s often better to do a part or assembly from start to finish, but in the shop, working in small chunks is much more efficient.

Improvements to the Course:

This class was recently revamped, so there were many rough edges about the whole thing, it seemed. The overall concept was good: to make a machine that actually performs a function, rather than something with no real purpose. One thing that I found was that the initial expectations were rather high. Not a single team was capable of scoring into the bins, and a large number of teams (my own included) were struggling with simply moving the ping-pong balls themselves.

A large part of this was time. I felt like the first half of the course was nothing but filler. Most of the homework assignments seemed like a combination of busy-work and basic physics or mechanics. What I mean by this is that anything that was covered by these, the students should already know, or be in the course that teaches it in-depth. Even if not everyone in a team knows basic mechanical analysis, there will be at least one member who can do it. All this time spent on these assignments takes away from the project, which is supposed to be the main purpose of the class. I felt that all the project milestones were extremely rushed, and the overall timing was poor.

That being said, the CAD assignments were very useful to learn Solid Works, in my opinion, and I enjoyed doing modeling for the most part. The CAD aspect of this class is just fine, though a slightly faster timetable might be considered to allow for more project time. With fewer homework assignments, this would be very reasonable.

My Improvements:

I could have improved my performance in one extremely easy way: constraint. I and my team had a good design, but the major shortcoming was constraint. Our initial design was grossly under-constrained, and this proved to be a fatal blow. The worm gear that we used was practically useless, which is not good since it was our MCM. Towards the end (i.e. the last few days), we added additional constraint to the worm shaft, but due to the last-minute nature, we ran into binding issues. We then added constraint to the other side of the worm (something we should have done to begin with), but that didn’t fox the binding. If we had designed the worm shaft properly, everything would have worked perfectly. However, I was stupid and thought that one-sided constraint would have been enough. I made the same mistake on the rack and pinion, only constraining it on one side. This was also a problem for us, though not as critical. We were able to constrain it with string, but that is clearly not a well-designed fix, and it showed. So that’s the major mistake that our team made: under-constraining critical parts.

Hello World!

Update 5: Machine Assembled, Problem with Worm Gear

So we finished manufacturing all our parts and finally put our machine together. The rack and pinion used to extend the arm works really well. We had to epoxy two racks lengthwise to the arm to make sure it could extend through the entire slot. In order to make sure that this gap would still have the same pitch as the racks (so the gear could run smoothly over them), we used the simple idea of holding the gear over the racks while the epoxy dried, which forced the pitch to be correct. There was also a slight deflection in the gear, but we simply used kevlar string to constrain it in place.

However, we also had a problem constraining the motor that's mounted to the worm gear. While the worm does control the gear for certain angles, Once the arm drops steep enough into the slot the arm's weight is too strong for the couple holding the worm, and the worm deflects back and the gear spins freely. We need to find a way to constrain the worm from deflecting back. The difficulty with this, however, is that we need the worm to be at an exact pressure against the gear. If it's slightly too loose, the worm will deflect back and the arm will fall down. If it's slightly too tight, the gear will bind. We did not account for how difficult it would be to constrain the motors in our original design.

We tried a quick fix of using kevlar string to constrain the motor, but this appears to only work sporadically. If we need a more consistent constraint, we will have to manufacture it.

Update 4: MCM Assembled!

Today we finished assembling our most critical module, the MCM. Most of the manufacturing we did, aside from mounting all the parts, was turning the axle down to the appropriate radius. This was tricky because our worm gear's mounting hole has a larger radius than the bearings used to secure it. This means that we needed to turn almost all of the axle down to one diameter (1/4"), with a small section in the middle a slightly larger diameter (5/16").

The way we mounted the motor and uprights was using the aluminum square tube stock and angle stock, and we secured everything using 1/8" rivets. To do this we used vice grips to hold the pieces together so that when we drilled the holes, they would be perfectly aligned.

Here is a video of the MCM in action:

Update 3: 3 Parts Manufactured

Today we had our three manufactured parts graded by our GSI. The three parts we manufactured were the two uprights and the baseplate.


The baseplate is from the 1/4" aluminum plate and will serve as the foundation for our project, which each module is attached to. The manufacturing for this part was extremely simple, we made one bandsaw cut to cut it down to the correct dimensions.


The uprights will be used to hold the axle that the gear is mounted to. We are currently planning on using epoxy to secure the axle to the uprights, and having the gear spin about the axle. To manufacture the uprights we used the rest of the 1/4" aluminum plate that was left over after we cut out the baseplate. After cutting them with the bandsaw, we used the mill to mill them to be perfect rectangles, so that when we mount them to the baseplate they will stand perfectly vertical. We then drilled holes for the axle in each upright.

Update 2: The parts arrive!

The Worm and Gear that we ordered from sdp-si.com has arrived. The pitch and lead angle are complementary so they fit together flush. We now need to assemble the rest of the MCM by manufacturing the baseplate, upright, and axle, and assembling them all together.



After receiving the actual gear, we began to visualize how our machine will actually look. Going over the dimensions of the materials we have and the parts we need to assemble, we believe that we should be able to assemble our project without a problem. The only potential problem we can see is attaching the motor for the rack and pinion which extends the arm. We will use all of our angle stock mounting the first motor (for the worm) and it appears we will need more to mount the second motor. We will be thinking about all the possiblities for the design in this upcoming week.

upadate 1

Our most critical module is a worm gear used to rotate the scoop. We've decided to buy the worm and spur gear from SDP-SI. Everything else will be manufactured from parts in our kit for this module (the aluminum plates, rod, square tube stock, planetary gearbox).

We will have to buy additional parts for the rest of our machine, specifically the arm. We're thinking of using a high carbon steel as the material. We also still have to find a way to mount our worm gear to the motor, but this will have to wait until we receive the parts. Once we get them, we can figure out the best way to attach everything together.

schedule

click!

BIG ARM SCOOP!

Our strategy is to use a big arm scoop to push balls into the opponent's side of the slot and play defense once in that position. A worm gear will be used to rotate the arm downward into our side of the slot and then the arm will be extended using a rack and pinion. Once at the bottom of the slot, the worm gear will drive the arm outwards, not only pushing all the balls over to the other side, but also blocking our opponents from scoring....ensuring our victory.