Bill of Materials

Linked is our finalized Bill of Materials for producing Wall-E and EVE.

http://goo.gl/WPUDC

Bridget Quick's Final Reflection

As this was my first experience with the entire design and manufacturing process, I have learned a great deal about this process as a whole.  The first concepts that I learned in this class that I know will be of value in the future, were the steps to the design process.  Although I am typically very good at the creative process, it really helped me to organize the process by separating it into parts (i.e. strategies, concepts, modules).  In addition, I learned a lot about Solidworks how to use the program to model my ideas.    As we began to manufacture, we realized that some of the parts that were created in Solidworks were not as easy to create in the machine shop.  From this I learned that not all ideas could easily be created even with the great amounts of technology we have available to us.  As a student, I need to have creative and innovative ideas but I also need to take manufacturability into consideration.  This class also taught me a great deal about manufacturing.  Before this class, I did not have any experience in machining.  Now, after getting the opportunity to fabricate parts on all of the various machines, I have gained a lot of experience.  Overall this class provided a great environment for me to gain the design and manufacturing experience that I had not gotten in other aspects of my college experience.

Because this class was very demanding in terms of what we were asked to accomplish in a small amount of time, I also learned to work efficiently with a team.  I learned that no one person could do this project entirely by himself or herself and that it was helpful to have others to bounce ideas off of.  We found that if we were all in the machine shop together it worked best to have two of us working on one task while the other two worked on something else.  This way no one was forced to take soul responsibility for a part and you could use both of your knowledge to manufacture.  We as a team quickly learned each of our strengths and weaknesses and because of that, we found the most efficient ways to divide and complete our work.

After making my way through this course, I have considered some changes that could be made to improve the course for future students:

1)   The teams should be assigned at the beginning of the semester and should be assigned rather than hand picked by the students.  Luckily, I wound up in a group that had a good amount of past experience in fields that applied to this class but I know others were not so lucky.  Had we all filled out a survey describing our background in manufacturing and design I feel the teams would have been much more evenly distributed and some of the groups would not have struggled as much as they did.

2)   More time should be spent in the machine shop practicing before the students are set lose independently on the machines.  Because I worked only on the mill during the FAB labs, when my team asked that I use the mill, I felt completely lost.  Thankfully, Bob, John, and other students were always willing to answer my sometimes-trivial questions.

3)    Overall, this class needs to be more focused.  The entire semester I had issues determining what specifically I was supposed to gain from the class.  There was simply too much going on and because of that, it made every assignment feel worthless.  With all the Milestones, Homework assignments, Labs and Design Reviews I was lost and frustrated that everything felt like busy work.

4)   Also, because there is so much information in each lecture, I feel that a short quiz at the beginning of each lecture on the previous lecture’s content would be much more valuable that an exam on all of the lectures that is nearly impossible to study for efficiently.  The exam also distracted from the huge amounts of work that needed to be done on the robot.

In summary, I gained a lot of valuable experience and information from this class but for the most part, I was disappointed with the class as a whole.

Individual Reflection - Jon Gold

I learned so much about manufacturing. I did not have much/any experience in a machine shop, working with a lathe or mill, or taking a solid model and fabricating its parts. I am so glad to have had this experience, and I am so much more confident as I continue with Engineering. I always used to feel like many other kids had a leg up because they could go into a shop and build things, but now I can, too!

I took Dr. Daida's E100- Design in the Real World. After that course, I had a very solid basis for design, teamwork, and time management. Our team in that class designed a deployable emergency shelter for use in disaster-stricken areas, such as Haiti. I gained experience in AutoDesk Inventor, and went through the entire design process similar to this class. Because of this, I did not learn as much as some other students about the design process, but I did see a different approach and gained more experience, the only real way to improve as a designer. Also, time management was much harder in that class than this one. We did not have as many checkpoints, so we had to be more self-governing to keep us on track. In addition, we had to use a GANTT chart and other tools to document our progress. These skills surely helped me with this class, but I am also grateful that we were not off as much on our own.

Our robot could have been better. It would have been nice to have our fence module to play defense, but as it turned out no one really made it to our side of the arena. The biggest improvements would have been in translating the solid model to actual robot. Some of our parts were not manufactured extremely well. Part of this is attributed to inexperience, part to a lack of mill time, but part could have still gotten better. Also, we sometimes overestimated our ability to machine, such as small dimension tolerances and accurate bending (for the record, there was no possible way to build that MIT box using our bender before it broke). Also, we were not able to drive over the center ball rack, which made us one-dimensional in terms of scoring. We could have moved the delrin attachment screws or used epoxy perhaps, but either way we would have had a better chance to make it over. Lastly, and this is for Nate, we could have put surgical tubing on our telescoping arm to make it lock the flipper faster.

Sometimes this term, the best way to deal with the workload has been to use humor; as such, I start with this story: About 2 weeks ago, I talked with Professor Skerlos in an advising appointment about Grad School, and he asked me to tell him about ME250. He said that the class had been totally overhauled a few years ago, and that it is growing every year. I also recalled what my econ teacher told me in office hours one day- The first through times teaching a class, you just try to say everything that you need to in order to present the information. Then you start to get familiar and add some things, cut out some things, and it really becomes a great class, but you have to get through the growing pains. With this term, I am afraid that we might have experienced more pains than necessary for the amount of growing.

I am going to begin at a logical place- the beginning. I, and most people I talked with, came into this class very eager and excited at the possibilities. We were going to have the chance to design a robot from scratch, show off our creativity, learn about applying what we were learning in the other classes, work in a real machine shop, drive a real robot in the slotbots arena, and maybe even win the whole competition! Over time, this enthusiasm turned into confusion due to the set-up of the course and assignments.

The first things we did were drawing up some strategies, concepts, and modules. This was good, in my opinion. We had to think about many different ways to approach the same problem, and really got experience with the filter design mechanism.

Then we started getting homework. In theory, the homework assignments would have been good. They made us really think about the material in class while letting us be creative. The execution was lacking, however, and took much of this value away. The homeworks were not properly introduced in class (they were just mentioned in the timeline), nor were they reviewed afterwards. It was as if there was some sort of random add-on that actually was not connected to our lectures or discussions at all. And, after we got them back, it was hard to see what we could improve on or how we could better approach them in the future. I would recommend making sure the homework assignments are clearly part of the class, and go over them afterwards.

Next, the GSI involvement. We did have MS checks about every week or two, which was good because we had to make sure we were on course to finish the robot. However, these reviews were more checks for effort than checks for competency. We had a design review presentation, but no one sat down and said, “this part seems good, this part will never work given these motors and gearboxes, this part could be modified like this”. Yes, there was some feedback, but the biggest advantage the staff has over the students is their knowledge of the practicality of our design based on the kit, and other than one Q&A session, it felt like it was entirely up to us to know what was feasible. This seemed to be reflected in the competition, where some teams had robots that could not physically function given their design and the amount of force applied. I think in the future, there should be meetings with the GSI every 3 weeks where everything is reviewed, discussed, and modified to make sure it would work.

I wish to discuss a few more constructive ideas for the course in the future, so I ask you to bear with this train of thoughts. Observation 1: attendance decreased in lecture as the term went on. Observation 2: some of the lectures seemed to drag on. Observation 3: this class is given an incredibly large allotment of time for lectures. Observation 4: when studying for the final, I realized how many of the slides seemed to be unfiltered information that was not really necessary for this class, but was thrown in because, frankly, filling an hour and a half with information about gears or bearings is difficult in a class designed to expose students to these for possibly the first time. With these in mind, I propose that the lectures be revisited and drastically altered. Instead of having long lectures with diagrams and text sprinkled with entertaining videos, please consider having short lectures and mini-design competitions. On a topic that may not need all 80 minutes of lecture, perhaps have 50 minutes of lecture and then 30 minutes of application. There could be one for applying strategy, concept, module to a totally different problem, one for gear ratios, etc. The problems at the beginning of the class were helpful, but, in the words of my E100 professor, “Engineering problems are not solved sitting down at a desk”. How about making us get up, form new groups each time, and tackling a small assignment by applying the newly introduced information? The class would be more fun, and we’d get to know more of the peers that we are going to spend 3 years in class with.

One last request: please make the arena and its CAD the same. Right now, the CAD has slightly different dimensions, and has the white ball racks flush with the carpet, not on top. This is very frustrating when designing in SolidWorks, given a SolidWorks model of the arena, and then seeing the real thing is different. A few small adjustments would go a long way to making our task of designing a robot to play on the arena much easier.

Thank you for all of your hard work this on this class, and especially this term. Please understand that there were many aspects of this class that were outstanding, such as the helpfulness of the professors, shop staff, and GSIs, but I felt that pointing out ways to improve would be more beneficial to future students. To sum up, by changing this class for the better, it will be much easier for students to be “someone who makes new things and thinks about them”. I look forward to seeing what this class can become in future years.

Here is our final Bill of Materials (BOM): http://goo.gl/NpAAM

Andrew Huang's Final Reflection

For me, ME250 was an interesting experience. I learned a lot about designing via CAD software and then trying to go about manufacturing those designed parts. I gained plenty of hands-on experience from all the time spent in the shop, and got some insights about the principles that mechanical engineers must include in all their designs. Furthermore, I learned a lot by just asking the more experienced staff questions about machining and design.

As far as the design aspect of engineering goes, I learned the most about appropriate tolerancing and avoiding overconstraint. For example, our design used running fits and press fits- the hardstop on our telescoping arm was press fit for simplicity’s sake, the axles were all made to running fits. Often we would have to check the dimensions of the stock given to us and machine it down to the appropriate dimensions for a running fit. Also, as a result of the design of our drivetrain, the rear axles were terribly overconstrained. Each axle had two pillow blocks supporting them (as they should) but these axles were mounted via a set screw to the output axles of the double gearbox. This meant the drivetrain was constrained in 6 places- 2 for each axle, and then twice for the gearbox mountings. This made manufacturing a pain, but the parts given necessitated such overconstraint. In other parts of the robot, we avoided it like the plague.

As far as the manufacturing aspect goes, I learned a lot about the tools and capabilities of the mill and the lathe. (I also learned how much I missed my dremel, but that’s a different story.) I had no previous experience with the lathe, but I learned how it is absolutely vital in making axles to the right dimensions, cutting grooves for e-rings, and most importantly, drilling centered holes through shafts. Some more subtle things I learned about the lathe was its use in chamfering the ends of axles (with a file) and how to get a good surface finish on parts (very slowly). I learned similar lessons on the mill- how critical it was to face off parts and then acquire the datum lines, how useful it was in drilling holes with awkward distances from said datum lines, and its utility in removing material that would have been impossible/impractical to remove with a saw or file.

As far as teamwork and time management goes, I feel like our team did well in both aspects. We were fairly cohesive and worked together well, and planned work sessions far ahead of deadlines. There wasn’t much to be improved or learned in this section – by now all of us have well-developed time management and interpersonal skills.

I feel that the layout of ME250 could be significantly improved. I believe that lab time and lecture time did not synergize, and as a result the class felt unstructured and valuable time was wasted. For the scope of the project in this class, especially given the fact that students are not yet expected to have any design or manufacturing experience this early in the curriculum, the structure and cohesion of the class is a critical part of how the competition turns out. There are several key points of improvement that stand out to me:

1. Assign groups first; this class is 99.99% about group work and to delay assigning groups is to delay the progression of the class. Group members can still come up with individual concepts and strategies if asked to.
2. The initial reviewing of concept and strategy selection should include a section on the practicality and likelihood of success of the strategy. For example, if a team proposes blocking the flipper with a screw-driven arm, the GSI should note that screw drives are typically very slow (especially with the motors given) and that another team will absolutely beat them to the flipper. This is not to necessarily discourage creativity on the part of the teams- merely to make sure teams know that their design is probably impractical. (As a side note, they might point out that robots with four wheels do not turn if the wheels don’t have a steering mechanism.) Ideally this step of critiquing designs would occur very early on in the class, giving teams time to come up with different concepts and designs. To encourage risk-free creativity, the concept should not be graded until it has gone through several revisions.
3. Lecture should be more focused on the design principles relevant to the Slotbots game. For example, lecture topics should encompass topics such as “drivetrains” instead of just “bearings.” A lecture about drivetrains could address specific difficulties in designing one- including overconstraint, manufacturing components, where one might use different types of bearings in a drivetrain, how one would go about getting the most power out of the drivetrain, etc. This would help teams create more robust designs, and make the class more competitive as a whole. Ideally concepts in these lectures would be looked for (not required) by the GSI’s when reviewing concept and strategy selections.
4. Because a significant amount of the learning in this class is based on hands-on application of engineering concepts, the times for lecture and lab should be reversed. Lab should be 1.5 hours and lecture should only be 1. This gives more time to learn how to use CAD software, how to machine (especially the finer points of machining which can’t really be addressed in lecture), etc. This would also potentially leave time for teams to get manufacturing practice in after training and before the robot construction phase begins.
5. Rules and the design of the arena should be set in stone before the class begins. Every change of the rules affects the validity of a team’s design. To have to keep changing the concept to accommodate rule changes halfway through the semester is a particularly frustrating experience.
6. As far as the kit goes, changing the wheels to a material which actually grips the arena surface readily would save a lot of teams a lot of hassle. Furthermore, having square angle stock versus rounded angle stock would make designing pillow blocks significantly easier- teams would not be so tempted to cut up their square/rectangular tubing as material for pillow blocks. Also, issuing 3/8” bushings would be nice, considering that 3/8” round stock is provided.
7. On the arena, making the ball-holders flush with the carpeted surface would have made the game significantly easier. From what I saw at the competition, no robots could consistently make it over the centerline using the stock wheels and the stock motors- the robots would inevitably get caught or simply lack the power the drive over the ball holding plate in the middle.
8. In any discussion of drivetrains, I would make a bigger deal of using the caster/including different types of casters in the kit. These robots are supposed to be simple, and there are only a few ways to make a robot turn using two powered wheels. These include a steering system (impractical at this level of complexity), a 6-wheeled arrangement where the middle wheels are offset (complex), and a tricycle-like arrangement where one "wheel" is actually a caster/slip plate. There may be other options for surface-based robots to move around, but these seem like the most successful options to me. Four wheeled designs simply cannot turn effectively without a steering system - these should be discouraged for this project.

 As far as my own performance in this class goes, I could have put more time and effort into the design section of the class. I went to our team-scheduled design meetings and contributed ideas, but a large section of the CAD was done by other members of the group. I feel that I made up for this by spending a significant amount of time and effort during the manufacturing section, but I would have learned more about using Solidworks had I spent more time in the design phase.

All in all, my ME250 experience was a stressful and time consuming one, but rewarding as well. Would I go through it again? Not willingly. Do I appreciate everything I learned? Definitely.

Nathan Van Nortwick's Final reflection

The majority of my learning in ME 250 occurred in the shop. With the help of Bob, John and my team mates, I learned a great deal about the various machines in the shop. While fabricating parts for our robot, I gained valuable hands on experience with the mill, lathe, water jet, and laser jet. I also learned a lot by asking questions to Mark, Davor, Sei Jin and Mike when our team was having difficulties with our double gear box. I also learned about designing parts with tolerances and I became more adept at using Solidworks. In addition, I learned how designs can be driven by the materials given and about the limitations a predetermined kit can impose on creativity and functionality.

The lectures were full of information, but the information they presented was too broad which made it difficult to grasp everything that was being presented. I believe narrowing the focus of the lectures would have helped exponentially with the class because so much information was presented in each lecture that it was difficult to see how the material applied to the project. Also by narrowing the focus, it would have been easier to prepare for the final because it would have made it easier to know what to expect and to prepare for the exam. I also believe that the final was too long in length. It was hard to thoroughly answer each question and finish every section. This made me feel that the exam was more testing how fast I could write the answers as opposed to what I knew about the subject.

I believe that the lecture and labs should be more directly correlated. At times, it felt that the lectures and labs were total separate classes. It felt like the homework assignments and the lab assignments could have more directly related to the robot designed. It is of my opinion that they could have been optimized to teach the students skills that they needed while designing their robots.

I also believe that we should have spent more time getting trained in the machine shop because it felt like we were immediately expected to know how to machine parts perfectly after just three sessions of basic training. Had we had more time to learn about how to use the machines, we could have been more efficient using the machines as well as been more precise making parts. This would have lead to better final machine, and more time to practice driving. I believe that the schedule should have driver practice built into it. I feel that many of the machines performances at the expo would have been better had the teams had time practicing with the robots they designed. This would have helped prevented driver mistakes during the expo, like driving into the slot.

In addition to having time for drivers to practice, I believe that having a third field, more control systems, and fresh charged batteries would have been useful. Having these items available would have allowed teams to test their machines and make sure their designs worked. By having more, teams would not just have to sit around in the shop waiting for time with the controller. Also by having fresh charged batteries teams would be able to see how their robots would act on a full charge and to determine how battery charge affected their performance.

I also believe that the competition should have a bearing on our grade in the class. It is of my opinion that part of designing and manufacturing a project is proving that it works, and that it performs. I believe it is unfair to just grade the performance on one single match especially when it was the first time some teams had ever driven their robots with the field fully set up. For example, with our machine, our motor blew out 30 seconds into our seeding round so we had to play without our most critical module working. We were still able to score 50 grams, but when we reran our robot with the motor working, we were able to score 154 grams. This however is not reflected on our seeding round. It would have also been nice to have known the setup of the balls prior to the day of the seeding, because it could have affected the strategy of picking up balls. I also believe that the seeding round ignored that some teams decided to design their robots to play a defensively and maybe they could not score many points, but they denied the other team from scoring points, so they could still win in competition.

The CAD model that we used to design our robots was different than the field that was created. In the CAD model, the ball holders are flush with the carpet, and in real life this is not the case. The majority of our teams brainstorming and original designs were made with the CAD model since we did not have that much access to the field. This lip however caused our team to have to change some of our drivetrain designs costing us valuable time. Another issue that arose from the field was the variance in the slots. Because the slots on the two tables were not cut the same, our robot deployed differently on each table and sometimes our robot was unable to score balls because of this difference. This lead to some design changes in the last few days which would not have been necessary had the field been built to specifications given to us in the rules, and the CAD model. It would also have been nice to solidify the rules prior to the start of the semester. At times, it felt that some of the rule changes eliminated ideas that our group had been working on and would cause us to spend more time redoing work we had already done because the rules had changed.

One other thing that I would suggest to make Slotbot’s a more exciting competition would be to change how teams compete in it. I believe that if the rules were changed so that it was a two on two competition the expo would be more thrilling to watch. This would also add an interesting strategy component to the game. Teams would have to figure out how they would play with and against other teams. There could be a round of seeding where teams are ranked by how they perform in the completion with other teams. Then the top teams could pick a team mate to play with in an elimination round. I would then change the elimination round to a best out of three to advance in each bracket. These changes would make the competition last longer, but I feel it would give teams more time to actually compete with their robot. In my mind, more time to compete is beneficial because teams put in a lot of time on their robots and just playing once in the competition does not seem fair for the amount of work put into the robot.

To improve my performance in this class, I could have gone to office hours more. Unfortunately, with my schedule it was difficult to make the office hours offered. Also, I believe my performance would have improved had I had more training on the various machines available to us in the machine shop.

Final Team Design

The telescoping arm module changed slightly over the course of the class. Our initial concept was rudimentary and did not consider how we would manufacture the components, or how we would attach the separate elements together. One of the biggest conceptual changes, however, was the addition of a deployable ramp which would make it easier to deposit balls into the slot to score. Previously, the ramp leading to the telescoping tube was only as long as the base plate, giving Wall-E only 8” or so of room to score balls into. This was expanded to cover the whole slot, more than doubling the scoring area, making it easier for the driver (and thus faster) to score.

As previously mentioned, the initial concept did not accommodate for the manufacturability of the arm. One of the key elements was the delrin sleeve which hung underneath the base plate; no companies made square delrin tubing, it would be obscenely expensive to buy a block of delrin in the correct size and machine out the middle, and we had no injection molding capabilities in the undergraduate shop. Instead, the design was changed so the tube was made of four different plates of delrin, each laser-cut in a tongue-and-groove fashion to fit securely together. These parts were then epoxied together.  An additional advantage of laser-cutting the delrin plate was that the arm could be easily made to the correct angle- had this angle not been within the tolerances, the aluminum tube would not have been able to properly block the flipper.

Overall, the concept of the car stayed the same throughout the semester though we had to make some adjustments as the manufacturing process went on and as we took the competition rules and options into deeper consideration.  The first design change came when we attempted to bend the brackets in the student shop for the roller arm and the walls of the hopper.  We realized that the bender was very limited in capabilities and unfortunately the bends that had worked nicely in Solidworks were not as practical in manufacturing.  To address this problem, we simplified the bends for the hopper walls and changed the brackets to a simple bend and two by one stock to support the roller arm.  Once we put more thought into mounting the double gearbox and the battery we found that it would be best to extend the base plate of our car and make the hopper slightly smaller.  The drive train was then moved from beneath the hopper to accommodate the larger wheels given to us in the kit, and to prevent the angle of the hopper from becoming too large. Once we adjusted the base plate, we decided that the motor for the roller would be mounted above the base plate extension on the back of the hopper and that we would use a timing belt from the motor to the roller axle to spin the roller.

Our final car functioned using the rear wheels to push the car while the front of the car slid across the carpet.  The plate that slid across the carpet was made from delrin to reduce the friction between the contact point and the carpet.  In the competition, a rubber band belt controlled the roller because we had problems receiving the timing belt that was originally ordered a week before thanksgiving break and never arrived.  The roller used bristles that were generously donated to us by Memtech of Plymouth and were mounted to our PVC pipe and axle.