And the winner is...

Not us.

But that doesn't mean that the semester was all for nothing.

Coming into ME250, I was excited to take my first true college level mechanical engineering course. Prior to the start of the semester, I ran across the Slotbots video from last year, giving me a general idea of what to expect in the class. Having completed four years of mechanical design in high school, I came in comfortable with the ideas of computer design, dimensioning, threads and fasteners, and had experience using many of the machines. After spending my senior year building an electric vehicle, I was looking forward to get back into designing and building.

Having focused on learning AutoCAD and Inventor in high school, trying to switch to SolidWorks initially seemed like a difficult, and possibly unnecessary task. However, with the labs and investing time outside of class, I quickly saw the similarities between the programs, and am now equally as efficient with them all. In fact, Solidworks has many analysis options that I wasn't aware of when using the Autodesk programs. I am sure having knowledge of additional software will be useful when entering industry.

The lectures were my first real opportunity to learn about mechanical components in detail. Information about parts such as gears, motors, bushings, bearings, and couplings is knowledge that every engineer needs to have to be successful. The lecturers did a good job of explaining the intended uses of each component. However, implementing and combining them into a functional design had a large learning curve, which probably could have been better assisted in class. More practical, hands on examples of how the components are chosen, assembled, and operate may have been more beneficial than slides of very specific equations that only relate to specific situations, and didn't affect our project. Similarly, while material processes were interesting to learn about, without an in-depth explanation to how they work, and with no need to utilize them for the project, the time may have been better filled with other information. Overall though, the lectures served their purpose and delivered a lot of new information, and the slides will serve as useful reference material in the future.

The assignments were well-intentioned, and helped teach the design process, but often were not able to be integrated with the project as planned. The initial assignments asking for strategies, concepts, and modules were drawn out over too many weeks, cutting into potential shop time that was desperately needed. Since nearly everything had to be repeated collectively once groups were formed, it would have been better to make at least the final stage a group assignment. This would have given the teams more time to get acclimated and come up with a final approach.

One thing I quickly got a feel for was tolerances. We discussed the idea in high school, but never took it into the manufacturing phase. After getting points docked for tight tolerances on one of the early milestones, I saw the benefits of accurately determining how much room for error there is on a given part.

In regards to teamwork, the majority of us were able to work together and had a common goal in mind. Though we all came into the group with our own ideas for the design, we were able to collectively choose a strategy and work towards carrying it out. However, some avoidable tension caused the team to divide and each focus on a module. During the process and in hindsight, it would have been much better for the problem to be settled at the beginning. Instead, I attempted to act as the connection between the two sub-groups, but often found myself unfamiliar with a new direction that the cart had taken.

Both modules underwent numerous design changes throughout the semester. Reasons for these changes included better ideas, manufacturability problems, performance issues, and time constraints. This involved making numerous CAD drawings, testing our ideas in SolidWorks, and creating manufacturing plans. Between these revisions, time was spent determining how to allocate the materials provided, what we needed to purchase, and what tools to use to make each part.

Time spent in the shop included both high and low points. Bob and John were always willing to help, and there immense knowledge of machine processes was priceless. I had never seen a waterjet or laser cutter before, and using both machines in our manufacturing process was a new experience. I was impressed with how quickly intricate parts could be cut straight from the CAD drawings. However, not everything came so easily. It is no secret that the shop was often packed, and with only a few mills and lathes, the supply of machines fell far short of the demand. Time spent waiting for the machines to become available often exceeded the time spent on them. Though a solution isn't easy, more shop time and more machines are definitely needed. I feel that the timeline should have varied more from last year's competition to account for the fact that multiple modules had to be created to compete this year. Throughout the semester and down to the wire, shop time was at a premium, and influenced our final product. However, considering the time given, I believe we were able to produce two functional modules that gave us a shot in Slotbots II.

A couple of our designed parts for the chute proved to be difficult to produce. We first attempted to build the two rails out of aluminum stock. A couple hours into the machining process, it became clear that the methods necessary to do it right were not available to us, and that we were unable to build them to the tolerances needed to ensure the sliders did their job. After much frustration, we finally decided that purchasing rails and sliders from McMaster would be the best option. This experience showed me the importance of making sure the parts you design are able to be made with the available machines.

Secondly, both the vertical and horizontal chutes we designed were made by bending thin sheet metal. Though the bends looked simple enough on the SolidWorks model, it became a whole different story when we attempted to use the metal bender. It took hours testing different techniques using a combination of the bender and a rubber mallet to get our desired results.

The imposed limited outside budget of $100 added another learning experience to the course. It is amazing how fast the cost of small components can add up, and how expensive some can be. In fact, we ended up using nearly every penny available to complete the project. with the rails consuming a majority of the budget.

The competition, ultimately, turned out to be somewhat of a disappointment. Watching team after team fail to score was not what I expected at the start. After seeing many of the modules teams had built function as planned during individual testing periods, including ours, performance seemed to decrease leading up to and during the final event. For example, our video shows our cart cruising across the table and depositing balls in the hole in only a few seconds. However, during the seeding round, and even worse during the competition, the power supplies seemed unable to provide the juice needed to run the machines as intended. It is disappointing that after months of work, the results could have been affected by inadequate battery packs. Having seen our cart operate much better than it did during the Design Expo, it is easy to believe that the results could have been different. Many other groups felt the same way, and more emphasis needs to be placed on ensuring that all power supplies are fully functional each and every time. Larger motors would have been beneficial as well. The competition would have been much more interesting and had better results if focus was put on these two things.

My performance in the course could have been improved by finalizing a design at the beginning and working out all possible problems, instead of having to go back and change ideas midway through. Finishing the modules earlier would have given us more testing time and allowed us to make a couple additional changes, as well as determine the optimal starting positions for the modules and plan of attack during the competition. With every group finishing nearly at the deadline, controllers were scarce and time was even scarcer.

Overall, I enjoyed ME250, and will use the knowledge I gained as I move forward through the rest of the mechanical engineering curriculum. The class was well run, and every professor and GSI involved worked to share what they know with us. A special thanks to Professor Hart, Mike Umbriac, Mark, and Bob and John for a successful semester!

Final Reflection - Aaron

I came into ME250 thinking that I couldn’t learn much from the class that I didn’t know already. After all, I had been on my High School’s robotics team for four years, had build robots much more complex than SlotBots, and already knew AutoCAD. What else could there be? As I quickly found out, a lot of things.

Although the lectures did cover a lot of topics with which I were already familiar, they included a lot of new, often conceptual, material that I had not dealt with before. Hearing the Fundamental Principles defined pulled together a lot of things that I kind of knew, and allowed me to implement them more intentionally. Tolerancing and dimensioning fall under this same category, and learning the formal definitions (and doing the practice examples) really helped me appreciate them more. The sections about the process of design and analyzing functional requirements seemed boring at first, but a few weeks later I found myself using them during the planning of a completely unrelated team project. 

This course also improved by CAD skills, mainly in the area of good practices and helpful tricks. Although I had experience in modeling and assembling in AutoCAD, I had never been taught simple things like dimensioning to midpoints, extruding along reference planes, or mating parts so they can be easily updated. By the end of the process, I had even overcome my reservations about SolidWorks and began to enjoy working with (and appreciating) the software. 

Manufacturability was probably the biggest thing I learned from this class, and was done though painful trial-and-error. Personally working on the mill, lathe, break, laser cutter, and drill press allowed me to better appreciate what processes were actually possible, and how a great concept in the computer might turn out to be a nightmare to produce. Take for example our chute module: The plywood parts seemed to assemble well, but the glued joints were not strong enough. As a result, we had to painstakingly drill and countersink dozens of holes for screws by hand. Similarly, the bent metal for the chute itself featured many convoluted bends that SolidWorks was happy to visualize, but actually took creative use of the press shear and violent use of a mallet to produce. From these hands-on experiences, I will be able to design better parts in future projects, which will reduce the amount of time and money I have to sink into the project.

Teamwork and team building were areas that I definitely developed in over the course of this class, but not to the degree that I wanted. Team Chaos Theory was formed under less-than-ideal circumstances – instead of four people who really wanted to work together uniting, two groups of two people ended up with incomplete groups and combined out of necessity. I had intended to talk to people in my lab section to get a group of four friendly people assembled before teams were due, but the call to formation occurred earlier than I thought it would.

There was immediate tension on the team, mainly because Josh and I didn’t exactly get along. We have two very different personalities, and this created tension in the design process. We both had a lot of ideas, and reconciling them required a lot of face-to-face negotiation. After this process, the team splintered back into two groups, with each taking on one of the modules. This was, in my opinion, our biggest mistake. I believe that both modules could have been a lot better if we’d had all four sets of eyes looking over the CAD models and physical assemblies instead of just two. 

Possibly the biggest example of where this schism caused problems was the design of the chute superstructure. Matt and I chose to manufacture it out of wood because we had initially thought we would not need waterjet cutting and ceded the team’s time on the machine to Josh and Cam. When w changed our design and suddenly needed different side plates, we were left with no time to waterjet them, and no material to make it out of. We ended up getting additional waterjet time and trading for materials for part of the module, but had the entire team been involved we could have made the change earlier and adjusted our machining schedules accordingly.

If I were to go back and do this course again, I would start by coming in with a much more open mind. I would actively seek out a team that I “clicked” with, and would have encouraged the team to stay unified and involved with all aspects of design and construction. I also would have stuck to a much more proactive schedule, as we nearly ran out of time at the end.

I didn’t have many problems with the way this course was run. One thing that I would like to see for future years is better motors, as a majority of teams that went to the arena were simply unable to function due to lack of available torque. This made the preceding weeks of hard work feel somewhat meaningless. If better motors are not possible, then a lecture section about steering and skidding would be a good idea. Additionally, I think there should be milestones inserted between the current MS7 and MS8, and between the current MS8 and MS9. This would force teams to stick to a schedule and be proactive about their design and construction process, and would help prevent the sort of logjam that occurred in the shop towards the end of the build cycle.

Overall, ME250 was a very enjoyable class. Professors Hart and Umbriac were very knowledgeable in their subject fields, and clearly showed their enthusiasm for the process. Mark was very helpful in the design process, and served as a valued sounding board and moderator for our process. Although our robot did not win, the process of designing and building it served as a valuable educational experience. I look forward to taking ME350 next fall!

It's so nice to be done

The overall process of designing and manufacturing our slotbot took a few twists and turns and hit a few bumps along the way. Our original designs for both the cart and the chute were modified as time went on. We also made a few mistakes during manufacturing process which chipped away at what little time we had to build our bot. However, our finished product turned out to be a very competitive design.

The initial process for design and creativity was done individually and also lead to the first obstacle in developing a final product. Each of us invested a large amount of thought and time developing our own ideas only to have them stripped down by the team. Comprimises were eventually made but it did slow the development of the final design. This could be remedied in the future by starting the group portion of the process before each person narrows their work to a single design.

The manufacturing of our MCM was probably the part of the assignment in which I learned the most. I was very unsure of how to properly and safely use the equipment in the shop prior to this portion of the project.  Bob Coury soon became one of the most valuable instructors of the class. I started working in the shop as soon as we were allowed and asked as many questions as I could. It wasn’t long before I became proficient using the lathe, band saw, drill press, laser cutter, and the drilling portion of the mill. However I never did get to use anything involving end milling or auto driven lathe/mill. Hopefully I will get the time to learn these in ME350.

Although the manufacturing process was successful for learning it was also a hindrance for multiple reasons. The first of these reasons is due to either a lack of prior experience or because of a careless mistake made by us. We had a tendency to either not be able to make a desired part or to make a mistake while making a part. A particular case when we couldn’t make a desired part we could not make a cut that we wanted using the available equipment so we turned the single part into two parts. This took more time and also required us to change our CAD drawings. As for the mistakes, there were a lot of them. We at times either did not come the realization about the how parts fit together or carelessly cut or drilled an area that did not need to be. A lot of extra parts were made in order to get the correct part completed.

The other reason the manufacturing process slowed our project was due to availability of equipment. There were 32 teams and 4 lathes and 4 mills (if they all worked). This led to a lot of wait and hope time. Hopefully, this can be resolved for future classes. Perhaps shorter time blocks per team and maybe an earlier availability for the manufacturing portion of the class.

The competition…. As fun as the idea sounded to me in the beginning, I ended up very disappointed when all was said and done. It seemed that the performance of our cart was incredibly dependent upon the power supply we were given. During preliminary testing our cart moved both forwards and backwards quit well, and only had some difficulties in turning right. In order to compensate for our lack of turning we decreased friction on our front wheels. This seemed to work well in the first round of the competition, but not so well in the second round.  The first round our cart maneuvered in all directions fairly well, but in the second we could barely even move in the forward direction. Because nothing mechanically changed between rounds it led me to believe the power supply was not as strong. Upon coming to this conclusion I spoke with a few other teams each of which seemed to have had similar problems. Though the competition did not affect our grade it was part of why we all worked so hard on our projects and was slightly irritating to think it could have come down to luck of which battery pack you received. In short yeah to mechanics and booh to electronics.

Reflection by Cameron McKenna

Looking back at the course as a whole I wish I could do it over again, with the change of doing things slightly differently. I learned a lot with regards to design and manufacturing, some during lecture, but most of what I learned came from working in the shop on our slotbot. Before this class, I had never used a mill or a lathe. Learning how to use these machines will be an integral factor in my success here as a Mechanical Engineer as I certainly will be using them in subsequent design classes. I also learned a lot about the manufacturing process, mostly in terms of the order that these processes be done.

Learning how to use SolidWorks was fun. I thoroughly enjoy working on CAD and was able to pick up SolidWorks pretty quickly as I have prior experience with AutoCad Inventor. These programs are very similar and I found it very interesting to learn another as there is not one program that is used in the industry.

Being that this is the first semester of slotbots II it is understandable that there were aspects that needed improvement. The biggest, as many other students have probably stated is the amount of time spent in the beginning of the semester on the creative process. I agree that creativity is important, but learning more about the design process and the resources available to us would have moved the final stage of manufacturing along more quickly. I also think that creating teams earlier and opening the machine shop earlier would be beneficial. And if it is a concern that teams will not take advantage of this time, a stricter requirement of attended shop hours for each team should be enforced.

The most beneficial part of the lectures for me was the material relating to our actual project i.e. couplings, gears, bearings/bushings. I would have liked to see more material presented that we could use on our project. Things like how to use the machines, safety tips, good practice for machining, like which edges to measure from and use the edge finder on, center drilling, and mounting pieces in vices. I am sure many teams had to make major changes in their machines because they were not able to do something that they needed to or simply because when they tried to it did not work and ruined their material

A good way to avoid this is to have more in-shop assignments like we had mid-way through the semester during the beginning weeks when the work load is very small. After everyone is trained having these assignments would help open people up to all of the available processes. From personal experience I know that Josh and I did not once use an end milling bit, simply because we really didn't know how. We just stuck to using the band saw and then filing our pieces smooth.

Overall I think the course material was good aside from learning too much about industry processes like "cold-rolling" and steel types and not enough information relevant to our project.

I was also disappointed in the power supplies used because they were not reliable because some rounds our car would drive just fine and others it would barely move. stronger motor could also be used because as this competition is much more complicated than slotbots I more elaborate bots were created that required more power.

My performance in the class could have been improved by knowing more about how our gearboxes performed under loading. It seemed that when we included our timing belt/pulley assembly it made our wheels harder to turn and consequently harder for our motor to deliver our desired output. I could have also performed better had I known more of the machining principles before entering the shop seeing as our group spent the whole first week making and remaking wheel shafts because we were making holes the wrong size, tapping them wrong, or bending them in the arbor press.

This course has taught me many things and I enjoyed the project. I did not have much contact with Sei Jin but Davor and Mark were both really good GSIs.

I look forward to ME 350 and as I believe it was Toby who said it, I will probably regret suggesting more manufacturing time for the 250 students. But if it makes for a higher scoring and more exciting competition than that sounds good to me.

Final Team Documentation

Our Slotbots strategy required two modules. Our Most Critical Module (MCM) was a cart that was driven around the table top. A pen and gate assembly allowed us to collect and secure balls on the table. Our second module was a chute that, when deployed, served as both a way to toggle the lever and score the balls carried by the cart. A small secondary ramp was placed in the slot and used as a dumping zone. The balls rolled down it, into the hollow chute, and finally down the scoring ramp.

This approach was chosen because it offered multiple scoring options. For example, if our opponents were able to toggle the slot before us, we could use the cart to carry balls to the opposite cone instead. We also wanted a creative way to attack the problem, which we believed this would accomplish.

The two modules are pictured below, and explained in more detail:

The Cart

As mentioned above, the cart was designed as our primary offensive option. Though our focus was to use it to deliver balls to the slot, it was equally capable of taking balls to our cone if the chute was beaten to the lever. Therefore, it was critical to any success we hoped to have in seeding and the competition.

The pen and gate assembly on the front utilized gears and linkages. The gate could be raised and lowered, allowing us to capture balls. The shape of the pen helped ensure that the balls could not escape as we were trying to collect more. The gate was bent at the bottom so that it pushed underneath the squash balls, and prevented them from getting stuck. The open bottom provided an extremely simple deposit method into either the horizontal slot chute or the cone.

The laser cutter, waterjet, mill, band saw, drill press, and metal bender were used in the manufacturing of this module.

The Chute

The chute was designed to act as a fast way to toggle the lever and open our side of the slot, and to accept and score balls from the table. A solid, stationary base was placed in position with velcro, ensuring it wouldn't move during game play. Two rails, purchased from McMaster, were attached to the inside of the vertical walls. Two sliders were attached to the aluminum chute. Slots on the walls allowed us to adjust the angle of the chute, and test for the optimal setup prior to the competition.

At the start of the match, the chute was kept in position by a short aluminum pin. When play began, a motor was used to pull the pin. Utilizing only gravity, the sliders then moved down the rails, allowing the chute to fall toward the lever. A two pound block was also secured inside the chute at the top to allow it to hit with more force.

A horizontal slide was placed into the slot. When the cart drove over the slot, balls rolled down it, into the hollow vertical chute, and finally into the scoring ramp.

A combination of the laser cutter, waterjet, mill, band saw, drill press, and metal bender were used in the manufacturing of this module.

Other Notes:

• The power supply was mounted directly to the cart to reduce wiring.
• A quick-disconnect was used to allow the car to detach from the chute once the pin was pulled. This allowed it to travel freely and eliminated the possibility of getting tangled up in extra wire.
• A complete parts list, including costs, can be found in the post below. We remained slightly below our $100 allotted outside budget.
• We were able to rank 4th in the seeding round, and advanced once in competition.
  

Parts List!

Our final parts list can be found at http://goo.gl/th3JY.

Final Video: Shorter Version!

Our final video was apparently a bit too long to be shown as filler material before our rounds. To remedy this, we present - "Final Video: Blitzkrieg Director's Cut!"