ME 250 Reflection: Justin Croop

This course was a valuable introduction to design. I had zero CAD experience coming into the course. Learning to use Solidworks and the months of experience acquired throughout the semester have greatly improved my proficiency with the program. Although I'm sure there is much more to learn, after completing the course, I feel that I have learned a great deal about the design process, how to create solid models of parts and how to assemble them efficiently. Using Solidworks to design our slotbot was practical and gave me a sense of what designing is like in the real world.
Manufacturing parts in the shop was a challenging process at first. To be honest, I did not remember most of what I learned in the shop training at the beginning of the semester. After a few sessions in the shop, I learned to use the mill, and lather properly. I also learned the processes needed for working with different materials. This course also showed me the capabilities of the laser cutter, water jet, and other various shop machines.
The combination of the design and manufacturing process in this course gave me a better understanding of the importance of each process individually. Solidworks drawings take time to construct assemblies that fit together perfectly, but the time is definitely necessary. Without the precise and thorough designs the manufacturing of the slotbot would have been near impossible. I did not realize how much thought has to be put into the design of even a simple mechanism. Having to manufacture the parts ourselves brought attention to the restrictions of the machines and what designs are more difficult to produce in real life.
Working in a team for the majority of the semester was difficult at times. With the amount of work done throughout the course, we needed to divided the team to complete all the assignments by the due date. Good time management was essential to surviving this course. Once the manufacturing stage began around thanksgiving, the course work increased and the pace sped up with it. It was a challenge to plan meetings and time in the shop in order to meet deadlines. This course dominated the majority of my time in the last few weeks of the semester, which taught me to be more efficient with my time and to balance work with other classes better.
There are a few areas that this course could improve on. The CAD training at the beginning of the semester was not enough in my opinion. Having added the class two weeks into the semester I was already behind and it was difficult to catch up in the fast passed tutorials. Having a few more lessons would have made the design stage of the slotbot much more pleasant. The shop training should be more hands-on and closer to the beginning of the manufacturing stage. I forgot the majority of what I learned by the time we started working in the shop. I felt that the lectures were informative but almost too in-depth for what we needed for the course. I think that more time explaining machining processes would have helped immensely in the manufacturing stage and on the midterm.
Our team could have improved our performance in the expo if we had started sooner with the manufacturing and design stages. At the start, we did not really know what to expect in terms of how long it would take to finish the project. As the deadline came nearer we suddenly had a much better understanding and rushed to finish.
I could have improved my time management, especially at the beginning of the project. Having finished the project and now knowing the time requirement, I definitely would have approached the assignment differently.

Individual Reflection-Chris Harris

The ME 250 class was a decent introduction to the design and manufacturing process. I learned how to use a mill, lathe and many other machines involved in manufacturing our slotbot. I was given the opportunity to use the laser cutter and the water jet machine as well. I had very little machining experience prior to this and this course was a good introduction to that. I had already had experience working with Solidworks so I didn’t gain much from that aspect of the course. However, I did get a chance to see some of the new features of Solidworks, since the versions I was using were older. The biggest thing I learned about design and manufacturing was how to complete a project in a very short period of time.

Time management was a huge thing when it came to this course. Once we started machining I believe we only had a couple weeks to have our machine fully up and running. This meant that, ideally, nearly all of the design and drawings needed to be completed a week prior to Thanksgiving break. Also, the best way to get things done was to try and divide everything up among the team members. Being on top of the assignments once to manufacturing started was challenging as well, and I learned better skills for planning and making sure things got done on time.

There are a few things I would like to touch on involving the improvement of the course. Firstly, the CAD lessons were not sufficient enough for how vital Solidworks was to the project. If I hadn’t already had experience using the program, it would have been a nightmare trying to create the solid models. I understand there is limited time in the semester and even less time when you factor in how much time is needed to actually manufacture the machine, but even having the CAD lessons continue during the manufacturing would have helped.

Another thing that I had a huge issue with was the absence of the two professors during the semester and especially during the manufacturing process. Professor Umbriac was around the most with his office being close to the machine shop, and he was always helpful whenever I had question, and if he had to look something up or ask someone else he always did it right away rather than telling me he would get back to me which was great. However, apart from the few lectures that he taught and the actual slotbots competition, Professor Hart was absent the nearly the entire time we were manufacturing. I understand he has other classes and obligations, but the fact that I didn’t see him around the lab or machine shop once during the semester was astonishing. In the future, I think more interaction with the professors would be hugely beneficial to the students.

Lastly, I think that more shop training than the few hours we received would help things go more smoothly once we start making the bot and would therefore cut down on the huge time crunch towards the end. Also, having more hands on labs in the shop would also help out a lot.

Things I could improve on:

• Better time management
• Awareness of when assignments are due and what is required in each one.
• Not getting too sucked up in one aspect of the project. (I often completely forgot that we had a blog to update, thankfully my teammates updated it).
• More time on the lathe. I was never very comfortable with it and tended to stay away from it if I could.

Slotbots II: Reflection

Experience/Knowledge Gained in ME 250

Design and Manufacturing

The most valuable experiences I had in ME 250 were in the shop and in the computer lab. In the computer lab I learned the basics of CAD through Solid Works. Although I doubt my proficiency even counts as a tip of an iceberg, I now know how to draw and assemble simple designs. I found these skills useful, especially when they were applied to a real world manufacturing case. The Slotbots project did a good job of taking us through the design and manufacturing process. The experience of modeling in Solid Works, creating a drawing, then machining the part in the shop was very valuable.

One of the most important practices I learned in the shop was how to dimension accurately. I learned how to do this by learning how to mark stock material with a height gauge. I already knew how to use a few machines, but machines I learned how to use in the shop include the mill, lathe, and shear. I also learned that different materials must be machined using different processes. During my time in the shop I was also introduced to the capabilities of a laser cutter and water jet.

Teamwork and Time Management

ME 250 was not my first endeavor in working on a team, however it was one of the most challenging because of the plurality of deadlines. These often forced our team to divide into sub groups in order to complete the assigned tasks more efficiently. This was an effective technique our team had a chance to refine in the course.

Course Improvements

And I do mean course improvements. ME 250 needs more than fine tuning. Here is a breakdown by category.

CAD

The CAD lessons were too rushed. I learned most of what I know about Solid Works out of class. If you missed a beat in class, you would be behind the rest of the class period. I think CAD is really important to the design process. And I think students would be better off if CAD was introduced in the Tuesday and Thursday lectures and then the Wednesday discussion sections could be used to run through the material again.

Machining and Hands On Labs

I think the hands on labs would be more helpful if done earlier in the term. In terms of machining. Students obviously were not prepared to start and finish their slotbots in the four week span available. A lot of that had to do with the level of knowledge going into the manufacturing process of our slotbot. None of my team had machining experience coming in, and three, fifty minute shop lessons with 20 other students two months before you're allowed to actually touch the machines are not the best way to gain knowledge of the powerful and dangerous machines we were set loose on. On our first day in the shop we did not even know how to turn the machines on. There needs to be more teaching done before students are set loose in the shop. If for no other reason that for the safety of others in the shop. The best way to learn how to safely use the machines is through instructor, guided hands on experience. Bob cannot do this alone, especially with 50 students with no experience in the shop all asking him questions simultaneously. The Professors and GSIs should step up and pitch in with helping students through the process of using the machines.

Lectures and Exam

The lectures were often too in depth for the course. Students would have benefited if more lecture time was spent learning how to machine and use Solidworks. Professors and GSIs did not do an adequate job at preparing students for the exam. Topics of emphasis on the exam should be covered more than once in lecture and at least once in homework. And in an exam review session examples and topics of what are going to be emphasized on the test should be covered. An example of this was being expected to know the machining processes when it was not covered in the review and at that point I did not have any worthwhile experience using machines in the shop.

Personal Improvement

I could have improved my performance by attending office hours more often. I could have started planning how we would machine and assemble our machine earlier. I did not realize how great of a time commitment the project would be.

Concluding Post: Final Machine

The 8th Wonder slotbot had a unique approach to the game. It aimed at wondering the crowd with a combination of defense and scoring both in the slot and on the surface. It competed by going through a series of interconnected steps. First, the slotbot had to pull a pin out of its crossbow action, pivot locking arm. This rapid first motion was how we would win the pivot. After the pivot is won in our favor, we could then lower our rack to the desired height and drive forward, using our spring steel "broom" to sweep ballsinto the goal. Once we have finished taking care of business in the slot, we are then able to drop the rack and move onto collecting balls and playing defense on the surface. We could collect balls using our "U" shaped ball scoop to deposit balls into a bin located behind the front right wheel of our slotbot. When the match was near the 90 second mark, we could drive to our goal and deposit any balls that we collected into the goal using a unique door opening mechanism.

Limitations of Machine

Our slot modules were difficult to align properly at the start, which resulted in improperly mounted components. The crossbow locking arm needed to be mounted in the slot perpendicular to the flipper. We did not have enough time to secure it properly, making it sag and aim at the bottom of the slot. Also, the pin that fires the mechanism was impossible to pull out with the given orientation. The crossbow arm just rotated around the only bolt that was placed correctly instead of staying fixed and allowing the pin to be pulled out.This process was critical to our performance in the competition. If this had worked correctly, the crossbow arm would have fired out, locked the flipper in our favor, and allowed the balls to be pushed underneath the crossbow mechanism.

Our design was not as robust as we had hoped. The failure of a preceding step in our strategy caused failure in the resulting process. The failure of pulling out the pin resulting in our robot being tethered to the crossbow arm, unable to push balls into the bin, and unable to drop the slot arm. The original strategy was to empty the majority of the balls from the slot into the bin, then drop the slot arm into the slot and drive around on the tabletop. Since we were unaable to move the slot balls out of the way, our rack was about two inches too long and could not be dropped. This rendered our robot useless. Our strategy for scoring balls on the table top required us to drive up to the balls and pick them up with a forklift-like mechanism, place the balls into a bin on top of the robot, and then open the bottom of the bin once the robot is positioned over the funnel. Unable to drive around freely, we were unable to execute this strategy as well.

Modules:

Rack and Pinion (not pictured)

Our rack is key to scoring in the slot. It is powered by a motor attached to a planetary gearbox. At the bottom of the rack we bolted a spacer, to make up for the offs

et from the rack, a shovel, to provide support for the spring steel, and spring steel, to usher the goals into the goal.

Main Motor (pictured on right)

We used a double gear box and motor to

power our wheels and steer our robot. To gain extra traction we added sandpaper to our wheels (rubber bands are pictured because the epoxy mating the sand paper to the wheel is drying)

Pivot Arm Lock (pictured on right)

Our arm lock uses two extension springs that create a crossbow like mechanism that quickly locks the pivot when engaged. First we load the crossbow by pulling the locking arm back. At this stage a pin is inserted to keep the arm locked

until the match starts. When the match begins, we pull out the pin which allows the springs to compress, this shoots the arm lock forward. Once the arm lock has won the pivot an interior bolt keeps the arm from being moved in the opposite direction.

Ball Collection Arm (not pictured)

We used two techniques for collecting balls with the forked collection arm. To collect a ping pong ball, we lowered the arm to the level of the white, nylon "tee", drove the car underneath the ball, and placed the collection arm underneath the ball. To collect squash balls and sand-filled squash balls, we lowered the arm around the ball. The squash balls deformed, and the added width of the ball caused the ball to lodged in the front of our collection arm. Once the collection arm was underneath the middle of the ball, we raised the arm and picked the ball of the ground. The gap between the tines of the collection arm widen as they got closer to the motor axle. This allowed balls to roll down the tines of the arm and when they reached the strategically placed wider gap they would fall into the bin. Once the bin was full, the robot could line up the bottom of the bin with the funnel and raise the arm until the bottom of the bin opened enough to let the balls fall into the funnel.

Bin Door (not pictured)

The bin mounted behind the forked collection arm consisted of three aluminum plates secured on end, and the flat side of the mounting block for the planetary gear box. The floor of the bin was a small t shaped piece of sheet metal that was laid loosely across the gap in the bin floor. The forked collection arm rotated from the ground to an upright position for dumping the balls into the bin. Once, the bin was full the robot drove to the funnel and lifted the collection arm passed the dumping angle. A small thin piece of metal was mounted to the backside of the collection arm. This piece hit the bin bottom when the collection arm was rotated to an obtuse angle, sliding the sheet metal passed the edge of the gap and allowing it to swing freely into the funnel. The sliding bottom piece opens the gap and allows the collected balls to fall into the funnel.

Final Bill of Materials

https://spreadsheets.google.com/ccc?key=0AovVMX_CIix6dElCZkpKM2RkYmljT2xFRUpEeExRbkE&authkey=CPvh09cC&hl=en#gid=0

8th Wonder Video!

Home Stretch

MS 9 was due to today. Our grade didn't exactly live up to our name. Even though we have spent a minimum of two hours in the shop every day for the last four weeks, we just weren't ready to display a functioning machine. A lesson we learned is that the assembly process is never flawless, even when using parts that were machined within specified tolerances. The most disconcerting example of this involved our pinion and rack from the kit. They didn't mesh well together and the result was a stationary rack. In summary, a positive from all of this end of the term craziness is that we've learned some of the basics of machining. However, we wish we had more instruction initially and more time in the shop would've helped with the deadlines at the end of the term. Let's just hope we can get our robot functioning by Wednesday!

Week of Nov. 29 Update

This week we were very busy in the shop. However, our hard work has paid off and we are very close to finishing our slot bot. We have completed most of the major parts for our machine and have only 10 parts left to complete (mostly drilling holes). We are excited to be nearly done with machining and look forward to testing the bot in the arena next week.

Scott soldering wires to motors

Justin waiting to get tools