Final Post

On Monday, Tuesday, and Wednesday we spent a lot of time machining last-minute components and making adjustments. One of the adjustments was to lighten our scoring arm, which backfired and cost our team valuable time. By the day of the seeding though, our machine was completely finished. If we had some more time, there are a couple of minor adjustments that we would have made to increase our motor efficiency. Our finished robot consisted of a jamming arm and a scoring arm. The jamming arm was made of square tube stock and a ratchet, both of which attached to a piece of aluminum hex stock. The jamming arm started in the upright position and was driven by a motor with a string. The string came off the jamming arm when the jamming arm swung down. The momentum of the hammer (the heavy weight at the end of the jamming arm) pushed the flipper backward. The ratchet locked and held the jamming arm in its position.

The second part of our robot was the scoring arm. The scoring arm had an outer tube, an inner tube, a threaded rod, two planetary gears and gearboxes, a coupling, a motor mount, and a mounting plate. The scoring arm was driven by a motor outside of the frame, which was connected to an axle (by a coupling), which was fastened to the motor mount by some set screws and e-clips. The inner arm contained a threaded coupling, which allowed the inner arm to be driven up and down by spinning a threaded rod. The threaded rod was connected to a coupling, which connected to the motor, which was mounted vertically. We used a low gear ratio to allow the inner arm to move as fast as possible. The motor was mounted by an L-bracket and the mounting plate.

In the slot bots competition, our robot failed to successfully score as the result of a lack in power from the outer motor. This power was lost because of the flexible coupling. If we had more time, we would have made a different type of coupling. Our jamming arm worked successfully, but unfortunately, our first and only opponent’s strategy was to score on top, not in the slot. Even though our team didn’t win, we feel that if we had more time, our robot would have done much better in the competition.

Final Bill of Materials

Reflection - Peter Williamson

What I learned:

During this course I have learned about how to sketch model, CAD, and finally build a functional robot. I learned that the first step in design was not to just draw out a basic sketch of what you wanted, but to weigh different methods of solving a problem then creating the design based on that.

This class also taught me how to use SolidWorks to CAD parts and create drawings. I had experience creating engineering drawing before, but I had never used a three-dimensional CAD program like SolidWorks. Previously, I would simply sketch two or three views on a piece of paper for what I wanted to make. Now, I will create the design in a CAD program and let the program create the drawing for me.

I also learned how important correct tolerances are in designs. Some parts only need to be within one tenth of an inch to still work, while others must be correct to the thousandth of an inch in order to work correctly.

How the course could be improved:

My one major gripe about this course was the constantly changing rules during the first half of the semester. I realize that shifting goals and requirements are an unfortunate reality in the business world, but having to reevaluate the design and alter parts of the bot in CAD every single time the rules were changed became ridiculous. I would advise coming out with a solid, unchanging set of rules for the competition within the first month of class. Preferably, the rules would be set before the class even began so that any possible loophole abuses would be noticed and corrected for before major design work had started.

How my performance could have improved:

I found that one of the major issues during the semester was just not getting the blog posts assigned and posted in time. If I were to take the class again, I would have the blog post assigned to a group member by the weekend, with the post being due Sunday afternoon. This allows ample time for making the post, and, should someone not do their work, allows another group member to cover for them.

Another issue I noticed was that we were constantly redesigning the robot as time went on. Even beyond the normal level of, “This doesn't work, how can we fix it?” An example of this is our jamming arm. That part was designed at least three separate times by different group members each time. The designed was finalized on the very last day we were allowed to alter our design. Even after that date, though, we found issues that had to be solved quickly before the part would work. From putting weights at the end of the arm to changing where the ratchet attached to the arm, the jamming arm was a mess simply because it had been redesigned so many times and nobody was quite sure how the final version was going to work. The best way to fix this particular problem would have been to finalize the design a week before it was due, then run through the entire design for the next week and fix any problems that cropped up.

The final issue we ran in to during the semester was being unable to find shop times that worked for every group member toward the end of the year. In the last week, it was impossible to get a shop time unless you either signed up a week in advance, or came in at 8am and hoped that someone who did sign up didn't come in. Fortunately, since so few people were willing to come in at 8 in the morning, we were able to get the worked we needed done. Our performance in this area could have been improved by simply signing up for times a few days in advance at least, and not leaving a large amount of work for the last couple days before the competition.

-Peter Williamson

SELF REFLECTION

Paul Stam

Mechanical Engineering 250 is my first real taste of what it means to be a mechanical engineer. In this course I learned fundamental design principles of engineering, different components such as springs, bearings, and screws, and also essential pieces in creating a working robot such as motors and control boxes. In the beginning of the semester I learned the basics in creating parts in SolidWorks, and I learned how to machine parts on the mill, lathe, bandsaw, and on the waterjet. The class also required students to take fabrication labs which I really appreciated. Overall, this was a demanding course, but it was well worth the effort.

Over the course of this semester, I learned design principles (e.g. simplicity of design, risk management, cost-performance diagrams) that were applied to my team’s robot. One of my favorite parts of this class was the machining. Before this class, I had done very little machining before and was even intimidated by those who could machine well. After taking this class, I feel much more confident in my machining skills, and I believe I am much better prepared to take ME350 next year.

One of lesson’s I learned from this class was to plan ahead. For example, it’s good to cut a part long if it is going to be lathed. I also learned a lot about team formation and how a team can be successful. In my ENGR 100 class from my previous semester, teams were required to create team contracts, and gantt charts. Unfortunately, this class didn’t require this.

Though I learned a lot from this class, I think that there were several areas that should have been improved. The most noticeable was the inconsistency of the rules created by the staff. I understand that the staff tried to even the playing field, but it appeared as if the staff was unaware of the students’ possible scoring strategies. I would have appreciated rules that were set in stone at the beginning of the semester. Another improvement that would have benefited students would be to reduce the duration of lectures. Lectures contained copious amounts of information, but I feel like the key concepts weren’t stressed heavily enough. The tedious calculations took away from practical engineering. Also, the staff should have encouraged more learning by doing.

I also strongly disliked the way the method of the deterministic design was taught. Rather than have students understand the concept of funneling ideas from to broad to narrow, students were required to follow a specific way to problem solve. I believe that many design approaches should be offered to students, and I was very disappointed with the strict grading for the required design approach.

On a different note, there are several changes I could have made to improve my performance in this class. The first would be to review the information presented in lecture earlier rather than later. I also should have asked for more help in designing our robot. The ME250 staff has a lot of experience in this area and their input would have been extremely beneficial. Another thing I would have done differently would have been a better team formation. If our team went one step further and created a team contract and a gantt chart, we might have been more productive during meetings and machining times.

Final individual reflection - Kai Li Yu

Design and Manufacturing

The design and manufacturing process that we have gone through in this class was similar to what we did in my ENGR 100 section. However the level of intensity and time needed for this class is at a whole other level.  For me, this is the most intense class I have taken yet.

After the competition and actually manufacturing I learned a lot about designing. The thing that had the greatest impact on me was how detailed we have to be during the designing process. I knew that the design process was going to be like a funneling process, but never quite realized how narrow the end of the funnel would be until I was done with this class.

In terms of manufacturing, I learned quite a lot as well. I had very little machining experience prior to this class, so this was really something new to me, working with the mill and the lathe. I really enjoyed working in the machine shop, although it was sometimes challenging. It also helped me appreciate some designs around us that may seem simple to make, but in fact required some effort.

Teamwork and time management

Again, this wasn't the first time that I had to work in teams.  After this class, my view on teamwork still remains the same. That is communication is the most important thing. It is extremely important that we make sure what each other is trying to convey, it is more important though, that we have the eagerness to make sure that our message is delivered and that we know exactly what the other members are trying to convey. If any of the members gives up on trying to understand what the other person is trying to say then the team will not work. And this is something I will try and continue to improve in the future, since I don't think I did a very good job in terms of that in this class.

In terms of time management, personally I think our team started each assignment a bit late every time, we often find ourselves constantly trying to finish out task a few hours before the deadline, sometimes even minutes before the deadline.

How the course can be improved

Personally, I think the lectures should be shorter, and we should spend more time in the machine shop. It would have been better if we had started tackling the problem as soon as possible. Although the beginning design process were important, but in my opinion we spent a bit too much time on that. It would’ve been great if the ratio of lecture time and lab time were slightly modified.

It would also be great, if we can be presented with clear slotbots rules at the beginning.  I am aware that this is new, and slight modifications would always happen, since the game has changed drastically compared to last semester, but setting out clear rules at the beginning might help the students next semester.

One last thing is that, it would be better if we can be more clearly informed in terms of what will be tested on the midterm exam.

How I could have improved my performance in the course

Like I previously mentioned, it would have been better if I put in more effort in communicating with the other team members. I could’ve also put in more effort to try and start assignments earlier, so we do not rush towards the end.

Another important thing that I could have done is to finish, often I find myself starting good, with most of the things set, but failed to finish it all the way to the end.  For example designing a small component, but failed to clearly mark up all the dimensions needed.  And I find myself wasting lab time trying to just putting in the finishing touches of the previous assignment, rather than working on the next one. This could also be related to my time management skills.

ME 250 F10 Reflection

Yusuf Yanikoglu

ME 250 Fall 2010

MASSIVE DYNAMIC TEAM REFLECTION

We began the year using design techniques that I thought were unnecessary like the FRDPRRC tables to refine the strategies, concepts, modules, and components of our robot. However as the semester progressed, these techniques allowed us to consider many more methods of attacking the problem of scoring balls in the arena. Our design process continued throughout the semester, as we changed our course of action many times. The end result was very different from what we envisioned from the beginning of the class, and I believe this is a good example of real life engineering.

Since this is unlike any class I have taken so far at any level, I learned an immense amount about manufacturing and machining as well as the design process. This started with SolidWorks, where we got a strong grasp of visual bases necessary to build an effective machine. As I have taken CAD classes in the past, this was by far and away the most advanced and useful, directly leading to our machining process. These connections between creating strategies, creating a CAD model, and making the components by hand in a shop are what I believe are the strengths of this course.

It is difficult to get in touch with other students sometimes in a school of this size, so getting into groups to work on something like this was a great way to meet people and use team work in engineering. Our group did a great job of balancing each other’s ideas and opinions evenly with minimal disagreement. Although we had differences throughout the semester, it showed the interest that we all had and the number of paths we considered along the way. Working with others well is a very important aspect of engineering and the structure of this class was a good opportunity for us to learn to adapt to other viewpoints and work on our team working skills.

If I would take the class again, I would have tried to structure my time better throughout the semester, and maybe start building the robot earlier. We were very pressed for time towards the end of the semester, especially when unforeseen problems arose, such as cancelled shop times. We also chose a very complicated strategy for scoring and ended up failing to do just that. If I could go back, I think we might have used a simpler strategy, such as scoring on the top using a robot with wheels. The lever arm turned out to be very difficult to jam, and our hammer did not work as effectively as we anticipated. Considering that less that half of the robots in competition scored, we would have been very successful by making our machine simple.

If I could change anything in the course, I would adjust the arena to make the lever arm easier to jam, or anything that would make a robot that attacks the slot stronger. I just felt that we had a general lack of knowledge of how the arena would work, and the adjustments to the starting positions and rule changes during the semester did not help.

EDIT:
Due to the sound issue (I'm not really sure why that happened) I've rendered the video again. Here is the now (hopefully) sound enabled video:

This week, our team used the water-jet to cut the sides of our bot. We also spent a lot of time in the machine shop milling and lathing. Unfortunately, the lathe that we signed up for broke before we had a chance to use it and some quick thinking on Peter's part got us a new time slot. Some of the machining we did included:

E-clip slits,

finished L-brackets,

Completed the jamming arm assembly (the ratchet and aluminum plate came on Tuesday),

Milled cut in our stainless steel rod

We also tested our scoring arm to make sure it worked fast enough (which it did).

The only thing left to do assemble all the pieces together, which we will do on Monday.

To Do List

Here is the list of items to be completed in the next week:

• Fabricate hammer arm
• Fabricate hammer head
• Fabricate hammer release plate
• Fabricate hammer release pin
• Fabricate frame
• Fabricate motor mounts (#2, #3)
• Groove hex stock
• Groove 1/4" aluminum axle
• Assemble hammer/lever jammer
• Assemble frame
• Final assembly of scoring arm
• Assemble misc. components
• Final assembly of robot

Updated Schedule

MS8 and Last Shipment

This week we finished the MS8, including our MCM and our CAD Model for the final bot. One of the errors in our MCM was that the rpm's were too low. They need to be near 1000 for our MCM to work effectively. If needed, we can always make a new nut with fewer threads per inch and buy a new threaded rod to help ramp up the linear speed.

Peter will be buying the last of the needed parts for our bot over the weekend. Hopefully they should arrive by Monday or Tuesday. This week is going to be busy and require a lot of machining.

Quick Update

After two hours at the shop today.

We managed drill holes on the L bracket for mounting the motors
and the coupling device is one step away from being completed.

Meeting deadlines

Nov 24th is the due date of our MS8. Right now we still have a lot to do before we can meet that deadline.

Below are some tasks that are yet to be done for our MCM and MS8.

- device to mount motors on.
- milling the key way for our shaft
-machining the two coupling device for our MCM
- Bill of materials of our entire bot
- CADing the full assembly
- Manufacturing plans for the rest of the robot
- Drill holes on the threaded rod.

Hopefully we will have enough time to be able to finish all this before the deadline.

Desiging the Coupling device for the MCM

After our motor lab, we had to now design the coupling device and how we will mount our motor on to our MCM.
Our MCM needs two motors, one to drive the leadscrew, and one to rotate the arm. Instead of using a flexible coupling device that we used in the motor lab, we decided to use something that is more efficient because of the nature of the leadscrew (<50% efficiency)


WE decided to use the 1/2" square stock Aluminum as the raw material for our coupling device. I designed it so that it will tolerate misalignment of the motor shaft and the lead screw, since it will be really hard for them to be totally alligned.

We decided to use the same coupling device for the other motor that will coupled to our MCM too, because making two similar parts means simpler machining for us too.

Doing this made me appreciate the details that one has to pay attention to when engineering something. A simple component such as the coupling device requires much thought, and the difference between a bad and a good design may be quite big. It may certainly affect the performance of the whole machine.

Milling a Square Hole

Sometimes you have to put a piece of tube through a plate. When the tube is round, there isn't any problem. You just need to drill a hole large enough to fit the tube. When the tube is square, however, you run in to problems.

See, mill bits and drill bits are round. This means that no matter how small a bit you use to mill out a square hole, the corner of that hole will always be rounded. However, there is a workaround.

How to mill a square hole:

1. Drill a hole (I usually use a 1/4" bit) at each of the four corners of the square
2. Drill a hole somewhere inside the square large enough to allow the mill bit through
3. Switch to whatever size mill bit you think you need
4. Mill from the hole in the center of the square to one of the edges of the square you want.
5. Continue milling around the edges of the square

If done correctly, this method will create a hole with straight edges but no real corners. Congratulations, you can now fit your piece of square tube in the hole without having to worry about filing the corners square.

Manufacturing parts of the MCM

This week, we continued machining different parts for our Most Critical Module.
We planned to manufacture the cube inside the inner scoring arm, so that the arm can be attached to the thread and extend down as the motor turns the thread.

What we learned is to always expected some modifications to our original design. It took us four separate tries to successfully finish making this part. When the initial cut has been made from steel square stock, we found out another material that could be used as our inner scoring arm. Instead of using the Aluminum square stock with 1/8" thick walls, we decided to switch to a 1/16" wall because it will significantly reduce the weight of our arm. Thus to compromise to this change in design, we had to change the dimensions of the cube too.

We then made a few errors in filing down the cube to size, and also not aligning the drill bits of the mill correctly. On the thrid try, the hole was drilled 0.25" away from where it was supposed to be, and thus we had to re do the whole part.

In the end, We had to work extra hours in the shop just to make up for it. But we do realize that this kind of things happen during machining, so we did not dwell on it too much.

Choice of Suppliers

When it came to designing our scoring arm, we found that the materials in the kit just wouldn't cut it. Sure, the kit has the tubing for the inner arm. It has the stock to make a motor coupling and a custom nut. It even has the longest screw I've ever seen, a 24 inch piece of steel that's perfect for driving the inner arm. The kit was missing one thing though: The 1.25" square tube we would need to create the outer arm.

When it came time to order the part, I knew exactly where I could find it:
McMaster-Carr.
For those of you who don't know, McMaster is the go-to place for just about anything an engineer could want. It has everything from fasteners to fire extinguishers, calipers to 100 foot long pieces of steel bar stock. In this case, however, we needed a piece of aluminum tubing that was 1.25"x1.25" with 1/8" walls. It just so happens that McMaster has a piece with those exact specifications. 6063 Aluminum Tube, 36" long. The order was placed on a Friday afternoon, and the material came in the following Monday.

So if you ever need a piece of material, any material, fast, just go to McMaster-Carr's website and place an order. Just be sure not to get caught up browsing through their 480,000 item catalog.

Schedule

Our Strategey and Concept

After detailed discussion, we have decided to choose a strategy of "Scoring inside the slot, and playing defense on top".

Our strategy would be to somehow push and lock the flipper, push the balls down the slot, then we will play defense on the top of the table to prevent our opponent from scoring in the funnel.

To execute this strategy, we came up with a concept of two rotating arms, and a rack and pinion playing defense on top.
The first arm will have a fixed length, and be swinging back and forth to push and keep the flipper in place. The second arm, will have two motors mounted on it. One to spin a screw and deploying the arm down to the balls, and another one to rotate the arm about the x-axis to push the balls down the slot.

The Third arm will move left and right linearly to block opponents' path to the funnel on our side.

Below are a few screenshots of the solid model of our concepts.

This is the few assembly of our Concept

Our Scoring Arm

Our funnel blocking mechanism that allows us to play defense.