Individual Reflection By Chan Pey Yuan (Chris)

Final Documentation

This ME 250 is, by far, the most informative engineering class I have taken so far. Instead of focusing on theory and formulas, this class immersed me in the true essence of engineering. To me, engineering is about having an aim, visualizing a series of steps or solutions to achieve that aim, and formalizing something palpable to complete the objective. This essentially is what this class aimed to do and hence has opened my eyes to engineering. Now, I am able to look beyond the formulas and theory, and actually be able to see the real world application of mechanical engineering.

What I learnt in ME 250

Design and Manufacturing:

I initially felt that designing a machine to accomplish our objective was time consuming. But as I found out, manufacturing the machine was worst. It is while manufacturing that I saw firsthand all the imperfections of our design, some of which were too late to correct. Most importantly, I saw the issues that were taken for granted of, and hence never discussed, during the design process. Yes, even now, I feel that the manufacturing process is more arduous than the design process, but if proper planning was done during the design process, the manufacturing process would be a lot smoother.

Ways to Improve:

For my next design class, I am sure that the design process my team undertakes would be a lot more comprehensive. This class gives us a great insight on what it would be like once a team moves from the designing process to the manufacturing process. With this insight and experience, I believe that I would be able to make more accurate predictions of potential stumbling blocks and try to avoid them early on.

Teamwork:

For a class like ME 250, teamwork is imperative for a team to complete their objectives. There are just simply too man y components to this class, like designing, planning, manufacturing parts, assembling parts and troubleshooting concepts. I have learnt that it is so much more efficient to ‘divide and conquer’ rather than have all members focused on one aspect of the class at a time. To accomplish this, each member has to know their strengths and weakness, and focus on tasks that exemplify their strengths. For example, I enjoyed man managing and assembling parts. Hence, I tried to gain a bird’s eye view of the entire process so that I could delegate jobs quickly and swiftly. On top of that, I took special focus on assembling or disassembling my team’s machine.

As my team tried to maintain high levels of teamwork, I learnt the importance of actually having a plan. It truly aids the delegation of work as well as the prompt completion of processes. There are many potential stumbling blocks to disrupt a team’s plan, like needing to queue for an hour to use the band saw, and it is up to the team to be sharp enough to acknowledge that it more efficient to focus their energy on another important aspect of the project before using the band saw later when the queue is shorter.

Ways to improve:

It would best serve the team if the character of each member is known to everyone within the team. I feel the best way to achieve this is to organize a social outing where the entire team can relax and get to really know each other. For example, organizing a pizza party would be social enough an event for team mates to become friends and hopefully in the future be able to work together.

The roles of each team member, in general, should be made know to the team. To improve, I would have ‘interviewed’ each team member to find out their likes or fortes and try to allocate jobs to them based on their strengths.

Time Management

In this class, there is definitely a time constraint, and to overcome this, proper time management has to be practiced. To me, proper time management takes place when a team spends the right amount of time on each aspect of the project. I have learnt that in order to do this, the team has to be very clear of its long term goals. For this class, teams have roughly two weeks to complete the MCM, and a week from the completion of the MCM to the presentation of the machine. This means that teams have a week to complete all other ‘non-MCM’ modules. Problems arise when the MCM takes up 50% of total required work and the other modules take up the other 50%. Teams would then have half the time to complete their other modules than the time they had to complete their MCM. Proper time management would let them know that it is just simply not feasible to cramp the completion of the other modules to the last week, and this risks the completion of the project, not to mention that testing is also another important aspect teams have to take into consideration.

This is the important of having a long term plan, and ensuring that the rest of the team is aware of this plan. Only then can proper time management be undertaken, removing the scenario of needing to cramp a bulk of work to the last minute.

Ways to improve:

During my Engr 100 days, we had a plan in black and white to adhere to. I feel if I had done the exact same thing in this class, my team and I would have a better conceptual understanding of what is required from each of us as the weeks progress.

Testing

From this course, I have learnt that certain issues, like the shortcomings of my team’s machine, are realized only during testing. This shows that regardless how much planning and precaution was done before the manufacturing of the machine, only from testing the machine in a real world scenario can one actually be sure of the quality of the machine.

For example, it was only through testing that my team and I realized that the way we transmitted the torque from the motor to the rotating shaft was not feasible. Also, it was only through testing that we realized that one strain of Kevlar string was not enough to withstand the tension applied onto it.

The fact is, all these inefficiencies would not have been realized if testing was not done. It is important that the team’s time manage properly and leave ample amounts of time to put their machines through rigorous testing.

Ways to improve:

I believe that at least a week of testing would be ideal to spot errors and change them. Whilst I believe it might be difficult to complete the machine and have a week to spare to test, my team should have expedited the process of manufacturing, and at the same time not compromise quality, to leave as much time as possible to put our machine through vigorous testing.

Calculations and Estimations

From this class, I have seen firsthand how an inaccurate measurement of 0.5mm can have disastrous effects on the machine. Most of the students have not assembled anything from scratch before, and based on calculations from other engineering classes, 0.001m is not significant and is commonly rounded down.

Now take the arena table for example, me team wanted to fit the arm of our machine into the compartment with the PPBs. The gap of that compartment is 41 mm and the width of our arm was manufactured to be 40.5mm. Initially, we thought that our arm will have no problems entering the slot since mathematically, it is thinner. However, due to the non-ideal nature of this project, our arm had troubles fitting into the slot, let alone rotating in it.

Hence, I have learnt that more leeway to calculations has to be given, and that it is not feasible to fit an arm of a machine that is 40.5mm wide into a slot that is 41mm wide especially if the arm needs to move within the slot. It would be more sensible to manufacture the arm to a width of 39.5mm at most.

Ways to improve:

When designing, we should be walked through the process of assembling the entire machine. By doing so, we can pinpoint areas of our machine where the calculations would be flawed in a real world scenario.

Pointers for the class:

More personal attention from GSI during design process

As I have realized, the concept that my team has chosen did not best suit this competition. We wanted to utilize a rotating arm that could extend as well. This means that the entire mechanism that extends the arm has to be rotated along with the balls. We initially thought that this concept could be created easily which unfortunately was not the case.

The fact is, my team made the effort to make calculations in ideal scenarios, but making the actual machine was a hassle and many problems arose due to the accuracy the machine requires. Many factors can be attributed to my team’s problems, like carelessness or failure to do research. However, I feel that my members and I are just too inexperienced to be able to foresee most of the potential stumbling blocks when we manufactured the machine.

I feel if there are more interaction between faculty and each individual group, like GSI meeting with each individual group to discuss their design in fair amounts of detail, I believe valuable information can be imparted to the students. For example, a GSI could say, ‘ please be weary of this component of your design as it requires high amounts of precision and many problems like ‘so and so’ could arise’. After all, most of the students in ME 250 have not taken a design class before and would probably need help during the design process if the class requires students to come out with a concept that has to work perfectly.

Time Commitment

This class aims to accomplish a lot by providing students an amazing learning experience. And I believe that this class is an amazing learning experience that would gear me up for upper level design classes. The catch is that students have to be put through hours and hours of work throughout the semester, and being students, they would obviously find it least desirable, even if the knowledge they acquire is priceless.

I feel that if the enthusiasm of students can tapped into and manipulated, not only will they be able to enjoy the class more, but with more enjoyment, the possible lessons learnt from the experiences in ME 250 would have a more profound effect

What the Class did Well:

Informative

As I said above, the class was ridiculously informative and I did open my eyes to the essence of engineering. Throughout the semester, my focus in engineering moved from mathematics and equations to linkages, pulleys, bearings and other important engineering tools. HW 4 & 5 was the start of it.

HW 4 allowed students to mix the real world side of engineering, by requiring us to analyze in detail the body of a bicycle, with the mathematical side of engineering, by requiring us to us the knowledge acquired during lab to make calculations.

HW 5 simply showed how complicated it is to transmit torque generated from a motor to a shaft. I honestly never knew how a simple process like this requires large amounts of precautions for the process to work efficiently, like bearings to prevent misalignment and the existence of radial forces. There are certain kinds of information that can only be acquired from viewing an apparatus at work, and this is one good example.

Hands-on Approach

There are some lessons that can only be learnt from actually performing a task, in this case building a machine. This hands-on approach requires students to see the repercussions of their ideas and design concepts. From there, students would be able to assess the quality of their ideas and acknowledge the ideas’ strengths and weaknesses.

Individual Reflection By Sean Bong

This is my first semester in the University of Michigan, and I cannot emphasize on how I love it here! The university has given me a whole new kind of experience; the different environment, interactions, activities, society and especially my first design class.

I've heard from my friends whom have taken the course in their sophomore years and they told me it was not as crazy as I would have imagined. However, the class was not really as how they described it. It was such a hectic class that put my time management skills in test. Maybe its just the transition from a community college life, but I do feel that the design class is a whole different kind of level for me. Despite the amount of workload given to us, I enjoy the class really much!

Before I took this class, I have not a single idea on what CAD is. It is such a foreign term in my mind. After the course began, I've then realized how important CAD is to the real engineering world. It's the backbone to every manufacturing. Thanks to the course, I've learned how to create engineering drawings and complex solid models. This experience has broaden my horizon on what I know about engineering.

The lectures are really educational as well. I learned that designing is a never ending process, and one has to know when to stop and get started for manufacturing. Moreover, discussing and interacting with each other in the class is crucial in getting new ideas and sharing your wonderful and creative thoughts.

And oh of course, the manufacturing process. I am proud to say that I have learned a great deal of manufacturing processes that I have no idea about before I took this class, such as milling, lathing, tapping. I was even more amazed when I know that we will be exposed to laser cutting and waterjet cutting! Manufacturing is not as complicated as it may look, but it is not as simple as I thought. There are just little stuff that you have to remember before using the machine, and always think safety first!

What I've learnt a lot from the course is that critical thinking and teamwork is crucial in design and manufacturing. Lots of problems just occured to us in the middle of manufacturing, and this would have been prevented if only the team think deeper into the idea. An example would be using brackets to make joints more sturdy. By looking through our solid model, everything looked really fine and almost flawless. But in reality, things are subjected to unexpected external forces, and we have to consider every single possibilities that our machine will be exposed to. That is when critical thinking comes into play.

For teamwork, I have learned that the best way to help the team is to dedicate yourself into doing more than what you have to do. If you feel forced to do things for the team, you will never do the best you can do, and this will affect the team as a whole.You have to set the attitude right in your mind, and then you wil be focused in what you are doing thus contributing to the team.

In the end, this course has been the most educational course that I have for my entire life. Not only it educates me how to design and manufacture, it has also taught me a lot on interaction skills, time management, teamwork, discipline and many more. I am really glad that the course is harder than it used to be, and this gives the students an opportunity to better grasp what design and manufacturing really is. Many thanks and appreciation to Professor Hart and the GSIs (Mark, Sam, Sei Jin and Jean) for giving me this experience to manufacture something.

Lastly, a great thank you for all my teammates Yundi, Chris and Eugene. You guys have been a great bunch. I learned a great lot from you guys and I would really love to work with you guys again in the future!

Rock on ME 250!

Sincerely,
Sean Bong

Individual Reflection by Eugene Ho

As a computer engineering senior, it was both an exciting and intimidating experience taking a mechanical engineering design class. While taking the Engr100 class during my freshman year, I discovered the usefulness of knowing how to produce CAD drawings. CAD drawings presented an elegant and effective way to communicate model/machine ideas to an audience. Inspired by that, I wanted to learn more about CAD drawings and hence decided to take ME 250: Design and Manufacturing I as my flexible technical elective class.

To this end, this course had proved extremely beneficial. In the very first CAD lesson we were taught basic Solidworks commands like the various views and zooming, measuring and panning. Subsequently we learned sketching and drawing commands such as extrusion, revolution, fillets and chamfers. Finally we were taught to create engineering drawings which were essential in communicating the specifics of our components to other engineers and machinists. Throughout this period, we were given CAD assignments weekly to help us grasp the commands better and put our new skills to the test. This certainly gave us a chance to practice what we learned in class. However, the workload was sometimes very heavy, especially when we had the regular and strategy homework due in the same week. I feel that the homework could alternate between weeks, i.e. CAD assignments every 2 weeks (covering 2 weeks’ worth of lessons) and regular/strategy homework every other week. The quality of the CAD assignments was good as it tested us on a variety of drawing commands. The regular homework (Introduction to materials and Bicycle) were rather challenging for a non-ME major like myself. With only high school physics background, I had trouble understanding and solving all the questions. Fortunately, my teammates were very patient in explaining the required concepts and Office Hours with Sam helped too. However I feel that the focus of this class should not be so much on complex problem solving than on “design” and “manufacturing”.

The manufacturing part of this class was a real eye-opener for me. Being a hands-on person at home, I have used many power tools in the past and love getting my hands dirty building a dog shed or fixing up a new cupboard. Even so, I was introduced to many new manufacturing processes such as milling and lathing. I also learned how to tap holes, laser-cut plastics and water-jet thin sheets of aluminum. The staff in the machine shop were really friendly and always ready to help us. Manufacturing can be tricky, and sometimes a slight misjudgment could cost us precious machine shop time as we would have to re-manufacture a particular component. I realized that it is always important to check, and double check our engineering drawings and specifications before manufacturing the different components. For example, we overlooked the zoom level (aspect ratio) in the engineering drawing for our machine's guide rails and ended up water-jetting half its intended size. We were able to correct our mistake on the spot and make a new piece with the correct dimensions. This is an area where I could improve my performance in the course, by learning to be more meticulous and careful. It will certainly help save time and effort.

Over the course of this class, teamwork was key to meeting project deadlines and producing a successful machine. While there were inevitable disagreements amongst us when it came to design principles and strategies, we were able to compromise and stay focused on our goals and objectives. This is evident in our team “Brute Forcier” seeded 6th and advancing into the 2nd round of the competition. Time management was critical too, especially towards the end when several rounds of testing revealed flaws in our machine. We had to come up with solutions quickly to fix those problems. We finally had our machine working just 2 days before the competition date.

Overall, I had no regrets taking this class. While the amount of workload could be made less heavy, I graduated from this class with an appreciation for the complexity and effort that goes into every design and manufacturing process. Of course, I also met my original objective of learning CAD drawing. I would like to thank Professor John Hart, Mark, Sejin, Jean and my teammates for this great experience.

Final Bill of Materials

The latest bill of materials can be found: http://bit.ly/36YHQn

Individual Reflection by Yundi Lin

Throughout the whole course, I learned many valuable knowledge about the design process, CAD modeling, manufacturing and prototype testing and troubleshooting.

For the design process, I learned that a good design is usually conceived from top down, ie, the big picture is worked out first before the details are finalized. Probably the most important thing in the design process is to consider the many alternatives and work out the best approach to the problem. I realized that this was a critical and yet very difficult task to accomplish. This is because at the start, we only have a rough idea of how our machine is going to work, yet this initial vision is going to determine how our machine is going to look like, and work, in the end. Using the Slot-Bots competition as an example, if the initial idea is not good, then regardless of the quality of engineering in the later stages, the final machine is not likely to win the competition.

Also, I learned that it is really hard to come up with a good, detailed design. The drawings we made initially may look good, but, as the saying goes, all plans fail upon initial contact with the enemy. I realized that throughout the manufacturing process, there are a lot of factors that can influence the manufacturing of a part. For most of the parts, imprecise manufacturing is the cause. However, there are other unexpected problems that I ran into, like imprecise dimension of the parts given. For example, I designed the box of our machine to be 12in by 9.6in. However, the piece of acrylic that we were given turned out to be slightly shorter than 12in. Thus, the cuts made by the laser cutter was not accurate and as a result, many other parts in our design was affected. Thus, I believe that in the future, I shall design parts that are smaller than the size of the material that I am given.

For teamwork, I realized that it is often better to have one person be overall in charge of one part of the project and let the rest assist him or her, rather than having everyone do the same things and then combine efforts. This is because I realized that every person has a different working style, and if two or more people are working on the same part, there can easily be a clash of ideals, for example, disagreeing on how the report should be written. Therefore, I think that it is better to have one person handle one part of the project rather than risking having too many cooks to spoil the broth.

For time management, I realized that good planning of work is really important, as time easily flies when one is working in the shop. Thus, my group usually hold a meeting the previous night to decide what is to be done the next day, rather than going to the lab and then working out what to do for each person on the spot.

I think the course can be improved by allocating us more time to manufacture and test our parts. I honestly felt that we had quite a lot of time to do the solid models, but the manufacturing time given was very limited. We often have to spent long hours in the lab, waiting for other teams to finish using the mill or the lathe, because everyone else from ME 250 to 450 is using the same shop. Also, I realized that it is almost impossible to just use the drawings we have to manufacture the parts, and then hope that everything fits together. There are most likely errors present, either due to errors in calculation or errors during manufacturing. Thus, we may often need to make multiple trips to the shop to make corrections to our parts. This is not helped by the fact that many others are using the same machines. I often experience up to one hour of waiting time for machine usage, and this hour could be put to use elsewhere, like testing.

I could have improved my performance in the course by making more careful measurements and calculations in the beginning of the course. I realized that a successful design require the designer to make calculations more precisely while the design is still on the drawing board, not while it is being manufactured. Using my team as an example, we could have realized early on that the bevel gear system will not work if we had made the appropriate calculations regarding torque required, and used the string idea instead. However, that calculation was not made, and as a result, we were staring at a nonfunctional machine 6 days before it was due to be completed. Even though we did manage to come up with a solution, I feel that we could have done much better by realizing that the gear idea will not work before we completed designs and made the necessary changes to our design.

Overall, I would say that I learned a lot on how it is like being an engineer, designing and manufacturing my own design and troubleshooting it. Also, I learned about how it is like to work in a team, especially team management and task allocation. Last but not least, I learned a lot about the different functions of the machines in the workshops and their capabilities, and machining techniques that are really hard to learn from just about any book.

Competition Day

It is competition day and Team Brute Forcier is all pumped up. This is the culmination of a semester’s worth of strategy planning, CAD drawings, manufacturing and testing. Based on the seeding round the previous day, Brute Forcier was seeded 6th out of 32 teams. What a good sign! We headed to the Design Expo at 1.30pm where we were greeted by a huge crowd which had gathered to watch our Slot-Bots in action. We wasted no time in preparing our machine Tate against our first-round opponent Team Juggernots. Juggernots made use of an arm design as well but that is where the similarity ends. In a closely contested battle, Tate prevailed and Team Brute Forcier advanced into the second round where we faced Above Average Joes. Unfortunately for Tate, we were up against a better team and lost. Nevertheless we felt a proud sense of achievement having come this far.

This course has been a great experience for the team and we sincerely thank our Professor John Hart and GSIs Mark, Sejin and Jean.

Team Brute Forcier

Final Machine

Our final machine was completed on last Tuesday afternoon.

Our machine works in 4 main steps:

1. The machine is placed at the top of the arena, with the arm inserted into the arena slot. The base of the machine is lined with velcro which adheres tightly to the arena, thus making it difficult for opponents to push or move our machine during operation.

2. The rack and pinion motor guiding the arm is switched on, lowering the arm to the bottom of the arena.

3. The two planetary gears and motors are rotated at the same time, tightening the kelvar strings attached to the arm and pulling the arm and the motor holder forward together in a swinging motion. This motion will sweep the balls up from the bottom of the slot towards the opponent's side.

4. The length of the arm is adjusted as it swings, finally coming to rest on the separation wall, blocking any attempt by the opponent to move balls over to our side. This serves as our defensive mechanism as well, which proved very useful against similar "arm" machines.


We decided to use kelvar strings to pull our arms in the end because the strength of many strands of kelvar tied together is very strong and meet our requirements. Also, steel cable, which at one point was considered by us, was too large in diameter and also not easy to tie together. Given the limited space available to us in the box, we decided to use the more flexible kelvar strings.

We believe that the main strength of our machine is the speed at which it is able to sweep balls over. Also, our arm is able to effectively block all attempts at putting balls to our side of the arena.

However, the main draw back is that the rack and pinion motor holder is designed to fit exactly into the arena, with about 1mm of free space left. If the arena slot is narrower than that, our machine is probably not able to execute the full swinging motion, and as a result, fail in its intended purpose.

Here is the link to our video on youtube.

Our Machine manufacturing is complete!

Here is the video to prove that it is working!

http://www.youtube.com/watch?v=zNJJWmxCqw0

Problems Met During Testing

Our team's MCM and extenable arm has been manufactured. Once assembled, we would have our completed machine which is ready for testing.

Our MCM:


Our extendable arm:


We tested our machine on Thursday, and immediately ran a severe problem.

The meshing between the bevel gears on the side of the box was really bad. The torque could not be translated properly to the axle, and thus our whole machine cannot move at all. Also, we realized that the torque needed to rotate our machine is so large that a length of flexible tubing fitted onto the axle was actually twisted and torn.

Thus, we decided to give up our original idea and instead, use strings to pull the arm and the rack and pinion holder up. We attached the string to the rack and pinion guide rod because it is the most feasible point of attachment and the amount of torque needed to lift the arm and the rack and pinion holder is the least. Kevlar strings were used, and each length of Kevlar string we used was made up of 7 strands of Kevlar to ensure that the string will not snap during operation.

To help reduce radial load on the motor axle, we mounted a pair of brackets along the axle to help support it and reduce the radial load felt.
We also added in a second motor to help share the load of lifting the arm and the rack and pinion motor. To accomplish this, we drilled holes in the back of the pinion holder and ran a string through it, which is in turn attached to the motor.




Currently, we are planning to shift the location of the holes on the back of the pinion holder to a lower position to reduce the torque required to lift them. This will put less stress on the mounting walls and allow the motor to lift a larger load. This will be done on Monday (7^th December) morning before the lab sessions start.

This is how our machine will interact with the arena.

A close-up of the pinion holder and arm deployed.

Rotating and Extendable Arm

With our MCM complete, we have progressed to manufacture the bar and extendable arm assembly.

The main idea is to have a 2 part arm that can be extended by a motor mounted in the rack and pinion holder. Thus, one part of the arm will be constrained to the axle and thus able to rotate, while the other part is extendable to reach into the depth of the arena.

To manufacture the arm, these were the steps that we took:

1. Used the band saw to cut two surfaces of the 1” hollow aluminum stock off. A 1” part of the bar was left on top to allow the axle to fit through it. Then, using a 3/8” 2 flute in mill, we milled the slot along the side of the bar.

2. Used the ½” by ½” square aluminum stock to manufacture extendable arm. Using a mill, we milled the end of the rod to resemble a sharp pointed end (covered with tape so as not to damage the arena) so that it can get behind the balls with ease. Also, we drilled two holes that are 5” apart along the side of the bar. Using Epoxy glue, we glued the rack onto this arm.

3. Inserted screws through the slot on the constrained arm and the holes along the extendable arm. This will constrain the arm to move only along the direction of the slot.

4. Mounted an aluminum bracket to the side of the rod so that the arm and the rack and pinion holder and the arm can be attached tightly together. This is to ensure that the rack on the arm mesh with the pinion on the motor in the rack and pinion motor holder.

This is the arm assembly with the axle through it. Note the screw in the center connecting the arm to the axle. This is to allow the axle and the arm to rotate together, and it also holds the arm in position during the operation of the machine.

Future Objectives:

Now that we have completed out MCM and this arm, what's left if the assembling of the machine.

MCM Assembled

All Right! So here is our MCM, the most critical module that will help us in the competition!

please click to enlarge picture

Here is the 3D view of our machine. Looks pretty simple, but that's what we are trying to achieve! Simplicity is not to be overlooked, but rather be viewed as an art :) However, although the machine might look pretty simple, it was not as simple as we thought to manufacture it.

Here is the side view of the machine.......

And a closer look to the machine.......

Overall, we are proud of our MCM and it definitely worked out!

Future Objectives:

Now that the MCM is done, we have to move on to the manufacturing of our other module.

This will not be as easy as our MCM. Lots of process will be involved just to create that arm, and here is the materials that we will be using:

1. Aluminum Square Tube Stock - 1"x1", 1/8" Wall --- Rotating Arm



2. Aluminum Square Stock - 0.5"x0.5" --- Extendable Arm


3. Nylon rack, 24 pitch, 12" length --- Rack

4. Aluminum 90 Degree Angle Stock - 1"x1"x6', 1/8" thick --- Brackets


So stay tune for our machine and we will be able to finish it by next week!

The updated schedule and to do list can be found at: http://bit.ly/3ZmBqs

Next post: The whole machine!

5 MCM parts manufactured!

Hurray! We are done building and assembling the 5 MCM parts! However, we came across certain problems that we did not foresee while planning. Thankfully, we have come out with solutions for these problems.

Brackets

Original plan:
-For the assembly of the box, we decided to use screws to constrain the whole box together. The plan was to screw the sides of the box and the top of the box together.

Problem:
-This method does not hold the box well. Firstly, by screwing the box together, the screws could only withstand moments from one axis, leaving it unstable if any external forces would apply on our box. Secondly, the wood is really thin for us to put some screws on, and this would cause the woods to splinter, which is not desirable.

Solution:
-We decided to utilize brackets to constrain the sides and the top of the box together. This is a much better idea as the brackets are able to hold of moments from 3 axis, making our box fundamentally sound.

-We manufactured the brackets by using the aluminum 90 degree angle stock. First, we band saw the long piece of aluminum to the bracket sizes that we wanted. Then, we marked the brackets for us to drill holes. Finally, the brackets are drilled using the drilling machine to create holes for the screws to enter. We also created more holes on the sides and the top of the box for the brackets to function.

Guide Rails

Original Plan:
- The guide rails are to be constrained to the base of the MCM by using screws.

Problem:
- Since the guide rails are only constrained at one point, they will be able to rotate about its pivot since there are no counteracting moment at the pivot.

-The guide rails are not parallel to each other, causing our guide rails rod to be misaligned.

Solution:
-We decided to buy a 4" long #4-40 threaded rod that goes through both holes on the guide rails. Firstly, this will ensure that the distance between both the guide rails are kept constant. Meaning, the guide rails will be parallel to each other. Secondly, due to the square shaped holes on the acrylic, the guide rails will not rotate about the pivot's axis uncontrollably. Having said that, there is some space for the guide rails to rotate slightly to prevent overconstraining the part.

Another issue that we have is how to apply a torque onto the rotating shaft using a motor. This is what we plan to do:
1. Construct a mounting platform using the plywood that we have left into slightly a bigger size than the motor.
2. Constrain the mounting platform to the side of the box by using 2 brackets.
3. Tap 4 holes on the mounting platform to constrain the motor by using screws.
4. Utilize bevel gears to translate the direction of torque which allows the rotating shaft to rotate.please click to enlarge picture

Building MCM

For the past week, we met to decide the engineering drawings of the MCM. Most of the details of the MCM (e.g. dimensions) were worked out. Starting this week, we can use the waterjet and laser cutting machines to manufacture our parts. We plan to complete 3 parts of our MCM, namely, the box, the base and the guide rails by Friday 20th Nov, and the last 2 parts, the rod and the motor holder will be completed next week.

Here is a summary of what we are planning to do for each of our MCM Part:

1. Box

-We decided to use 2 different materials for the sides of the box, the hardboard and the birch baltic plywood. We decided to use the acrylic for the top of the box so that we can look at the process of the machine working, making it easier to detect errors if anything goes wrong. We will laser cut the whole entire material along with hole on it to make everything as precise as possible.




2. Base

- We bought a material for our base; a thick aluminum plate with attached rubber padding on its bottom. We needed this material as the rubber on its bottom provides us with a higher coefficient of friction that will prevent the whole base to slide along the arena's carpet. For its manufacturing process, we will water jet the whole material to get the precise shape and size of it. As for the holes, we decided to drill them using the drilling machine.


3. Guide Rails

- This is really tricky to make, especially with the materials that we have. We decided to use the thin, wide piece of aluminum, 1/ 16" thick and water jet them along with the holes to their planned sizes and shape; a base and curved beams. Then, we will use screws and nuts to constrain the water jetted plates, making them into the shape of the guide rails that we wanted.


4. Guide Rails Rod

-First, we cut a 3/8" aluminum rod to its specific length that we wanted using the bandsaw. Then, we decided to lathe the ends of the rod. The ends will be lathed so that it will fit to the guide rails perfectly. This should be relatively easy.

5. Rack and Pinion Motor Holder

-The motor holder will comprise of pieces of plywood and thin steel sheet. We decided to laser cut the plywood and water jet the thin steel sheet to its planned size and shape. For its assembly,
we decided to use epoxy glue to constrain the pieces of plywood and thin steel sheet.


Additional Note:
Also, we solved the problem of driving our rack and pinion inside the arena. The solution was to use one side of the double gear box, and attach a gear at the end of the shaft. The motor will rotate in the x-axis, the shaft will rotate in the y-axis, and the spur gear attached to the shaft will drive the rack in the z-axis.

MCM parts

Our most critical module consists of 5 different parts, listed as follows:-
1. The box, made of wood and acrylic, houses all the other parts. It acts as a support for the whole machine, and also functions as the part that connects the whole machine together.

2. The base, which is made of aluminum with a layer of rubber padding at the bottom, is designed to provide support on the table and ensure that the machine does not move laterally during operation. It also acts as a mounting platform for the guide rails and the motor holder.
3. The motor axle, made of a single aluminum rod, is used to hold the rotating arms in place and also acts as the axle on which the arm rotates about.
4. The motor holder. It is made of sheet steel on the sides and acrylic on the bottom. It is designed to hold a motor which drives a rack and pinion on the arm so that the arm can be extended and contracted at will.
5. The guide rails. These 2 rails serve to guide the motion of the motor holder as the arm sweeps up, restraining its degree of freedom and also providing support to the motor holder. When assembled, the MCM looks like this:

The fully assembled machine looks like this: Here, you can see how the arm is made to rotate about the motor axle, and how the motor holder is interfacing with the arm. The guide rails are also supported through a cut on the top of the box so that they will not break under the weight of the motor holder and motor combined.


The detailed list of materials can be found here: http://bit.ly/36YHQn

The step-by-step manufacturing plan can be found here: http://bit.ly/1YgNyU