Personal Reflection

Mechanical Engineering 250 has taught me more than any other class.  Not only did I learn a lot of practical knowledge in lecture, but I also learned valuable lessons on how to put my knowledge to the test, how to work within a team and also gained a lot of hands on experience in the shops.  Most classes you follow a book, chapter by chapter, learning material that you would only need to know for a test, whereas ME 250’s material is applicable in all real world situations. 

Over the summer I worked briefly at a manufacturing facility and while I was never a part of the engineering, I was able to see first hand a lot of the day to day operations.  While taking this class, I saw how the things I was learning directly correlated to the real work place.  From the manufacturing drawings to the design process, what I was learning was something that I knew I could take into my career and apply.

I think the most important thing I learned was machining the parts.  Anyone could have a great strategy or concept, but if it is close to impossible to machine, then its not a viable product.  Being able to take a concept and make it fit into the cheapest and most efficient manufacturing processes is a difficult task and from working in the machine shop I realize how important this is.  Making this connection and looking at designing something from the machinist perspective is something that I can always apply to help become a better engineer.

Another important lesson from this class is working with a team.  Usually most classes the only teamwork you have is on a homework assignment and never really puts the concept of teamwork to the test.  In this class we had to learn how to work in a team or else we would never make any progress.  Everyone has their different ideas and schedules and I had to learn to not look at the variations, but see how I can take what we have and direct it together to create something even better.  During the last week or two of the building process I also had to understand how to deal with the stress of the project and not lose my cool to the team, which would only push us in the opposite direction, and try and stay as cooperative as possible.

While I did learn a great deal in this class, there were areas of the class that irritated both me and other students.  First of all, the assignments and grading were very unorganized and vague.  If there were a little more clarity in everything we were supposed to do, then it would reduce the stress of all of the students (which is definitely needed towards the end of the semester).  Also, everyone is very inexperienced in the machine shop and by only have 3 weeks to machine our entire project it makes it very difficult.  If we had either more time to work on our projects, or have a smaller project for a week before the final project to gain experience, it would make the quality of machining increase greatly and give the students a little more confidence in what we are doing.

Still, this class is one that I feel like I can take what I learned and apply it in a multitude of areas, which I can’t say for most of the classes I take.  It prepares us for the real world, in both the work place and for other conflicts in life and makes me look forward to the next project in Mechanical Engineering.


-Christian Groesbeck

Kazem Alidoost - Individual Reflection

Over the course of the fall 2010 semester, I learned a great deal about design and manufacturing in mechanical engineering 250. The hands on experiences with the mill, lathe, and water jet were a great learning experience that convinced me I made the right decision by transferring into the mechanical engineering department. Prior to this semester I had no experience using any of these machines (or a band saw or drill press), and I now feel confident that I could use these machines in tandem to machine any of the parts I saw during the slot bots II competition.

This course helped me develop my team work and thought process a great deal. Almost every assignment forced me to think outside of the box, while I was also taking pause at every step to consider my teammates thoughts on the same subject and how those could be combined with my own. I am now, at this course's conclusion, a much more creative and understanding person.

The time that this course required was far and away more than any of the other four credit courses I've ever taken at the University of Michigan. The strong competition for hours in the shop was hard to manage, especially because my teammates and I had conflicting schedules very often. There was more than one occasion where no more than two of us could make it to the shop at the same time on any given day. The way that the MS were structured helped me a lot, because it really forced me to do work ahead of time and make sure I was prepared for the next step in the course.

The biggest problem that my team had was that we thought too much about what other teams would do. Our slot bot was able to move about all the axes that we intended it to, and all of its modules were able to function. The problem was that we dedicated too much time to these modules being able to meet resistance, and not enough time to making sure that they would function in the absence of resistance. A good example of this is our front arm, which did not make contact with the flipper all of the time. When it did, it was strong enough that it was able to hold the flipper even when other teams were pushing against it, something that happened twice during the slot bots II competition. When the front arm missed however, we were unable to score, which ended up being the reason we were knocked out of the slot bots II competition.

To improve the course I would have GSIs (or others with shop knowledge) help the students use the various machines in the shop for the first couple weeks much more than they did this semester. Before I started doing any shop work this semester, the extent of my experience in the shop was the training I registered for in September. With everything going on in the shop Bob and John only had so much time to spare, and over the first couple weeks much of my time in the shop was used on figuring out simple things. Small imperfections that my teammates and I made while machining which could have been avoided ended up requiring the remachining of many parts later on in the semester.

If I could have changed the way this semester has gone, I would have improved my performance by starting every MS and every piece of shop work earlier. 99% of the problems my team and I encountered were not problems that we would have ever predicted, and while we usually thought we were ahead of schedule, one setback could set us back as much as a day on any given MS. I would also have made sure to have applied more of what I learned in lecture to my machine from a much earlier date.

Mechanical engineering 250 was a challenging course. At times, I wanted to rip my hair out, stopping only when I realized that it may never grow back if I did. The saving grace was that at the end of each assignment and MS, and ultimately at the end of the course, it was always rewarding to see the finished product in front of me. I had a great time over the course of the semester, and I learned a lot about design, manufacturing, teamwork, and myself that I will be sure to remember over my future coursework and life experiences.

Thank you for the a great semester,

~Kazem Alidoost

Scott Kleiman - Individual Reflection

This semester of Mechanical Engineering 250 was a great experience. I learned a great deal about the design and manufacturing field and gained valuable hands on experience actually applying what I learned in the classroom. I’ve done some woodworking in my high school career, but this was my first time working with metal and I feel like I gained a very solid knowledge base of the design process and steps of manufacturing. I learned the basics and fundamentals of the design process such as sketching, the fundamental principles (simplicity, self-help, etc), narrowing an idea vague to specific, and CAD modeling. I learned all about the different components and various parts of design and manufacturing such as screw specifications, gears, bearings, and materials. The best part though, was being able to actually put all of this knowledge to use while building the machine.

While the actual design and manufacturing was obviously a main component of the class, the experience of working with a team was also very important. Fortunately, my group all got along well with each other and we were able to complete all of the milestones and assignments to the best of our abilities. Everybody was able to add something to group to help move the team forward. However, I found that tensions can run high as the due dates are nearing and things aren’t working quite the way we expected. We experienced Murphy’s Law firsthand on several occasions such as the mill and lathe we signed up for both breaking the night before our most critical module was due.

I thoroughly enjoyed the course, but there are several modifications that I think could be made to the course to improve it for the upcoming semesters. The first change that I think should be made is to clarify the grading of the course and the assignments. Many of the assignments were vague and did not clearly specify what exactly was going to be graded or what we were supposed to do. Another change that I think would benefit the class is to make the lectures more interactive with the students. There is a lot of information packed into the slides and I think some small in-class activities could go a long way to help students pay better attention as well as understand the material more clearly.

I’m satisfied with my overall performance in the course, but there is always room for improvement. I feel that if I would have done a better job of keeping up with what was taught in the lectures, I could’ve applied that knowledge more efficiently to our machine while we were still designing it. I made the mistake of waiting until right before the exam to re-read the lectures and really try to comprehend what was being taught. Another thing I should have done is to complete the milestones and manufacturing as early as possible. We ran into unexpected complications that we could’ve dealt with more efficiently and effectively if we had more time. Basically, I would have been better off if I didn’t procrastinate as much.

All in all, I really enjoyed this course. It was very time consuming, but it gave me a great fundamental understanding of the design and manufacturing involved in engineering. It was great being able to apply the lessons in lecture to the machine. I would have to say my favorite part was seeing how our design varied from the other teams’ machines and then facing off against them in the big competition at the end. This class has given me good reason to look forward to other design and manufacturing courses and experiences in the upcoming years.

-Scott Kleiman

Quantity	Description	Dimensions/Specifications	Use	Distribution	$/Piece	$/Team	Vendor	Part #
1	Nylon Rack	12" long, 24 pitch	Rack and Pinion	Kit	2.98	2.98	SDP-SI	A 1N12-N24
1	Spur Gear	24 D.P.,24 Teeth, 20° Pressure Angle, Acetal/No insert	Rack and Pinion	Kit	1.32	1.32	SDP-SI	A 1M 2-Y24024
1	Architectural Aluminum Tube (Alloy 6063) Square, 2" x 1", 1/8" Wall	24"x2"x1", 1/8" Wall	Track	Kit	7.02	7.02	ALRO	Quote
1	Aluminum Plate - 1/16" Thick	12" x 24" x 1/16"	Rack Mount	Kit	13.22	13.22	ALRO	Quote
1	Tamiya 72001 Planetary Gearbox Kit	GRs: 4:1, 5:1, 16:1, 20:1, 25:1, 80:1, 100:1, and 400:1	Drive Rack and Pinion on Main Arm	Kit	14.25	14.25	Pololu	70
1	Tamiya 70168 Double Gearbox Kit	GRs: 12.7:1, 38:1, 115:1, and 344:1	Drive Wheels	Kit	8.75	8.75	Pololu	114
2	Tamiya 72005 6-Speed Gearbox Kit	GRs: 11.6:1, 29.8:1, 76.5:1, 196.7:1, 505.9:1, and 1300.9:1	Rotate Main Arm	Kit + Trade	13.25	26.50	Pololu	74
5	Flanged SS Bearing	1/4" ID, 1/2" OD, 1/8" Thick	Rotating Mounts	Kit + Trade	5.62	28.10	McMaster	57155K304
1	Aluminum 6061-T6511 Stock	3"x3"x2"	Motor Mounts 1 and 2	ALRO	8.00	8.00	ALRO	ASTM-B221
1		2"x1.5"x1.5"	Rotating Cylinder 1		2.00	2.00
1		1"x1.5"x1.5"	Rotating Cylinder 2		1.00	1.00
1		26"x2"x1"	Main Arm		23.11	23.11
2		3"x1.5"x1.25"	Rotating Mounts		2.50	5.00
1		1"x2"x2"	Angled Guide - Front		1.50	1.50
1		1"x1"x1"	Angled Guide - Back		0.80	0.80
1	Aluminum Rod, 1/4" Diameter	1/4" D, 18" L	Front Left Axle, Front Right Axle, Rack and Pinion Axle	Kit	2.07	2.07	ALRO	Quote
1	Aluminum Square Tube Stock - 1"x1", 1/8" Wall	24" x 1" x 1", 1/8 Wall	Front Arm	Kit	4.71	4.71	ALRO	Quote
1	Aluminum Plate - 1/16" Thick	12" x 24" x 1/16"	Baseplate	Kit	6.28	6.28	ALRO	Quote
1	Aluminum 90 Degree Angle Stock	1"x1"x12", 1/4" Thick	Pillow Blocks	Kit	3.70	3.70	ALRO	Quote
2	Polypropylene Wheels	3" Diameter, 1/4" Bore	Front Wheels	Kit	1.43	2.86	McMaster	2781T72
1	Ball Caster	3/8" Ball	Back Wheel	Kit	2.65	2.65	Pololu	951
4	Rubber Bands	#64, 3.5" x 1/2" wide	Traction on Wheels	Crib	0.03	0.12	McMaster	12205T83
1	Adhesive Velcro	1.2 pull-apart, 200 cycles, 1"x 0.188"x12"	Attach Power Supply	Crib	0.10	0.10	McMaster	94985K816
1	Tote Box	24"x12"x10"	Storage	Kit	3.75	3.75	Global	WB652956
NA	Sotck Fasteners	screws, washers, bolts, nuts	Fastening	Crib	0.03	0.63	NA	NA
Kit Cost	$ 129.01
Purchases	$ 41.41
Total	$ 170.42
	Traded Items:	Tamiya 72005 6-Speed Gearbox
		Flanged SS Bearing

Final Team Documentation

Our final machine is in many ways a representation of the original team strategy ("hold the flipper and score balls in the slot while pushing balls from the top of the arena" and concept ("car that drives a wedge into the flipper and using a rotating arm to then score balls") that we came up with for our first team MS at the beginning of the semester.  The machine is composed of three modules, the most critical of which is a rotating arm powered by two six speed gearboxes with motors  and a planetary gearbox with a motor which pushes balls in the slot towards the flipper.  The second module is a pair of a wheels at the front of the car driven by a double gearbox and motor which drives the machine several inches forward from it's starting spot into the slot.  The third and final module is a front arm which falls down several inches from it's starting spot once the wheels drive the machine, which results in the arm falling into the flipper and pushing it towards the opponent's side of the arena.

(The image on the left is our initial solidworks assembly, whereas the image on the right is our final solidworks assembly - note that the empty spaces on the final solidworks assembly are spaces left for the motors)

On an individual level each of the three modules from our machine is able to function the
way that we intended.  The rotating arm is able to move up and down by the mechanical advantage of a rack and pinion, and it is also able to rotate almost the entire width of one side of the slot with enough force to push balls far enough that they score.  The wheels at the front of the car are able to drive the car forward and backwards over the slot with ease, and the front arm falls down at an angle and to a depth that pushes the flipper towards the opponent's side.

The problem with our machine is that the modules do not function in tandem the way that they need to.  Specifically, the front arm does not fall at the right angle or to the right depth when it is forced to do so by the force generated by our machine "falling" into the slot (a desired occurrence created by the driving of the machine's wheels) or by pushing at it's back end by the rotating arm.  Without the front arm pushing the flipper towards the opponent's side of the arena, our machine is unable to score balls even when the wheels drive it to the correct spot and the rotating arm is able to function as desired.

The main reason behind the front arm dropping to the wrong spots and the wrong times would seem to be the machine's angled guide (pictured above).  The angled guide is an aluminum mount which stands in front the front arm to ensure that the front arm is at the correct angle.  After machining our first angled guide it was obvious that the guide could not be too snug on the front arm, or else the front arm would not drop.  Subsequent machining of angled guides revolved around deciding how snug (or loose) to make the angled guide.

Over the course of the semester, our entire team learned a great deal about design and manufacturing.  The machine that we produced is simple but robust, and for the most part we are more than satisfied with how it turned out.  If anything, our experience in mechanical engineering 250 this semester showed us that you are only as strong as your weakest link (ANGLED GUIDE!).  We all look forward to future work in design and manufacturing, and we wish the best of luck to all future slotbot participant and mechanical engineering 250 students, staff, and faculty.

Best regards,

Kazem Alidoost
Christian Groesbeck
Scott Kleiman
Geunbae Lee

~Prestige... Worldwide!

Final Stretch

So it's wednesday night and we finally finished our machine.  We will be in the shop tomorrow morning to finish balancing the main arm and to do some final testing and tweaking, but will be ready to turn our project in at our lab section.

Also here is a video introducing our team and machine and giving a brief overview of the design and strategy.

Machining nearing end

We've basically finished all the machining needed for the machine. We put it a lot of hours in the lab this week, but the machining for our slotbot is basically finished. Several unseen problems set us back throughout the machining process such as the mill unexpectedly breaking, but we were able to successfully adapt and overcome these challenges. We took the machine back with us today and Christian will finish assembling it over the weekend. I'll go in Monday morning to solder the motor wires and we'll be all set to demonstrate the completed machine during lab section.

We're also going to meet up on Sunday to make the team video and possibly discuss any small changes to the machine for the final demonstration on Wednesday.

A few more upcoming dates

Here are a few more dates we need to keep in mind besides the machining days.


Tuesday Dec 7 - We will all get together in the evening to make the team video. It must be uploaded to the blog and ctools by the next morning.

Thursday Dec 9, 1:40-3:00 - Slotbots competition

Sunday Dec 12 - We will finish our final team documentation and upload it to the blog. The individual reflections are also due the next morning (Monday 9AM).

Upcoming Due dates and Machining

I hope you guys are having a fantastic Thanksigiving Break.

Here are the upcoming due dates and our parts that we need to machine out.

December 6th - MS 9 is due - Demonstrate working machine
December 8th - MS 10 is due - Finalization of the machine and the machine is locked until the expo

In order to catch up on our due date, we need to get machining!!

So, after Thanksgiving, we should try to machine at least four times for next week so that we are confident in our machine. Here's the schedule that I think would be nice:

Monday November 29th - getting started on the base and the back block of our machine
Tuesday November 30th - Continuation of our base and the back block and if this is done, front arm
Wednesday December 1st - Contination of the front arm and getting started on the angled guide and the motor support
Thursday December 2nd - working on the front left axle and the Rack and pinion axle.
Friday December 3rd - Checking on all of our machined parts and get them together so that we are ready for Monday.

The Newest Update

On Wednesday, November 17th, in class, we decided that we need more aluminum in order to continue our machining. We figured out the exact dimension that we need so that we could purchase at Alro's.

On Thursday, November 18th, we went to the Alro's and bought two 6160 Aluminum parts that we will use to make our machine. During our regular lecture time, we were able to use the shop and we cut out small parts from the aluminum parts that we have bought to make several needed chunks.

On Friday, November 19th, we were able to use the shop from 4 ~ 6 and we managed to get our rack screwed into our solid metal piece. There were some risks in chance of drilling through the rack with the mill but with the maximum precision, we were able to be successful.

On Monday, November 22nd, it was the due date for our three completed parts of our machine and we showed it to Mark. We received 17/20 on our drawings. We decided to meet back at the shop from 6:30 ~ 8:30 in order to keep working on our machine. During our shop time, we used milling to drill all the holes into our motor mounts and the rotating mounts and we were able to screw in our parts together.

On Tuesday, November 23rd, we decided to meet from 4 to 6 in order for the due date the next day to show Mark our final MCM (MS8). We checked back on our parts and looked carefully at the things that we have might have missed in our final MCM and polished our work so that we felt comfortable to show Mark the next day.

On Wednesday, November 24th, it was the due date for our final MCM as an MS8 with all of our rest of the engineering parts completed. During class time, Mark met with us and we recieved 58/60 on our MS8.
Happy Thanksgiving to everyone!

Machining Started

We machined several parts over the past week and are going to show Mark 3 of them on Monday for MS7. We were scheduled to use the mill and lathe on Thursday from 4-8:30 but the shop was closed at 5, which set us back a little bit. We were still able to do the machining on Friday though. Here's a picture we took of us milling one of the motor mounts.


Something we overlooked in our design was the weight of the rotating arm. It was originally going to be 28"x2"x1" but we realized that would be too heavy for the small motor to power. However, we can just mill out the back of the arm into a "U" shape to decrease the weight.

Pic of front arm

Here's a picture of the aforementioned change to the front flipper-blocking arm.

Blocking arm

We've come up with a better idea for the front blocking arm that will hold the flipper. It was initially going to be a simple arm extending down at an angle from the robot, but we realized it probably will make the machine too large. We were then considering coupling the arm to the front axle so that it flips down into the slot at the beginning but we've decided on something better. We will still couple the arm to the front axle, but instead of flipping and rotating downwards, the arm will slide through an angled slot in the bottom of the chassis and into the flipper.

First parts manufactured

Today we used the mill to make two of the components of the MCM. These parts were the track for the main arm and the base used to mount the rack. Bob was very helpful in getting us started on the mill and making sure we made our part efficiently and accurately. We'll be using the lathe and waterjet in addition to the mill next week and we'll hopefully finish or come close to finishing our MCM.

Motor lab

We'll be doing the motor lab in class in a few days. Our machine will be powered by 3 different motors, so hopefully the lab will make us more familiar with them. I expect that after the lab we will be able to apply some of the concepts and tricks we learn to our design, such as decreasing the radial load on the motor and choosing the optimal gear speed for each motor depending on its task.

Machine possibly too large

A few days ago we noticed that our machine may not fit into the 24x12x12 box with the long extension arm out in front. We will need to fully dimension the whole machine to see if this is indeed the case. If we need to, we could possibly couple the extending front arm to the front axle so that when the machine first drives forward into the slot, the extending arm will flip down into the slot. This way, the machine will initially fit into the box but still allows the front arm to block the flipper.

MCM ready to be manufactured

Here's a picture of our solidworks model of our MCM. Now that we've fully designed the MCM, it's ready to be manufactured. We're going to buy the aluminum we need for the module from ALRO some time in the next few days so we can get started working on it in the lab. ALRO sells aluminum 6160 stock for approximately $0.44/in^3 and is located in Ann Arbor which is the main reason we decided to buy from them.

More design changes

After putting some more thought into our design, we've made a few more minor changes. We are now attaching the nylon rack to our machine by screwing it into a thin slab of aluminum which will then screw into the main arm. This is the method that was described in the manufacturing and assembly guide on ctools. We're also tinkering around with how we want to couple the rotating mounts to the track, which is proving to be more difficult than we imagined given the thin walls of the track.

Small design changes to MCM

Today we had a team meeting to discuss MS6. We decided on making several small design changes to our MCM. One of these changes that was brought up by Mark was to add another bearing on the other side of the pinion for more support against a radial load.

We also made another small change to the track that the main arm follows because the old design would be very difficult to manufacture given our tools and machine access. Basically, instead of making the track from a single piece of aluminum, we are going to cut 3 pieces and then screw them together.

Schedule until rest of semester

http://img841.imageshack.us/img841/5964/schedulew.png

This link leads to the prestige worldwide schedule for the rest of the semester.

Description of machine

The design for our machine is based around the strateg of collecting and scoring 

balls in the slot, while blocking half the width of the top of the arena.  

Our concept is a car that drives an extending arm into the flipper in the slot,

pushing the flipper towards the opponent’s side of the arena.  Once this is done

the car uses a rotating arm to score balls in the slot while simultaneously using blocking armsto prevent the opponent from scoring on the top of the arena.