For the second half of this semester the main focus of IPD is to design and build a prototype for your final presentation. My group has recently made a change in the direction of our design. Like I mentioned last time, my group planned on making a gear train that was powered via a worm shaft. Initially this was the plan we agreed upon but the design of the worm and corresponding worm gear proved to be too difficult to conquer in the amount of time we had remaining. To overcome this, we looked in the storage room in Packard Lab and found a large worm gear and worm that we could modify for a prototype. Our plan was to have a working gear train that would explain our product, but not to the right size and scale of the final product that Dresser-Rand would need. However, the spare parts for our prototype are very big and heavy (see below) and we aren’t sure that we can build a rig necessary to hold these parts in place. So, we went back to the drawing board and made a change to our design. The overall gear train is the same, only now its powered via a rack instead of a worm. This makes designing and making our own components easier because there are tools built into SolidWorks that help design these components (see above). We plan on making our gears out of acrylic using a laser cutter and gluing layers together to get the proper thickness. We figured this was the best method to get accurate parts for the least amount of money. Another update to come with the finished prototype.
Last Friday my group finally got to mold our cars with the injection molding machine. Unfortunately, our molding process didn’t go as smooth as we had expected. There were several issues with our mold design that caused some headaches and improvisation to get our mold to work. Pictured above were three of the many rejects we made while we tuned the machine and fixed our mold.
At first, the major problem we experienced was that our top half of the plane was sticking to the stationary mold plate after the plates separated. This was a very annoying problem because it required us to remove the plate from the machine and pry it out pliers. Our vertical stabilizer on the tail of our plane was the culprit to this problem. To fix it, we replaced the ejector pins for the part with shorter ones. This meant that the extra space filled with plastic and allowed the part to stay on the proper plate when they separated. Another problem we had was that our bottom half of our plane wasn’t filling. The CNC machine didn’t remove enough material from the extrusion, so the whole cavity was blocked off. We used a Dremel tool to remove a small amount of material so the plastic could fill the cavity. After a bunch more tries we finally dialed the machine in properly and molded a big set of cars, probably around 30. From there we had to post-process them because of the impromptu changes we made to our mold. This involved shaving down excess plastic and removing flash.
Next, we had to prep our planes for our partners at Broughal Middle School. They are in charge of painting the cars and specifying which one we will race. But before they can paint them, we had to glue parts together and coat them in primer. Once that was done we wrote up some simple instructions for painting and shipped them off. We’ll get back our race cars next week and are eagerly awaiting their arrival. In the meantime, we are tasked with going out and acquiring axles and wheels to attach to our painted cars to prep them for the race. More updates to come!
This past weekend was the 2016 AISC Steel Bridge Competition. Lehigh is part of the Mid-Atlantic Region (MAR) and this year Drexel University hosted the event. For the past several months the team has been designing, training, and building our bridge for competition and we finally got to see it tested on Sunday.
Saturday is the first day of the competition which involves a judges review of each bridge, along with an essay presentation required by each team, and other meetings as well. This year the topic of the essay was about international ethics, in which Lehigh did very well. Sunday is the main event, bridges are built under a time limit and are then load tested with thousands of pounds. The actual event took place across the Delaware river in Cherry Hill, NJ at the Camden County Boat House. Overall the team showed improvement this year as it was the first time in recent history the team was not disqualified. In previous years the team has been disqualified for different reasons like exceeding the build time limit and failing the lateral load test.
This year we just barely built the bridge in time at around 42 minutes of the allowable 45 minutes. The overall design was similar to last year with a few tweaks made to the arch, cross bars, and connections. These tweaks helped us to reduce build time by a lot since last year it took about an hour to build. Even though we were disqualified last year they still let us load test and we did quite well. Last year’s bridge easily passed the lateral load test and failed the vertical load test at around 1700 lbs. The bridge this year performed about the same in the lateral test but unfortunately did not do as well in vertical loading. the bridge only took several hundred pounds before the arch bent and twisted in an “S” shape along the longitudinal axis of the bridge (see below). During our build some of the arches were slightly askew and the addition of weight caused the arch to buckle at these points since it was designed to be in total compression. It was unfortunate that it occurred but there was not enough time during construction to fix this mistake. On paper the bridge performed very well, even better than last year’s bridge, but in practice is where we fell a little short. Next year well be sure to make improvements to the design to cut down on build time and make connections as easy as possible.
Next year the competition will be held at the University of Maryland in College Park, MD. The team has been making steady progress over the years that I’ve been here at Lehigh and participating. None of our team member’s are graduating this year so we’ll all be a little older and wiser next year. I’m hopeful this translates to an even better improvement than the one we made this year!
Last night was a proud moment for myself. Towards the end of freshman year, an upperclassmen I was friends with told me about an honor society called Tau Beta Pi. TBP is the oldest engineering honor society in the nation and was founded here at Lehigh in 1885. It has a lengthy list of notable members including astronauts and Nobel Prize winners. It’s difficult to get in, only the top 1/8 percent of juniors are invited. On top of that, there is an interview process that judges the content of one’s character. TBP prides itself on not only the intellectual capabilities of it’s members but the virtue of their character as well. I thought several years ago that getting into TBP would be a great goal to set for myself and would keep me devoted to my studies. Now two years later I can proudly say that I’ve reached my goal. It took a lot of hard work but it has paid off in the end.
But now that I’ve reached this goal I must set for myself another, I hope to get the Presidential Scholarship when I graduate. This scholarship provides students with cumulative GPAs greater than 3.75 a fifth year at Lehigh tuition-free. Getting this scholarship would allow me to pursue a Masters in Mechanical Engineering for free so I’d love to seize that opportunity. So far I’m on track to get the scholarship, I just need to keep up the good work. Hopefully this semester will push me one step closer to getting this as well.
Getting our tool paths approved was quite an arduous process. Each time we approached Prof. Angstadt he would point out something bad about our process and we’d have to make changes. And since there are about 30 groups all asking him the same things, it takes him a while before he comes back to check our tool paths again. All-in-all he reviewed our tool paths 3 or 4 times before we got to machine.
Once our tool paths were finalized, we had to post process them as .txt files and make changes to the code that the machine would read. We had to remove redundant lines of code as well as colons the CNC-machine couldn’t understand. After making a few fixes in the code we were ready to machine. The whole process was relatively quick since our molds only took ~1 hr. and 15 min. to machine. Most of my team was present during the whole process so that we could verify that everything was going as it should. Pictured below is shot of our molds being milled.
Once our molds were finished being machined we had to inspect them to make sure they would work in the injection molding machine (pictured above). Unfortunately there was a slight problem; the two plates did not come together nicely. The CNC-machine left two very small bits of geometry just a slight fraction too big. These little struts would define the cavity the axles would fit into. They were just a tad too big for the cavity they sat in and caused a non-insignificant gap when you put the plates together. We had to manually file those pieces down until they fit snugly. Hopefully this wont affect our cars when they are made using the injection molding machine. We also accidentally dropped one of our mold plates as well and dented two of the corners. Again, we are hoping this wont have any effect on our final product. We are scheduled to mold our cars this upcoming Friday so more updates are to come!
Our IPD class is set up is so that before the midterm we do all the planning, market research, intellectual property research, etc. to develop our idea. Once all that is done, then the design phase of the class starts and we are in charge of developing and creating our product. This is where we are now in the class and its actually very difficult. The past few weeks were spent brainstorming different ways to accomplish our goal. After talking with several professors from different disciplines, along with our company sponsors, we have decided to pursue the design pictured above. What’s pictured above is just a sample mock up I made to convey the idea.This mechanical drive system consists of a worm, worm gear, and pinion. We have just recently covered these items in ME 252, Mechanical Elements. What’s tricky is that we now have to figure out the design parameters of all these elements, like the number of teeth, pitch, pressure angles, etc. In class, these parameters were usually given and we had to calculate other parameters. Now that we are designing this from the ground up, its very difficult and we are having trouble just figuring out where to start. We have size and dimensional constraints along with strength requirements we must consider that will hopefully get this design off the ground. All of the professors we’ve talked to seemed enthusiastic to help so I’ll definitely be seeking their advice if we continue to get stuck.
This week was registration for the Fall 2016 semester. Usually I have a good bit of luck when scheduling my classes and almost always get what I want. Unfortunately for me, this time around was a little different. First of all, I had to wait a whole day to register because I technically only have junior status. The way the Registrar schedules registration is they split the student body up into different sections based on the number of credits you have completed and assign each section a starting time. The cutoff between junior and senior standing is 87 completed credits…I had 86 credits completed. Students with senior standing register a day before juniors, this is a huge advantage for those registering for classes that have a limited number of spots. Even though I have been closely following the standard curriculum guidelines laid out by the department, I ended up one measly credit shy of the cutoff.
As a result, I was wait-listed for ME 321 (Intro. to Heat Transfer). The course is offered in the spring so I’ll be able to take it regardless, but it could conflict with certain electives I planed on taking, which would be a real bummer. There was another bug in registration, ME 333 (Propulsion Systems). This class used to be offered in the spring but they changed it and now offer it only in the fall. MECH 326 (Aerodynamics) was a prerequisite for it, but now it’s a co-requisite. Unfortunately, the Registrar never made that change. An error was given saying that I wasn’t allowed to register for the class. To overcome this I had to fill out an override request form and get it signed by several faculty members. So far I’m only registered for 14 credits so I’ll stay on the waiting list hoping to pick up another 3 from ME 321. If not I’ll have to see what other class I can take in its place. I hope next registration goes a little better.