Week Four (Nov 21 - Nov 27)

There's less than two weeks until the ball tower contest! Fortunately, we have made a lot of progress on our building and manufacturing, and we think we will be able to finish by the end of this week. Last week, we completed all the machine work for the most critical module, which is completely assembled and looking good! The only small issue we had was with the axles, which we had to re-lathe so they would fit into the bearings.

We also began the construction of both the arm and the front tray this week. In terms of the arm, we cut the main piece, and drilled and tapped the bottom of the piece (so it would attach into the MCM) and the side of it (so we could attach the pieces that knock balls off the tower perches). We also cut the steel threaded rod and screwed it into the top of the arm. As for the front tray, we used the water jet on Wednesday to cut out the tray pieces. Unfortunately, one of our triangular cut outs got caught in the jet and messed up one of the side tray pieces. Therefore, we have to go back after break to re-cut one of the side trays.

In the next couple weeks, we are going to have to assemble the front tray using sheet metal screws and bent 1/16" aluminum stock. Originally we were planning on welding the pieces together, but Bob informed us that it would be easier to use sheet metal screws to assemble it. We will include a picture of the tray construction when it is complete. Additionally, we have to figure out how we are attaching the L-shaped component at the top of our arm. The spring hinge came in, but we have to drill new holes in it, and when we tried using the mill to do this, the hinge bent a little. Therefore, we think we're going to have to use a hand drill to drill the holes.

Although this is our last blog post before the ball tower contest, look for The Team, The Team, The Team to be a top contender in the 2011 Fall ME250 Ball Tower Competition. We'll each post a blog after the competition, and hopefully we have good news!

Week Three (Nov 14 - Nov 20)

Everyone on our team is getting ready to celebrate Thanksgiving this Thursday! But before we can eat turkey and watch football for 12 straight hours, we have to get through this week, as milestone 7 and 8 are due on Monday and Wedsnesday, respectively.

For milestone 7, we had to complete 3 manufactured parts. While we have begun progress on almost every aspect of our driving module, we only have 6 parts fully completed. These 5 are the acrylic base, the right and left side tubing, the back side tubing, and the (2) wheels. We completed those early last week using a variety of processes, including the band saw, the laser cutter, the mill and a broaching tool.

Meanwhile, we have begun making the bushings and cutting and lathing the axles. However, we still have to finish each item by putting a knurl on the bushings and a mill for the axle set screws. Once all of this is done, we will be able to assemble everything by press fitting the axles through the bearings and into the wheels, and then our MCM will be complete!

Once we completely finish the MCM module, we are going to start building our front tray. Our first step in doing so will be to cut out the aluminum plate using the water jet. We're all pretty excited to use this machine, since we didn't get to see it operate during lab when the air pressure wasn't functioning. If we are efficient as a team, we can also drill the holes, bend the aluminum, and possibly even weld the parts together by the end of the week. This would give us a lot of time after break to finish the rest of our design, and make sure that we have the best machine by the ball tower competition!

Week Two (Nov 7 - Nov 13)

Over the past week, our team has met several times in an effort to finalize our Solidworks model. We wanted to complete the entire design, bill of materials, and step-by-step manufacturing plan before starting to build our machine so that we could make sure we could trade for or buy all our materials with plenty of time to get them shipped. We did run into a couple problems while designing our arm and front tray. The first problem arose when designing the arm.

During the entire process, we planned on using the 90° or 180° torsion spring that is provided in our kit, but we realized there was not a good way to connect either spring to the arm while ensuring durability. Therefore, we went online and purchased a spring hinge, which appears to be a perfect solution. This component combines our idea of having a spring and hinge separately attached, and makes the machining much easier to build.

Additionally, we realized that on the front tray of our machine, we want a 30° angled piece at the bottom of the tray to avoid having too much friction between the balls and the ground when pushing them around the table. We originally only had this angled piece on the back wall, but we realized that when our machine turns, we may have the same problem on the side walls. Therefore, we had to add this design to the entirety of the tray. We also thought it would be easier to just bend the 1/16" aluminum to make the 30° angled piece at the bottom, as opposed to attaching an extra component.  Thus, we had to redesign the tray on Solidworks and adjust our list of materials and manufacturing plan. This makes the construction of the front tray much easier, as we will just have to cut out the aluminum, bend it, and weld it together.

Now that our design is complete (pictured below), we will be able to start the construction of our machine this week. We plan to start building the driving mechanism in class on Monday, and use lab time on both Tuesday and Thursday to hopefully complete our most critical module. Once this driving mechanism is finished (and working!), we will begin the front tray construction. Because it is the most difficult component to construct, we do not intend to to start building the arm until the front tray is attached and we have gotten a better feel for working in the machine shop.

Week One (Oct 30 - Nov 6)

Our goal so far this week has been to finish everything necessary in order to meet with our GSI for the most critical module (MCM) milestone. Our MCM is our driving mechanism, which is shown in the picture below. A large part of the MCM assignment is to create engineering drawings on Solidworks that include specific dimensions. One of our key struggles in designing our driving mechanism was deciding whether to put the motors and axles of the wheels on the top or bottom of our base platform. After looking at the dimension of the wheels and the back ball caster to make sure our machine's body does not tilt, we decided on putting them on top, as you can see in the picture. Hopefully we don't have to change this later!

Meanwhile, we ordered new wheels a few weeks ago because we did not think the kit wheels provided enough friction. The wheels (pictured below) came in today, and they are 3.87" diameter, 1.95" thick, and made out of foam. The total price was $35.93 (tax + shipping included), but we think this was a smart way to spend some of our $100 allowance.

One aspect that we have to look at more is the material that we use to hold our axles. We believe the Aluminum 90 Degree Angle Stock (1"x1", 1/4" thick) will work, but we are going to talk to our GSI tomorrow to make sure that will work, and that we don't need another constraint for each axle. The 3D and orthographic views of our driving module are below.