Updated Schedule and To Do List

MCM Complete!

This week was mad scramble to finish our MCM. With forty plus man hours spent in the shop this week we finished our arm module enough to get it working for Wednesday. After seeing the arm in action we decided we needed to tweak the gearing a little bit, as the rubber band conveyor belt was producing a greater radial load then we were expecting, which produced greater friction in the system.

As of Wednesday afternoon we had completed most of the modifications for our arm module, as well as the engineering for the rest of our machine. We decided to drop our screw design and go with a two wheel drive cart instead. We came to this decision after realizing that we would be able to get almost as much torque if we designed the cart better. We also realized that since the top of the arena was now covered in carpet, it would be easier to get traction. This new design will also be easier to make, which will allow us to finish our machine earlier, thus have more practice time.

We hope to have our entire machine finished by Friday, December 4^th, at the latest. We want to finish our machine early so that we can spend the final week improving our machine, and working out any bugs. As of right now we are on schedule, and ready for, what we hope, is our final build week.

Update #3

This week was a very hectic one for all team members. However, proper schedule planning provided us with the means to accomplish the tasks we set out to do in what little time that was available to us.

A big task for this past week was planning the use of the double gearbox on our conveyor arm. We needed a means to gear our motor and conveyor system in order to provide the necessary amount of torque we calculated to push any ping pong balls out of the arms way. We cut the double gearbox in half using the band saw and took plenty of time sanding and filing it down to provide a proper fit. All that is left is to cut down the drive axle. This will be done later because we need to properly align the gears that are attached to our conveyor belt system and our gearbox. As of right now, it looks like the double gearbox will safely fit into the arena slot on our arm. Our plans are to apply a small amount of epoxy to hold the motor and gearbox in place on our arm and use hose clamps wrapped around our arm to permanently secure it. Images of the modified gearbox are shown below.


On top of that, we also manufactured our conveyor belt wheels. We took a scrap piece of wood in the shop and used the drill press and a hole saw to cut out the basic shape of our conveyor belt wheels. To make sure our belt doesn’t fall off of our wheels, we curved the sides of the wheels with sandpaper so the belt is pulled back to the middle of the wheel if it slides horizontally. Over break, we will swing by a hardware store and record the price of a similar block of wood with a camera to provide evidence of the amount of money taken out of our budget.

We mocked up our arm to get a good idea of how it will look and function in the arena. We also came up with a great idea of how to mount the side panels to the square tube stock. We discovered that we have access to rivets as well as a rivet gun in the shop, so we plan to rivet our two side panels onto the tube stock. They look as if they will provide a secure and convenient hold for our system. We also came up with the designs for delrin spacers that we will place in one of the gears that has a 3/8” diameter so it can fit on a 1/4” axle. This gear and its spacers will be held with epoxy. In the next week we plan on finishing up our arm and as well as all the other parts to our machine. Images of the arm put together are shown below.

Update #2

This week we finalized our drawings for the most critical module, the arm, and started to begin machining the parts for it. Due to conflicting schedules, we decided to split up the parts among the members of the team.

Jeff’s Part: My part was to make two arm side plates. These side plates will be bolted to the inside of the square tube arm and contain the conveyor belt. The derlin slider plates will also be attached to the bottom of the arm to reduce friction as it slides on the bottom of the arena.

I manufactured this part out of 1/16th inch aluminum plate. I first had the outline cut out with the water jet, from there I used the mill to drill the holes. This was a long process because I first had to use the edge finder to zero the x-y axes. Next I had to drill center holes using a center drill and then either drill holes with the proper sized drill bit on the mill or or use a step drill and reamer combination to get the proper tolerance to create a tight fit for the bushings that will be pressed into some of the holes.

Here is the drawing used for the arm side plate, pictures of the machined part will be posted next week:



Nate, Dave, and Michael worked together on the laser cutter, band saw, and drill press. We cut the aluminum tube stock to our desired length using the band saw then drilled the holes to mount the side panels on using the drill press. These steps were rather simple and followed our manufacturing schedule; however, due to a lack of machine availability, we decided to deviate from our schedule and work on the delrin sliders (see drawing below). We used the laser cutter too manufacture these. With a little help from Marv, we uploaded our drawings and ensured the correct cutting order. These parts came out very well, but after matching them to the side panels we realized the delrin should have extended further beyond the bottom of the panels. Thus we filed down the bottom edge of the side panels so that only the delrin sliders would contact the bottom of the arena.



Altogether, our first week in the shop went extremely well. We somewhat stood out as the newcomers in the shop, but with a few hours of hard work we got a surprisingly large amount of work done. Most of our team members are extremely busy this week, so we are very lucky that we are almost complete with MS7

Update #1

This week we finished the CAD and drawings for our most critical module, our Arm / Wall. After going over our work with Sei Jin it is clear that we have to fix up a couple of our drawings. This includes modifying some small measurement errors so that the side panels fit within our upper arm (the 1" x 1" square hollow aluminum tube), adding some needed dimensions, and getting rid of unneeded views.

As for our design, there were a couple areas of concern brought up during our meeting. First of all the belt will be off center in the arena. We need to make sure that the belt hits the center of the ping pong balls to move them out of the way; however I am not too sure how much it would hurt us if we pushed the ping pong balls at an angle because they would bank off the walls and go forward. We should definitely try to fix it if possible. We have to weigh out the possibilities of driving the belt another way and somehow adjusting the belt so that it would be centered between the walls.

Next, was the issue brought upon by the wheels being too large thus blocking the balls from getting to the belt. This was an easy fix: we will mount a small rounded delrin piece to the bottom of each side panel. With the low friction qualities of this material, it will help the arm glide along the bottom of the arena.

Lastly, Sei Jin was concerned with the difficulty of machining the female threaded 'axle' for the lower conveyor wheel. One easy fix would be to use a shoulder screw. These screws would allow the bearings in the wheel to roll freely on the shoulder. It wouldn’t be too large of an investment and would save us a lot of time in the shop. Here is a link to the shoulder screw we are thinking of.

http://www.mcmaster.com/#91259a539/=4f3tjr