Before we could move any further we had to do some crush tests to determine the forces our machine will need to produce. We used a Tinius-Olsen materials testing machine here at VTC. This machine is normally used to determine the forces required to destroy a material in shear, stress, or strain. Here are a few pictures of the machine:
The Tinius-Olsen machine
The middle plate can be set at any height, and the bottom plate is lifted using hydraulics
Our first round of tests was for a target 1" cube. We used various forms that we created to crush the cans similar to the way we would on our crusher. For the first crush we jumped right to the 24oz. cans, since we knew that would provide the most resistance, and therefore require more force to crush. The final crush came in at a whopping 8,000 lbs of force! This was far more than either of us expected, and brought into question whether or not we could feasibly crush down to this size. Either way, we knew we would have to test other sizes as well. Here is our first set of results.
We started with the 24oz can but tested all three sizes for more complete test results
After some brainstorming, we came up with a solid first prototype design. As with any prototype, our purpose here was to show fit, form, and function. Here's a video explaining how it would work.
It's important to note that since we have such a short timeline, we had to begin design immediately and change things as our research and testing require. This means that this will by no means be a final design, and spending several hours on a model is impractical because it's likely to change. So using cheap materials and quick building methods are a must.
Having such a model does allow us to have something tangible though, which is helpful in explaining our concepts to our professors and our client. It also gives us a way to test interaction of the machine parts, such as the hopper being able to clear the piston arms. Lastly, it gives us a chance to understand how big our machine will have to be to perform the task.
We'll be posting the changes as they come through.
As part of our initial design work, we took some time looking up precedent, or existing solutions to the same problem. The point is not to copy another's work, but rather to find ideas for your own solution and to see if you can improve on existing designs. In our case, there are several "can crushers" to be seen on the web and several variations are on Youtube. Most of these use similar methods of power, as shown below.
The first method is a manually operated crusher. This simply uses a lever as mechanical advantage to crush the can, and the can then falls out the bottom of the machine. Highlights here are the lack of electrical/gas power, and the simplicity of the machine.
The next machine is another manually operated one, but with a crank instead of a lever. This is a little more complicated, but still easily operated.
Of course, the next step up is a powered version of the crank design. There are examples of both electric and gas motors powering this type of crusher.
And for the impatient can crushers out there, a pneumatic piston variety.
And last but not least, the black box, which apparently takes the cans and teleports them to another dimension. At least that's what I can tell from the video.
These are just a sample of the machines to be found, with several variations of size, power source, and fabrication methods. The problem is that none of them crush a can in more than one direction, and we need to crush in three directions. However, we can possibly take the methods shown in these videos and translate them to a three dimension machine. There were also some good ideas for hoppers shown online, so we'll have to incorporate some of those ideas as well.
So from here, we've got to come up with a solid first draft of a design, and put together a basic model to show a proof of concept to our professor. We also have to do testing to find the amount of force it takes to crush the can in each direction.
One of the first things we needed to do was test the feasibility of our constraints. Mostly we just needed to prove that it is possible to crush a can down to the required size. While we will have to do the math for this and do more formal machine testing later, for this early step I just grabbed a can and smashed it with a hammer and a vise.
We used a hammer and a vise to crush the cans
A crushed 12oz. can next to an uncrushed can
While this wasn't very scientific, it did allow us to determine that it was feasible to meet our size requirement. As I said, we will be doing formal materials testing so we can find out the actual forces involved, and compare them to solid aluminum.
The client for the project melts down aluminum cans so he can use the aluminum for various casting projects. He wants a device that will crush the cans down so that he can put more cans into his furnace at a time, and to make it easier to load into the furnace/crucible.
While he has left the project pretty open in terms of design and construction, he did have a list of requirements for the crusher:
-Cans need to be crushed to 1.5" or smaller in each direction
-Crusher must crush up to the "Monster" or "Arnold Palmer" size cans
-Crusher must have a hopper to accept at least a dozen cans, and larger cans need not fit the hopper
-After crushing, the machine must eject the crushed piece automatically into a bin below the machine
-Must be powered by one of the following:
-100psi compressed air (least favorable option)
-120VAC
-240VAC
-Manual operation, so long as it's easily operated
We're both pretty excited about the project, and look forward to building it.
The purpose of this blog is to document the design and construction of an aluminum can crusher. The project is part of the 2nd year in the Mechanical Engineering Technology degree program at Vermont Technical College. The students are given a variety of possible projects to work from, which are submitted by VTC faculty and members of the community.
We've got a two man crew for this project (Steve and Jacoby) and a semester to finish it in, which means we'll need to work quickly and efficiently to complete on time.
