PROGRESS
We have been looking for material for the past two weeks and focusing intensely on the machining process. This consisted of visiting Best Industrial Services Co., a supplier that carries a lot of material we need. When discussing how we will machine our parts, the sales engineer informed us of what is possible and what isn't. This allowed us to step back, redefine our design, and ensure every little part of our design could be machined. He also advised us to visit construction companies and ask for their spare parts since our device will be made mostly of small aluminum and steel parts. Down below, you can see our device's most up-to-date 3D print. Which has changes like expanding the tolerance of the spring carrier, which keeps the spring from deforming, and the angle of the groove, which holds the carrier at a nice 90-degree angle, which is what we were looking for. We have also added a safety lock mechanism to ensure the axe stops at a 90-degree angle.
During this visit, the sales engineer told us that he would look for the block of aluminum, which we need for the carrier, and give us the best price. As for the “Chassy,” we have suggested a piece of c-channel with the shape of our Chassy. This will allow us to not spend money on buying a sheet of steel or aluminum. Below is the CAD of the Chassy and a picture of the C-channel.
Plan B: Carbon Fiber PLA
During this time, we also discussed a plan B since our time is limited, and we want to be prepared if something doesn’t go as planned or takes longer than expected. Our plan B was to make our device out of carbon fiber PLA. This will save us time and money; this plan also benefits our design since we can modify the geometry as much as we want because it doesn’t have to be machined. To make sure this plan is doable, we talked to the 3D printer guy, Kevin, from the ASME lounge and discussed how 3D printing with carbon fiber PLA works; he let us know that he has already ordered material to start testing next week, which gives us enough time to decide whether we will be continuing with Plan A or start Plan B.
Another benefit of using carbon fiber PLA is that it would weigh a lot less, which is perfect for a device that is being used for skiing. Knowing this, we decided to do dynamic FEA on our device to see how it would behave if it was made from carbon fiber PLA. However, we noticed that our analysis program, COMSOL, does not have carbon fiber PLA as a material available to test. To get around this, we selected acrylic plastic as the material, and modified the yield strength to match that of carbon fiber PLA. This method is unusual, and our team is looking for more sophisticated methods to simulate carbon fiber PLA. However, for now, we believe this method is satisfactory to initially determine if carbon fiber is worth pursuing.
In this modified acrylic plastic FEA, our device is very close to failure for some parts, and beyond failure for other parts. The pin, for example, would most definitely fail if it were made of carbon fiber PLA, therefore it almost certainly needs to be made of metal. The harness and chassis, however, have potential to be made of carbon fiber. The geometry of our device is still unoptimized; there are sharp corners and edges everywhere, so if our team makes minor adjustments to eliminate stress concentrations, carbon fiber PLA might be a possible plan b.
Furthermore, our advisor, Patrick Wilson, has informed us that the 4624 N load we have been testing for in our FEA is a very extreme value. The whippet was not made to withstand such a force, so our device being strong enough to withstand that value is overachieving, and possibly even unnecessary. Our team is talking about lowering the force goal of our device, which is undesirable, but doing so might allow us to create a product that is better overall. This realization, along with geometry optimizations, might allow carbon fiber to be even more of a viable alternative.
TEAMS PLAN
Our plan for the next three weeks would be to have a device close to done, whether a steel piece or a Carbon fiber PLA piece. We will continue to search for the parts and start the machining process. Still, if the acquisition of the parts takes too long or the machining of the device takes longer than expected, we will begin the 3D printing of our device, which is a lot faster than machining. We plan to start machining the chassy since that part is the c-channel, which is fixed, so we need to design the carrier based on the dimensions of the chassy. Then, once the chassy is completed, we would have a designed easy-to-machine carrier. As for the pins, our supplier said that he can easily find those. By March 9th we should close to done with Milestone 4 which is having a final working mechanism completely machined.
OBSTACLES
As discussed earlier, we do have a backup plan for our device. This backup plan could quickly go from being plan B to plan A. Time is against us, and although, as of now, we are according to plan, we could easily not be. We each have a role, and we will know exactly what action plan we will take next week. If by February 24th, we still need to get all the materials required or have yet to start the machining process, we will change course and start our plan B. To start plan B, we will purchase carbon fiber PLA and discuss with the ASME 3D printer guy, Kevin, when would be the soonest he can use our device. There are pins in our device that must carry a lot of force, but we are planning to make those out of metal regardless to reinforce our device so our device will not fail.
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