Planning
- Next time, verify all the manufacturing processes that will be necessary to make our toy before deciding upon a final design.
- Never start manufacturing anything until you know all your dimensions and are certain you will have the materials necessary. It was hard for us because it all hinged on how big the wheels were going to be, but it's better to wait until the design is fleshed out before doing anything else.
- It is important to take precautions when planning a timeline or determining the processes that will be utilized. Machines will break and certain project limitations will restrict certain capabilities.
- Start well ahead of time if you want to use CNC. Each 5" diameter 1" rings required approxminately one hour to machine on the CNC.
Design
- Marbles serve well as temporary ball bearings, but for extended use it would be best to use metal ball bearings.
- Must always leave a tiny bit of space between pieces so they will be able to fit together comfortably.
- It is better to start at maximal dimensions for parts because, once they are manufactured, they can get smaller, but they can't get bigger. This was a problem with the axle (didn't quite fit in the hole in the wheel) and the rings (weren't big enough to fit together with the marbles in there).
Manufacturing
- CNC machine time is expensive, and so are
materials. It is better to minimize what is built using automated
processes.
- CNC is particularly expensive when creating large hollow objects because the processes are reductive, meaning it subtracts material. As a consequence, substantional quanities of material is removed and wasted.
- CNC is used in industry primarily for parts that are going to be made hundreds of times or more. This way it's worth setting it up. If a part is only going to be made a small number of times, it's better to machine it manually.
- CNC machines utilize G-code instructions to carry out their tasks. G-codes can be generated by running a Solidworks file through Master CAM.
Problems/Difficulties
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Making a board in the shape of an equilateral triangle with 20" legs would not leave enough foot room once the three 5" diameter holes for the wheel bearings were drilled out.
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For the size and quantity of the cylindrical wheel bearing pieces that we had to make, the material and the time costs for CNC milling were far too expensive to create all six pieces.
- Did not have metal-based 3D printer. So several parts were made from plastics.
Other Notes in Production
- It would have been best not to sand the wheels down too much because that eliminated some of the friction needed to get the wheels to roll.
- Welding was not the best way to attach the axles to the large rings. The two types of metals were different and were therefore not fully compatible with welding.
- If the hole-cutter attachment of the drill press creates smoke when it is cutting a hole in the wood, it is probably because the blade is either dull or out of place.
- Carnegie Mellon does not own a metal-based 3D printer (Laser Sintering). The starch-based and plastic-based printers would be able to print the parts, but the structural integrity would be compromised because all manufactured parts are load-bearing.