To properly test the prototype hammer design, we have created several specifications that need to be met by the design. These include, but are not limited to: geometric considerations, print time, durability, weight, and temperature sensitivity.
An explanation of the reasoning behind these choices are as follows.
· Printing Process and Material:
The reason the material and printing processes above were chosen had to do with cost. FDM is the most available and cost efficient process. Through contact with vendors, other processes could cost nearly twice as much even when printing with the same material. For this same reason ABS was chosen because it is the most widely available printing material and the cheapest. Though other plastics offer superior strength and low temperature performance, they were also nearly three times as expensive. To keep the already high costs down we went with ABS.
· Strike Face Diameter:
Due to the nature of the design and multipurpose role of a hammer, we must have a strike face large enough to be useful in a wide variety of tasks. In addition to being used to potentially assemble other products on the mission, the hammer would also be used to place stakes and set up equipment on the Martian surface. Through research of commonly available stakes we found that the average stake has a head diameter of 0.5-1 inches. Considering this, a diameter of 2-3 inches would be ideal for the hammerhead in order to allow for a margin of error for the operator when striking the stake head.
· Handle Length:
Another important geometric consideration is the length of the handle. This needs to be long enough to generate a high swing force and short enough that it doesn’t impede use in the confined spaces of a spacecraft/landing module. In addition, there is the potential of increased wrist strain and loss of control when using a hammer with a long handle. As a result, it was decided that a handle length of between 10-14 inches would be ideal. We felt this would be the longest the handle could be before running into the issue of usability and safety.
· Print Time:
Depending on the complexity and size of the design, 3D printing can be a very long process. For a group of astronauts relying on possibly only one machine to produce most if not all necessary commodities, a short print time is of the utmost importance. This correlates to a reduction of complexity and size that could also reduce performance of the part. Performance and print time must therefore be traded off. As a result, a maximum print time of 8 hours was chosen. This would allow for a fairly large and complex part without preoccupying the printer for an inordinate amount of time.
· Durability:
As mentioned in the previous specification, print times for complex parts can be long. Therefore, durability needs to be relatively high in order to reduce usage of printing material and printer time. A major hurdle however is the condensed schedule and limited budget of our project. This prevents us from running any sort of high intensity durability testing over any long period of time. Therefore, the hammer should be able to last 200 consecutive strikes per day over a period of a week without any noticeable deformation or loss of performance. This would give us a reasonable level of durability testing considering the aforementioned constraints.
· Weight:
Due to the use of ABS plastic as the printing material, the hammer will require more material than an equivalent metal hammer to produce similar results. This can lead to an issue of increased weight which could reduce performance and waste valuable printing material. In order to combat this we have come up with a target for the weight of around 2-3 pounds.
· Temperature Sensitivity:
The Martian surface is often much colder than what you would find here on earth. Combined with the lack of a substantial atmosphere to retain heat, any tools that will be used on the surface must be able to withstand low temperatures. Leveraging the assumptions that the landing would take place near the equator and any work done outside would only be done during the day, we can find an operational temperature range for the hammer. Research has shown that the temperature at the equator is between 0 and 70 degrees Fahrenheit on most days. Adding in a small amount of leeway, the operation temperature range should be between -10 and 80 degrees Fahrenheit.
An explanation of the reasoning behind these choices are as follows.
· Printing Process and Material:
The reason the material and printing processes above were chosen had to do with cost. FDM is the most available and cost efficient process. Through contact with vendors, other processes could cost nearly twice as much even when printing with the same material. For this same reason ABS was chosen because it is the most widely available printing material and the cheapest. Though other plastics offer superior strength and low temperature performance, they were also nearly three times as expensive. To keep the already high costs down we went with ABS.
· Strike Face Diameter:
Due to the nature of the design and multipurpose role of a hammer, we must have a strike face large enough to be useful in a wide variety of tasks. In addition to being used to potentially assemble other products on the mission, the hammer would also be used to place stakes and set up equipment on the Martian surface. Through research of commonly available stakes we found that the average stake has a head diameter of 0.5-1 inches. Considering this, a diameter of 2-3 inches would be ideal for the hammerhead in order to allow for a margin of error for the operator when striking the stake head.
· Handle Length:
Another important geometric consideration is the length of the handle. This needs to be long enough to generate a high swing force and short enough that it doesn’t impede use in the confined spaces of a spacecraft/landing module. In addition, there is the potential of increased wrist strain and loss of control when using a hammer with a long handle. As a result, it was decided that a handle length of between 10-14 inches would be ideal. We felt this would be the longest the handle could be before running into the issue of usability and safety.
· Print Time:
Depending on the complexity and size of the design, 3D printing can be a very long process. For a group of astronauts relying on possibly only one machine to produce most if not all necessary commodities, a short print time is of the utmost importance. This correlates to a reduction of complexity and size that could also reduce performance of the part. Performance and print time must therefore be traded off. As a result, a maximum print time of 8 hours was chosen. This would allow for a fairly large and complex part without preoccupying the printer for an inordinate amount of time.
· Durability:
As mentioned in the previous specification, print times for complex parts can be long. Therefore, durability needs to be relatively high in order to reduce usage of printing material and printer time. A major hurdle however is the condensed schedule and limited budget of our project. This prevents us from running any sort of high intensity durability testing over any long period of time. Therefore, the hammer should be able to last 200 consecutive strikes per day over a period of a week without any noticeable deformation or loss of performance. This would give us a reasonable level of durability testing considering the aforementioned constraints.
· Weight:
Due to the use of ABS plastic as the printing material, the hammer will require more material than an equivalent metal hammer to produce similar results. This can lead to an issue of increased weight which could reduce performance and waste valuable printing material. In order to combat this we have come up with a target for the weight of around 2-3 pounds.
· Temperature Sensitivity:
The Martian surface is often much colder than what you would find here on earth. Combined with the lack of a substantial atmosphere to retain heat, any tools that will be used on the surface must be able to withstand low temperatures. Leveraging the assumptions that the landing would take place near the equator and any work done outside would only be done during the day, we can find an operational temperature range for the hammer. Research has shown that the temperature at the equator is between 0 and 70 degrees Fahrenheit on most days. Adding in a small amount of leeway, the operation temperature range should be between -10 and 80 degrees Fahrenheit.