Trivet Project

For this project, we were tasked with creating a design that would fit in a 3.25"x3.25" box that was centered within a 5'x5' aluminum square. This design would be created using Mastercam as it can directly be converted to G-Code. This G-Code would then be loaded in a CNC Mill where we would secure the Aluminum and the design would be cut using a 0.25" ball nose end mill.

To go above and beyond, I decided that instead of putting a single letter or just my plain initials, I would instead create a badge design that in corporate my initials (seen to the left).

Lessons Learned

This was my second work piece in my Introduction to Manufacturing Processes class, and at this point I had never used a CNC mill, the only machine used in this project, so I was on for a difficult time.

The first lesson I learned from this project was to always ask questions. When it came to the design I had no issues as I had used other types of modeling softwares before, however the operations on the HASS CNC at our lab I had never seen before. So, instead of being among the students who tried to do it themselves and fail, and have to go buy a new piece of aluminum, I decided this was not the type of project to figure out on your own. After having someone who is skilled with the CNC operate it and the steps they go through, it became significantly more simple for me to operate.
The last lesson I learned from the project was to always look ahead, I mentioned this in the screwdriver lessons learned section, however I felt this project had new reasons to look ahead, and also further reinforced the point. Instead of finishing the surfaces on my trivet I lightly sanded them expecting to finish the sanding after my design was cut, however the surface of the aluminum itself was slightly changed after running through the CNC. I also ran into the issue of finding out it's very difficult to sand a surface flat when it has dips and edges in it. This is an example of the finished product being within tolerances and having all of the correct features, but still not looking the best due to a poor surface finish. There is no detail that can be overlook, especially for something with aesthetic value.

Cost Estimate

This estimate will take into account the price of the raw stock and the labor cost. To view links of individual stock click on the size of each to be redirected.

Raw Stock Cost:

Aluminum:

$18.76

(Oversized Multipurpose 6061 Aluminum Sheets)

Total Material Cost:

$18.76

Labor Cost:

Colorado hourly wage of Machinist:

$18.53

Days spent (Rough estimate):

Rough average of hours per day:

Total Hours:

Total Labor Cost:

$185.30

Total Project Cost:

$204.06

Improvements to be Made

When being asked how would I reduce the time and cost of this project, there are not really any way to further make this project cheaper or faster. It was a fun project, however it was not very complication, so instead of making it faster and cheaper, I will do the opposite and explain how I would make it more complex.

New Project Idea

To keep the overall project similar we'll keep the trivet itself the same but change the material it is made of and the process to achieve that.

New Project Process

Before I start, I would like to say that I have do not a a lot of personal experience with the necessary processes, however I believe my idea is sound.

To start, we will create the trivet in the same way however this time we need two, one the original and one the inverse. This will act as a mold, so almost perfect mating would be required. This means the stock would need to be oversize to account for screw would would need to be drilled in the corner to secure the mold.
Second, will drill the four holes for screws and bolts. This can be done on the CNC to insure correct positioning.
Next, the sprue and air vent will need to be drilled in the mold. To do this, the mold would be positioning vertically in the CNC. The position for both holes would need to be designed carefully before they are drilled.
Fourth, this mold would be injected with plastic, and after cooled would need to be sanded and finished to ensure acting with the ceramic tile.
After, the ceramic will need to be finished. Depending on what the student want their finished product to look like, they could paint the ceramic and kiln it for a unique look.
Sixth, the finished ceramic would need to be CNC'ed to have the design cut into it.
Lastly, the injection molded piece would be secured in the ceramic using some type of adhesive.

Final Note

I believe this new process may take some trial and error to perfect to work well as a class project, however I think it would expose students to two unique materials and processes. Those being injection molding and working ceramic.

Mass Production Estimate

I've been tasked to answer the question of how would the price compare if I made 10,000 of these trivets vs the price of 10,000 trivets manufactured through automation. To establish a baseline we'll first find the price of a machinist hand producing 10,000 trivets.

Cost of 1 Machinist Produced Trivet:

$204.06

Time Spent on 1Machinist Produced Trivet:

10 hours

Cost of 10,000 Machinist Produced Trivet:

$2,040,600

Time to Produce 10,000 Machinist Produced Trivet:

100,000 hours = 4,167 days

Cost of 1 Automation Produced Trivet:

$18.76, this is the price for only the stocks, no labor cost.

Time Spent on 1 Automation Produced Trivet:

10 minutes = 0.17 minutes

Note: The average time for the CNC to cut a trivet in my class was around 8 minutes, the extra 2 minutes would be to get through the production line.

Cost of 10,000 Automation Produced Trivet:

$187,600

Time to Produce 10,000 Automation Produced Trivet:

1,700 hours = 71 days

Finals Notes:

I think this piece specifically due to its simplicity would be the easiest to design a full automated manufacturing process for.