Over the past week, I have been working on the CNC Machining assignment for ENGI 21o. The image that I selected from the noun project was a Bluetooth logo, as can be seen in the images below. This blog post will cover my process, areas for improvement, and cost analysis for my CNC Bluetooth logo.

Figure 1: My first CNC Bluetooth logo (right) and my second CNC Bluetooth logo (left).

 

 

My Process

It is worth noting that I did not make the two pieces at the same time as one another. I was not aware that we were supposed to make two pieces, so I completed the first piece and then repeated the process to create the second one. This is why the second piece is smaller than the second – I could not find wood the same size as what I used for the first piece!

I began this project by looking up an SVG file of a noun to use from the Noun Project. I decided that it might be fun to do some sort of technology-based icon, and the iconic Bluetooth logo came to my mind quickly. After looking it up, I saw that the Noun Project had plenty of images related to Bluetooth. I selected one that had the logo with a thin, square border surrounding it.

Figure 2: The image from the Noun Project that I selected.

Now, I moved onto machining my project. I imported this file into easel, decided to make the inner logo about 1/8 inches deep, and the border about 1/16 inches deep to accomplish the task of having two separate depths in our project. I had some difficulty using the X-Carve machine – a few bits fell out of the receiver mid-cut, sometimes I had the machine going too deep and cutting the sacrifice wood below, and one time I had to run the cut for the outer edge of the piece (where the piece was cut out of the wood plank) about five times because the depth kept being too little, despite having input a material depth that was >.1 inch deeper than the material actually was.

Figure 3: One of my pieces of wood pre-carve.

Once my piece was finished, I moved onto post-processing it. I began by rubbing the faces and corners down with a low-grit and then a high-grit sandpaper to get rid of the stray splinters from the X-Carve and then to smoothen out the faces.

Once my pieces were sanded down, I began to paint. I began by spray-painting the entire piece black, and waiting to dry. Once the black paint was dry, I put tape around the edges of the top face and sprayed the inner square blue. Once this layer was dry, I took white paint and painted the inside of the Bluetooth logo white by hand with a paintbrush, which was difficult due to how stiff the OEDK’s small paintbrushes are from previous use.

Like I mentioned earlier, once I finished this process for the first piece, I then did it all again with the second piece.

Figures 4, 5, & 6: The black, blue, and white paint that I used for this project, respectively.

 

 

Areas for Improvement

Although I am happy with how my final products turned out, there were some aspects that could be improved.

One aspect that could have been improved is on my original piece. After I took my piece out of the X-Carve, I realized the drill bit had caused some rough edges on the inner edges of the Bluetooth logo. In addition, there was a layer of the wood that was either partially ripped out by the machine or rotted out prior to being used. Since I do not know which it was, I am not sure if this was user error on my behalf or an error inherent in the material or the machine. I was pleased to see that the same issue did not happen on my second piece.

Figure 7: Piece with partially missing layer.

Another aspect of both pieces that could have been improved is my method for paining the inside of the Bluetooth logo. For both of these pieces, I used small paintbrushes from the OEDK to hand-paint the logo with white paint. However, the brushes were very stiff from previous uses, and it was almost like painting with a stick. I think that the paint turned out well given the circumstances, but if I had access to a newer paintbrush the coats might have been smoother and cleaner.

 

 

Cost Analysis

For this project, the elements that could have accrued cost are the wood, the various paints I used, the time spent using the X-Carve, and the opportunity cost of my time.

Wood

For this project, I used roughly 1 feet of wooden plank. Using average prices between various retailers, this totals about $2 worth of wood.

Paints

Most retailers seem to sell cans of the spray paint I used for around $5, and the white paint for about $10. I did not use anywhere near the entire can for any of the paints, but it is impossible to know how much of the cans I used since I cannot visually see how much of the contents are left. Therefore, I will make a generous estimate of $2 for the amount of paint that I used.

Cost of Using X-Carve

For this project, I used the X-Carve for roughly 4 hours. This is a very specific machine to find a rental price for, but based on the fact that I found a figure of $10/hr to use a woodshop in a prior blog post, I will make a generous estimate for the cost of using an X-Carve for an hour to be $5/hr. Therefore, this element would accrue a cost of $20 for the project as a whole.

Opportunity Cost of Time

I spent about 7 hours of my own time working on this project, and my time as a Tech TA is valued at $12/hr. Therefore, the opportunity cost of the entire project is $12 x 7 = $84

All together, the total cost of this project is $2 + $2 + $20 + $84 = $108. As usual, a large portion of the cost of this project is associated with the time it spent to create it. The majority of this time was spent trying to get the X-Carve to do what I wanted it to do, so if I were to go again, I likely could reduce this price significantly now that I am more familiar with the machine.