Author: Gabby Lea

Overview

(Sorry for the bad Alice in Chains reference). Unfortunately, I got very sick the weekend before this assignment was due and had to do my actual laser cutting Monday morning. However, because the majority of the challenge of this assignment was using the 2D digital drawing tools, I was able to get most of my work done at home before bringing my finished design to the OEDK.

 

Training

I completed my laser cutting training by designing and cutting out a nameplate for our crate.

Design

I went to the MakerCase website to create a basic cubic box with finger joints. The dimensions of the box were 4x4x4 inches with 0.5625-inch joints. I set the material thickness to be 0.1875 or 3/16 inches since this is what I measured with my calipers. I then added the various images and text I wanted to place on the faces in the box via InkScape.

Testing

When I initially tried cutting out a test piece, I did not set a kerf on the online box plans. As a result, the teeth of the joint were too far apart. From here, I decided to cut out a kerf box and measure the kerf associated with the settings I used. The kerf came out to be 0.0118 inches, which is much higher than the 0.005-0.007 range the TAs gave us.

I entered this kerf into the box maker plan and tested out a joint. The kerf turned out to be far too high, a problem that several other students also seemed to face. I then tried going down to 0.009, which was still too tight. Finally, I decided to just go with 0.007, which gave me a good solid fit without being too tight. In retrospect, I probably should have dropped it to around 0.006 because the arranging of the box faces could have used some more flexibility. However, the teeth still fit together snugly.

Final Box

I finished my design and loaded the svg file into Adobe Illustrator. Because of some incongruities between the InkScape and Illustrator software, I had to tweak some aspects of my design on the laser cutter computer. When I first tried running it, the machine told me my design would take 35 minutes. This seemed much higher than it needed to be, so I split up the cutting and etching parts of the design into separate files. I was worried that the machine was just etching all my cutting lines, leading to more time than needed when cutting the wood. The split files ended up taking 18 + 4 minutes, so it seemed my theory was right. After the cut was finished, I cleaned up and put my extra wood in the scrap area as a good portion of it was still usable.

Cost Model

Cost Type	Cost	Price	Source	Quantity	Total
Materials	Plywood (1/4” 2×2 ft)	$8.99 /board	Home Depot	1 Board	$8.99
Labor	Laser Cutting Operator (me)	$19 /hr	ZipRecruiter	3 Hour	$57.00
	Prototyping Engineer (also me)	$36 /hr	ZipRecruiter	1 Hour	$36.00
Overhead	Laser Cutter Access	Free after Training	Harris County Public Library	1 Hour	$0.00
				Total	$101.99

 

I would like to take a moment of this cost model analysis to shoutout the Harris County Public Library system. Certain library branches have makerspaces that include equipment such as laser cutters. After attending a training/orientation, library card holders can reserve the equipment for free through the HCPL website. While the training session is free, I added two hours to the laser cutting operator’s labor time because the trainings take 2 hours. As will continue to be the case in this class, labor is the highest cost of the project. This assignment took much less time than the previous two, but there is still a sizeable labor cost.