This week I made a push fit box made out of laser cut wood. 

For the first step, I used en.makerspace.com to create the dxf file for the box. The settings I chose included 4in x 4in x 4in dimensions, a material thickness of 0.18in (based on caliper measurements I collected from the wood I had), a closed box configuration, and finger joints that were 1.0915 in in width. I decided to go with a kerf of 0.008 inches since that was shown to be an effective kerf by my peers.

Figure 1. Box parameters

 

Once I converted these constraints into a dxf file I opened the file in Adobe illustrator. I then copy and pasted the vectorized image of my graduate school crest from my nameplate file into the center of one of the sides of the box and typed out the required information in a text box placing, that into another one of the sides to be cut out. Afterwards I centered both the image and the text box within their respective sides.

Figure 2. dxf file on Adobe Illustrator

I cut out two kerf boxes with different characteristics. First I used the Epilog Fusion M2 to cut out the sides with these settings: for raster 50% and 600 DPI. For vector cutting settings used 5% speed 100% power and 10 for frequency. This resulted in a near perfect roster cut, but the vector cut had excess char. For the second cut, I used all of the same settings, except I increased the speed of the cut from 5% to 6%. This resulted in less excessive charring on the vector cuts however, the raster image and text had some excessive char. I think this was due to having to recalibrate the height of the laser between boxes which impacted the repeatability of the fabrication process. In future iterations, I would maybe use the Fusion Pro instead of Epilog Fusion M2 and also place masking tape along the path of the edges of the box. Additionally, a major source of char seemed regions where there is too small of a separation between the sides. In the future, I would increase the space between the sides to prevent this from occurring.

Figure 3. Locations of excessive char

                                   

Figure 4. Box 1 vs Box 2

 

After laser cutting the box, I removed the pieces and was able to press fit them together, resulting in a successful assembly.

Figure 5. Assembled Box

For post-processing, I decided to use 400 grit sandpaper to sand the sides to remove the excessive char from the box. Through gentle sanding, the char was removed, resulting in a higher quality build.

Figure 6: Before and after sanding

 

Overall I am satisfied with my build but I look forward to applying the insights I discovered in future cuts.

Figure 7. Cleaned up work space

The total cost of the boxes I produced was $49.16 which is more expensive than expected. One major source of the cost was the quality control component of post processing. I think that using improved laser cutting settings in addition to using tricks like covering the wood with masking tape before cutting will allow me to avoid the majority of the time I spent post processing. Additionally, more experience with the laser cutter will allow me to step up prints more rapidly, likely taking me as short as half the time. These improvements could decrease the cost of the box to under $18.

 

Cost Type	Cost	Price	Source	Quantity	Total
Materials	Plywood sheet for laser cutting	$2.76 /sheet	Amazon.com	1 sheet	$2.76
	Sand Paper	$0.40 / sheet	Amazon.com	1 sheet	$0.40
Labor	Laser cutter operator	$17/ hour	Ziprecruiter.com	1.5 hours	$25.50
	Prototyping Engineer (You!)	–	–	–	$0
Overhead	Facility Cost (powering machine)	$2/ hour	shop.machinemfg.com	1.5	$3
	Quality Control (sanding)	$35/ hour	salary.com	0.5	$17.50
Design	Engineering and Development	$0	me	–	$0
	Iterations(2)	$0 (both iterations came from the same sheet)	me	–	$0
Misc.	Waste and Scrap	0$(scrap returned to OEDK)	me	–	$0
Total					$49.16