A Study in Laser Cutting
Part I
In this study I began to look at how I could use different digital tools to create some of the same objects that I had created with the hand tools. I wanted to know how my design process would change and how the material and machine limitations would effect that? I was also interested in how the final piece would physically hold up and look in comparison to the first one that I had made by hand.
I started with the exact same drawings and intent to make my piece as close to the original as possible in size and construction. I started by using wood for this, but it was a bit different than the last time as the laser cutter could only cut up to 1/4" thickness, so I had to use plywood and then cut extra pieces to laminate together to get just the right size.
The first thing that I learned about the laser cutter is that you need to have a digital file pattern to run. I had to figure out exactly how many pieces and of what size that I would need first in order to make the pattern. I drew the pattern on illustrator, which was simple enough, it probably took about 10 minutes. Though I had to be careful because I learned that there are only certain line weights that the laser will cut in a single stroke and if there are any overlapping lines it will double cut, which could change the size of the piece to something just slightly smaller than you had anticipated. Understanding all of these quirks about the technology in order to properly prep my file was crucially important to get the right cut the first time.
After the file was prepped and ready, I had to put the sheet of plywood in the laser cutter. plywood can slightly warp sometimes, so the piece had to be clamped down by the side ruler and a screw outside of the bounds of where the laser would be cutting. The laser also had to be focused so that it made as accurate a path with its cut as possible, but this could be done quickly and easily with the touch of a button.
After about 7 minutes all of my pieces were cut perfectly to size. That in combination with the time it took to prep the file meant that getting all my pieces took less than 20 minutes, where I spent several hours over 2 days to get all of my pieces cut to size for the original version of the bookshelf that I made by hand.
Though after cutting out all of the pieces I realized that I had forgotten to include one set of screw holes that I would need for the construction of the piece. In the process of making this by hand it most likely would not have been a big deal because I could just go back, measure, and drill the holes. With the laser cutter it’s different though because to put the piece back into the machine it has to be absolutely perfectly aligned to where it was previously to get the holds at the right measurements. Thankfully the outline edge scrap from the board was still in the machine so I was able to align my piece with the top corner and run the laser cutter again with the additional holes in the pattern this time.
Once all of the pieces were cut out I had to use an awl to punch out a few that did not detach entirely. Because of the way that plywood is made there are certain parts that might have glue in between the layers, which is difficult for the laser to cut through, so not all the pieces cut fully. It was easy to punch them out but it did cause some splintering of the wood layers which I needed to either sand down or be careful to hide under another layer later in my assembly process.
Though the cutting out process was much quicker with the laser cutter the assembly required a bit more finesse than the previous version of the piece. Because I could only cut 1/4" thick boards I had to cut 3 per board and then layer them to get the original 3/4" thickness. To do this it meant that I would have to laminate them with wood glue and then brace them together with tape wrapped around to make sure that they were as perfectly aligned as possible. Even while taking the most care it would still be necessary to sand the edges even later on most likely.
After bracing together all of the boards did a quick test fit into the channel that I had left for the full assembly and realized that there was not a tight fit. Even though the boards were cut to the perfect size and there was no way there could be a machine error there was still a gap and the board did not fit as snugly as it should. I soon learned that this was because even though the plywood says 1/4" it’s actually just slightly smaller than that. All in all I was 1/32" off because of this.
In order to correct for the 1/32" I had to use a mallet and chisel to carefully pry off the small end board and re-glue it 1/32" closer to the other side so that my vertical pieces would fit snugly later on when I put everything together. This also meant that I would definitely have to sand down both ends of the center board by 1/32" to make the whole piece even on all sides.
After allowing the glue to dry overnight I took the tape off of all of the boards and since all of the edges were burned from the laser I decided to sand down the sides back to the wood grain. I did this by hand using sandpaper because I wanted to avoid using the shop tools as much as possible and stay within the capabilities of the laser cutter. After about three hours of sanding (and with a very sore arm) I had sanded down all of the edges to remove the burnt finish left by the laser cutter.
My next step was to cut the screw the board together in the same way that I had for the previous shelf as well as to cut the plugs for the screw holes. Because of the tolerance on the laser cutter I had to experiment and do a bit of trial and error testing to see exactly what size would fit as tightly as possible.
Once I had found the size that would work best I cut the 6 plugs that I needed in this size. Because the laser cutter cuts vertically and doesn’t taper i had to sand the under side edge of the plugs a bit so that they would slide into the holes smoothly. I aligned the grain in the same direction as the board, similarly as to how I did the original solid wood bookshelf. What I learned when I sanded the plugs down flat though, was that because of the way the plywood is constructed in layers, even though I aligned the top grain after sanding it down, I sanded through a few layers of the plywood, and the grain actually ended up being perpendicular to the main base board.
I also ended up with a very small black ring on the outer edge of the plugs once they were sanded down. This was once again due to the laser cutter burning the edges of the wood when it cut the pieces. It actually looked nice on the piece though and I think it was an interesting mark of the manufacturing process that helped to give the piece a sense of character. I finished the piece by sanding down all of the faces until they were smooth. This I learned was not quite as easy as it had been with the solid hardwood though because of the way that the plywood is manufactured. It can be very difficult to get as perfectly smooth a finish as might be desired.
Part II
The next exploration that I decided to take on was the construction of the same shelf using the same methodology of the last shelf, except this time it would be in clear acrylic material. I wanted to learn how the different material would effect my process of making. The initial cutting process was similar to that of using the plywood. I was able to use the same illustrator template and the same thickness of material to create my pieces.
My process began to differ a bit when I started looking at how I might assemble this piece. As I chose to use a clear acrylic to better see the joinery and understand what the interior of my assembly might look like I decided to start by experimenting with the different types of adhesive that I would use to assemble the piece. I tested the slow, medium, and high strength drying adhesive to see what would give the the most transparent finish. From the small samples that I tested out it seemed that the medium drying would give the clearest finish.
I taped up the edges of all of the acrylic as I was gluing so that the glue would not run onto the edges and make it difficult to separate the acrylic from the surface that it was on or to make the pieces messy at all.
Despite my efforts to be careful about the way that I was gluing the pieces together this particular type of adhesive for the acrylic was not easy to work with and I did end up getting a bit stuck to the edges of the acrylic that would not come off with acetone when I was finished.
I after soaking the edges in acetone and attempting to hand sand the edges of the piece I eventually had to resort to using the disk sander again to get the glue and tape off of the edges of the piece. This left the edges with a nice clean translucent finish. After taking all of the protective film and tape off of the piece I also noticed that in my gluing process there were a few air bubbles and pocket left between the acrylic.
I thought that this would be alright once again, and could be seen as an interesting detail and part of the craft, except for the fact that one of the corners of the piece the glue dried translucent instead of transparent, which took away from the interest of the pattern created. Some of the air spaces also left room for dust to get trapped between the pieces of acrylic and the overall appearance of the finished components was not exactly as I had hoped it would be.
After measuring out where the screws needed to go in I used a drill press to create holes in the specified places. Again creating new details that could be seen in an unusual way because of the transparent nature of the material.
I then used a thread cutter to create the threads for the screws to hold the piece in place more securely and easily.
After assembling the piece with the screws in place I realized that aesthetically it was becoming more and more less pleasing. In order to create a uniform finish between the flat planes and edges as well as to hide the air pockets and resulting trapped dust, I did a light sanding over the entire piece to give it a translucent and uniform finish that looked a bit like frosted glass. Another reason why I had to do this was because of the plastic plugs that were covering the tops of the screws. They needed to be sanded down flat, which would scuff the surface at those points, which I hadn’t considered earlier and this basically made the decision for me that I would have to sand the entire piece.
Overall the final piece did not come out exactly as I had anticipated, it was much more difficult to manipulate the material the way that I had planned and in this case the material, end goal, and processes didn’t entirely match up I think. I forced three different things together that were not necessarily meant to be used in the way that they were. The piece also came out extremely heavy, much more so than any of my previous attempts. It looked interesting and the translucent sanded finish in the end saved it aesthetically, but overall the material and the process combination were just not meant to be.
