This past week (or two) has been about putting everything we learned in the first few weeks of this class together to create a model of a mechanical system. A few weeks ago we were supposed to model a mechanical system in Adobe Illustrator (see post here). At the time, I was a novice Adobe illustrator user. Now I can proudly say that I am….still a novice AI user. Maybe I’ve moved into the “usable” role, but I’m by no means an expert. That comes up several times in this post.
The reason I mention at the start that I am not very good at AI is because that piece of information motivates a lot of decisions I made on this project. The first decision I had to make was whether I wanted to use my file from the AI week or create a new project. I decided that making a new file would be too stressful (i.e. if I couldn’t I would waste a lot of time) and I would rather use the file I had and improve upon it while getting better at AI. This way I could still learn what I was weak at without the stress of mastery (side note: turns out I was overthinking the AI portion and there’s a handy tool that would have done practically everything in modeling it for me, but I didn’t learn about it until later).
Step 1: Analyse existing solution
My mechanical model is the image on the left. It’s fairly simple om terms of interlocking pieces. The lever-bar pushes a pin on a horizontal bar to convert rotational motion to translational motion. As far as difficulty went, the actual model was not very complicated and I could get it done relatively quickly. In fact, in my previous post I had already gone as far as coming up with all the geometries needed to laser cut a small version of the model. It worked fairly smoothly, but I realized that friction would become a large issue in making it run smoothly. The flat bar was touching the surface of the wood and the pin in the top was also causing problems. I decided to solve this by replacing the top pin with a bearing and putting a layer between the rectangular bar and the surface of the back wall.
Step 2: Spicing things up
But I wasn’t happy. Sure I had a large portion of the project done, but that was more due to my limited AI ability than my ability to create an interesting model to begin with. I had two goals in creating a project: I wanted to address my limited AI ability by working with something I haven’t done before and learning new finishing techniques. I would also go on to challenge my skills in learning how to cut different materials in a laser cutter.
But back to the problem at hand. I wanted to tie my motion into an interesting shape. To do that I brainstormed several ways that you could utilize the motion in daily life. I has settled on a pendulum clock for a while when I also realized that the lateral motion of the bar perfectly mimicked a window latch. I could then do a stained glass window (like the on on the left) with different techniques to both create a more visually appealing piece as well as help me learn to manipulate things in AI. I specifically looked for a “coloring book stained glass window” because I wanted something that would be clean lines that I could work with in AI. I found the one on the left and I fell in love. I’m also a student of architecture in my free time and I loved the shape of the Gothic arch, the inclusion of a partial Rose window, and the quatrefoils.
From here I had a plan in mind. I would create a “window latch” that would model both the mechanical motion as well as show off everything I would learn about AI and finishing techniques. I broke the problem into two main parts: Part 1 would consist of the window segment (modeling, cutting, painting/finishing) and part 2 would consist of the motion itself. This was fairly easy to do as my previous model was basically broken into the green wood plank and the laser cut moving parts.
Part 1: The window
I knew I wanted to do a stain glass window so I broke that down into the components of the window: The “ironwork” lines would be on the front most layer, a plane of acrylic would mimic the glass feeling, a plane for the actual colors and then the supporting layers.
Step 1-1: I downloaded the image and used the Image Trace function. This is the function that I had mentioned before. When I was trying to use it originally I couldn’t figure out the details of how to manipulate the image once it was traced. After playing around with it a bit, I learned my image was grouped together. By un-grouping and double clicking on the part I was able to manipulate the image. When Live Trace created a vector file of the image it created both and inner and outer shape of each line (due to the thickness of the lines). I was able to eliminate the innermost line of each image to create my initial file of the ironwork section of the window.
Once I was able to create the shape of the window detail I used the layers function in AI to create the other shapes to laser cut. For the acrylic layer I just had the outline and the hole for the bearing and for the colored layer I etched on the shape of the ironwork. This way I could know where exactly the the holes for the colors would be.
1-2: Next was laser cutting all the files. I was working with 1/4 inch plywood so I used an appropriate speed and power setting. Unfortunately not all pieces cut out on the first try so I had to make another pass on some sections. As all of the cut out pieces would be scraped and the rest would be painted I was not as concerned with burning as I would normally be. It was more important that the wood was cut cleanly as the ironwork section would be somewhat fragile. Some of the sections took a third pass, but I cut everything out with minimal damage.
I also got to cut acrylic for the first time with the window layer. I used the recommended settings, but was still having an issue with it not cutting all the way through. I did a second pass at double speed and it popped out.
1-2.5: Before I moved forward with staining my stain glass window, I wanted to test some sample sections to see how long I wanted to stain each section and using which stain. I didn’t get a change to play with the different stains for the finishing week because we were working with metal and not wood. Therefore I had insufficient data on how each stain would look. On the image to the left you can see some sample sections. These were all applied to the same wood I would be using.
1-3:The first thing I did before staining was I painted the in between sections black using a paintbrush and black paint. This took a very long time, but was very helpful for marking the boundary between sections and giving me a base to work with when I would put on the final version of black.
I wanted to move from lightest to darkest for stains due to the “creep” factor of stains when they seep along the grain. I put tape down around all the sections I was working with before I put anything on, but for this first stain (honey gold, see left) it really moved into other sections, even through the laser cut grooves. An interesting phenomena I observed later is that this was the only stain that had that effect. I also used a dark gel stain which did not do that (probably due to the gel properties) and the linseed oil I used on some of the lighter sections did not seem to move through the laser cut grooves.
As a final layer I spray painted the rose center and the quatrefoils. The spray paint turned out looking the worst on the wood due to the splintering of the wood from placing and removing tape for all the different techniques. If I were to repeat this procedure I would use a higher quality wood than luan for the window segment.
On the left you can see the painted over black lines. I then used the grooves from the laser cut layer to guide the reapplication of the black lines. I also did touch ups across the whole face.
1-4: For the ironwork segment I cut out an inner window shape and an outer window shape. This is so I could have a “window” and “frame” for the latching display. I spray painted the ironwork cut out black and the frame sliver. I glued the two pieces together. To attach the acrylic I researched the best way to attach acrylic and wood. The answer, by the way, is Epoxy. I used Epoxy to attach the first two layers together.
Now I had the window and stained glass part of my stained glass window, but before I attached them I wanted to build the base that would support the whole structure. This is because I knew attaching everything would require wood glue (read: clamping) and the window part is fairly fragile.
1-5: For example, the image on the left. The left-most layer is the stained layer being glued to three more layers of luan. These three layers have tabs attached to the bottom that can be slotted into a base to support the structure. The base layers were spray painted with the same stone texture the outer layer of the ironwork window section was . This is so the eventual piece has continuity.
Once stained layer and the base layer dried, I put the bearing in the hole and used a small amount of epoxy on the outside to keep it in place. I also used Epoxy to glue the two layers completed in step 1-4 to the front face of the window. I was now done with the back part and moved onto the mechanical movement.
Part 2: The Mechanical Movement
2-1: I had already prototyped the movement, but I also needed to scale up the version to know it would interact with the rear piece. On the left you can see the rapid prototyping I did using some laser cut pieces and tape extensions. From this prototype I knew I needed to raise the bar off the surface of the ironworks layer or it would become and issue with friction and would eventually break. I also was able to measure the distance I would need to extend the end of the swinging bar to extend down past the bottom of the window to drop down. I was able to modify the AI file for both of these parts to cut appropriate sizes. I laser cut the bar and slots and plasma cut the swinging bar file.
2-2: Once the swinging bar was plasma cut, angle grinded, sanded and painted, I created a stopper that could fit into the bearing and support the swing bar. I put beeswax on the horizontal bar and the side supports to make them slide easier. The image on the left show the whole mechanism set up drying. The stopper has layers of wood in the center to hold the bar up a layer from the horizontal bar so it will minimize friction. From here I created a nub from a dowel and spray painted it black to connect the swing bar and the horizontal bar.
2-3: Last steps. I created a base out of three layers of wood. The base was created so the three holes matched the end of the window segment (created by utilizing the function of layering in AI) and the distance between the front edge of the hole and the front of the base was the same distance as the distance between the front of the peg and the front face of the window. This is so it would cleanly sit on the front lip of the edge of the shelf it was sitting on. I also created a designated handle so people would know where to move the device.
Final Design:
This is how the final product turned out. It is stable as long as the person using it is gentle on it, so for general display purposes I would recommend clamping it to a table. Additionally there are issues moving the bar at the extreme reaches of the device (at large angles) so that might be a concern for breaking the device, but it is easily reset by just taping the outside bar.
Overall I am very happy with the way it turned out. Here are the AI files for the window segment:
