Geometric Fun: Creating a Symmetric Coaster from Laser Cut Wood

Sometimes it’s fun to just doodle some ideas on paper and see where that takes you. One afternoon I was looking for a new idea to cut and just started drawing some layered coasters and ended up with a fun model to cut. I ended up going with a three-layer coaster having two of the same base sandwiching a unique middle layer.

Creating the Base Layer

The inspiration for this was to just design some fun shapes within a coaster size workspace. To make sure I was working with the right constraints, I first measured a coaster, I had laying around. The standard size seems to be about 4 inches so working in SolidWorks, I used 100mm. I drew a simple 100 by 100mm square and extruded that my working wood thickness of 3mm. Like other coasters, I didn’t want sharp corners so I did a fillet on each of the four corners with a radius of 10mm to get the following part:

Now that I had a base coaster size, it was time to make some extruded cuts to give it some character. My first cut was just a simple triangle in the corner with the three corners filleted. I decided I wanted something a little fancier later on in the design, so I added some splines through the middle of the cut that would contain two 5mm thick portions of wood for a little extra fun. This was drawn in the bottom right corner of the coaster to give me something like this:

Next, I wanted to make this corner design symmetrical across the entirety of the coaster. To do this I took advantage of SolidWorks mirror feature. I drew two planes down the center of the coaster both vertically and horizontally to be the mirror planes. From there I selected the mirror feature to mirror this cut around those centrally located planes and ended up with this:

I was pretty pleased with how this turned out and now just want to add a center portion to complete the base part. Following the same format for the center and cut out four triangles with rounded corners, I used a similar mirror technique. I also added in center connecting posts at the same 5mm thickness. Using the 5mm thickness made for a nice-looking standard thickness across the entire part. That left me with what I thought would be the final base part:

After looking at the part for an extended period of time, I didn’t like how the solid portions of the coaster were looking in between the outside triangles. It seemed like too much wood concentrated in one spot. I wanted a lot of negative space throughout the part to showcase the middle layer. This was actually after the middle part was designed (getting to that design a little later), but since I hadn’t cut anything yet, I figured I could make as many edits to the model as I wanted. I ended up offsetting each of the surrounding edges by 5mm to again stick to that standard thickness. It was as simple as connecting each of these offset entities and trimming of the excess portions to create a fun extruded cut seen below. Just to get as much SolidWorks practice as possible, I replicated this cut with the circular pattern feature around 360 degrees with 4 features to get the final base part:

I was really happy with how this turned out and thought it gave the proper amount of negative space to let the middle layer show through.

Creating the Middle Layer

To start with the middle layer, I began by copying the file for the base layer. I removed all the extruded cuts and left the 100 by 100mm rounded edge square. This made sure that the new layer would be the same size with a different internal pattern. I began with a similar triangular cut that was the inner portion of the base layer. I spaced it out so that when I performed a circular pattern around the part it would have the 5mm thickness for the internal segments. It gave me a middle layer like this after the circular pattern:

For the next portion of the middle layer I knew that I should add in another piece in the center as the base had a lot of empty space toward the center. I went with a simple circle centered around the middle of the part. Again, I used the 5mm thickness to keep things on the same scale.

I was almost finished with the middle but I wanted one final feature that would show up in the corner windows of the base part. I went with some fun curves that would run up away from the center circle. There wasn’t really any rhyme or reason but just tried to sketch a shape I liked. I drew a center line of the curve and then offset the entities to create a 5mm thick piece. I then did another circular pattern around the part to get the final middle part looking like this:

It was on to check the final assembly at this point to see how the layered coaster would look in the final design.

Creating the Three Layer Assembly

Creating the assembly was relatively straightforward in SolidWorks. In a new assembly file I inserted two of the base parts and one of the middle parts. I usually don’t go for the perfect mates when making my assemblies. Most of the time I’m just looking to see if the overall model looks correct. I made three simple mates between the first base and the middle portion. The first was for each of the faces that would be touching, the second the top edge of the pieces that would be touching, and the third was the left edge of the faces to be touching. I ended up doing the same three mates on the other side of the middle part to the other base part. This made sure to lock each of the parts together and gave me a good looking final model:

I was happy here after a few iterations that were outlined above and I was ready to move the model into LightBurn and make some cuts. If you haven’t checked it out, check out here for my quick post on how I move my SolidWorks files into LightBurn. This saves me a ton of time when I get ready to cut out my files.

Cut Settings and Cutting

With my design imported into LightBurn, I was almost ready to go. I just needed to set my cutting parameters. Running my 40W XTool Laser on 3mm wood I like to use the following settings to cut:

• Layer 0 – 100% power, 22 mm/s, 2 passes
• Layer 1 – 100% power, 22 mm/s, 3 passes

Layer 0 is the outside cut (in black) and that’s to make sure the piece doesn’t fall out when cutting. I typically pop this out after cutting. Layer 1 is for my inside cuts and I add an extra pass to make sure that the wood is fully cut through. This is what my LightBurn file looked like:

After setting up in LightBurn, I saw how long it was going to take and figured to bump the size down on the coaster to make it a little bit quicker of cut. This was just a fun little project, so I didn’t want to cut forever. I ended up shrinking it down 25% and the final size was 75 by 75mm.

Final Product and Wrap Up

I had some slight charring on the parts after cutting but, overall I was happy how the parts came out!

I gave them a little light sanding to clean up a few of the edges and faces. After, I dabbed some wood glue on each of the pieces. To line up the glue portions correctly, I lined up the pieces beforehand to make sure I wasn’t gluing a portion of the wood that wouldn’t be contacting the adjacent layer. Overall, for a fun little afternoon project I was really pleased with how it turned out!

I hope you enjoyed the journey for this geometrically charged coaster and maybe even learned something along the way!

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