Epoxy Illuminated CNC Sign

Hello, I'm a Pennsylvania Tech Ed teacher that was looking for a project for my 10-12th grade Engineering 2 students. With the help from my wife, we came up with the idea of an inlay project that required the laser and the CNC router. The idea stemmed from me needing a project, and my wife needing a congratulatory sign for her new real estate career. I incorporated epoxy, vinyl, and led strip lights in my design. I ended up not even incorporating an inlay into my design, but included some pics of my students work with inlay examples that turned out great.

• Glaze coat epoxy
  
• Epoxy Mixing containers
• Heat Gun
• 5V SMD 5050 LEDs ~ 12ft
• Mica Powder
• Epoxy Resin Colorant
• 3M Packing Tape
• Soldering Iron and supplies
• Hardwood of your choice

• Birch Veneer Plywood - 1/8" thick

The first step of my journey was coming up with a design. I needed the design to be catchy, big enough to accommodate a 3/16" router bit, and have the ability to provide details needed for the display. This forced me to use a combination of vinyl with the epoxy. My wife was stuck on using script text as the font for her name - which is tough to get the detail with a 3/16" CNC router bit. Vinyl proved to be a good solution to provide the detail needed. I used Adobe's Illustrator 2020 for my vector-based design. It was my first run at it and after being a long time CorelDRAW user - I like Illustrator more and more each time I use it.

Needing the stock to create my base, I went with black walnut. I know I was going to face glue two pieces to achieve a depth thicker then my S2S .75" stock. To create toolpaths, I went with Fusion 360. It's been my go to after battling w/ MasterCAM for so many years in the beginning of my career. I like Fusion 360 for the ease of use, and the templates and tool library I can create and share with my students. Fusion actually allowed them to use the program to generate toolpaths, rather than follow a 30 page step-by-step tutorial they had to do w/ MasterCAM.

I love utilizing NCViewer.com to look at the G Code w/ points to see how many arcs and straight lines are created. This shows if any modification is needed to reduce the size of the GCODE file. In this case, my file contained just over 16k lines. Definitely more than it needed. I did A LOT of playing around and found that using 3D Pocket toolpaths produced MUCH better results compared to the 2D contour toolpaths. The 3D pocket has less lines with a TIGHTER (more accurate) tolerance. In the example video I have the 2D pocket simulation shown.

The project needs to allow light to shine through the front cutouts to make it vibrant during the day, while containing supports for screwing my back plate to house the lights. The toolpath geometry was made easier by utilizing layers in Illustrator to make copies of parts of my design and placing supports / offsets / cutouts where needed. I then offset the outside edge and ran a contour toolpath to allow a groove for my 1/8" birch to rest in as my back plate. We use Velocity CNC program by Forest Scientific to control the router. This program reads the G code created by Fusion 360 in a language in can interpret for my specific machine.

Making an effective inlay comes down to how good your vector geometry matches your finished toolpath. There are dozens, if not hundreds of programs that can create toolpaths from vector based geometry. I haven't found one yet that can translate toolpaths into geometry to use as an inlay. This is where creating geometry that is perfectly aligned from using two different machines and software packages takes time and skill to produce good results. As described in the step below, marrying the two designs can be tedious to make sure corners are rounded to the radius of the tool.

Toolpath generating programs (like FUSION 360) love working with DXF files. In order to create proper inlay geometry using Adobe Illustrator, it's important to be able to create graphics that contain rounded corners that are the same radius as our router bit's radius. We use a 3/16" fluted downspiral bit shown above.

In order to find the radius, you must find the decimal equivalent of 3/16" and divide by /2.

After finding the measurement, round up to the nearest thousandth and use this value to create a circle to represent our router bit in Adobe Illustrator without a stroke.

Notice the size of the Artboard - we are limited to our detail level in our design based off of the size of the bit involved. If fine details are a must, we must resort to other methods, such as raster engraving w/ the laser or vinyl cutting decals to achieve the desired look.

In this example, we will transform the font "PATRIOTS" to work with our router bit to create a seamless inlay. With the "P" selected with the Direct Selection Tool (Hotkey "A") Double click on the dynamic corner button to enter in the radius of .094" (1/2 of our router bit diameter rounded up) to create a smooth corner. You know should have a beautiful corner that will fit perfectly to our bit as seen in the pics above.

IMPORTANT NOTE: Only OUTSIDE CORNERS need to be rounded. The router bit can sharp edges on inside corners as the bit travels AROUND the object. Think of the inside triangle of the "A". The bit can go around the triangle to produce the exact shape with sharp corners. It's important in the design phase to create something where MOST of the detail of a desired image is achieved.

NOTE: Although sharp corners can be achieved with inside geometry, different material thickness and densities react differently and may chip out if too thin and or narrow resulting in voids in your inlay. Practice with your material of choice.

I ended up not even creating an inlay with my design as changing my design to a epoxy pour, but students' work turned out awesome as seen is some of these pics.

On to the epoxy..... what an experience. Definitely a lot of highs and lows when working with these resins. It helped that I took a lot of time prepping to see how it reacted to certain material, colors, powders, and different pours on top of one another. This had me prepared for what was to come. I highly recommend you do the same! There are a lot of epoxy brands out there and they have different viscosities, mixing & curing times, and required pour thickness to achieve a fully cured result. Glaze Coat / Super Glaze from Home Depot and Art Resin were my faves.

Packing tape is good to use to separate epoxy from a surface, but not to protect something from getting epoxy on it - it will find a way to seep behind the tape and make the wood look wet. Finishing the wood with an oil or water base poly before pouring helps prevent the wet look and epoxy seepage. Even if epoxy is poured into a cavity on the face a board, the edges of the cavity on the face would look like wet as the epoxy flows into the grain through the cavity wall. The way to fix this is to pour a top coat of epoxy to cover the entire project and make the whole project look wet.

After it cures, the tape can be easily removed from the epoxy. If applying a top coat where the epoxy is running off the sides, applying tape to the underside of your stock will allow you to easily remove hardened drips by peeling away the tape. This works best if your stock has a 90deg bottom edge as compared to a smooth transition from side and bottom of a project. In my case I was pouring in an opening as I wanted to illuminate the epoxy from the back. Blue/masking tape did not work at all. Expensive Tyvek tape worked ok, but not as good as the 3M packing tape. In my case I taped the bottom on all my pours, then removed the tape later with little difficulty. Hot glue acts a good reservoir to contain the epoxy without adhering to test pour on a scrap piece.

What amazes me the most about epoxy is the ability to pour a 2nd layer over the 1st with defects like gouges or scratches and look perfect. You could pour a layer. Have it cure, scratch it up with 40grit paper, clean up the dust and add another layer and you wouldn't be able to tell it was done in two separate steps. In the above pic with the squares w/ diff colors, I poured the epoxy, then tried surfacing it flat and smooth which cracked the epoxy. After pouring another layer testing the hot glue reservoir all of the chips/scratches/cracked disappeared. I've seen people surface epoxy but my brand new JET 20" helical head planer didn't do the job. Any comments below on tips and tricks are welcome.

Overall Glaze Coat / Super Glaze were nice as mixing time was 3-5 minutes. Ecopoxy was 12min! With Super Glaze I would mix for 2 minutes, insert my alcohol based dye and mica powder, stir for another minute then pour. 24 hours the epoxy would be fully set, 48-72 hours it was fully cured. Using a heat gun is a must to aide in removing air bubbles that proved to be nuance in my project.

After gluing up my two CNC halves, I tested out a light config by running LED strip around the perimeter of my design hoping it would provide enough light. Unfortunately - it didn't work. I realized that I needed more light where the epoxy was located to really shine through. To see exactly where to place the lights, I lightly lasered the front design into the back plate so I could place my lights in the right locations.

I soldered all of the strips onto the back plate to provide ample light to penetrate through the front. The key to soldering LED strips is to:

• Make sure your soldering iron is cleaned frequently - I use THIS
• Apply flux paste to all strip contacts
• Add solder to stranded wire ends to bunch together (I used 22ga.)
• Add solder to contacts
• Put wire onto contact and apply iron to top with a touch of fresh solder

One issue was that you could still see each LED which I didn't like. I added a sheet of vellum to help diffuse the lights and create a nice balance of light. In the last pic above you can see the balanced light compared to the pic before it.

Unfortunately details are limited in the walnut due to the CNC bit of 3/16". In order to add more flare to my design, I incorporated vinyl using Roland's GX24 cutter. It's simple to use and Roland's CutStudio is just to hit print. All of my design work is completed in Illustrator from offsets to weeding lines. I simply lit up the sign, aligned the vinyl and stuck it where it needed to go. More details can be followed HERE on vinyl creation and application.

An unexpected issue I ran into was how the vinyl produced air bubbles when I put on my epoxy top coat. Air seemed to come from nowhere underneath the vinyl and forced me to wait with a heat gun for close to an hour as the epoxy hardened. Eventually the trapped air from underneath the vinyl was outweighed when the resin began to harden which prevented the air from leaking out. Some portions needed an hour of me waving a heat gun every 3min to ensure the bubbles weren't trapped forever.