At Inventables we have an occasional event in the late afternoon called Beer and Making. Whoever is available goes down to the fabrication area and we socialize, drink beer and make stuff. It is the Inventables equivalent of eating our own dog food.
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I decided to make an official sign for the event. I grabbed a piece of 12” x 12” x ¾” bamboo plywood. I enjoy working in bamboo because it does not require a finish, machines amazingly well and smells cool when you work with it. On this project I did zero post machining clean up other than a light shot of compressed air. Total hands-on project time was about 1 hour. I did not take any pictures during the job unfortunately.
Graphic Design
I wanted it to to have a bar sign and beer look to it. I used Google Image search with the keywords of beer, Chicago, craft, and sign and found a Chicago Craft Beer logo on a glass. The bottle cap and beer sign theme was just what I was looking for.
I dragged the logo into CorelDraw. It was low res and at an odd angle so I just slid it off to the side for inspiration. The single color of the logo made it perfect for a V-Carve project.
V-Carving allows fine detail using a V bit. Normally the detail is limited by the diameter of the bit. With a V bit, you can choose any diameter by varying the depth of the cut. V Carving requires special software CAM to generate the tool paths. I used VCarve Pro from Vectric.
I played around with some ideas and came up with decent logo in few minutes. The logo was exported to DXF for importing into VCarve.
CAM
The next step is to setup a project in VCarve to match the size of the material. On jobs like this, I like to set X0,Y0 in the center. The next step is to move the graphic objects into layers. This was a relatively simple job, so I only made two layers. One for the outer cap crimp area and one for the rest of the project.
With V carving, the wider the space you want to cut, the deeper the bit needs to go. At some point that depth will exceed the material thickness. To prevent this, you can set a maximum depth and everything wider than that limit will have a flat bottom. The outer ring of the cap has a thin enough cut area so that is not a problem and a flat area would not look right anyway, so this was setup to cut without a flat depth. The interior has very large cut areas so a flat depth of 0.15” was chosen.
You need to choose the diameter of the flat bottom bit. A large bit will clear the area quickly, but have trouble getting into the corners. Where the flat bit cannot get, the V bit will clear up. You need to set a tiny stepover on a V bit to do a flat bottom, so determining the most efficient flat bottom bit requires a little experimenting. I used a ½” diameter straight flute V bit and a ¼” diameter straight bit for the flat bottom tool. All toolpaths were set to be done in a single depth pass.
Machining
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To make the painting step super easy I used the following trick. I used some white vinyl masking material from Avery to cover the top surface. I made sure there were no bubbles and rubbed it down hard with my palms to get it to really stick. I then draw a line from corner to corner to mark the center. The bits will cut through the mask and then it can be painted simply by spraying.
I did not need a sacrificial layer under the work piece because there are no operations that could cut through. I clamped at the corners because they are clear of cuts. You need to very carefully check the level of the top surface and shim as required. A change in height will change the width of cut areas. The bamboo was near perfect and did not require any adjustments.
I ran the two v carving paths first. The outer ring took about 8 minutes and the inner areas took about 14 minutes. The flat bottom cut took about 9 minutes.
Painting
The painting was done with a standard spray paint can. I have had issues in the past where the masking shrinks or shrivels at this stage. I think it is from too much paint. I now put down a few very light initial coats to stabilize it. After that you can spray at will. It usually takes about three good coats to get full coverage. You don’t want too much or you will see a lip of paint around all masked areas.
I let it dry for several hours after the last coat. After that I used an Exacto knife to catch the edge and lift each piece of mask. It is really fun to slowly reveal the finished project. The last thing you do of course is spell check the completed project.