I did a quick project to demonstrate some of our new products. As soon as I saw the green on white two color HDPE I thought of the Starbucks logo. I thought a nice, deep 60° V Carving of this would look great. The Inventables products I used on this project are:
Artwork
You want to use the highest resolution image you can get. This will give the best bitmap to vector conversion. I searched for "starbucks logo" using Google Image Search. You can use the "Search Tools" option to filter for larger images. I found one that was over 2000 pixels wide. You could search for a vector file, but I wanted to go through the more complex process of working with a bitmap for this post. A vector file would save several steps and give the best results.
V Carve Process
Start a new project in V Carve with the size of the material you are working with. I my case that was 12" x 12" x 0.50" thick. On jobs like this, I like to put the X,Y origin at the center of my work in case the piece is not exactly 12" square. I then draw from corner to corner with a pencil to mark the center and zero the machine on that mark.
Next, import the image into V Carve and adjust the size and centering. Use the Trace Bitmap tool. On a logo like this, I like to use the black and white setting. Adjust the threshold slider until you get the smoothest edge. While the logo looks like it is only two colors, the edges are usually anti-aliased to produce a smoother looking image. See the highly zoomed image blow. The adjustment allows you to choose what colors represent the the logo and which ones represent the background.
You can adjust the other sliders and preview the results. Here are the settings I used.
The idea is to get smooth curves where there are curves and sharp corners only where they should be. V Carving tries to highlight those corners by using the tip of the V bit. If you get a few accidental sharp corners it might affect the look and increase the time it takes to cut. The V Carve program usually does a pretty good job and beginners will usually be happy with the default results, but you might look for a few and try to smooth them out using the node editing tools.
Tool Paths
I decided to use a 60° V cutting bit to get a steeper angle on the pocket. I wanted to limit the depth to 1/4". I used a 1/4" diameter flat area clearance bit. I setup the tool's depth per pass to cut in one pass.
The selection of a large area clearance tool size is based on the size of the large areas. If you choose a large diameter, it will only fit in the largest areas and the V bit will have to make a lot of small moves to clear out the smaller areas. A smaller clearance bit will be able to get into more areas, but it will take a longer time in the large areas. See the image below of the V bit tool path. As the areas get thinner than the clearance bit, you can see the work the V bit has to do. The distance between v bit moves in this mode is adjustable, but I accepted the default of 0.01 inch for this project.
Preview
V Carve can give you a pretty good preview of the results.
Results
I was very happy with the results. The material cut great. The deep depth of the cutting gives a a really rich look.
Tips
- If you are using a spiral bit with HDPE, try to ramp it into the material. The material is a lot less likely to climb up the bit
- The corners come to a sharp point at the top of the work. In the case of two color HDPE this will happen above the color change. You might want to set Z zero as the top of the white if you have a lot of fine details. With that said, I did not do that on this job and it looked fine.