Milling materials like rubber and linoleum can be an interesting experience. Due to the elastic properties of these materials, some of the material will compress rather than being cut away by the bit or endmill the CNC is using. Getting the right feeds and speeds took a little bit of time and patience to get good results. For this particular project, we used a v-bit and F-engrave‘s v carving feature to create the negative image of the stamp.
The first step is to create a design. We used Inkscape to draw a black and white image. When we bring the image into F-engrave, the program will use the v-bit to carve all the profiles which are black and leave the white areas alone. Choose the v-bit you have and adjust the feeds and speeds for your project. A tutorial on using the v carve feature can be found here: http://www.scorchworks.com/Fengrave/F-engrave_tutorial.htm.
Next, we secure the linoleum with a bit of hot glue and let the Mill One do the rest of the work. After milling, a little bit of post processing, namely getting excess material out of the cuts, was needed. A small screwdriver or other tool works well in scraping out the material.
Here are the feeds/speeds:
V engraving at 2mm max DOC
1/8″ 20 degree v bit
28 minute engraving time
1/4″ 2 flute upcut router bit
8 minute milling time
We carved a quick block of wood to make a holder for the linoleum. Having a block which holds the linoleum is good because you want to be able to provide even pressure across the whole stamp, as well as keep your hands away from the ink. We pushed the depth of cut to 5mm, and the Mill One carved it out quite quickly.
The rest of the stamp came together pretty easily. The linoleum fit perfectly into the holder and no glue or adhesive was needed.
In conclusion, it was a pretty easy process to create a custom stamp. Next time however, we may try a harder rubber material, since it would be easier to mill.