CNC Milled Texture mats
Inspiration and Experimentation
I was inspired by teaching ceramics online in 2020 to create new work using the handbuilding methods I taught the students via the internet. This work was to be decorated with raised designs that wrapped fully around each slab-built piece. At first, I created cuneiform style roller stamps. These large cylinders took hours to create and didn’t allow for the quick refining of ideas. I then came up with a way to carve my designs into unmounted linoleum using a CNC milling machine
Hand carved roller stamp and early versions of the darted mug texture mat leading to final version.
The CNC milling machine can precisely carve my intricate designs into linoleum quickly, allowing me to easily revise my designs when needed. A CNC (Computerized Numerical Control) milling machine is a router on a series of motorized rails that can be programmed to cut a variety of materials. A very user-friendly milling machine is the X-Carve and is available at a MakerSpace near me. A MakerSpace is a place where members are able to use a variety of tools and machines for a monthly fee. Each MakerSpace is very unique and some may not have the machine that I use. The MakerSpace I work at, Fox.Build, is located in St. Charles, IL and the membership is $60 a month.
Darted mug texture mat being carved by the CNC milling machine
After learning the machine, testing different linoleums, trying several bits and cut settings, I developed a process that works well. However, this article should be viewed as a primer to the process of milling your own texture mats. Use my process as a starting point for your own learning and experimentation. This tutorial assumes you have some experience with vector graphics and the X-Carve milling machine. If this is not the case look at the following links to learn more about vector graphics, Easel and Inkscape.
Materials and Settings
Texture mat material: Blick Battleship gray unmounted linoleum. I found the Battleship gray held up better and carved cleaner than the tan Speedball linoleum.
Tool bit: A tapered bit is necessary to give your carving the draft needed for it to release from the clay. I use a very steep 6.2° angled bit to get the look I want to achieve. You may find a bit with a wider angle may work better for you. I also use a very fine tipped bit to get the level of detail I want. A wider bit will carve faster but gives less detail. I use a 1/32" tapered ball nose spiral router bit with a 1/4" Shank. It is an up-cut bit with three flutes. It is a Yonico 37310-SC.
Depth: I cut to a depth of 2mm. Sometimes, I accidentally cut too deep because there is some variance to the thickness of the linoleum. Experiment with a depth that works best for your design and materials.
Feed rate: 1400mm/min
Plunge rate: 700mm/min
Depth per pass: 0.7mm
These settings control how fast the router travels across the material. These settings work well for the bit I use. Depending on your bit or design, you may need to adjust these settings accordingly.
Close up view of the carving, note the ‘V’ shape of the cut.
Preparing the Graphic
The design must be a vector graphic which means it is created using points, lines, curves and shapes that are based on mathematical formulas instead of being created using individual pixels like most digital images. InkScape is a free vector drawing software that I use. The simplest way to get your design converted into a vector graphic is to have the software trace it for you. You can also use the vector drawing tools within the software to draw your design.
Closed paths of the example vector image. Click here to download this example svg.
Whichever method you use, the important thing to remember is that the design must be made of closed paths and not open strokes. The CNC milling machine will not understand the line width of your drawing strokes, objects or text. It needs only the outline of your design. So convert any strokes, objects or text into paths. Once you have your design as closed paths save it as an svg (scaleable vector graphic) and import it into Easel, the milling machine’s software.
Milling the texture mat
The X-Carve uses a free, web-based, software called Easel to convert your design into the machine code the milling machine understands. Using Easel, import your svg into the workspace. Click on the design being sure to have all parts of the design selected, then click the shape tab in the popup window. In the Position section, click the center circle and set the coordinates to 0,0. This will tell the machine to cut the design in the center of your linoleum. In the same pop-up, click the cut tab, set your desired cut depth and select ‘clear a pocket’ in the cut path drop-down menu. This tells the machine to cut away all the material inside the closed paths of your design at the selected depth.
Settings for the ‘Shape’ and ‘Cut’ tabs in the design setting pop-up window in Easel.
Now prepare your linoleum in one of two ways. You can cut it so there will be approximately a one inch border around your design, or if you want your texture to go to the edge of your mat, cut it to the size of your design. After cutting it to size, draw lines through the center. Take note that larger carvings near the edge of the linoleum can crack the linoleum. Leaving a border will give the mat more strength. Secure the linoleum to a very flat piece of wood using double-sided carpet tape. I use 3/4 inch MDF wood as it is very flat and smooth. Be sure the linoleum is square to the edges of the wood. Take note of the size of the linoleum and the thickness of the wood and the linoleum combined.
Apply carpet tape to wood and press linoleum firmly into place, making sure it is square to the wood.
Cut linoleum to size, mark center and note the size.
Clamp the wood down to the X-Carve platform making sure it is square to the printed grid on the platform. Be sure the clamps are clear of the tool path. You can preview the tool path on Easel. Next, enter the size of the linoleum and the thickness, you noted earlier, into the materials settings on Easel.
Secure wood to the X-Carve table aligned with the grid.
‘Material Settings’ and ‘Cut Settings’ drop-down menus in Easel.
Double check your settings and press the ‘Carve’ button. Follow the prompts and position the tip of the router bit at the center of the linoleum. Raise and lower the bit until a piece of paper barely slips out from under the bit. Be sure to set the ‘Home Position’ to the current position of the bit. This is very important to ensure the correct position and depth of the carving on the linoleum.
Left: Align tip of the bit to center of the linoleum. Right: Move the bit up and down until a piece of paper barely slides out from under it.
The example design being carved by the X-Carve Milling Machine.
After carving the linoleum, clean out any debris with a toothbrush and vacuum. Carefully peel the mat off the wood from all four corners. If you carved lots of material, the mat can be fragile. I apply duct tape to the backside of the mat to add some strength.
Using the Mat and Beyond
With some experimentation, any type of slab roller can work with the texture mat. Even using a rolling pin, with some flat sticks on either side of the slab to control thickness can work well. If you have trouble with the clay sticking to the mat, use a cooking oil spray on the mat as a release agent. The oil also helps the mat last longer as the clay will begin to dry out the linoleum which causes it to crack easily. The cracks will show in the impression which can be undesirable depending on your design. If the clay is not tacky and the texture mat design is open enough, a release agent may not be necessary.
Completed texture mat and clay slab ready for the impression.
I use a clay slab that is larger than the texture mat. I find this helps to ensure an even pressure across the whole texture mat. The slab is also thicker than what I want in the end. This initial thickness will take some trial and error to determine. With the texture mat on top of the clay, roll the texture mat and clay through the slab roller, pressing the mat into the clay. Next, carefully peel the texture mat from the clay starting from one corner. I find peeling it half way from each side can help it release more cleanly. Use your newly textured slab to create your desired piece.
Peeling the texture mat from the clay.
Cylinder made with textured slab.
I create mats specifically for each vessel that I am creating which allows the texture to interact with the shape. I also include cutting lines in the design of the mat to ensure the slab is cut the same size every time. I sometimes include the lines for darting the form. The design can even follow arc shapes to create tapered forms. Creating and refining these very specific details into bespoke texture mats can take a great deal of time. However, once complete, the mats will allow uniquely textured, slab-built, forms to be created quickly and uniformly.
Set of conical slab mats for a pitcher.