• Shelby McAuliffe

Barrel Cactus in Layers

Foam Barrel Cactus

This project is my first attempt to work with a 3D object within Rhino 6. The project will utilize a CNC router machine to carve a 3 dimensional object.

I used the polygon curve to create a 20 point start shape. After creating my initial shape with a star curve I copied and scaled each to act as the bottom, center and top of my closed surface. I lofted the three different sized star shapes to create the solid form pictured above. After closing the surface I used a bounding box and extracted the curve wire frame.

I used the divide tool to split one of the side curves into 4 sections. (seen above with 5 white points on the left of the bounding box)

Once I divided the height curve of the bounding box, I used perpendicular and near to draw a straight line across the bounding box. This allowed me to split the 3D surface into 4 pieces to allow for cutting and layering my object.

To keep the holes in even placement, I needed to add a 1/4" cylinder at the height of the object before splitting the object and moving the pieces. I used boolean difference to remove the space from the center of the object and create holes. This was an extra step as all I needed was to divide, split and extract the curves of the base of the cylinder piece for the dowels. When the software reads the curves as only circles, it can be told to just drill a hole.

Once I split my 3D object into 4 pieces, I used the cap function to make each piece a solid poly surface. Due to the center pieces in the middle object, I had to decide if I wanted the machine to cut these out of not. I decided since this will be the center of my object, I will not need to cut the holes and left the cap on top and bottom of the middle pieces as solid poly surfaces.

I labeled each piece with annotation dots on a different layer, the grouped each of the pieces together with their annotation dot.

Once I had each of these piece split, I realized the bottom layer 2 had some parts where it would be under cut. The CNC router I will be using, does not allow for more than 3 axis cuts. There for I needed to find the mid point on the bottom layer 2 where the piece begins to under cut and split this piece into two. (Under cut is referring to when the object is being cut it begins to curve under on the Z plane)

After setting up my file with a cut 3D object, the next step is to extract the curve layers for the bottom of each piece as the CNC router will only cut flat surfaces. This becomes the base for the objects and the we offset the curves 1/2" (the size of the bit) to allow for the CNC to cut around the object and not in. This maintains the proportions and dimensions allocated in Rhino for the material being used. Drill holes are made for dowels to be slid into the object to piece everything together.

With some assistance, as this is the first time I am using the CNC router, Camila was able to help me form tool paths and export the file into the CAM software. We then made a poly surface the size of my foam boards, 24"x 24", we combined this to one large 48" x 48" surface to place each piece of the cactus on top.

We then selected the curves to use and exported this file as an .stl for the CAM software

Then we exported the 3D surfaces as a .dxf file.

Once the files are open in the CAM software, we are able to dictate tool bits, tool paths and functions the CNC router will follow. We are able to include thickness of material, and thickness of each drill bit. Placing the material, zeroing the bits and the wood panel holding the foam is a crucial step in ensuring your project will cut properly. We used double sided tape as an extra piece of material to ensure the foam would not move from the table. Once the machine is ready to run, we turn on the vacuum and ventilation. Once everything has been set, zeroed, and checked again, we press go. The CNC can adjust speed and the first function was to drill the holes for the dowels, due to the material being foam, we were able to use a fast speed, harder materials should allow for slower drill speeds.

Acrylic Needles

After I began cutting with the CNC router, I made the design to cut needles out of acrylic. This part of the project will utilize the laser cutter, as this is a 2 axis cut.

I began by creating a 10 point star in Rhino using polygon function.

I created 1/8" notches to allow two pieces of the needles to slide into each other. (1/8" is the thickness of my material)

Once I had my needles cut and my pieces ready to glue together, I had to test some glue materials. I have some epoxy 6000 in my studio, I thought I would test this on my material.

I came to realize that the E6000 was a bonding agent and melted the foam. I would not recommend this unless your intent is to melt your material. (Always test your adhesive first with new materials)

Back to the drawing board.

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@ 2020 All photographs by Shelby McAuliffe 

Prints available upon request

Boulder, Colorado Artist

Available for travel worldwide