Parametric Surface Decoration for Double Curvature Ceramic Pieces

My goal for this project was to 3D scan ceramics to explore the types of decoration techniques that computational design and digital fabrication can play a part in, and create a set of pieces that demonstrate the possibilities in this space.

Supplies

Materials:

Clay
Underglaze
Vinyl
Paper

Software:

PolyCam - 3D Scanning App for photogrammetry
Fusion 360
Product Design Extension
Adobe Illustrator
Vinyl Cutter Software

Hardware/Digital Fabrication Tools:

Camera/Phone (for photogrammetry)
Vinyl Cutter
Tweezers or exacto knife helpful.
Laser Cutter

Ceramics Tools:

Pottery Wheel
Ceramics tools (for carving, smoothing, throwing/trimming)
Kiln

Step 1: Inspiration + Goals

For this project I want to experiment with augmenting thrown pottery using parametrically designed stencils. The modifications I want to explore are

1) glaze application

2) etching/carving

3) slip application

and will all rely on vinyl cut stencils to translate the digital design to ceramic surface.

I was inspired primarily by artist Kenny Sing: Turn Studio | Ceramics by Kenny , Sing Kenny Sing (@turn.studio) • Instagram photos and videos, who designs, stencils, and glazes/carves patterned ceramic vessels.

I plan to first create thrown pottery vessels, then scan them to create digital clones using 3d scanning technology. I wanted to then extract the surface/profile curves (ex. inside for wide bowls, outside for vases/cups) and divide it into flat sections that can be fabricated by a vinyl cutter into stencils.

My goal was to create a replicable workflow in fusion 360 for translating 3d scanned objects with varying levels of curvature into representative surface segments that can be unwrapped to flat patterns. I would further like to explore developing this workflow into an automated plugin for the software that can minimize the technical + frustrating portions of the process and allow focus on the pattern creation.

Step 2: 3D Scanning (Research/Experimentation)

I looked into mesh/solid body modeling capabilities of Rhino and Fusion 360 for translating a 3d scan capture into a solid that I could then 'extract' a surface from. I found that Fusion 360 supports some modes of mesh translation to solid body, so from there determined I wanted a 3d scanning application that would produce a mesh object representation (as opposed to point cloud or scene capture).

I started by testing out a variety of 3d scanners, specifically PolyCam, Scaniverse, and KIRI engine and compared modes: lidar vs. photogrammetry. While I initially considered using more robust/professional grade 3d scanning technology, I decided a phone application would be more ideal to support creators without need for additional equipment or transport of clay vessels.

PolyCam gave me the best scan by supporting object masking from photogrammetry, which I also liked for simplicity/ease of use over lidar. It also allowed me to control detail level of image processing, for which I found 'optimized' produced the smoothest model. The main requirement for mesh objects needed to translate mesh to solid bodies in fusion 360 is that it doesn't have holes, which are often created due to lighting conditions and glare.

Step 3: 3D Scanning Ceramics

The biggest issue I faced when testing my workflow on ceramic vessels was that 3d scanners struggled to recognize the texture/appearance of white clay. Due to this, I ended up testing all the 3d scanning applications again in both modes: lidar and photogrammetry for ceramics. The issue was persistent causing me to think it may be due to the material lightness + smoothness despite being scanned/photographed against dark backgrounds, as many scans didn't process and the ones that did were full of holes and couldn't support object masking.

My solution ended up being applying tape in a grid like pattern across the surface of each piece, allowing the processing software to recognize the curves/contours of the vessels and fixing the issue.

Other considerations at this stage were to apply dark underglaze across the vessel surfaces (drastic solution) or project a grid onto the surface while 3d scanning.

Step 4: Mesh Capture → Solid Body

To translate the mesh capture to a solid body, I went through a series of mesh manipulations that were mostly standardized across mesh captures I took with similar parameters, and which are described below.

Mesh → surface

Make sure mesh has no holes in the sides of the piece
There will probably be a mesh hole on the bottom of the bottom surface, which cannot be scanned as it's resting on the ground/surface.
That is an acceptable hole and can by quickly fixed in this stage by performing a "repair holes" manipulation on the mesh.
The mesh can then be repaired and re-meshed with ~80% shape preservation and ~70% density to create a more uniform and smooth mesh representation that will be easier/more successful to represent as a solid body.
Reduce mesh to minimize triangle count for conversion (if this step isn't done the mesh can easily contain 1000+ triangles and the conversion will cause the program to crash)
Mesh → surface conversion (settings: organic, fast)
This step required the installation of the fusion 360 product design extension to allow for organic method of mesh conversion.

Surface → profile

Find center of model (center of mass) and use the move/translate operation to move the body from the center of mass position to the origin position
this is important for obtaining a profile representative of piece
Sketch wedge from the center/origin to past the body radius, extrude this sketch in both directions to split the body

Profile → body

Examine profile and rotate the sketched wedge around the center y axis until an ideal profile is shown
Revolve profile around center to create a new, symmetrical body

If surface segments aren't good:

Body → Mesh (for face simplification) → Body

Tesselate body to recreate mesh
Simplify mesh by re-mesh + reduce
Generate/modify face groups
Mesh → surface (*faceted mode)

Step 5: Flat Surface Representations of Curves

At this stage we can see the profile curve has been segmented into face groups that separate the surface. I wanted to be able to unwrap these surface segments to create a flat pattern that represents the curve surface similarly.

After looking into options for this goal, I found the only solution to be by using sheet metal: Fusion 360 Help | Sheet metal overview | Autodesk. Sheet metal components have specific material and body representation requirements that allow for assumptions that enable flat pattern creation. To transform the solid body object into a sheet metal object I first tried the "convert to sheet metal" operation (on the curve segments faces) that looked a little too good to be true. Sadly it was, as it requires the input face to be a wide, flat area of the body. After looking into options, I had success creating lofted flanges between two profile edges, with the caveat they have to be arcs of the same degree and rotation. To do this, I first constructed planes at the z position of each face edge (highlighted in blue in the fifth picture) and created a sketch on each plane. I next split the body to remove a small slice (arc of degree 1) and projected that slice sketch vertically onto the surfaces to use as reference*. With those two steps done I could sketch arcs of the same degree and position on each plane, again using the face edge/boundary to determine radius. Finally I created lofted flanges between adjacent profile sketches to mimic the curved surfaces. Some comparisons of the original curved surface and flat surface representations are shown above and worked very well.

One important consideration in the above workflow is which side of the vessel you want to represent: interior or exterior. Due to thickness variation, these curves and dimensions will not be the same and neither are the face groups. In the first example I show the inside of the bowl, so those faces are used to create the lofted flanges, and the lofted flange orientation is set to 'side 1' (extruding the material outward). For the second example shown, the exterior of the vase is desired so the outside curve faces are used and the orientation is set to side two (extruding material inward).

*Upon later experimentation I found that the lofted flange just requires an arc profile, not an open arc profile so this step can be skipped. The issues I was having was due to trying to create a lofted flange between two circle profiles which isn't possible, however an arc of degree 360 works fine and is much simpler.

Step 6: Parametric Pattern Design

With the vessel 3d scanned and represented by flat surface curves that can be unwrapped, it was now time for the design stage. To support pattern creation, I created a workflow that sections the area into a number of slices, and replicates the design created in one slice around the piece. I did this by creating a circular pattern rotated around the y-axis and selected the profiles sketched in the original slice. For the design shown above (and for other symmetrical patterns shown in this project) I also created a midpoint construction sketch line constrained to 1/2 the arc length which was used to reflect the design created on one half across the line for a symmetrical slice.

I wanted to support designing patterns for both interiors and exteriors of vessels, so I created two workflows that allow sketching on the xz plane (flat plane - interior) or the xy plane (vertical plane - exterior). In the case of the second workflow, the slice boundaries are sketched on the xz plane and projected along the y-axis to the vessel surface. The design is then similarly rotated around the y axis at plane angles that map to each slice.

The photos above show the sketches rotated then extruded through the surface faces to visualize the resulting design.

Step 7: Emboss Pattern + Unwrap Surfaces

I had hoped the sketches could be extruded through the sheet metal faces to apply the pattern, however that appeared to break some sheet metal rule that prevented the faces from successfully unwrapping as a flat pattern. I looked into different solutions here and ended up going with the 'emboss' feature that supports transferring sketches to curved surfaces. After experimenting with embossing, I switched up my process from the previous step slightly- I embossed the original slice on the faces, then replicated that "feature" through a circular pattern rotated around the y-axis.

I was then able to select each face individually and "unwrap as a flat pattern" which I exported as a .dxf file. The final embossed designs for each piece I created are shown above.

Step 8: Pattern Testing

One slightly frustrating hurdle I encountered at this stage was a scaling issue when importing my .dxf files into other software- in this case Adobe Illustrator. I took the measurements of my design in fusion 360 and used them as a reference to rescale my design in AI which was typically off by a factor of around 0.9.

To test these patterns before vinyl cutting, I laser cut my patterns in paper and applied them to my pieces as a less time consuming and cheaper alternative for iteration. Aside from the scaling issue and slight variations from pieces drying and shrinking out, the patterns fit pretty well and didn't require adjustment which was a huge success for me.

Step 9: Pattern Fabrication

I next fabricated my patterns with the vinyl cutter. I imported my designs into adobe illustrator and set the line color to RGB red and line thickness to 0.05. I consolidated designs to waste less space and exported them to the vinyl cutter software.

Vinyl Cutter Troubleshooting: I initially had issues cutting all the way through the vinyl which I solved by increasing the cut power from 1 to 2. I also had some issues with the vinyl slipping so made sure the vinyl was loaded evenly each time and also tried to print designs so the long lines were not perpendicular to the cutter (the fast unraveling of the vinyl spool and passing it back though sometimes increased shifting). My last issue was the software interpreting my lines in a strange way, which I fixed by ungrouping all patterns thoroughly so there were no spline groups, only lines, and then joining adjacent lines.

Once fabricated, I cut the patterns down to their rough shape and peeled off the negative space (where the design would be shown) using an exacto knife.

Step 10: Pattern Application

With my patterns ready to be applied, I backed them on transfer tape to maintain the integrity of the shape as well as keep any floating pieces in place. The transfer tape gets applied to the non-sticky side of the vinyl while the backing is still on, allowing the backing to be peeled off to reveal the sticky side. At this stage I also cut the transfer tape down to size and further cut inward along the opening of the arc. This allowed me to join the edges and mimic the resulting shape, aiding in the application process. I also used some test pieces that had been cut in paper as guidelines for placement which proved very helpful, as seen in my wide bowl application process.

Finally I removed the vinyl backing as I pressed the vinyl on the clay form and rotated the piece. I pressed the vinyl and clay together with my fingers and pinched an excess vinyl together when necessary to minorly adjust the shape. I slightly overlapped the vinyl on my vase and bowl, helping it stick better as it adhered to itself significantly better than to the clay. I attempted to heat shrink the pattern at one point to the piece however this didn't make a noticeable difference. The vinyl didn't stick great to the vessels, which inspired me to look into other solutions for vinyl and application. While unfortunately out of scope for this project, I plan to explore this further.

Step 11: Surface Decoration: Glaze, Carving/etching, Slip

Finally I applied my chosen surface decorations using these stencils.

Glaze: For the bowl and vase I chose to apply underglaze over the stencil, applying several coats and waiting for each to dry in between, before removing the vinyl. I cleaned up some edges that bled by simply scraping the underglaze off, and went over some of the lines again.

Slip: For the top of the lantern I applied several coats of slip, let it dry slightly, then removed the vinyl. This created a raised effect with the clay that I really enjoyed.

Carving/etching: For the lantern base I used the stencil as a guide to carve out sections leaving three symmetrical 'legs' behind. I etched the flowers into the surface, tracing the edge of the stencil with a needle tool before going over it with a pencil to create a more defined and smooth line. For the lantern side I used circular hole cutting tools to cut out the stencil pattern, taking some creative liberties with the bottom row. Once carved, I removed the stencils and clay debris and smoothed with a wet sponge and paintbrush.