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CarouShell CrittersDesign Document

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Table of ContentsSan Diego Circle of Regional Effigies 3CarouShell Critters ID 3Stripper Poles 3Summary of the Overall Process 43D Modeling - Establishing the Process 53D Modeling - Establishing the Process (continued) 63D Modeling - Scanning the Turtle 7What Happened Next in 3D, or Wow This Shit’s Hard 9Floor Plan 10First Published Model 10Creating Cut Files - Initial Difficulties 11Creating Cut Files - The Saga of Slicing a Turtle with a Rhino 12Creating Cut Files - Back to Cut3D 15Creating Cut Files - Hand Finishing Stair-Steppy Edges? 16Creating Cut Files - Creating Vector Drawings from 123D Make 18Creating Cut Files - Editing 19CNC Cutting - Edit and Cut Log 20CNC Cutting - How the Board is Laid Down on the CNC 21CNC Cutting - How the Board is Cut 22Assembly - Art Center 243D Modeling and Cut Files - The Dolphin 26Second Published Model 273D Modeling - The Yellowtail 28Creating Cut Files - The Yellowtail 293D Modeling with 123D Catch 30Third Published Model 33Using an Existing Model 333D Modeling - Selecting The Shark 33Creating Cut Files - The Shark 343D Modeling - The Seahorse 35Creating Cut Files - The Seahorse 37Sheets and Parts Required Per Critter 37Visual Impact - Bounding Box Volume as Independent Variable 38Assembly - The General Idea 39Turtle - Critique, Challenges, Problems, Solutions 40Dolphin - Critique, Challenges, Problems, Solutions 41Yellowtail - Critique, Challenges, Problems, Solutions 42Seahorse - Critique, Challenges, Problems, Solutions 43Shark - Critique, Challenges, Problems, Solutions 44

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CarouShell is San Diego’s 2012 entry for the Burning Man Circle of Regional Effigies (CORE). It is a combination of a shell-like carou-sel with a stationary observation tower. The platform rises about two feet above the playa level, and is free to rotate on hidden wheels. Carousel animals are lo-cated between the platform and a virtual ceiling, which is open to the space above. The ceiling level is visually defined by decorative panels around the perimeter. The space above the ceiling is defined by a textile spiral that evokes the shape of a seashell. Within the spiral are found wind vanes which we hope will enable the carousel to turn itself. Also within

the spiral are hanging various mobiles and mechanical contrap-tions. All of this rotates with the platform.

The central tower is fixed to the playa and does not rotate. It is an eight-sided prism. It is fully sheathed with plywood except for door-sized openings in four of the sides at

platform level. The interior sheath is solid (I’m assuming that any slots intended to create a flame vortex will be blocked off until burn prep). The exterior sheath has cutouts in patterns evoking a kelp forest, from ceiling level to just below handrail level. A ladder

runs from the center of the tower at platform level to the side of the tower near handrail level, pro-viding access to an upper deck through a hole in the deck.

San Diego Circle of Regional Effigies

CarouShell Critters ID

The following critters were selected at meetings held over the past year.

SharkSurfboardSeahorseDolphinSea TurtleYellowtail

This is the current list of critters that are intended to be produced full size in wood for the project. However, 3D software models of many other creatures, and variations on these creatures, will be produced in the process. All of the 3D models will be shared as open source models.

Stripper Poles

Critters Last updated 08 July 2012

by Abraxas3d, MustBeArt

An initial vision of CarouShell

Iacta alea est! Ars gratia artis, ars brevis, vita brevis.CarouShell ad finem, ad extremum, ad infinitum.Fortes fortuna iuvat.

Stripper poles are incorporated in order to provide pole dancing amusement. In the United States, stripper poles are generally 2” in diameter1.

The pole needs to be fastened at the floor and at the ceiling for stability. Poles are usually made of hollow steel or brass tubes. We recommend brass in order to coordinate with the brass ring carousel concept.

4” of clearance around the pole is desired as an ideal for safety. 1 http://en.wikipedia.org/wiki/Pole_dance

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3D Modeling of the critters was done with a Kinect, a laptop PC, and software. Modeling began with either scanning or photography of real-life objects. Point clouds captured by the infrared project/camera of the Kinect or from photographic analysis were converted into mesh models. These mesh models were edited into “watertight” models and then sliced into vector cut maps for plywood on the CNC router. Critter Team used MakerPlace, a membership-based

commercial establishment, for the CNC routing of the plywood panels. Routed pieces were held in place in the plywood with tabs.

Each piece was marked as to the

critter and layer it belongs to. Critters were formed by layering the slices back together in order.

Routed panels and/or individual cut pieces were delivered to the build site at The Art Place in San Marcos to be lamintated together and finished.

Critters were intended to be suspended with rope bondage from the superstructure of the CarouShell.

Summary of the Overall Process

For more information visithttps://www.facebook.com/pages/Sol-Diego-San-Diegos-CORE-Project/349121351814899

See our effigy at Burning Man 2012.

CNC Router at MakerPlace San Diego

Process flow diagram

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3D Modeling - Establishing the Process

Two tool set explorations were required to refine the 3d model production process. The second exploration was more successful than the first, and resulted in the definition of a satisfactory 3D modeling process.

The Kinect was chosen as the camera for capturing 3D model information for two reasons. I wanted one for gaming, and it’s become established as as a prevalent front-end for 3D printing in the Maker community.

A Kinect was ordered from Amazon 28 April 2012 at a cost of $144.99. Below is a screen capture of Kinect first light.

The projector and camera were operational, and depth data was captured. The Kinect works by projecting a grid of infrared dots. The dots are read by an infrared camera, and provide depth information similar to radar or sonar. A color camera captures visible light images. In the screen capture, both types of camera images are visible with the depth map on the left and the color camera image on the right.

Spatial sound with multiple microphones as well as motor drive to orient the camera assembly are additional (unused for CarouShell) features of the Kinect.

The first exploration was with the Kinect connected to a laptop PC running Processing with the Modelbuilder library installed. Both Processing and Modelbuilder were free. OpenNI drivers provided the interface between the Kinect hardware and the PC software. OpenNI drivers were also free.

This configuration of software produced a mesh map of the

object’s view being scanned by the Kinect. This step was similar to producing a still photograph.

These mesh maps were opened in Meshlab, a free and open source

3d modeling software package. The various views of the objects scanned were merged using Meshlab.

While the resulting model appeared as expected, the number of errors and discontinuities in the composite

model was very high, and the process was very tedious.

The second exploration was with the Kinect connected to a laptop PC running ReconstructMe. Microsoft Kinect Runtime 1.0 drivers provided the interface between the Kinect hardware and the PC software. (continued)



Kinect first light

Processing with Modelbuilder library

Meshlab

Model completed using first exploration

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3D Modeling - Establishing the Process (continued)

This configuration produced superior 3d models. The Kinect was moved around the object, and painted the infrared dots on the surfaces, building a model as the infrared light was passed over the surface. Upon program exit, the model was saved as an .stl format mesh map. This mesh map was opened in Meshlab for editing. The fundamental difference between ReconstructMe and Processing/Modelbuilder is that ReconstructMe did not require stitching together multiple photographic views of the object. Instead, it produced a mesh

model from a process more like making a video than taking multiple still photographs. The mesh models produced by ReconstructMe required editing in order to be useful for our purposes. There is a difference between models that are produced for visualization and models that are produced for printing or for cutting. The printed and cut models have to have a surface that is “watertight”, meaning without holes or extraneous edges or floating vertices.

First, manifold (unconnected or incompletely connected) vertices

and edges were eliminated using Meshlab filters. After these were eliminated, holes were then filled using both the Remove Hole filter and the Fill Holes function.

Meshlab was not stable. There were multiple crashes and reboots required to use the software. Two holes refused to be filled, with the program consistently producing a visual C++ runtime error. The holes were filled in a trial version of Rhino 3d modeling software.

With a watertight model produced, the next step was to slice the model.



Resources:http://reconstructme.net/http://processing.org/http://code.google.com/p/codeandform/http://meshlab.sourceforge.net/http://www.xbox.com/kinecthttp://en.wikipedia.org/wiki/3D_modelinghttp://www.shapeways.com/

Non-watertight model completed using the techniques from the second exploration.

Kinect on left scans box on right. Box is on turntable to enable capture of all surfaces.

Watertight model completed using the techniques from the second exploration.

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The first critter modeled was the turtle. George Jemmott shared a photograph of a hollow turtle play sculpture at San Diego Zoo Safari Park. Interactive and attractive, this object seemed perfect to model, build, and ride. The Kinect, PC running ReplicateMe software, and still cameras were brought to the park, the turtle sculptures found, and the scanning commenced on 9 May 2012.

Difficulty was expected with the interior. The interior, however, turned out to be the easier part to scan with the Kinect. The exterior, a shiny fiberglass layer,

was so reflective that it appeared invisible. The infrared dots bounced off in directions that did not include the infrared camera.Therefore, a depth map of the interior was taken with the Kinect, and still images of the turtle were taken and uploaded to a site specializing in creating 3D maps from digital photographs.

The interior maps were taken in several passes. The resulting depth maps had to be aligned to form a single surface, then that surface was prepared using the Poisson surface reconstruction method in MeshLab. This produced a single smooth interior

surface. The exterior model was edited, repaired, and simplified in Rhino.The resulting interior and exterior 3D models were then combined in MeshLab on 11 May 2012.

This was not a complete model, as the task of stitching together the open edges of the holes in the interior and exterior mesh models remained to be done. Surface reconstruction methods close these holes, instead of bridging them. A new methodology was required to successfully bridge the gaps between the borders of the interior and exterior models.

3D Modeling - Scanning the Turtle



At left, the Kinect was held with the IR projector and camera pointed at the interior of the turtle shell. The Kinect was connected to a power supply and

the laptop. The laptop was running ReplicateMe software.

Multiple passes were attempted of the exterior, with little success. Multiple passes of the interior resulted in succesful surface captures.

Above, succesful captures were reviewed on-site in MeshLab.

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This is what all the

interior surfaces

look like when they

are imported into

MeshLab. They

are unaligned and

unedited.

Above, red border indicates unclosed mesh boundaries

After the surfaces

are aligned,

simplified, and

reconstructed,

the turtle shape

emerges.

What Happened Next in 3D, or Wow This Shit’s HardThe interior and exterior surfaces, once they were edited into stand-alone surfaces, had to be positioned correctly. The method used to do this was to import the interior and the exterior into a new MeshLab project. Each of the two surfaces was treated as a distinct layer, similar to Photoshop layers for 2D editing.

Since they came from two very different sources, they were drastically different sizes when first imported. They also had

entirely different orientations. Aligning the interior with the exterior using translation filters in MeshLab took some learning and practice.

The most useful MeshLab filters were:

Rotate in x, y, and z axisMove in x, y, and z axisScale in x, y, and z axis

Another filter, discovered late in the game, snaps a layer to the

closest given axis. Doing this to both layers made the axes independent, and therefore easier to predict and apply.

The layers were merged, and the Poisson surface reconstruction applied to the resulting layer. Experimentation resulted in satisfactory filter settings, where the new surface didn’t close off the holes.

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Final 3D model of the turtle.

Climb inside and be the turtle!

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Floor Plan



Proposed Floor Plan

In early May, we took a crack at sketching out the floor plan for the lower level.

The dotted line indicated the possible positions of the poles that support the upper layer of the CarouShell.

Critters can be placed either along the support pole path, or inboard of it.

First Published Model

The empty turtle shell was uploaded to Thingiverse on 24 May 2012. This was the first published model from the project, and is in the public domain, free for anyone to use.

Find it at the following link.

http://www.thingiverse.com/thing:23699

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Once the 3D model was completed, it was tested. In order to use 3D models in most manufacturing software, models need to be “watertight”. This is almost as it sounds. The model can’t have any holes, nor can it have double edges that meet without really being connected. There are several other errors in mesh models that prevent them from being processed by software. There are a variety of filters and fixes for these errors. MeshLab fixed almost all the holes. Rhino was used to fix the final remaining hole. The model was then watertight, and ready for slicing.

A software program called Cut3D was identified as the right tool for the job. The tutorials were completed on 6 May 2012. The turtle model was imported

and opened in Cut3D on 9 May 2012 (see above image).

Right away, there were two problems. The software didn’t seem to be able to handle hollow objects, and it would not create cut paths for overhangs.

The backup plan was Rhino, 123D Make or Google Sketchup. 123D Make and Google Sketchup create cut paths with discrete steps between layers, and the information between the layers is lost. This makes for a very “stair-steppy” model, which is an outcome we very much wanted to avoid.

The model was reoriented in Cut3D in order to limit overhang (see below).

This did not work because the transitions were not planar. There was no orientation that eliminated overhang. Splitting the model was proposed, but rejected because of the editing limitations in MeshLab.

The model was configured as a dual-sided design, where the cutting planes would come down from the top and up from the bottom. This did not result in an acceptable outcome.

Cut3D was abandoned on 15 May 2012 and Rhino was tried.

Creating Cut Files - Initial Difficulties



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Creating Cut Files - The Saga of Slicing a Turtle with a Rhino

1 June 2012Paul Williamson

Having failed to find fabrication software that knows how to slice up a complex model (one that isn’t convex and has interior holes) and preserve the contours of the edges, I decided to do it “manually” in a general-purpose 3D modeling program.

The input is a mesh model created by Abraxas, named “working turtle”. This represents the shell of a turtle, scanned by a variety of methods from a physical model.

Some research suggests that the 3D modeling program of choice is Rhinoceros (“Rhino”). Rhino has been a Windows-only program for years, but they are now working hard on a Mac version. The Mac version is available for free as a “work in progress” pre-beta, but my brief experience working with it suggests that it’s not ready for serious use yet. The Windows version, on the other hand, is a mature 4.0 product. Rhino is expensive (about $1000 for a basic license) and I’d rather buy a Mac version than a Windows version, but I need to use the mature version now. Luckily the Windows version can be downloaded as a free trial, fully functional but limited to a small number of file saves. By working more carefully than usual and saving only the final result, I can live within that restriction for now.

I’ll keep more careful notes than usual (this document) so I can reproduce the procedure on demand. For narrative convenience, I’ll mostly write as if these are instructions for somebody else to follow. In reality, this is more of a log of my experience.

Launch Rhinoceros 4.0 Evaluation from the desktop icon. Its version is reported as Rhinoceros 4.0 SR9.

At the Startup Template dialog, choose “Small Objects - Inches”File, Openset “Files of type” to Allopen working-turtle.stl

The turtle is at an arbitrary angle to the axes. Our first task is to align it.

In the window where the flat base is most clearly visible (the Right window), choose the Rotate 3D tool and visually pick two points that appear to be on the flat bottom of the mesh, and rotate them to horizontal (holding Shift to snap to axes).

Repeat for an orthogonal view (Front).

Alternate between views and repeat until the model seems well aligned.

It will be even nicer if the turtle is also aligned rotationally. In the Top view, rotate the turtle so it

appears aligned with the axes. Since it’s asymmetrical, this can only be approximate, and is not critical. You should now be able to clearly see through the turtle (in the Right view) and also see the overhangs at the front and rear of the turtle shell (in Front view).

The next task is to set the scale of the model to the desired size. We need the slices to fit nicely on a sheet of plywood, so we want the longest dimension to be a little less than 48 inches. Use the Analyze,Distance tool to determine the current size from front to rear of the turtle. It’s 1734mm, or about 68 inches. We want about 46 inches, or 1168mm. So we need to scale it to 1168/1734 or 0.6734. Use the Transform,Scale tool to apply that scale factor. Remeasure just to be sure.

Now we need to slice up the mesh into slices the thickness of plywood. Half-inch plywood is nominally 31/64 inches thick, or 0.484375. Real plywood is somewhere near that, but we don’t have an actual measurement for our plywood, so we’ll stick with the nominal thickness value. (Later we found that cheap plywood is really 15/32 inches thick, or 0.46875, plus or minus about 0.01 inches.)

We need to construct an array of parallel planar surfaces at that spacing. In our case, we want



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horizontal planes. We don’t care very much about exactly how thick the base is, so we will align the planes so that the top plane is a tiny bit above the highest point on the turtle. This will allow the top slice to be nearly full thickness.

Start by drawing the top plane. Exact dimensions aren’t important, but it should be bigger than the maximum footprint of the turtle mesh. Draw it in the Top view so you can see that. Use the “Rectangular Plane: Corner to Corner” tool. Then in the Front view, move the plane up to just clear the peak of the turtle. Zoom in so you can see it.

Now use the “Rectangular Array” tool in the Front view.Number in X direction = 1Number in Y direction = 100 (too many, but it’s easy to delete extras)Number in Z direction = 1Z spacing = -0.484375” (must specify inches or you get the wrong units)

Z spacing needs to be negative so that the array will be built below the current plane.

This should create a bunch of evenly-spaced planes. They may look raggedy on screen at low magnification, because the screen pixels are big. Zoom in to see that they’re really even.

Press enter to accept.

Select the planes that are below

the turtle and delete them.

Now to slice! Use the “Mesh Split” tool.Select objects to split: click on the turtle and hit enter.Select cutting objects: select all the planes and hit enter.Now wait. This process takes a minute or two because the mesh is so complicated.

We now have slices of mesh! Verify this by clicking on the turtle and noting that only the slice you clicked on gets selected.

We don’t need the planes anymore. Delete them.

Now we need to spread out the slices so we can deal with them separately. Zoom in the Front view far enough that you can easily click on individual slices. Zoom out the Top view so you have room to place them in rows. Now systematically go from bottom to top of the turtle. Select a single slice in the front view, then move it into place in the Top view. You want to end up with rows of slices in a known order. Don’t lose track of which slice is which!

Anomaly. All of the top-shell slices seem to also have a copy of the top slice of the interior surface. Why? Hmm. This will have to be repaired. Later.

I ended up with 67 slices.

If you look at these in the Front view, you can see that they’re

all at different heights. We want them at the same height, so we can slap a plane on top of all of them, and another plane on the bottom of all of them, and cut those two planes up into top and bottom caps for the slices. We’ll be fixing that soon, but first we need to repair these anomalies.

Use the Mesh,Mesh Repair Tools,Split Disjoint Mesh tool and select all the slices that have an extra appendage. It found 11 of them, which are split into 22 meshes: 11 we want to save, and 11 spurious copies of the interior top surface. Select each of the spurious copies and delete them. Whew!

Now we have a bunch of meshes of equal thickness, but the top and bottom slices are a bit thinner. We need to be careful with them. Let’s temporarily group them with their neighbors so that we have only items of all the same thickness. Select the bottom two slices in the Front view and “Align Objects”, Top. Then Edit,Groups,Group. Select the top two slices in the Front view and “Align Objects”, Bottom. Then Edit,Groups,Group. Now we have all the same thickness. We just have to remember to ungroup these guys later.

Now select all the slices in the Front view and “Align Objects”, Bottom. Top would also work, since they’re supposed to be the same thickness. Zoom in and inspect the results. You should see no variation in thickness except



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around the edges where the slices are contoured. Looks good!

Saved.

The next task is to supply each of these mesh slices with a top and a bottom, where the planes split them. We need two planes, one exactly aligned with the top surfaces and one with the bottom.

First, we need to convert the mesh slices into NURBS polysurfaces, because that’s what Rhino knows how to split with. Select everything, then invoke “Polysurface from Mesh”. This leaves the meshes still selected. Choose “Hide Objects” to get them out of the way for now. You should still see all the slices; those are the polysurfaces we just created.

Uh oh. Six of the meshes didn’t get converted. Why? I don’t know, but rebuilding each one by doing a “Reduce Mesh Polygon Count” seems to fix whatever the problem was. Unhide the meshes. Select one that didn’t get converted. Choose “Reduce Mesh Polygon Count” and select a number of polygons just slightly less than it already has. Then select “Polysurface from Mesh” and note that it worked. Repeat for each mesh that didn’t get converted. Select all the meshes (Edit,Select Objects,Polygon Meshes) and hide them again. Whew.

In the Top view, use “Rectangular

Plane: Corner to Corner” to draw a planar surface that spans all the slices. Select everything. In the Front view, “Align Objects”, Bottom. (It will take a moment “Creating rendering meshes”; don’t panic.) We now have a plane aligned with the bottoms of the slices.

With everything still selected, Edit,Groups,Group. This will keep the bottom plane where it belongs while we create the top plane.

In the Top view, draw another planar surface as before. Select everything in the Front view and “Align Objects”, top. Now we should have planes aligned with the top and bottom. Zoom in the Front view to verify. Select the new plane, you should see the selected plane as a line exactly at the top of the slices.

Oops. It’s too high. Why? I found a couple of faces on the polysurfaces that were sticking out. They were on one of the slices I had to do a Reduce Mesh Polygon Count on. Sigh. I had to go back and try a different value in Reduce Mesh Polygon Count for that slice. Fortunately, that solved it.

Ungroup the bottom plane and polysurfaces.

Now we can finally split those planes. Click Split.Select objects to split: choose the two planes and hit enter.Select cutting objects: choose the

polysurfaces and hit enter.Wait. This takes a while.

You should now have both planes cut up into areas: the interiors of closed slices, the tops or bottoms of slices themselves, and the rest of the plane.

Uh oh. Only about half the boundaries were effective at splitting the planes. Perhaps there are tiny mismatches in height that make some of the polysurfaces not intersect the plane. If so, we can try to extend the polysurfaces so that they’re guaranteed to cut the plane.

What’s more, it appears that only one plane was involved in the splitting at all. Did I fail to select both or is there a problem with cutting two planes?

Further investigation reveals there was about .004mm gap between one of the polysurfaces that didn’t cut and the plane. That’s very small. Perhaps it would be enough to just move the planes inward a tiny bit.

Try moving planes in .001” before splitting. Tried and crashed. Try again. Crashed again.

Try with one plane at a time, moved in .001”, and maybe just a few polysurfaces at a time.

OK, progress. But not all the slices split the plane. Why? Pick just one that didn’t work and try to split with it. “Split failed, objects may not intersect or intersections may



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not split object.” Hmm. It sure looks like it does. Maybe there’s something odd about these complicated polysurfaces (created from meshes) that tickles a bug in Rhino. I can’t think of a good workaround right now.

So, let’s try a different approach. Plan B. We’ll try converting the whole mesh to a NURBS polysurface before slicing. Make it a solid. Then split with planes.

Unfortunately, that doesn’t work. The split results in 7028 pieces!

Casting about for another approach, I notice that there’s a “Cap Planar Holes” command in

the Solid menu. Will it work on the polysurfaces of the slices? Go back to the beginning and re-create the polysurface slices. Try the Cap Planar Holes on one of them. It works! Now try it on all the slices. Well. It works on all but the six that wouldn’t convert from mesh to polysurface without being reduced. Interesting!

So I just need a better way to repair those six meshes. Try doing a Rebuild? No, that doesn’t work. Try doing a Weld? Works on one! Doesn’t work on another. Cull Degenerate Mesh Faces? Works on one. Doing it on all 67 faces finds 9 degenerate faces on 6 (!) meshes. Maybe these are

the same six that were causing trouble before? If so, maybe the Cull Degenerate Mesh Faces command is what I should use to fix up the meshes. So start over again, slice up the mesh, run Cull Degenerate Mesh Faces, and convert them into polysurfaces. Hey! This time they all worked! Now we can try Cap Planar Holes on all of them. This takes a while. Waiting, waiting. But it seems to have worked! Now we have a solid model of 67 slices with the proper contours around their edges.

All that’s left is to find a way to fabricate them efficiently.



Creating Cut Files - Back to Cut3D

As soon as the turtle pieces, with contoured sides compliments of Rhino, were ready, Cut3D was re-employed. The purpose of Cut3D is to create three-dimensional cuts. This was expected to almost completely eliminate the “boring” type of material removal (getting to the general shape of the critter), while preservingt the “fun” type of material removal (artistic, corrective, and suspension carving).

A piece was selected at random and rendered in the program. The calculated cut time was disastrously long. It would take approximately 6 weeks to cut the entire turtle. The reason was that Cut3D makes its cuts in a raster motion. It travels along the work

piece as if reading a page. In our case, there are very few “words” on the page, but the “eye” of the endmill travels along every last row and every last column regardless of whether that particular position has something to “read” (cut) or not.

After some research, what was needed for this job was not a raster-cutting program like Cut3D, but what is known as a waterline-cutting program, where the bit follows the contours and doesn’t spend time crossing back and forth in a slow march down the piece.

A suitable trial version of a waterline program was found, but the cut time was not significantly

reduced. Unwilling to purchase another program just to see if the cut time could be reduced, we decided to proceed with plain cuts. Stair steps appeared to be unavoidable in this project.

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Creating Cut Files - Hand Finishing Stair-Steppy Edges?The desire to finish the critter as much as possible on the CNC router was driven by two desires. One, to reduce the amount of work required at the build site, and two, because there was a concern that finishing the edges of the plywood with hand tools would create nothing but splinters.

Then, during research on the Cut3D problems, an article on Make Magazine’s website was found that directly addressed this

concern.

http://blog.makezine.com/2012/05/13/the-four-rocking-horses-of-the-apocalypse/

“Diving right in, first, with artist Carrin Welch’s Four Rocking Horses of The Apocalypse, of which one (Pestilence) is still incomplete. Shown here are War, Famine, and Death. They were built from timber and laminated CNC-machined ply-wood sections, then hand-finished

and painted. Carrin’s website, linked below, has more information about the project, and her Flickr stream has some cool work-in-progress shots.”

Confidence built that the pieces could be hand-finished. Additional photos from Flipside’s work parties (next page) provided more evidence that the laminate could be ground down with good results.

“Heart of War”, from The Four Rocking Horses of the Apocalypse by Carrin Welch

pieces of “Famine”, from The Four Rocking Horses of the Apocalypse by Carrin Welch

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Above, pieces of “Death”, from The Four Rocking Horses of the Apocalypse by Carrin Welch

Above, pieces of “Death”, from The Four Rocking Horses of the Apocalypse by Carrin Welch

Below, work party photo from Burning Flipside’s Design and Fabrication Team

https://www.facebook.com/pages/DaFT-2012/366100670091318

Above, work party photo from Burning Flipside’s Design and Fabrication Team

https://www.facebook.com/pages/DaFT-2012/366100670091318

Carrin writes, “I used a Dremel on the first two, “Famine” and “War”. But I used a combination of chisels, Dremels, and a die grinder with rotary wheels on “Death”, so it is way more sculpted.”

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Creating Cut Files - Creating Vector Drawings from 123D MakeWe settled on using 123D Make, a free cloud-based program from Autodesk, to create the slices. Each slice is like a single pancake in a stack of pancakes. When put all together, the slices make a larger shape.

We developed a custom configuration for 123D Make for a full sheet of plywood. The default materials in 123D Make are intended for smaller desktop projects. Therefore, common paper and cardboard sizes are offered.

Our full sheet of plywood configuration consisted of the following items.

• 0.46875 inches thick• 96 inches long• 48 inches wide• 0.5 inches kerf

Once this configuration was set up, it was a simple matter to select it after importing a 3D model.

123D Make appears to select the cut angle that minimizes the number of parts. This doesn’t necessarily minimize the number of sheets, and vice versa. For an example of how dramatic a difference the cut angle can make in terms of parts count and sheet count, look at the images below.

Once the cut angle is set, you can choose to make the solid body hollow, to save weight. There are other options called thicken (“Thicken your model interactively to make thin parts more manufacturable or to give your model a more cartoony look.”) and shrinkwrap (“Great for closing models that have holes or very fine details.”), but they were not used on this project.

At left, the angle of the slices has been moved around by grabbing the slice angle handle (the blue dot at the tail of

the righthand shark half) and moving it around. This is done by left-clicking on the mouse, and moving it around while

watching the sheet count change. The process was stopped when the minimum number of boards of plywood was found.

This is an experimental and not an algorithmic process. We noticed that when the cut angle function is started, the

program picks the cut angle that results in the smallest num-ber of parts required. This may not be the smallest number

of boards, but compare the two images on this page and decide which one you’d rather build. The extra three sheets of

plywood may be well worth buying.

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Creating Cut Files - Editing



Below left is one of the two processes used for creating the vector-based cut files. Below right is an *.eps cut file from the Turtle.

Note the black

piece in the *.eps

file. This is a leaf of

kelp. Decorative kelp

leaves and fishes

were added to the

empty space on the

layouts.

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CNC Cutting - Edit and Cut Log



This page: Cut log for the Turtle. MakerPlace has site licenses for VCarvePro and Corel Draw, both of which were highly useful in editing the vector-based cut paths and producing the machine control files.

Vector-based cut file editing began 7 June. Cutting began on 11 June. There was one wave of re-edits due to a necessary change in the profile cuts. A misalignment of the turtle_15 sheet on 8 June resulted in a recut for part number 18. A recut sheet populated with additional kelp was created and cut on 13 June.

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CNC Cutting - How the Board is Laid Down on the CNC



A small number of plywood panels were purchased independently of the project budget in order to experiment.

A panel of plywood was laid down on the bed of the machine. The surface that the plywood contacts is called the spoil board, and is a thick piece of medium density fiber (MDF) board. In general, when you are cutting through a board, you allow the bit to go slightly below the board in order to ensure that the work is cut all the way through cleanly. In other words, a spoil board is slightly cut into with every pass of the bit. Over time, it has to be resurfaced.

Below that is a wooden base with a multiplicity of holes in it. This is the main bed of the machine and is what the spoil board is protecting. You do not want to cut into this. The base is divided into sections, and these sections are outlined with a rubber seal.

Each of these sealed sections has a larger hole in the center that leads to a vacuum system. When the vacuum is turned on, the air is sucked into the holes, pulled through the MDF, and pulling down on the plywood and locking it into place.

The vacuum system sometimes does not pull enough air to hold the board down throughout the entire cutting process. The system has three known problems. When the spoil board is worn, when the compressor on the roof acts up, and when the seals on the hoses below the table wiggle free or develop a leak. The vacuum system has to work harder with cheap, warped plywood. And, that is exactly the sort of plywood we were working with.

In order to assist the vacuum system, brass screws are installed. They go through the plywood, into the MDF. Brass is chosen because it is soft, and in case the

bit hits it, it won’t destroy the bit. It’s of course better to put the screws in places you are almost sure that you will not hit, as we found out when we hit one by accident. This lead to the files being redesigned to allow for a one inch margin all around the board, in order to allow for brass screws at the edges to help hold the board down. Once the board is down on the CNC machine, the bit is installed, the control computer turned on, control software started, the CNC machine is turned on, warmed up, mechanical limits checked, and the three coordinates of control “zeroed out”.

This means that you tell the machine where it’s origin is. The origin of your work and the origin of the machine need to be as close to the same as possible. Being off by a few millimeters is noncritical when you have avoided the outer inch all along a full sheet of plywood.

At left, Michael assists with plywood storage at MakerPlace. Above, spoil board surface after cutting. The deeper cuts are from a bit slipping, and digging down into the spoil board at a greater

depth than intended.

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CNC Cutting - How the Board is CutAfter the board is placed and the machine prepared, the *.nc file is loaded into the control software.

An *.nc file consists of lines of text. Each line of text is a command in a language called “g code”. These commands are, essentially, “Move here. Now move here. Now move here. Speed up. Lift higher. Move over there”. All of these motions are done while the bit is spinning at a high rate of speed, therefore cutting along the paths designated by the lines of text.

Wherever there were vectors in the vector-based cut files, there are lines of motion in three dimensions, coordinated to the dimensional space of the machine. This is how the vector drawings are translated into CNC machine motion.

It’s good practice to simulate the cut paths at several stages of the process. VCarve Pro, where the profile cut paths are edited, has a preview function that cuts a virtual board. If it doesn’t look right in the software, then it won’t look right on the table. After the previews look like what’s intended, then the software simulation at the table provides another layer of assurance that once the bit spins up to 12000 RPM, it won’t plunge through the table, wrecking itself on the bed, or wander off the edge of the board and wipe out a clamp1.1 We destroyed a clamp during resurfacing of the spoil board. The 1-inch bit and vacuum hood (for dust collection) crashed into an unused clamp off to the side of

The software simulation draws on the screen what it thinks you want to cut, showing the outline of the table. While in simulation mode, you cannot start the machine. Once the simulation is checked, the simulation mode is ended, and you hit “play”. The machine starts cutting.

At this point, several things can go wrong. The board can slip. The bit can slip (see photo previous page). Early on in the process, we failed to run through the mechanical limits in the setup procedure, and the machine faulted becasue it tried to go past its mechanical limits. We had to read the manual to figure out how to clear the flag and restart the machine.

the board. Because resurfacing travels much farther afield than the cuts, we didn’t realize it was a problem until it broke something.

Our one consistent problem was with the warped boards “popping” up and leaving a gap in the middle. This proved to be a problem. When the board rises up, the tabs, which are one-inch sections of wood deliberatly left in various points along the cut path to hold the piece steady, are then sliced through. At the point when a piece completes, the bit

can grab it and wrench it out of its hole, or fling it at your head. Flat (i.e. expensive) plywood does not pop up like this.

There are ways to stop the machine. There is an emergency stop, which shuts everything down. There is pause, which simply stops the machine right where it is. There is stop, which is similar to pause except that the bit is raised up away from the work.

Resume returns to the place where the machine was paused or stopped. Stopping, and then

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resuming, allows you to address any safety issues with the boards popping or slipping. Usually, another one or two brass screws were all that were needed.

Once the panel is finished, the machine moves the bit out of

the way, and the pieces on the board can be labelled. Each piece has a number. Without these numbers, it’s difficult to put them back in order. Many pieces look very similar to other pieces, and getting them upside down is easy to do.

After labelling, the board can be released from the vacuum and/or screws. The next step is to cut the board down on a panel saw for transport, or to remove the pieces and stack them for transport.

The more we worked on the pieces, the more admiration we developed for this as a fabrication technique for making large art accessible to small groups. Traditional large sculpture materials have required different sets of specialized skills, and construction techniques that limited their deployment. Laminated plywood panels, cut out in shapes, are a very democratic solution for large art.

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Assembly - Art Center



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3D Modeling and Cut Files - The Dolphin

The artistic direction of the dolphin critter was proposed via photograph (below) on 26 April 2012 by Bret Gerber.

Experiments with the Kinect showed that the object would probably not scan reliably enough to preserve the shape, so we decided to use 123D Capture instead, with a similar, larger, found object from the Del Mar Fair.

Those surfaces were opened in MeshLab and edited. At right is a screenshot of some of the filters available. Editing included reducing the height of the base, deleting the flippers, and then closing the three resulting holes. MeshLab crashed 13 times during these operations. It seems fragile, and saving your work at every step is the best way forward.

The resulting model was

smoother and simpler than the found object. The intent was to capture the playfulness and elegance of Bret’s object. The curve of the body was deepened,

and the dolphin’s orientation was changed in order for the rider to be “played with” by the dolphin, instead of sitting on the dolphin’s back. The dolphin also needed to include a base. The base would

allow the finished critter to stand, if necessary, in the case it could not be suspended, as well as to aid in working on the constructed dolphin. Stand can be cut away completely if desired.

The flippers were removed, with the intention of flippers being decorated onto the sides, with paint, woodburning, collage, etc. as possible methods of execution. The reason the flippers were removed is that they would be in the way of the rider.

Another possibility proposed for



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the flippers was creating wooden (or leather, plastic, fabric, etc.) flippers and attaching them flat down to the sides, out of the way of the rider, or as foot pegs.

The model was saved, then imported into 123D Make. Stacked slices were selected, full sheet of plywood material selected, and experiments with the slice direction started.

Choosing the direction of the

slices has a large effect. Choosing one direction over another affects the strength, appearance, ease of assembly, and number of sheets of plywood required. The number of sheets of plywood required ranged from 24 to 41 depending on slice direction. A problem with incorrect dimensioning caused some difficulties. The height had been set to 30 inches instead of 90 inches. This caused the program to cut the long pieces into two pieces, once the long

dimension exceeded 30 inches, in every case.

After it was corrected, the model sliced successfully, and a slice direction was chosen that simplified assembly at approximately 25 sheets of plywood.

The *.eps files were exported and placed in Dropbox. The *.stl file was uploaded to Thingiverse.



Second Published Model

The dolphin was uploaded to Thingiverse on 6 July 2012. This was the second published model from the project, and is in the public domain, free for anyone to use.

Find it at the following link.http://www.thingiverse.com/thing:26367

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What do a Yellowtail and a tire swing have in common? Well, just about nothing. Except, perhaps, at Burning Man.

Touching on the theme of fertility, the Yellowtail is formed into an endless ring of fish power. The shape also recalls the Ouroboros1, a symbol of the cyclical nature of life, as well as the shape of Yellowtail that many of us are already familiar with. That of sushi.

First, an image of a Yellowtail was obtained from the internet.

Second, clay was formed, as closely copying the contours of the Yellowtail as possible.

Third, the clay was formed into a cylindrical shape, with the head on the outside and the tail on the inside. It was set on a plate and evaluated. The resulting torus was

1 http://en.wikipedia.org/wiki/Ouroboros

very bulky. While satisfactorily fish-shaped, it was feared to be unbuildable as a suspended object.

Another fish was made, this time reducing and normalizing the thickness, and putting the tail on the outside.

The desired shape was a section of a tube, similar to a tire swing. The two models were compared.The second model (at right) was chosen.

The size and shape was further edited with clay forming tools until it appeared to be in the ballpark of what was desired as an end result. The plate was carried to the photography studio and photographed for 123D Catch.

The images were uploaded to 123D Catch, and the 3D model

was created succesfully on the first try.

The model was imported into MeshLab for editing.

3D Modeling - The Yellowtail



There was little love for the Yellowtail. When talking about this model, it was the only one that consistently received counterproposals.

No designs were submitted from the community.

One burner pressed for swapping it out for seals, since Children’s Pool is populated with them, and there is a very enthusiastic crowd of potential non-burner donors that would love to see us build a seal instead of a third fish.

Instead of swapping the Yellowtail out for another animal, which was considered undesirable since the list was set over the course of several community meetings, the model needed to be something other than simply “man rides fish”.

Relying on the event theme of Fertility 2.0 turned out to be more “fertile” than at first expected. In this case, Yellowtail utility as an ingredient for artistic sustenance and the symbolism of fertility were combined to guide the design.

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Creating Cut Files - The Yellowtail

The model was imported into 123D Make. Our half-inch plywood material configuration was selected.

The Yellowtail is intended to be a tire swing. Strength was selected as the design criteria for the cut angle. This happily also worked out to reduce the parts count and the sheet count. There were, as well, plenty of room within the rings for more kelp.

The software work was, as has been customary for the project, done mostly at MakerPlace. While Abraxas worked on the Dolphin

files, Paul worked on the Yellowtail files. Unfortunately, after two hours of work, the files appeared to not be in the expected directory. Paul writes:

“I was using CorelDraw to do some manual processing on cut layouts generated automatically by 123D Make, before bringing them into VCarve Pro for toolpath generation for the CNC router. Import file in EPS format, edit for a few minutes, export file in DXF format, close file, go on to the next of the 27 files. Unfortunately, the DXF export was failing silently. Nothing was saved, and no error

message was generated. When I went to count the 27 output files to make sure I hadn’t missed one, there weren’t any. Arrgh!

We suspect the CorelDraw installation was tampered with, mainly because all their laptops seem to have the same serial number for CorelDraw, and it isn’t one of the serial numbers MakerPlace is authorized to use! It might be a bogus serial number, and who knows what CorelDraw does in that case?”

Another two hours of work and the files were redone.



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3D Modeling with 123D Catch



Above, a mosaic of the photos used for the exterior surface of the turtle. Below, the

camera angles used during photography.

Autodesk has been releasing components of their free maker-oriented 3D modeling system, which they call 123D (www.123dapp.com). Just in time for our project, they released 123D Catch, which allows you to create a detailed 3D model of a real-world object by simply taking photographs of it. The program you run (currently on Windows or on an iPad or in a web app) just collects those photos and sends them to Autodesk’s cloud servers, where magic is performed. The program then downloads the results from the cloud for further local processing. This takes just a few minutes.

Remarkably, the photos don’t have to be taken especially carefully. They don’t have to be from any precise angle, or even consistent with one another. The cloud processing looks at the images themselves, without knowing in advance how each was taken. By comparing the content of the images, it’s able to figure out how the various parts of the object relate to each other in 3D space, and indeed where the camera was in 3D space when taking each picture. Because it works that way, there are some easy constraints on how the photos must be taken. The object must remain stationary, and the lighting on the object must stay consistent (so no on-camera flash!). Details in the background are helpful for the matching algorithm, so you don’t want to isolate the object from the background. If the background happens to be too plain, you might

even want to add some features to it to help the cloud do its magic.

Our first attempt to create a model with 123D Catch was unsuccessful. Parts of the object were captured, and parts were grossly distorted or not captured at all. Autodesk has tutorial videos that show how best to shoot the photos 123D Catch needs, and you should watch

them, but they do leave some details to the imagination. It seems to be important that the photos are sharp and have extensive depth of field. Shooting indoors by normal house illumination just didn’t work well enough.

The first successful model we made was of the turtle. This was an outside shoot on a sunny day, so light wasn’t a problem.

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The camera was simply set for automatic exposure. It chose exposures around 1/200th of a second at f/10 using ISO 100. The original turtle is rather large and in a constrained space, so a very wide-angle lens was used. The resulting 3D model captured the exterior surfaces of the turtle shell very nicely, but treated the dark shadows within the shell’s interior as solid.

After some experimentation, I found a recipe that works consistently for me indoors as well. I use a photo studio strobe light, aimed at the ceiling through a photo umbrella to give soft overall lighting but with some residual directionality. The strobe must be stationary, not moving around with the camera, so a wireless remote strobe trigger is a nice convenience. With my room and my strobe, I am able to expose at 1/160th of a second, f/11, ISO 100, making it easy to take sharp images hand-held with plenty of depth of field. I use a fixed focal length lens (50mm on a 1.6X crop factor DSLR body) to avoid confusing the issue with zoom changes, and I shoot hand-held and direct to JPEG. I shoot a full ring of images at a near-horizontal angle, and another full ring from about 45 degrees above the object. If the object has deep hollows like the yellowtail model does, I shoot a few more images from a high angle. This resulted in 40 to 72 images for these four models, all of which worked fine in 123D Catch.

You can see here the sets of individual photos that went into making each model, plus a capture of part of 123D Catch’s window showing a view of all the camera positions it computed. You can see I wasn’t especially consistent about camera height or angle or spacing around the object. That doesn’t seem to cause any problems. You can also see that I didn’t worry much about getting a perfect exposure or white balance. 123D Catch doesn’t care about those things, either. I just made sure to point the camera at the object from a

nice variety of angles.

Notice that this is a completely different method than using the Kinect. At the beginning of the project, the objects to be scanned were assumed to be large outdoor objects, such as statues and models, and it was assumed that the Kinect would be used to capture them. However, it turned out that most of the models used were very small, which lends itself to 123D Catch, instead of 3D scanning with the Kinect. Both methods work well. Use the one that fits the job.



Above are the camera angles and a mosaic of the photos used for modeling the Yellowtail.

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Above are the camera angles and a mosaic of the photos used for modeling the Seahorse.

Below right are the camera angles and a mosaic of the photos used for modeling the

Dolphin.

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The Yellowtail was uploaded to Thingiverse on 7 July 2012. This was the third published model from the project, and is in the public domain, free for anyone to use.


Third Published Model

The Shark was downloaded from Thingiverse on 7 July 2012.


Using an Existing Model



3D Modeling - Selecting The Shark

Having donated several models to Thingiverse, we now found ourselves using Thingiverse as a source. There was one submitted design for the Shark, which was to model a photo booth at Birch

Aquarium. While it would be fun to “be the shark” or “be inside the shark”, it was determined that this would not qualify as rideable. Advantages included ease of assembly. The CNC router wouldn’t be required.

We modeled up in clay a shark’s head, that would explode up from the floor of the CarouShell. We rejected it for the same reasons as the photo booth. It just wasn’t rideable.

After making a final call for ideas for the shark, we decided to search for an existing model.

This is not an unusual step, in that a model search had been done for each of the critters in order to establish whether or not there were existing 3D models. If the model was satisfactory, then a lot of work could be eliminated.

What we found is that there are a large number of 3D models out there, and a few would have been acceptable. However, they were not open source. In some cases they were very expensive. Thingiverse, with it’s community of open source 3D model developers, is one of the most active communities. The Shark came from Thingiverse, and is a traditionally-shaped Shark, ready for suspending and riding.

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Creating Cut Files - The Shark

The model was downloaded from Thingivers and opened in MeshLab. It came in two halves (see below left). The model was not watertight. Using the Close Holes function, the two holes were sealed using the trivial method. The model was exported out of MeshLab and imported into 123D Make. Our half-inch plywood material configuration was selected.

The Shark is intended to be ridden in as traditional a manner as one rides a shark. Reducing sheets required along with ease of assembly was selected as the

design criteria for the cut angle.

During the initial cut it was noticed that the program didn’t distribute the parts as if the two halves were independent. The program assumed that we wanted to assemble something that looked exactly like what we’d given it. In order to efficiently use the sheets of plywood, each half was going to have to be constructed separately.

The model was reopened in MeshLab, and split into two files, each half exported as a separate mesh. The reason the designer split the

model is that many construction techniques will not do any overhangs. Recall our troubles with Cut3D and the turtle. If the model is split to where each half can be presented with only convex surfaces facing upward, then the vast majority of CNC and 3D printing machines can handle the model.

After the model was split into two files, work proceeded as expected. The slices were written out to *.eps, converted to *.dxf, opened in VCarvePro, kelp was added to the empty parts of the sheets, and the *.nc files writen out for the CNC machine.



The Shark was converted from a single file to two files in order to efficiently distribute parts

on the plywood sheet layouts.

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While there was little love for the Yellowtail, there was a lot of love for the Seahorse. Unfortunately, the interest didn’t translate into submitted models. A burner at the Open House said “I don’t know how you’re going to do that one. I tried to draw it and it looked dumb.”

I wondered what she meant, but soon found out perhaps why.First, reference images were downloaded from the internet.

Second, attempts were made to make a clay model that was rideable.

There is a reason that seahorses don’t show up often in carousels. Sea Dragons sometimes do, but they are almost always presented as hippogriffs, instead of in their native form.

Seahorses look like snails when you attempt to shape them more like a rideable creature.

A model search on Thingiverse and on the wider internet didn’t turn up much that looked good and was rideable.

Four options were developed.

• Porch Swing Seahorse with Globe Belly

• Seahorse Chair• Snail Seahorse• Sea Dragon Style

The Sea Dragon was rejected for looking too much like a horse. The Snail seahorse looked silly. The Seahorse chair was attractive, but the first response from everyone that saw it was “Oh, that’s going

to break.” See below.

This left the porch swing, which was very nontraditional, but offered a seat option for those unable to ride astride. Also, the globe could be used as a treasure chest, if part of it was hinged.

Since the slicing program predicted a very small number of boards required, it was decided to go ahead and built it and see how it looked in real life.

3D Modeling - The Seahorse



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Above left, the photographed version of the porch swing style seahorse, as seen from above.

Above right, the edited mesh three-quarter front view. Below left, the unedited point cloud, before cutting out

extraneous surfaces and before closing holes.

The Seahorse requires the most amount of assembly work in that it may not be self-supporting as assembled off the CNC. This is unlike the other critters, which are expected to be self-supporting as assembled (if properly suspended).

It may require some reinforcement in terms of a base plate or pan.

It’s the most experimental design of the collection. The center of gravity is predicted to result in it tipped back slightly, like a rocking chair. You could sit on the upward-facing side of the seahorse, or on the globe itself. The globe is hollow, and will be used as a treasure chest/geocache.

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Creating Cut Files - The Seahorse

The model was created with 123D Catch, opened and edited in MeshLab, and then exported as a watertight model.

It was imported into 123D Make. Our half-inch plywood material configuration was selected Reducing parts cound and

number of sheets required was selected as the design criteria for cut angle.



Sheets and Parts Required Per Critter

Critter Bounding Box (inches) Sheets Slices PartsDolphin 90x45x30 26 66 125Seahorse 26x46x38 13 56 104Shark Left 15x30x90 6 33 33Shark Right 15x30x90 6 33 33Yellowtail 29x43x44 28 64 66Turtle* 36x47x37 20 70 89

*Before height modification. Two additional sheets of side pieces were required to raise the height.

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Visual Impact - Bounding Box Volume as Independent Variable

It was predicted that the critter with the largest volume of bounding box would have the greatest visual impact. If that theory holds, then the dolphin will dominate.

Research in computer vision often assumes that objects can be identified independently of the background, and contained within a bounding box.

A question for the participants and potentially for the docents to ask the participants is “which critter do you notice first? Which one has the greatest visual impact?”



The volume of the bounding box of the dolphin is roughly twice that of the next largest critters. The other critters are all very similar in bounding box volume. Remember that the shark is two halves that fit together, and not two separate critters.

This analysis, along with that of the previous page, leads to a proposed rank ordering of critter value. This will be useful in design review. Assigning each

of the statistics a weight, and then adding up the values, gives an overall score for each critter. Maximizing visual impact while minimizing sheet, slice, and parts count is the goal. If visual impact can be reduced to bounding box volume, then visual impact can be replaced by bounding box volume. The question of whether it can be or not is highly debateable, It would be fun to try and determine the strenght of the relationship between bounding

box volume and visual impact for 3D models.

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Assembly - The General IdeaCritters are not intended to be complete off the CNC. The stair-step edges must be removed at a minimum, but it’s worth explaining that the models themselves are intended to be worked down.

In decreasing order of completeness, with what was considered before assembly to be the most complete model on top:

SharkDolphinTurtleSeahorseYellowtail

In other words, if our assumption is correct, the Yellowtail needs the most additional carving to look like a fish ring.

While the designs are intended to be as close as possible to a finished critter, there is really no replacement for hand finishing and sculpting the lines and details of the critters in person. The options for decoration alone would take a long time to explore. We’re optimistic that the decorations will be vibrant and exciting, provocative and unexpected.

The *.eps drawings have layout markings for alignment. These are the yellow lines. We considered changing bits in order to scribe these lines to aid in alignment, but feared the amount of time this would add to the CNC process.

Changing bits for every sheet was deemed unnecessary, especially since the sheets were expected to have alignment holes. This is an aspect of the slicing program. The holes, however, turned out to be less helpful than anticipated.

To aid in alignment, it’s recommended to make a stack, see if it looks good, and then lightly spray it with a can of spray paint. If someone wants to trace with a pencil lines for alignment, that would be fine. The spray paint option may speed things up, and the paint should disappear with the grinding process.

During the first round of stair-step-removal experiments, it was found that:

• The angle grinder with a coarse flap wheel takes off material quickly.

• The multitool with various attachments and the orbital sander were too slow to be feasible.

• The belt sander works fast enough, but can’t handle complicated surfaces.

• As reported earlier, Carrin used a Dremel on the sculptures “Famine” and “War”. Carrin used a combination of chisels, Dremels, and a die grinder with rotary wheels on “Death”, and achieved very sculpted work.

.

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Turtle - Critique, Challenges, Problems, Solutions



Problem: Turtle too short in Z-axis. Larger people had difficulty getting in to be the turtle. The fit was especially tight in the rear. Usually this is a feature, but here it’s a problem.

Solution: the middle section was extended with additional pieces. The turtle grew in the Z-axis.

Repercussions: Small increase in weight.

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Dolphin - Critique, Challenges, Problems, Solutions



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Yellowtail - Critique, Challenges, Problems, Solutions



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Seahorse - Critique, Challenges, Problems, Solutions



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Shark - Critique, Challenges, Problems, Solutions



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