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How to scan and replicate a footprint

Scan a fossilized dinosaur footprint and CNC machine a replica

The south-west coastline of the Isle of Wight (Great Britain) is known for the many dinosaur fossils that can be found along the beaches. The area round Brighstone Bay is also known as the Dinosaur Coast. For background information you can also check the DinoWight website.

DeskProto hobby user Mark Porter has teamed up with his son Jason, who is a keen amateur palaeontologist. Combining their skills they have recreated the footprint of a dinosaur, that was made in this area about 160 million years ago.

Photo of the original fossile
A fossilized dinosaur footprint as found on the beach. This footprint is sized about 700 mm.

Mark and Jason often visit a site where fossilized dinosaur footprints can be found. The site was populated by a species of dinosaur named Mantellisaurus, similar to Iguanodons, about 160 million years ago. These creatures left their three-toed footprints behind in the mud. Over the years, the impressions filled with sand and silt, which eventually hardened into the fossils which we can see today.
The size of the fossil is impressive: this dinosaur was about 7 m long. The shape of the fossil can be used to recreate a cavity that matches the original footprint, long time ago.

Artist impression of a mantellisaurus
One of the photos used for digitizing
The mantellisaurus, and one of photos used in 123D Catch

First step in this process is creating a 3D computer geometry, by digitizing or scanning the shape of the fossil. Mark and Jason used the free 123D Catch® service from Autodesk® to create the 3D model. This program stitches 2D photographs together to form a 3D model. They took 29 photographs and uploaded them, and the cloud service in 123D Catch® produced a perfect 3D model. Magic!

Mark states: Every day there seem to be more and more ways of generating 3D files from real-world objects. Laser scanners are becoming cheaper, and there are online services that can create 3D models from a set of photographs. We wanted to see if we could make a model of a real-world object. In fact, what we did was to make a model of something that has not been seen for millions of years!
123D catch works best with highly-textured objects. We tried to scan our heads, but the results were not great.

Screenshor of the Netfabb software
Screenshot of the 123D Catch scanning software
Two of the program used: 123D Catch® and Netfabb®.

The little camera icons in 123D Catch (see the above screenshot) show where the program thinks your individual photos were taken from. The nice thing about this project is that the footprint has a lot of detail, which makes it easier for 123D Catch to align the individual photos to make the 3D image. The result of 123D Catch® has been exported as .obj file.

Program Netfabb® Studio Basic has been used to convert the .obj to .stl, and to check the part was oriented the correct way up.
You can see from the figure above (on the right) that still a lot of beach was present surrounding the fossil, so a retry in 123D Catch® was needed to fix this: by cutting out and removing the unwanted parts. After these changes of course the file was converted again from obj to STL.

DP screenshot: part parameters
DP screenshot: the fossile geometry
the DeskProto part parameters, and the STL file drawn.

Next the .stl file was imported into DeskProto, like any other geometry. DeskProto has a nice capability that can be used to make molds. The idea is that instead of removing all the material around the part, it removes the part itself. This leaves you with a cavity (a 'part-shaped hole'), which you can use as a mold. In this case however the cavity has not been used as mold: the aim of this project was to get an idea of what the original footprint would have looked like.

In the Part Parameters the option needed to be checked is called 'Inverse milling', as shown in the left figure above. Note that this inverting is not visible in the geometry, only in the toolpaths and in the simulation.

DP screenshot: the subjects in view dialog
DP screenshot: the simulation
DeskProto screenshots: the subject dialog and the simulation

In the main screen of DeskProto you can select "View subjects" then check 'Simulations': what the result will look like after machining, for the currently calculated toolpaths. In the screenshot on the right the simulation has been turned on and the geometry has been turned off, so that the simulation can be seen without the part model (that has not been inverted) overlapping it.

The milling machine in action
The mold that has been machined
The footprint on the Step-Four milling machine, and the resulting model.

For the model shown above a light tooling board has been used, as that material does not have any grain. The cutter was a 2 mm ball nose cutter, which produced good results for this small scale model. The machine that was used is a Step-Four Basic 540 milling machine (manufacturer no longer in business).

Mark and Jason conclude: We found this to be a way to make a unique model in a quick and enjoyable way, and hope you can try the process out with your own subjects.