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How to CNC machine a 3D topographical model

Topographical model of the island Madeira

Spanish Model maker HCH Model in Madrid makes industrial, mechanical and architectural models. The company is very experienced in manually making these models using typical 'traditional' workshop tools. In the year 2000 HCH Model has invested in CAD/CAM software and a CNC milling machine, as additional tool for projects that would be complicated when done manually.

In order to use these new tools it was needed to acquire and implement knowledge of materials, machinery and computer programs, normally applied by heavier industries. The result: At this moment there is no piece, small or big, that could not be completed using these technologies.
HCH Model states: "Programs of CAD, CAM now are indispensable, both for the accomplishment of our models and for the exchange of information with the clients."

3D data in AutoCAD
The 3D terrain model in AutoCAD.

A nice example project is the topographical model of the island Madeira as shown here. This type of model would be virtually impossible to create by hand.

Starting point for this project was an ISO file, containing a topographic description of the geometry as a 3D point cloud. In AutoCAD this data could be converted to a Digital Elevation Model, using a special topographic application plugin that runs inside Autocad. In order to make the model more clear all Z-values were scaled up by a factor 1.5. The 3D data then were exported as STL file: file size for this Madeira geometry was 73 Mb.

Toolpaths in DeskProto
The milling machine in action
Toolpaths in DeskProto, and next the CNC milling machine at work.

The STL file next was imported into DeskProto in order to calculate the toolpaths. As can be seen in the illustrations above, to save machining time only the island itself has been machined, not the rest of the block (the ambient area). The machine used is a Siegfried Electronics FCN 100 machine made by Diseños Mecanicos y Electronicos del Centro S.L. in Madrid. The model was milled in Axon Modellab tooling board, in approx 6 hours. The resulting model is 640 x 280 x 50 mm.

This model has been used to create a mould, and next small series of models. Each copy shows different subjects, like roads, rivers, towns, etc. Destination of these models was the Santa Ana Thematic Parc Madeira, built by PQC Lucida.

The resulting model
The finished model
The resulting model, rough and after finishing.

Mr. Jorge Chirinos of HCH Model states:
"The geometry of the piece that we want to create by 3D machining is achieved by means of different programs. We are able to obtain both the geometries and the required texture effects. These programs provide us the DXF or STL files for DeskProto."
"Once in Deskproto we will calculate the toolpaths, rapidly and without mistakes. Next we will machine them in material blocks that can later be joined to form the complete model. This is a suitable solution to create both big topographies as well as small details of the model."

Toolpaths in DeskProto
The resulting model
STL geometry of an oyster bed in DeskProto, and the resulting model.

A very different type of project that was completed by HCH model using DeskProto is the oyster factory model shown above. It is a traditional 19th century oyster factory in France.
Only the actual tiles have been machined using DeskProto, from two sides. One series of tiles is about 40 x 60 mm, done in Axon Modellab tooling board.