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How to CNC machine a city model

Urban planning model of city Maastricht (NL)

European highway E25 connects Amsterdam in the Netherlands to Genua in Italy. On the south border of the Netherlands this autoroute traverses the old city of Maastricht, and this is the only location on the 'Route du Soleil' where the traffic is stopped by a series of traffic lights. Local traffic including cyclists and pedestrians have to cross the highway there. The city is in fact split into two halves, which is of course an unwanted situation. In addition noise and pollution are bad for the people living next to this motorway.

Since many years already plans have been made to build a tunnel that will lead the traffic below the city. In 2009, after a competition of three project plans, a definitive plan has been selected for such tunnel.
It is called De Groene Loper by consortium Avenue2, the consortium being a cooperation between contractors Ballast-Nedam and Strukton, supported amongst others by Arcadis consultants, West8 Urban designers and Humblé Architects.

Building will start in 2010, and the tunnel should be ready in 2016. The integral project also contains the development of real estate and the enrichment of nature, and will be finished in 2026.

3D CAD model of Maastricht
3D CAD model of Maastricht, detail
3D CAD data: De Groene Loper. Right detail 'Europaplein'

The three competing project plans have been presented to the general public and to the politicians (consultation period from Nov 16, 08 to Jan 16, 09), and on June 25, 2009 the winning plan has been selected: De Groene Loper by Avenue2. Part of the presentations during this consultation period were large urban planning models of each plan.

The model for the winning plan by Avenue2 has been created by Dutch model maker Made by Mistake, who contracted DeskProto user Komplot to machine the model.

Basis for the model was 3D CAD data of the complete city of Maastricht, as shown above. A simplified CAD model was sufficient: buildings are represented by simple block shapes (outer shape only). Detailed information was added only in the project area, as shown in the two CAD screens above.

The 3D CAD data in DeskProto
DeskProto screenshot showing toolpaths
DeskProto screenshots: first the south tunnel entry, next with roughing toolpaths.

Still the CAD model was very large: a 200 MB STL file has been loaded in DeskProto . Calculation time for the complete model would be too high (even in DeskProto), so Komplot has calculated using 14 separate regions (subsegments) of 500 x 750 mm each. Calculation was done on a Win XP 64 bits PC with 16 GigaBytes RAM, and took about 2 hours per region. In most other CAM programs it would have been absolutely impossible to create these toolpaths.

Komplot has has combined several strategies in different operations: parallel, crosswise, waterlines and 2D contours projected onto the 3D geometry. That way both the square buildings and the sloping surfaces could both be created. Also cutters af various sizes have been applied.

The Dynamight machine milling the maquette
The large Dynamight milling machine used by Komplot.

The Dynamight machine used by Komplot not only is large (working area is 5.4 x 2 x 1 meters!) but also surprisingly fast for it's high mass. The model of 3.5 x 1.7 meter fitted nicely in the machine.
7 slabs of Renshape tooling board (650 kg/m3) have been used for the model, thickness 50 mm. So the maximum height of the model is 50 mm. Scale of the model is 1 : 2000.

Virtual model of the north entry (Cad data and areial picture combined)
Design picture of the north entry of the tunnel ('De Geusselt'): 3D CAD model combined with an aerial photograph. Compare with the two pictures of the model below.

The picture above shows the north entrance of the tunnels in the virtual model, and the same area can be seen on the physical model in the two pictures below. Landmark points to be recognised are for instance the MVV football stadium (the large square on the left) and the series of 11 apartment buildings on a straight line, at the right side of the motorway.

The north entrance being machined
The north entrance finished
The north entrance of the tunnels.

The two pictures above show the north tunnel entry area of the model during machining (left), and the same part in the finished model (right). As you can see, after machining, Made by Mistake have added many details in the plan area like trees and other green, road surfaces, bridges, water, ...

The river being machined
The river finished
Maastricht is located at the river Meuse.

Again a part of the model (the river Meuse, in Dutch Maas), during machining and in the finished model. You can see that the river bed still has to be machined: the milling pictures have been shot during roughing. Made by Mistake have poured a resin in the river area to simulate water: the glossy area in the finished model.

The south entrance being machined
The south entrance finished
The south entrance of the tunnels.

The third detail pictures show the south entrance of the tunnels, with left the buildings of Maastricht University. Here as well the milling picture has been taken before the finishing operation: the sloping surface in the front has not yet been machined.

Presentation of the Avenue2 project plan
The official presentation of the three competing project plans.

The official presentation of the plans during the consultation period attracted a lot of visitors. And much was at stake for the three resenting consortia !

The Avenue2 maquette on display
The Avenue2 maquette still can be seen at the Information Center.

The model still can be visited by the general public: it is on display at the project's visitor's center called Informatiecentrum A2 Maastricht (the national road number for this highway is A2). Note: the visitor's center is opened only a few days a week. More information about the project (and about the opening hours of the information centre) can be found at

We are proud that DeskProto enabled creating this great model, a model that surely has helped Avenue2 to get their plan selected.