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How to CNC machine a relief model in wood

A relief model that shows the Dutch coast and sea bottom

The Netherlands (where DeskProto is made) are known all over the world for their coastal defenses: dykes and many other types of barriers. These are needed as a large part of our "low countries" is located below the sea level. So 'water management' is an important issue, and a number of information centers is present that show how we manage to keep our feet dry. One of these is at Maeslant Storm Surge Barrier (the world’s largest moveable barrier) in Hook of Holland, in Dutch the "Maeslantkering".

The 7 meter long model on display
The original 7 meter long model on display, with in color the projection of augmented data.

The Maeslantkering has its own Information Centre, called the Keringhuis. For a (temporary) exposition in this Keringhuis a 7 meter long relief model has been created of the complete Dutch coast, scale 1:50.000. From Cadzand in the south up to Rottumeroog in the north. In addition to the land, also the bottom of the sea is present: showing far more relief than the (flat) land !
A special feature is an animated projection on the (white) relief model, showing all changes in this coastline in history, from 5500 B.C until now.

The model was originally made for Atelier Kustkwaliteit and shown at the Deltacongres on Nov 1, 2012. It has been created by Dutch model maker Made by Mistake, who contracted DeskProto user Komplot to machine the relief.

Relief data: Zeeland and Rotterdam
Part of the DEM data that were used: the province of Zeeland and the port of Rotterdam.

Basis for the relief model was a huge Digital Elevation Model (DEM), created by AUBT, a young bureau offering 'tailor-made architectural and urban design solutions'. AUBT did a great job by combining information from various data sources (the seabed, the coastal defenses and the polder landscape further land inward), using powerful GIS software.
The result was a set of STL files that may indeed be called huge: 1.4 GB of STL data.
Only very few CAM programs are able to handle datasets of this size.

DeskProto toolpaths screenshot
Toolpaths for the isle of Texel (Noord Holland) and surrounding seabed.

The model was done in two parts: the north coast (Waddenzee en waddeneilanden) and the westcoast (Zeeland, Zuid Holland en Noord Holland). As a machining strategy in DeskProto, Komplot applied parallel toolpaths, both for roughing and for finishing.

Machining the relief in wood
The north half of the relief being machined. Colored in green are the isle of Texel (left) and the Afsluitdijk - one of the major dykes (right).

A second model of this same relief has been machined, on a smaller scale, to be shown at the RapidPro trade fair in Februari 2013. This model has been machined in Abachi wood, total size ca 2 by 1.5 meter. The picture above shows the north part of the model being machined in wood.
For this smaller model the total file size of the NC files was 515 MB, total machining time ca 11 hours (roughing done with ballnose cutter D 8 mm, finishing with ballnose D 4 mm).

The wooden relief on the RapidPro show
The wooden relief on display during the RapidPro trade show.

The RapidPro trade show (a yearly event in the Netherlands) features a special section "Eyecatchers", for which this relief has been selected.

Detail of the wooden relief
Detail view of Walcheren and other islands in the province Zeeland. Note the deep channels round the Oosterschelde Storm surge barrier ('above' the isle).

After machining, the wood has been treated with a wood oil. In two colors, one for the land and one for the sea-bottom. Amazing is to see how much more relief is present in the sea bottom (in reality hidden below the water) than on the land.

The coast hanging on a wall
Lower half of the coast relief at its current location: the Geofort.

When the trade show was over the relief needed a new destination, where it could be seen and admired. So we have donated the complete relief to the Geofort in Herwijnen (NL): an island fort that offers attractive education in the field of cartography and navigation. You can find the relief on the wall of the fort's 3D Cafe.