Five-axis milling machine with a machining space of 25 * 5 * 2.75 m
Test setup Pieter Schelte, 3D design
Model making to the tune of 150 a year
Last year, MARIN built model number 8888 and propeller model 7000. Readers may well wonder just how MARIN produces an average of 120 ship
models and 30 propel- ler models a year, as well as all the different parts and test set-ups in an efficient, cost effective way.
Well, here’s how!
3D CAD It all starts with drawings and recently, MARIN finished the process of transferring from 2D to 3D CAD. MARIN has opted for Autocad Inventor as its standard CAD software. The hull forms however, will still be made with MARIN GMS software. Hull forms are imported as IGES files into the 3D CAD models. 3D CAD offers new techniques that help to improve the design of models and test set-ups. MARIN uses 3D CAD to determine the weight and radii of gyration of the model and equipment in the design stage, making it possible to design lightweight models with accurate mass dis- tribution. This is very important for tests in the Seakeeping and Offshore basins. The local stiffness of a model can be adapted by changing the wall thickness of the model, while keeping the weight under control. This technique is adopted for models that have to be used for pressure fluctuation tests. Finite Element analysis is used to calculate the stiffness, for example, of splitting loads frames. This is crucial for the quality of the test. Now, MARIN determines the natural frequencies during the design and optimises them. The greatest benefit, however, is that 3D models offer much more information to users and clients and help to improve communication during projects.
Jan de Boer
j.d.boer@
marin.nl
CNC milling The 3D model is a necessity for the next step in the production process, as it is used by the CAM software to pro- duce programs for the CNC machines in the model and metal workshops. Recently, MARIN installed a new five-axis milling
machine for its models. The new machine is very large, with a machining space of 25 * 5 * 2.75 m. This space can be split into halves, with one section milling and in the other section parts are exchanged without stopping the machine. This makes it possi- ble to mill 24 hours a day/seven days a week. Of course, using the full length, the machine can be used for milling large objects such as plugs and buildings etc. CNC milling also helped us develop a new technique for building models. Starting with a block of polystyrene foam, an under- sized model is milled from the block. This model is covered with a layer of fibres and paste and than milled again into its final shape. Although the model is milled twice, the total cost of building a rough model is saved.
Rapid prototyping 3D models have another benefit because it becomes very easy to produce parts with rapid prototyp- ing techniques. MARIN has built rudders, fins, propellers, thruster housings, strakes, casings, buoys and many more. Specialised companies that produce these kinds of models within 24 hours after receipt of a 3D model are used.
As you can see, our models are made by a very strong production chain that includes 3D design, CNC machining, rapid prototyping and a highly-skilled workforce. This helps us to make models and test set-ups at the cutting edge of design and technique, answering the needs of our clients.
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