Above: An Azimuth Thruster. Image source: Wikipedia https://commons.wikimedia.org/w/index.php?curid=397859
Mirage orbital milling machines are used across a variety of industry sectors, especially those involving the manufacture of large circular components. The shipbuilding industry is a good example of this and one particular application which has cropped up several times is the machining of ship thruster flanges.
What are thrusters?
On large boats and ships, thrusters are used for either propulsion or manoeuvring into position. The different types include Bow thrusters (for manoeuvring the ship when docking) and the larger Azimuth type used as the main propulsion of the ship. An Azimuth thruster can also be rotated to any horizontal angle, making a rudder unnecessary. Advantages over the typical fixed propeller and rudder arrangement include better use of ship space and increased efficiency.
What flange needs machining?
The rotating thruster unit is bolted to a circular flange built into the ship’s hull, which needs to be machined flat and smooth, ensuring trouble free operation and maximum efficiency.
Machining of this flange is carried out in the shipyard and presents challenges such as mounting the machine into position, support it safely and ensuring accuracy over such a large diameter.
The project described below is one example where a Mirage Orbital Machine was used to create a successful project outcome.
Above: The vessel under construction at the shipyard.
The shipyard was building a 50 Tonne support vessel that required machining of the thruster flange. The orbital milling machine needed to be positioned within hull’s opening, allowing it to machine the inside flange face. The machine was centralised and clamped into position using the 8 extendable legs, but it was also necessary to construct a platform underneath to support the machine safely.
Above; The orbital milling machine and surface finish from inside the hull.
The OM4500 orbital milling machines was successfully used, enabling the ship’s thruster to be attached on surface machined to accurate tolerances. This particular machine is hydraulically powered and has the capacity to machine diameters from 98” to 178”.
The ship’s thruster in position after the flange was machined. Left: viewed from underneath and right: from inside the hull.
How orbital milling machines work
The machine’s milling head is powered by an independent hydraulic supply which is taken from the machines central hydraulic distributor. This means the cutter speed can be controlled independently of the machines rotational speed. Advancement of the cutter in the axial direction is operated manually with the hand wheel and locking slide. To apply the correct depth of cut the spindle hand wheel is used in conjunction with a digital Vernier scale fitted to the machine.
To find out more about orbital milling machines download the Orbital Milling Buyer’s guide, or if would like to speak to our technical team you can get in touch here.
You may also wish to visit our resources section, where you can download buyers guides, product datasheets or watch product videos.