Machining is a manufacturing process through which a workpiece is made by material-removal, whether by removal of shavings or abrasion. We are familiar with machining tools such as drills, lathes or milling machines. Usually the machined pieces are manufactured in machining workshops.
What happens when the workpiece to be machined cannot be moved to the workshop?
Usually some machining operations need to be performed in pieces that, due to their size, are impossible to move to the workshop or it is very complicated to do so. In addition to that, the dismantling of a broken piece within a machine to be moved to a workshop may be a costly and complex task. These are the situations where on site machining is indispensable and its application means saving money and time of production.
Cases where on site machining is usually applied:
When there is a breakdown of a vessel’s engine, it is necessary to machine some of its elements in order to fulfil the tolerance specifications demanded by the manufacturer. Typically it is necessary to machine the cylinder block (for instance, in the crankshaft bearings) or lathe the crankshaft itself.
To machine the cylinder block in a workshop, it is necessary to remove it from the vessel, taking into account any related drawbacks (cuts, logistic costs, long intervention times). Machining the engine on board of the vessel is the least expensive and the quickest solution.
Similarly, there are large machines which require on site machining in case of repair or maintenance:
Tunnel boring machines: the seats of the cutting blades in the cutter head are distorted due to rough work conditions. They are modified by wield overlay and the original dimensions are recovered by means of on site machining. This operation is carried out during the tunneling works since it is impossible to remove the TBM without disassembling it.
Trommel screens: These machines are used, for example, in cement industries or animal by-product processing industries to separate materials of different densities. They are cylinders of big dimensions that rotate while resting on bearing rings. These rings suffer wear and tear, which causes, for example, unwanted vibrations and consumption increase. The on site lathing helps restore the rolling surface and reduce vibrations.
Presses: they are machines frequently used in all industrial sectors. The mobile elements of the press suffer wear and tear. It is common to carry out the on site planning of the press hubs or on site broaching in the gearbox or in the bearing housings.
Flanges: They are joints frequently used in pipe systems, shaft coupling, machine mounting, wind turbine stretches coupling, heat exchangers, etc. With the passage of time and the effect of corrosion the flanges lose their sealing capacity. By means of the on site machining, the contact surface of the flange recovers the original features (serrated finish, roughness of the surface, flatness, etc. ). This type of machining is very common in refineries, metallurgies, chemical industries, etc.
In addition, through new manufacturing techniques, the flange is distorted and it is necessary to machine it in order to recover the original flatness. This usually happens with large flanges such as wind turbine flanges or the connection flanges of Voith or Schottel propulsion systems installed in any vessels.
Bolt removal and thread repair: When disassembling the pipe system or industrial plants, some bolts can seize up inside the thread, preventing its removal. By means of on site machining, the seized up bolts can be destroyed and the damaged threads can be repaired.
Shaft machining and lathe: It is possible to restore a seized up shaft to its original dimension by means of wield overlay, and subsequent machining and/or lathe. When the shaft removal is complicated, or when the downtime costs are high, the on site machining is the ideal solution. In addition, key seats can be machined in the shaft itself without removing it from the machine.
On site machining is also necessary in new works, in which the building processes do not guarantee the tolerance demanded by the equipment manufacturers. For that reason, on site milling of machine conveyor rollers (engine, gear motor, generator, etc.) is frequently used to correct flatness and levelness defects. In addition, broaching of shaft housings is frequently used when the clearance of such housings is large enough and the theoretical line must be complied with. Thanks to the alignment by means of laser tools it is possible to broach the clearance of housings by tens of meters with a precision of hundredths of millimeters.
How does Mecatec Vigo approach on site machining works?
Mecatec Vigo has designed and manufactured almost all the machinery and tools used for on site machining. We have a wide range of portable machining equipments: milling machines (turret and column), circular milling machines (up to Ø 6000), portable mills for flange facing, portable burnishers deep-hole drill, different tools, etc.
With our state-of-the-art machinery we carry out projects in a short time and with high levels of precision and finish, similar to the ones achieved in modern machining workshops.
In our design office we outline every machining project. By means of 3D design programmes we introduce the portable machining tool into the environment where it will work and we simulate the whole machining process It is often necessary to modify the machine or to manufacture adaptable elements to perform the machining work. Thanks to these simulations we prevent our machines in construction from having assembly problems. If neither of the available machines can adapt to the work to be done, we will design and build a new customized machine.
(*) Mecatec Vigo is certified to ISO 9001:2008 with Design.