Precise measurement and multitasking features are top priority when machining extra-large workpieces. By Alan Reynvoet, chief sales officer, and Bernd Duchstein, marketing, Schiess
Extra-large (XXL) machine tools, which process workpieces with a volume greater than 10 cubic m, face specific challenges not commonly seen in smaller machine tools:
- Due to the cost and time taken, it is very difficult or not feasible to build prototypes.
- Machines have a life cycle of more than 20 years.
- Very high accuracy is required.
- Economic concerns in a limited market.
From The Get-Go
How can these challenges be met? When prototypes cannot be built, everything has to work straight away, from design and production to assembly and commissioning. Measuring finished parts—of whatever the size—is a key factor in this case. Measurement keeps the potential for further work on the assembled machine to a minimum.
The machine should be measured geometrically and the positioning accuracy should also be measured at an internally defined stage of completion. If the results are within specified limits, the machine can be fully assembled and put into operation. The set of tests is then completed by checking relevant technical parameters and producing workpieces for acceptance, providing the conditions for an accurate machine.
The life of individual components cannot be extended forever. However, the machine can be designed to be easy to maintain and service. Multitasking has also always been a standard feature of XXL machines. A common principle in this case is to use a consistent interface between ram and head so that you can use heads for different machining processes on one and the same machine.
As finished workpieces are very costly, the reject rate has to be zero percent. High accuracy can be achieved by methods such as hydrostatics, which provide extreme vibration damping. Apart from these challenges, diversifying into other sizes or growth sectors could also be considered, such as aviation.
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