The alternating or multiple processing table is a technical method, used on CNC-machining centres and intended to increase the economic efficiency, especially in respect to the processing of smaller workpieces. Since the mid-1990s, most wood processing machines have this function.
Difficulties with the processing of a single workkpiece:
- The machine stands still while workpieces are being fed or removed.
- In most cases the presence of the operator is not necessary during the processing, yet time is often too short to run another operation.
- While processing a small workpiece the big remaining part of the table is unused.
Problem solution by means of alternating processing:
Alternating processing means that a workpiece is in process in one area of the table while workpieces are being fed or removed in another area of the table.
This function could be basicly possible without any special device by simply using an adapted programme for the simultaneous processing of several workpieces. Yet, such a programme hasn't been in use since many years due to a lack of flexibility and for safety reasons.
Today an alternating processing machine has the following features:
- Each separatly feedable working sphere has an idividual workpiece's reference point. Thus no individual programmes are necessary, yet only one programme is linked to individual working spheres. The most simple case is that of having one workpiece's reference point on the left, the ohter reference point on the right of the machine. On long machines, 4 working spheres can be set up in the x-axis. On big machines or for the processing of quite small workpieces, the machine table can be also set up in the y-axis, making it possible to use up to 8 reference points.
- For safety reasons a collision of moving machine parts with the operator must be avoided at any point during operation. Thus the safety devices must be designed to ensure that the Operator, feeding or removing a workpiece on one side, does not come in contact with the aggregates support.
- Bumper: The perfect safety device for multiple processing tables. Theoretically work with flexible field sizes is possible here, because the safety of the operator is absolutely ensured.
- Safety mat and light barrier: Because of the quite wide aggregate support a middle area is constantly active, causing the operator to be slightly limited in his free movement.
A special form of alternating processing is the mechanical separation of the table. This is to be found on fix gantries, where the y-axis is realized by the moving of the machine tables. There are completely separated working areas by using 2 tables. A safety distance - also with mats and light barriers - is not necessary.
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