General

The Flying Saw is a slave axis that can be synchronized to a moving master axis. The slave axis moves in synchronism with the master axis to perform machining processes. This kind of movement, synchronized to the master axis, means that a workpiece can be machined even while it is being transported.

An important difference between the "Flying Saw" and the "Universal Flying Saw" is associated with the initial conditions required of the slave axis for the synchronization. The "Universal Flying Saw", unlike the "Flying Saw", is able to start synchronization of the slave even when the slave has already started, and is therefore no longer stationary. The "Universal Flying Saw" also calculates improved set value profiles, and these can be influenced by the user through a wide range of boundary conditions.

The ratio of the master velocity to the slave velocity in the synchronous phase is parameterized via a variable coupling factor. This coupling factor in the case of a diagonal saw, for instance, is chosen to be unequal to 1, so that the velocity component of the slave axis in the direction of the master axis movement (vslave parallel to Vmaster) in the synchronized phase is equal to the master velocity (vmaster). (See diagram.)

General 1:

 

The Universal Flying Saw basically provides two different synchronization methods. In the case of synchronization to velocity the slave is synchronized to the master as quickly as possible, bearing in mind the coupling factor. The coupling position for the master and slave axes therefore results from having set the fastest possible synchronization as the target. In contrast to this, the coupling position of the master and slave axes is parameterized by the user under synchronization to position. The master and slave movements will in this case therefore be moving in synchronization as from the specified position at the latest.

Both of these synchronization methods permit a variety of boundary conditions to be specified for the synchronization phase. These boundary conditions make it possible to adapt the synchronization process to the needs of the machine.

General 2:

This manual describes the Universal Flying Saw TcMc2_FlyingSaw.lib, which is available from TwinCAT Version 2.9, Build 248. If you are using the previous version TcNcFlyingSaw.lib and need further information, see here.

Interfaces

The Universal Flying Saw is operated and monitored from the PLC using appropriate function blocks. For commissioning purposes, however, the Universal Flying Saw can also be started directly from the TwinCAT System Manager. In this case, the cyclic NC/PLC axis interface and ADS communication are used as the underlying interface.

 

Synchronisation to velocity

In Synchronisation to velocity the slave axis is synchronised to the master axis using the specified dynamic parameters as rapidly as possible. In the synchronous phase, the slave velocity is proportional to the master velocity, so that:

General 3:

The synchronisation procedure

Synchronisation of the slave axis to the master axis proceeds according to the following scheme:

  1. Starting the Universal Flying Saw. This corresponds to the logical coupling to the master axis. This moment is referred to as the coupling time.
  2. The synchronisation phase: The slave is accelerated from its initial condition up to the velocity of the master whilst observing the boundary conditions for slave movement specified by the user. The time at which the synchronisation phase changes to the synchronous phase is referred to as the synchronisation time.
  3. Synchronous phase: The slave moves synchronously with the master.
  4. Uncoupling the Universal Flying Saw. This is an online change. The coupled slave once again becomes an independent master that continues to move without limit with the velocity resulting from the online change.
  5. This could mean that the former slave restarts or stops. The full functionality of a TwinCAT NC master axis is once more available.

Synchronisation to position

In Synchronisation to position the slave axis is synchronised to the master at the specified synchronisation position using the specified dynamic parameters. This means that the slave axis reaches the synchronous velocity at exactly the synchronisation position of master and slave, after which it moves in synchronism with the master. The slave velocity in the synchronous phase is governed by:

General 4:

The synchronisation procedure

Synchronisation of the slave axis to the master axis proceeds according to the following scheme:

  1. The start of the Universal Flying Saw. This is the logical coupling to the master axis. This moment is referred to as the coupling time.
  2. The synchronisation phase: The slave is accelerated from its initial condition to the master's velocity, reaching the slave synchronisation position and synchronisation velocity precisely at the specified master synchronisation position. The boundary conditions specified by the user for slave movement are maintained during this process. The time at which the synchronisation phase changes to the synchronous phase is referred to as the synchronisation time.
  3. Synchronous phase: The slave moves synchronously with the master.
  4. Uncoupling the Universal Flying Saw. This is an online change. The coupled slave once again becomes an independent master that continues to move without limit with the velocity resulting from the online change.
  5. This could mean that the former slave restarts or stops. The full functionality of a TwinCAT NC master axis is once more available.

Parameterisable boundary conditions governing synchronisation

In principle, any initial conditions may apply to the calculation of the synchronisation profile for the master and slave axes.

The transition of the slave's movement from its initial state to the synchronous state is calculated in such a way that boundary conditions that can be specified by the user and that govern the slave's movement are maintained. These boundary conditions can be used, for instance, to limit the maximum slave velocity, or to prevent an overshoot in its position.

The calculation and checking of the parameterisable boundary conditions proceeds on the basis of the characteristic values determined for the synchronisation phase. In the determination of the characteristic values, the idealised assumption is made that the master axis will continue to move at a constant velocity, i.e. with no acceleration, after the coupling time. Exact calculation and checking of the parameterisable boundary conditions is only possible if this assumption is made. Any other reasonable assumption about the future movement of the master is not possible, since the master's future movement is not known at the time of coupling.

An acceleration of the master that might occur in the future will also affect the slave dynamics as a result of the coupling. Such acceleration by the master will have the effect that the calculated and checked values may be overshot or undershot in some cases, depending on the master's acceleration. Characteristic values that may be affected by master acceleration can be seen in the tabular description of the characteristic values.

Characteristic values describing slave movement

The characteristic values governing the movement that the slave will undergo during the synchronisation phase are available to the user after the Universal Flying Saw has been started. This value structure contains magnitudes such as the maximum slave acceleration, the minimum and maximum slave position, and so forth. These values are calculated under the assumption that the master is free from acceleration, and are therefore in some cases only exactly correct for such a case.

Note

The master acceleration at the time that the "Universal Flying Saw" starts has a significant effect on the profile calculation and its optimization. This means that if an encoder axis is the master, the velocity and the acceleration must be carefully filtered, or even the calculation of the actual acceleration must be deselected (see. "Encoder mode").