Installing and Running

The FIFO Axes example program reads in the position data for a FIFO group from a file, feeding it to the group’s FIFO memory. The FIFO group is started, continuing until the data stream comes to an end. The data stream can only come to an end if the logical end of the positioning process has been reached, or if the "topping up" data rate is not adequate.

• Download FIFO Axes example program: fifoaxisv3_00.exe

The example program uses the library TcNcFifoAxis.lib which can be ordered as an additional product. It uses simulation axes (axes with simulated encoders) and can thus be run on any Windows NT PC without additional hardware. The file TcNcFifoAxisSample.wsm is loaded into the TwinCAT System Manager, and the system is started with this setting.

The NC configuration contains a PTP channel with four PTP axes and a FIFO channel that does not initially contain any axes. The FIFO group is configured under the FIFO channel. The FIFO memory has room for 250 position entries for four axes.

The FIFO store’s timebase is 2 ms. In this case the timebase is synchronous with the NC timebase, but this does not have to be the case. The timebase for the FIFO entries determines the interval at which a new axis positioning value is taken out of the FIFO memory. There is more information about this in the TwinCAT FIFO chapter.

The axis speed results from the difference in position of two neighbouring FIFO entries divided by the FIFO timebase. This speed can be affected by altering the channel override. The override can be varied between 0% and 100% during the positioning. A value of 0% brings the axis to a stop, yet without halting the positioning task. The override types are described in the "Override" section.

The example program assumes that a file with position data exists in the directory C:\CamDesign, although the directory can nevertheless be changed as described further below.

• FifoTableBig5.Bin

The example program, TcNcFifoAxisSample.pro, is loaded into TwinCAT PLC Control, compiled and run.

TwinCAT Scope is used in order to be able to examine the result. The supplied setting, TcNcFifoAxisSample.scp, allows the axis movements to be recorded.