HEIDENHAIN TNC 306 Technical Manual - Manual (Page 156)

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TNC 406/TNC 306 4 Gap control 3/97
4 Gap control
The gap control is switched on with M36 and switched off with M37 (see Chapter 7 M-Functions).
The control responds to the analog gap signal (0 to 5V), and the input of the gap signal as described
in the following, by sending an analog voltage to the nominal value outputs. If the gap is too small
and there is a tendency towards short-circuiting or arcing, the electrode is retracted along the
programmed contour. If the gap is too large—or at the start of the eroding process—the electrode
advances along the programmed contour. When the eroding process is stable, the gap is only
controlled to within a few
µm.
Feed forward control allows the control to react extremely quickly to the gap signal, resulting in very
low servo lag at low speeds. In particular this improves the gap control behavior when eroding with
graphite.
Machine parameter MP2130 defines the maximum speed at which feed forward control is to be
maintained during the eroding process. If the value is exceeded, the control switches to servo lag
mode. During an active eroding process marker M2785 is set.
MP2130 Maximum speed for feed forward control during eroding
Input range: 0 to 500 (mm/min)
Set Reset
M2785 Eroding process is active NC NC
4.1 Input characteristics of the gap signal
The input characteristic of the gap signal can be adapted to the particular machine being used. The
input characteristic is defined with machine parameters MP2010, MP2020 and MP2030 (see also
Chapter 13.2.1 "Servo sensitivity").
Machine parameter MP2070 defines the speed at maximum gap voltage (5V) if MP2010 = 1 and
MP2020 = 1 and thus the scale. With machine parameter MP2080 the gap can also be inverted
(MP2080 = 1). The input characteristic can still be influenced by machine parameters MP2131 and
MP2132 over the gap signal range of 2.5 to 5V.
For calculations in the PLC, the current value of the gap signal is stored in word W392.
MP2010 Characteristic gradient
Entry range: 0.1 to 10.000
MP2010.0 Input characteristic range 2.5 to 5V
MP2010.1 Input characteristic range 0 to 2.5V
MP2020 Multiplication factor
Entry range: 1,000 to 10,000
MP2020.0 Input characteristic range 2.5 to 5V
MP2020.1 Input characteristic range 0 to 2.5V