388 HEIDENHAIN Technical Manual iTNC 530 HSCI
Differences
between the
HR 520 and HR 410
handwheels
Due to the modified internal wiring of the permissive buttons, a cross-circuit-
safe signal for evaluation through the safety circuit is now available for the HR
520 FS and the HR 410 FS. Cross-circuit-safety is necessary in order to prevent
a line short-circuit (e.g. defective handwheel cable) from leading to an
unintentional permissive situation on a machine tool.
With the current principle behind the permissive buttons (handwheels without
FS), in normal operation a faulty switching contact (permanently at "1") cannot
be distinguished from a cross-circuit.
With functional safety, only a specific retrograde switching signal of the
permissive buttons is used for enabling (permission), and a cross-circuit or a
defective permissive button can already be detected during the idle state.
Another advantage of the new FS handwheels is that only one of the two
permissive buttons (PB) must be pressed during permissive mode. This is
realized through an additional switching contact per permissive button (see
figure). Each of the two permissive buttons triggers a normally closed contact
and a normally open contact. The two contacts are not positively driven,
meaning that if one of the contacts gets jammed, it will not continuously and
erroneously grant permission.
PB.1
PB.1
PB.2
PB.2
X1/
1
X1/
3
X1/
2
X2/
1 3
X2/
4 2
X1/
1
X1/
3
X1/
2
X2/
1 3
X2/
4 2
HR 410FS/HR 520FS
HR 410/HR 520
No cross-circuit safety
for permissive buttons
Emergency Stop
Emergency Stop
Cross-circuit safty for
permissive buttons
Handwheel adapter
ID 296 466-xx
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