Making light work of machine safety
Safety mechanisms include an override for smooth restart and built-in external device monitoring.
protective height of 240 mm; and the F3SG-4RA0910-30 hand/arm protection system with 44 beams and a protective height of 910 mm. Three resolutions Panasonic Industrial Automation Sales has also recently upgraded its ranges of light curtains. The Type 4 SF4D models, for example, feature new housings with a seamless structure and minimal joints, providing improved environmental resistance and easier installation and operation. Improved self-checking circuitry enables the system to constantly check for correct operation and to identify fault conditions, such as cable wiring disconnects, short circuits and interference. Response time is 14 ms irrespective of the number of beam channels, axis pitches or the number of units connected in parallel. Additional features include an easy to set up muting control function with handheld controller to control specific beam axes. Thus, the unit can be programmed to allow objects through a line but not people. Fixed and floating blanking is also achievable. Safety mechanisms include an override for smooth restart and built-in external device monitoring. Potential light interference is minimized with automatic scan
timing shifts and a double scan/ retry function. The company offers a wide range of units in three resolutions for finger, hand and arm/foot detection. The SF4D-F79 high resolution model, features a sensing distance of 14 mm to detect fingers, with 79 beams on a 10 mm beam pitch and a protective height of 790 mm. For hand protection, the medium resolution SF4D-H12 is a compact unit with just 12 beam channels on a 20 mm beam pitch, providing a protective height of 230 mm. Units up to 1.9 m protective height are available. Finally, for hand/foot detection, the SF4D-C range provides from 16 to 48 beams on a 40 mm beam pitch, sensing objects of 45 mm diameter, for protective heights from 630 mm to 1.9 m. The SF4D-A24 is a typical example. Summary Advances in microprocessor control, high reliability infrared LEDs and compact yet robust mounting design are giving industrial light curtains a new
lease on life in the modern manufacturing plant. Easier installation on complex machinery and better choice in terms of protective height and resolution, make this safety system more widely applicable. Programmable functions such as muting and blanking ensure that the light curtain can be adapted to most production lines and machine guard applications, as well as to changing production requirements driven by the need for responsive, flexible automation systems in a more competitive market.
Figure 2: With a muting control function, the Panasonic Industrial light curtain will allow specific size objects through, but will detect a hand, for example, and the machine will stop instantly.
diameter. Operation range is from 30 cm to 10 m (long) and 30 cm to 3 m (short). The medium resolution hand/ arm protection units range from 8 beams at 190 mm to 124 beams at 2.51 m protective height. With a beam gap of 20 mm, object resolution is 30 mm diameter. Operating range is from 30 cm to 20 m (long) and from 30 cm to 7 m (short). Response time from on to off is 8 to 18 ms maximum normally, depending on the model, or it can be set to a slow mode at 16 to 36 ms. Off to on response time is 40 to 90 ms. The effective aperture angle of Type 4 units is +/-1.5o with emitter and receiver operating range of 3 m or greater, and +/-5o for Type 2 units.
Compared to earlier versions, these units are installed in a more robust housing for long- term use in harsh conditions and withstanding shocks from impacts from tools or material. The housing is more compact, yet torsion resistant. Quick connect cables and connectors reduce the time required for wiring and set up. Optical synchronization between emitters and receivers now requires only a single cable. The use of advanced electronic controls together with facilities such as a smart muting actuator, allows the system to be easily configured and reconfigured to suit different production lines and/or work pieces. An advanced muting function detects the zone where work pieces pass on a conveyor, for
example, and tolerating vibration, will disable only the relevant beams until the object has passed. Where different sized objects pass on the same line, partial muting can be automatically performed. Additional features aim to reduce the number of accidental machine stops while maintaining safety. The reset switch, for example, can be programmed only to operate when certain conditions are met (i.e. all detected objects are removed). A reduced resolution function allows the system to differentiate between objects, such as an automated transport vehicle, and the potentially dangerous ingress of a human foot. Typical models include the F3SG- 4RA0240-14, a finger protection unit with 23 beams and a
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