Light curtain to protect operator safety

Summary

During semi-automated heat staking of assemblies for domestic white goods, manufacturers use light curtains to preserve operator safety without compromising production throughput. The active optoelectronic protective device (AOPD), mounted directly in front of each bench-mounted heat-press, prevents the press-head from descending if it detects any intrusion in the working area, halting the operating cycle immediately.

Application

Heat-staking is a popular process for fastening metal parts to plastic moldings, and is commonly used by white-goods manufacturers during production of sub-assemblies. At each station, an operator loads a molding and one or more metal parts into a slide-mounted assembly fixture. Once the components are correctly inserted, the operator pushes the slide into position beneath the press-head, triggering the automated heat-staking cycle.

The heated press-head, which may reach temperatures in excess of 350oC (660oF), descends toward the pre-positioned components. It applies heat and pressure to specific areas of the molding, causing a controlled thermal deformation that creates a permanent joint between the metal parts and the molding. Following a pre-determined dwell period, the head returns to the raised position, ending the cycle; the operator withdraws the slide and removes the assembly from the fixture.

Existing mechanical safety barriers are cumbersome and inconvenient; throughput is constrained as a result of the time taken to open and close the guards during each cycle. The company requires an alternative safety guard that provides effective hand protection while allowing unobstructed loading and unloading. It must be simple, space-saving and operate reliably in the production environment.

Solution

The company’s risk assessment confirms that Type 2 AOPDs (active optoelectronic protective devices) will ensure appropriate operator protection. Designed for applications where the risk has been evaluated as moderate, Safetinex IEC 61496 Type 2 light curtains from Contrinex are rated to EN/ISO 13849-1 Category 2, Performance Level PL c and IEC 61508 Safety Integrity Level SIL 1, making them ideal for the application.

The heat-staking press is housed in an open-fronted enclosure with clear impact-resistant walls. The light curtain has an operating range of up to 12 meters and a resolution of 30 mm, ideal for hand protection; it safeguards the open front area of the press, allowing easy access when required. Detection height is 795mm, ensuring safe operation without impeding the operator during loading and unloading.

Manufactured with rugged aluminum housings and IP65 + IP67 protection, these units are well-suited to the production environment and will withstand shocks and vibrations. Industry-standard PNP normally-open configuration allows connection to the customer’s control system via an integral 5-pin M12 cable connector. These units have an integrated alignment LED and permanent autocontrol – a feature not usually found on Type 2 safety devices.

The new sensors take up much less space than the mechanical guards they replaced, improving workplace ergonomics. Loading and unloading is no longer impeded, increasing productivity while actively safeguarding operators. Safetinex Type 2 light curtains provide a reliable and cost-effective solution.