Enhancing machine safety and throughput in heat-staking applications

(See PLUS Automation at FoodManufacturing.Live, 15 October 2025, on stand 48)

In semi-automated assembly processes, manufacturers continually strive to strike a balance between stringent operator safety requirements and the need to optimise production throughput. For a press operation to heat stake an assembly, traditional mechanical guarding can prove cumbersome. Therefore, Active Optoelectronic Protective Devices (AOPDs), more commonly known as Safety Light Curtains, can offer a streamlined and effective solution.

Heat-staking is a widely adopted low-cost method for securely joining metal components to plastic mouldings, particularly in the manufacture of automotive and electronic sub-assemblies. The process typically involves an operator loading a plastic moulding and associated metal parts into an assembly fixture. The fixture is positioned beneath a press-head, and an automated cycle is initiated.

The press-head, operating at temperatures that can exceed 350degC, descends to apply precise heat and pressure. This action causes a controlled thermal deformation of the plastic, creating a permanent, robust bond with the metal parts. After a pre-set dwell time, the head retracts, and the operator withdraws the fixture to remove the completed assembly.

The primary challenge at the customer's facility was the existing mechanical safety barriers. These were effective but unwieldy, requiring operators to open and close them for every cycle. This not only slowed down the loading and unloading process, constraining overall throughput, but also impacted workplace ergonomics. The company required a new safeguarding system that would provide reliable hand protection without obstructing access, all while being simple, space-saving, and robust enough for the production environment.

A streamlined solution with active safeguarding

A comprehensive risk assessment identified that a Type 2 AOPD solution would provide the appropriate level of operator protection; however, the customer opted instead for a Type 4 system, in line with its other units on their site. The chosen solution was Contrinex's 'YBES' 'Extended Slim', IEC 61496 Type 4 safety light curtains.

These robust units feature an aluminium 26 x 26mm (1") profile and are rated to EN/ISO 13849-1 Category 4, Performance Level PL e, and IEC 61508 Safety Integrity Level SIL 3, making them ideally suited for this application.

The customer preferred the 'YBES' 'Extended Slim', because it speeds up commissioning time, reducing costs and risks. The YBES curtains feature inbuilt alignment LEDs to expedite installation and a Bluetooth connection to a mobile phone or tablet running the ContriApp, which facilitates their commissioning.

The ContriApp enables fast diagnosis and, if required, commissioning of replacement units. Using a Bluetooth wireless connection, ContriApp also means that there is no need to find a 'special' commissioning cable or tool before the light curtain can be connected. ContriApp is a free-of-charge app available to download from the Apple App Store or Google Play, which means there is no additional cost for every maintenance engineer to have a copy ready for when it might be required.

Mounted vertically across the open front of the press enclosure, the light curtain creates an invisible protective field. Its 30 mm resolution is optimised for hand detection, and its 795 mm protected height ensures the entire access area is safeguarded. If an operator's hand or any other object intrudes upon this field while the press is active, the light curtain immediately halts the operating cycle, preventing the hazardous descent of the hot press-head.

Key features of the implementation included:

Robust Construction: Housed in rugged, extruded aluminium profiles with an IP65 + IP67 protection rating, the units are built to withstand the shocks, vibrations, and contaminants of a busy production floor.

Seamless Integration: An industry-standard PNP normally-open configuration and integral 5-pin M12 connector ensure straightforward connection to the existing machine control system.

User-Friendly Operation: Features typically reserved for higher-specification devices, such as an integrated alignment LED and permanent autocontrol, simplify setup and ensure reliable ongoing operation.

By replacing the cumbersome mechanical guards with Contrinex Safetinex light curtains, the manufacturer has achieved significant improvements. The new system occupies less space, enhancing ergonomics and providing unimpeded access for loading and unloading. This has directly translated into increased productivity, all while actively safeguarding operators with a reliable and cost-effective solution.