Weld Select Series

One of the most common and frustrating applications in automated and robotic welding is reliably detecting the presence of a weld nut. There are some solutions and technologies on the market that have varying levels of success. Detection of the weld nut is very application specific: sense it during the load or in a secondary check station? How much space is available for a sensor and connector? Is it sensed from under the part or on top of the part? What is the size or shape of the nut? What are the tolerances? Each type of technology brings benefits and weaknesses based up on the answers to these questions.

Non-contact inductive proximity sensors must perform a wide variety of clamping and nesting indication, as well as poka-yoke functions in harsh welding environments. Hot weld-spatter accumulation, elevated ambient temperatures, and strong electromagnetic fields emitted by weld guns can cause false triggering and degrade sensor performance.

Incidental sensor damage caused by impact during parts loading can significantly degrade sensor performance, shorten sensor life, or even destroy a sensor. Balluff steel face inductive proximity sensors can withstand multiple heavy impacts and abrasion, and often have a long sensing range so it can be placed out of harm’s way.

Weld cells demand the toughest connectivity solutions. Weld debris shortens the life of a cable in different fashions. Weld-spatter can build up on the jacket, pulling the cable out of the connector. Weld sparks can burn through the cable causing shorts in the connection, and the extreme environment temperatures can cook components. Balluff’s family of high durability cables were designed with weld environments in mind. The bodies of the connectors are weld spark immune with PTFE coated nuts to prevent spatter from sticking or burning the connectors. This family has multiple cable jackets to endure different environments.

For inductive proximity sensors, size matters. The larger the sensing face, typically the longer the range of the sensor. This has two ramifications in an automated welding application. First it can be challenging to detect the edge of a part with a sensor, so it is recommended that the surface, not the edge, be detected. If an edge needs to be the target, it is recommended that the sensor face be similar in diameter to the thickness of the part. Second, it is important to not use mini sensors for detecting large parts. Mini sensors are more prone to damage from large parts due to their short sensing range and small mass. These mini sensors are powerful when used properly but should be used sparingly with large parts, or kept for use in sub-assembly fixtures.

Sensors with cable out are one of the cheapest options from most suppliers, but they aren’t typically suitable for welding automation. The sensor cable is one of the most common points of failure in a weld cell due to damage from weld spatter. Having to replace a perfectly working electronic sensor due to cable damage is not operational excellence. Quick disconnect sensors allow for replacement of only the failed component and reduce time to replace. Including a short sacrificial cable in extremely harsh applications can reduce cordset replacement downtime when it is inevitable due to application design.

I/O hubs have become a very common device used for connecting the many sensors used in automated welding. These devices are nice because they are connected to a network and can provide diagnostic data, such as short circuits and overloads. However, many manufacturers struggle with damaged network cables or homerun cables that can cause intermittent communication issues that are difficult to troubleshoot. By using IO-Link hubs and masters for I/O, the master can be mounted out of harm's way so it can always communicate with the PLC and network. The I/O and sensing devices are mounted in the workcell where the damage can occur. If a device fails, the master can report the details up the chain. This architecture allows for improved troubleshooting through constant communication and readily available diagnostics.

Time is a valuable resource. When a problem occurs, maintenance crews and operators need to quickly find a solution and get the equipment running. By implementing IP67 machine mount I/O, the failed points become more visible and accessible. In addition, diagnostics provided by the individual intelligent devices can help narrow the scope of the problem and speed recovery. Operators can provide technicians exact details of the failure and time can be saved for the technician by knowing and preparing for the problem before they even arrive at the equipment.

When moving materials between production facilities, it is vital to keep track of what left the building and what has been returned. This becomes even more important when shipping parts to a customer. Specialized dunnage carts and racks for moving finished parts can be high priced. If these racks are not returned or go missing, it can eat away at profit margins or make it harder to deliver parts safely to a customer. By using UHF RFID systems, manufacturers are recording every cart that leaves the facility, they know which truck and at what time it left. This allows for documentation of delivery as well as chain of ownership awareness of valuable dunnage carts and racks.