plunger probes Archives - AUTOMATION INSIGHTS

Weld cells are known for their harsh environments, with high temperatures, electromagnetic field disruptions, and weld spatter debris all contributing to the reduced lifespan of standard sensors. However, there are ways to address this issue and minimize downtime, headaches, and costs associated with sensor replacement.

Sensor selection

Choosing the appropriate sensor for the environment may be the answer to ensuring optimal uptime for a weld cell environment. If current practices are consistently failing, here are some things to consider:

- Is there excessive weld spatter on the sensor?
- Is the sensor physically damaged?
- Is there a better mounting solution for the sensor?

For example, sensors or mounts with coatings can help protect against weld spatter accumulation while specialized sensors can withstand environmental conditions, such as high temperatures and electromagnet interferences. To protect from physical damage, a steel-faced sensor may be an ideal solution for increased durability. Identifying the root cause of the current problem is critical in this process, and informed decisions can be made to improve the process for the future.

Sensor protection

In addition to selecting the correct sensor, further steps can be taken to maximize the potential of the weld cell. The sections below cover some common solutions for increasing sensor lifetime, including sensor mounts and bunkers, and entirely removing the sensor from the environment.

Mounting and bunkering

Sensor mounting enables the positioning of the sensor, allowing for alignment correction and the possibility of moving the sensor to a safer position. Some examples of standard mounting options are shown in image 1. Bunkering is generally the better option for a welding environment, with material thickness and robust metal construction protecting the sensor from physical damage as displayed on the right in image 2. The standard mounts on the left are made of either plastic or aluminum. Selecting a mounting or bunkering solution with weld spatter-resistant coating can further protect the sensor and mounting hardware from weld spatter buildup and fully maximize the system’s lifetime.

Plunger probes

Using a plunger probe, which actuates along a spring, involves entirely removing the sensor from the environment. As a part comes into contact with the probe and pushes it into the spring, an embedded inductive sensor reads when the probe enters its field of vision, allowing for part validation while fully eliminating sensor hazards. This is a great solution in cases where temperatures are too hot for even a coated sensor or the coated sensor is failing due to long-term, high-temperature exposure. This mechanical solution also allows for physical contact but eliminates the physical damage that would occur to a normal sensor over time.

The solutions mentioned above are suggestions to keep in mind when accessing the current weld cell. It is important to identify any noticeable, repeatable failures and take measures to prevent them. Implementing these measures will minimize downtime and extend the lifetime of the sensor.

Leave a comment for a follow-up post if you’d like to learn about networking and connectivity in weld cells.

Last week’s blog spoke about reducing waste and downtime by implementing LEAN manufacturing procedures. This involves taking a proactive approach to improving efficiencies. This post will focus on selecting the right part for the job to reduce failure rates that lead to avoidable machine downtime and increased costs.

Hardly a day passes by where we are not contacted by a desperate end-user or equipment manufacturer seeking assistance with a situation of sensors failing at an unacceptably high rate. Once we get down to the root cause of the failures, in most cases it’s a situation where the sensors are being applied in a manner which all but guarantees premature failure.

Not all sensors are created equal. Some are intentionally designed for light-duty applications where the emphasis is more on economic cost rather than the ability to survive in rough service conditions. Other sensors are specifically designed to meet the challenges of specific application environments, and as a result may carry a higher initial price.

Some things to think about when choosing a sensor for a new application:

What kind of environmental conditions will the sensor be exposed to? For example:
- Very low or very high temperatures
- Constant exposure to or immersion in liquid
- Continuous vibration
- Extreme shock
- Disruptive electrical noise (hand-held radios, welding fields, etc.)
- Chemical contamination
- Physical abuse or impact
- Abrasion
- High pressure washdown procedures
- Exposure to outdoor conditions of UV sunlight, rain, ice, temperature swings, and condensing humidity
Is it possible to relocate the sensor to move it away from the difficult condition?
Is the sensor technology the best choice given the kind of application environment that it must operate in?
Is there a way to protect the sensor from exposure to the worst of the damaging effects?

When you reach for a catalog or jump on the internet to look for a sensor, it’s a good practice to just stop a moment first and make a list of the environmental challenges that the sensor could face. Then you will be prepared to make an appropriate selection that best meets your expected application conditions.

Heavy metal parts being loaded into a welding cell can damage specialty nut detection sensors designed to stick through a hole in a part. Plunger probes are a better solution.