Answer: Because it has the extreme potential to save a lot of money. The general mentality these days, with regards to inductive proximity sensing, has been, “Lowest price wins the business”. Some manufacturers and industrial consumers alike have been accused of treating these devices as true commodities. Some salespeople have also caved in over the years with regards to price pressures in exchange for the big win. We’re all guilty to a degree, for leaving money on the table and hastening price degradation for this category of automation device over the years!
Maybe a little of this is justified. As electronic device manufacturing volume increases, prices for sub-components used to make these sensing devices decrease while manufacturing methodologies become more streamlined. The result is that cost comes out, prices drop and the game becomes more globally competitive. But with regards to application specific, hostile sensing applications, there must be a paradigm shift otherwise consumption can become gargantuan, both for material and for labor costs in the real world of factory automation. Using “generic” non-application-specific sensors in rotten environments, like welding for parts presence or Poke-Yoke applications, creates a problem. “Generic” sensors fail with regularity, change out becomes a massive maintenance issue, machine down time becomes costly and even bad parts can potentially be made (a really bad problem….audits and everything associated with shipping bad parts must obviously be avoided as much as possible).
Recently Hank Hogan published an article in Control Design titled “Sensor, Diagnose Thyself.” (To be honest, I really wanted to steal his title for my blog entry.) I think Hank did a great job dissecting the key benefits of smart sensors and the amazing things you can do with them. Utilizing the technology IO-Link (that we have discussed in many past Blog Entries), sensors can communicate more with the controller and provide more data than ever before.
Some of the key points that I really thought are useful to maintenance and engineers at end-user facilities or machine builders:
Being able to detect and notify about pending failures; for example a photoeye’s lens is dirty and needs to be cleaned.
A failed sensor needs to be swapped out quickly; IO-Link allows for the smart sensors settings to be cloned and the swap to be executed super fast.
Configure a sensor before installation; program with your laptop: sample rate, response time, measurement settings, on/off switch points, anything!
One platform can be used for many sensor types; this gives familiarity to a single interface while using multiple sensor types and technologies.
In the future sensors in a wireless cloud would self-heal; this is an amazing concept and if we can figure out the price for radios and batteries to make it cost-effective, I think this could be a game changer someday.
But all that being said, it really comes down to the total cost of ownership doing it the standard sensor way versus the smart sensor way. I think you will pay more upfront in capital but down the line there will be less cost in maintenance and downtime.
We often hear companies talk about how great their products are or how well they hold up under adverse conditions, but many of us wonder just how much of that is hype. While I cannot vouch for all the claims out there, I can relate to you (the reader) and share my Balluff prox story and how I’ve seen them survive.
I was working in the industrial maintenance field when I came across the prox in this tale. The prox was being used to sense motion of sanding tape in a polishing machine. This system was designed to polish the part in two directions and the purpose of the prox was to ensure that a proper amount of sandpaper had advanced with each direction change. The sandpaper was on rolls, which threaded through some rollers, including a plastic one that had a piece of metal embedded inside. The prox was set up to monitor this plastic roller and register when the metal piece rotated by and thereby indicating to the system that the sandpaper had advanced. If this prox did not change states, the system would fault out and turn on an error/alarm light. To reset the alarm the operator had to hit a reset button and then start the system again.
Whenever you are providing sensor training or even talking with someone about sensor inevitably, you will be asked about the applications where they are used. Try as you may, it’s sometimes difficult to explain the various ways sensors are used to solve the multitude of applications that exist.
Recently, one of my colleagues brought an interesting article to my attention that I am passing on in this blog post. Check out this article on Sensoring for In-Die Tapping. The author explains the application and provides possible solutions varying from mechanical sensors, photoelectrics, and inductive proximity sensors. In my opinion, it is worth reading to give you another perspective on how to solve one of the many ways to use sensors. Let me know what you think! Did this give you another perspective?
Inductive proximity sensors in a welding environment face a variety of hazards. Hot metal particles – called weld spatter – are ejected from the welding process and can melt or burn their way through unprotected plastic sensor faces. Built-up weld spatter (often called weld slag) can eventually cause a sensor to trigger on falsely. If the slag can’t be removed, the sensor has to be replaced.
One solution to these issues is sensors made with tough ceramic faces. The ceramic face stands up to the hot weld spatter without melting, and doesn’t provide a good surface for slag adhesion. Even if slag does build up on a ceramic face, it can typically be removed during maintenance without the need for sensor replacement.
Flush-style sensors actually have a shield that restricts the magnetic field so that it only radiates out of the face of the sensor. Flush-style, or shielded sensors, can be mounted flush in a metal bracket or even in your machine without the metal causing the sensor to false trigger. When mounting two shielded inductive proximity sensors next to each other, you should typically leave one diameter of the sensor between adjacent sensors. The shielded-style of sensor will typically have approximately one-half of the sensing distance that a non-shielded version will have. For example, a 12mm shielded inductive sensor will have a sensing distance 2mm whereas a non-shielded version will have a sensing distance of 4mm. Although shielded style sensors have a shorter sensing range they can be buried in a machine or a bracket that will offer protection against damage.
An inductive proximity sensor is a non-contact device that is used to detect a metal target. When power is applied to an inductive proximity sensor the sensor’s coil will generate an oscillating electromagnetic field out of the face of the sensor. This field will vary in shape and size depending on the diameter of the sensor and whether the sensor is a shielded or non-shielded model. For example, a M12 size sensor will generate a smaller electromagnetic field than an M30 size sensor. When the metal target gets close enough to the sensor’s face it begins to penetrate the electromagnetic field. When this happens, eddy currents are generated on the surface of the metal target. As the metal target gets closer to the sensor face – the eddy currents increase – which in turn decrease the amplitude of the electromagnetic field. Once the electromagnetic field’s amplitude is reduced to a certain level – the sensor will activate indicating it has detected the metal target.
This explanation is a little wordy and, as in most cases, a visual demonstration can be of great help. Watch this short video explaining the basic functionality of an inductive proximity sensor.
For more information on inductive proximity sensors, click here.
I have led many inductive proximity sensor training classes where an “Ah ha” moment happens when discussing the effects of target size on an inductive proximity sensor. As more and more extended range sensing models arrive on the market, it’s even more critical to understand how target size affects sensing distance performance.