Detecting Small Bubbles? Consider These Factors First

BubbleDetectionBubble or air-in-line detection is a common lab automation application. In these types of applications it’s important to know whether or not liquid is flowing through a line to ensure safe and proper function in liquid-handling processes.  As these processes utilize smaller and smaller volumes of liquid — which provides cost and time saving benefits — it becomes more and more difficult to detect the potential air pockets forming inside the line. The most common approach in detecting these minute air pockets is a through-beam, photoelectric bubble sensor.

Photoelectric bubble sensors provide non-invasive detection of fluids and air pockets residing inside a tube. They have fixed opening dimensions for standard tube sizes allowing the selected tube to sit in perfect position between the sensor’s optical components. When the sensor’s light beam is blocked by fluid (or an air pocket) inside the tube, the received signal varies and external electronics determine if the signal variation is above or below the set threshold. Once the threshold is met the sensor’s output is switched.

Detecting bubbles sounds quite straightforward and simple, but in reality the application can be somewhat complicated. Several factors should be considered for reliable detection. Listed below are a few factors to consider:

  1. Tube diameters (inner and outer)
  2. Tube transparency
  3. Liquid type(s)
  4. Liquid transparency

Tube Diameters

Tube Sensor DrawingBecause a tube acts as a lens for light to travel it’s important to factor in the tube diameters. If there is a large difference between the outer and inner diameters of a particular tube, the outcome is a relatively large tube wall. A large tube wall will allow light rays to travel from the emitter through the wall straight to the detector without passing through the inner diameter of the tube, where the liquid or bubble is present. This causes unreliable detection. By accounting for both the inner and outer tube diameters a proper determination can be made in selecting what type of sensor to use to ensure that light only passes through the inner diameter of the tube and not through the wall.

Tube Transparency

Since photoelectric tube sensors operate on the principle of light detection, light must make it through one end of the tube and out the other end. Therefore, the transparency of the tube is critical. If the tube is opaque a photoelectric sensor solution is unlikely; however, in some cases it’s possible for a photoelectric tube sensor to detect through an opaque tube.

Liquid Type(s) and Transparency

The liquid type(s) and transparency are critical when determining which photoelectric tube sensor to use. If the liquid type is non-aqueous, without factoring in its transparency, it’s best to use the principle of light refraction through the liquid. If the liquid type is aqueous and is completely transparent or semitransparent, it’s best to use the principle of light absorption through the liquid. The following table will help determine what type of sensor to use with respect to the liquid type present inside the tube.

BubbleSensingChart

Since the type of applications that require precise bubble detection range in specifications from the use of hundreds of different liquids to specialized tube dimensions, this post only touches the surface of the photoelectric sensors for bubble detection.  For more information on tube sensors, please visit the Balluff website.

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Which cable jacket is best for your application?

There are many different types of cable jackets and each jacket works well in a specific application.  The three main sensor cable jackets are PVC (Polyvinyl Chloride), PUR (polyurethane) and TPE (thermoplastic elastomer). Each jacket type has different benefits like washdown, abrasion resistant or high flexing applications.  Finding the correct jacket type for your application can extend the life of the cable.PVC

PVC is a general purpose cable and is widely available.  It is a common cable, and typically has the best price point.  PVC has a high moisture resistance, which makes it a good choice for wash-down applications.

PURPUR is found mostly in Asia and Europe.  This cable jacket type has good resistance against abrasion, oil and ozone.  PUR is known for being Halogen free, not containing: chlorine, iodine, fluorine, bromine or astatine.  This jacket type does have limited temperature range compared to the other jacket types, -40…80⁰C.

TPETPE is flexible, recyclable and has excellent cold temperature characteristics, -50…125⁰C.  This cable is resistant against aging in the sunlight, UV and ozone.  TPE has a high-flex rating, typically 10 million.

The table below details the resistance to different conditions. Note that these relative ratings are based on average performance. Special selective compounding of the jacket can improve performance.

ResistanceTo

Choosing the right jacket type can help reduce failures in the field, reducing downtime and costs.  Please visit www.balluff.us to see Balluff’s offering of sensor cables in PVC, PUR and TPE.

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A Simple Way to Improve Speed and Efficiency

We are all efficiency-hungry. We want everything from service in restaurants to production on our plant done efficiently. Sometimes we use the term “speed” interchangeably with efficiency. Is that really a big deal? Of course it is.  How many times have you placed an order at the drive-through window of a fast-food chain and gotten wrong items or incomplete orders? Why do they make mistakes? Because, they are measured on customer response time (speed) and not on accuracy of the delivery (efficiency) — again speed replaced efficiency.

So is the maintenance team at your production plant efficient or speedy?  In my opinion, once you have the right maintenance person for the problem at hand they would be both efficient and speedy. The point I want to make is that identifying what type of maintenance service your system needs is the important part in making your maintenance team efficient in responding. Another way would be hiring all-rounder maintenance person who can handle electrical, mechanical and all other issues that your system can throw at him/her. How many of those all-rounders you can find and keep?

Today, in most plants we see three-segment or five-segment stack lights on almost all sorts of equipment that tells you the status of the work-cell: Green = everything good; Red = Need maintenance now!!! But, does it tell you about type of maintenance? So, what do we do? We send our maintenance tech out to the system; he looks up error codes on the small 8×10 HMI and figures out that the system needs an electrical tech to handle the situation. Wouldn’t it be nice, if that stack-light was a little smarter to tell you that “Hey, this system needs {electrical, pneumatic or mechanical} maintenance” instead of just flashing a red light? If it was that intelligent it would probably also tell you that this work-cell is running out of raw materials, or how the system is performing to the production quota etc.

SmartLightWell, I have great news: since the introduction of our one of a kind SmartLights our customers shared so many novel uses of this intelligent LED tower light that it is hard to capture all of them in one blog. I would like to share some quick examples though. As this SmartLight has three programmable modes of operations; stack-light mode, run-light mode and level mode, there are several possibilities of showing different information about the system using the single SmartLight. In one application, when the system needs operator/maintenance intervention, the controller (PLC or computer) switches the SmartLight in run-light mode and utilizes different combinations of foreground and background colors to indicate what type of maintenance and what severity of maintenance is needed. In another application, our customer utilizes the level mode of operation to show how different stations are performing so that plant supervisor and pin-point the bottleneck of the process and provide needed support to ensure efficient operations in the plant. Furthermore, lots of these applications were done as an after-thought to the existing systems in place.

SmartLight is one of the ways to improve your efficiency and speed. If you have unique SmartLight application to share feel free to comment on this blog.

Learn more about the SmartLight in our video library or on our website at www.balluff.us/smartlight.

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High Pressure Inductive Sensors with Analog Feedback

In my previous blog post we covered the Anatomy of a High Pressure Proximity Sensor. That post covered the different mechanical housing designs and special properties that go into high pressure sensor products with discrete outputs. That is great information to know when specifying the correct sensor for a particular application. In today’s competitive market and constant goals to improve processes, sensor’s that offer continuous feedback are required.

Hydraulic systems regulate speed of an actuator by regulating flow rate. The flow rate determines the speed of the cylinder spud that actuates inside the system. For example, an analog sensor can provide measurement to the controls with indication of slowing down or speeding up the actuator based on the analog feedback from the sensor in regard to position of the tapered section of the actuator. So, if the internal target gets larger with more position movement (stroke) the distant measurement changes and indicates that the end of stroke is near causing the controller to initiate a soft stop. This provides better control of the system offering a more efficient reliable process.

500barAnalog Inductive sensors provide an absolute voltage or current signal change proportional to the distance of a ferrous target. In high pressure applications that require more position feedback, an analog distance sensor can offer a solution as they also offer high – strength stainless steel housings with special sealing designs that allow pressure up to 500 bar and 85°C temperature ratings making them an ideal solution for valve speed control and soft starts with a non – contact design.

More information on high pressure analog inductive sensors is available on the Balluff website at www.balluff.us.

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What’s best for integrating Poka-yoke or Mistake Proofing sensors?

Teams considering poka-yoke or mistake proofing applications typically contact us with a problem in hand.  “Can you help us detect this problem?”

We spend a lot of time:

  • talking about the product and the mistakes being made
  • identifying the error and how to contain it
  • and attempting to select the best sensing technology to solve the application.

However this can sometimes be the easy part of the project.  Many times a great sensor solution is identified but the proper controls inputs are not available or the control architecture doesn’t support analog inputs or network connections.  The amount of time and dollar investments to integrate the sensor solution dramatically increases and sometimes the best poka-yoke solutions go un-implemented!”

“Sometimes the best poka-yoke solutions go un-implemented!”

Many of our customers are finding that the best controls architecture for their continuous improvement processes involves the use of IO-Link integrated with their existing architectures.  It can be very quickly integrated into the existing controls and has a wide variety of technologies available.  Both of these factors make it the best for integrating Poka-yoke or Mistake Proofing due to the great flexibility and easy integration.

Download this whitepaper and read about how a continuous improvement technician installed and integrated an error-proofing sensor in 20 minutes!

Posted in All posts, Analog Position Sensors, Industrial Networking, IO-Link, Machine Vision, Photoelectric Sensors, Ultrasonic Sensors | Tagged , , , , , , , , | Leave a comment

Inductive Coupling: Simple Concept for Complex Automation – Part 2

Image provided by Yaskawa America, Inc., Motoman Robotics Division

Image provided by Yaskawa America, Inc., Motoman Robotics Division

In the new era of flexible or customized manufacturing, where manufacturers are producing multiple products on the same production line or performing multiple operations in the same space, robotics is becoming cornerstone of automation. Industry innovators are applying a robot’s agility and multipurpose form to solving some real life challenges and stretching horizons of possibilities to all new levels. These next generation applications bring with them a new complex age of automation that was nearly unthinkable a decade ago.  When we think about flexible manufacturing what comes to mind first are the challenges of handling product changeovers. With robots that would mean changing out the end-effectors so the robot is ready quickly for next operation.

Figure 1: Tool changer example with pin couplers

Figure 1: Tool changer example with pin couplers

With the current trends in automation, demand for robotic tool changers (quick change for end-effectors) is growing at a fast pace. This is not only limited to automotive or heavy industries but also in packaging, bakery automation, food and pharma, and importantly in life sciences. End effectors are where these innovators primarily focus on to create value for their customers by handling products in most application suitable way.  The smarts of the end effectors, sensors and actuators, need power and the ability to communicate with the controller. Traditionally, this is achieved with pin-based coupling, where the robot approaches the tool changing station, engages the tool and very accurately mates the two ends of the pin couplers to power up the tool’s smarts.

The pin based coupling is effective and widely used today but it has few of its own issues: First, the pins of the tool when not in use are open and exposed to the environment- accumulation of dust, water or oil- causes nuisances in the connection process. Second, these are mechanical contacts and over time they wear out, bend, or break and cause un-intended downtime in the application.

Inductive coupling addresses all these issues and adds further value to automation. As explained in my previous blog. Both sides of the inductive coupler (Base and Remote) are fully encapsulated, typically with IP67 protection class, so that these couplers have no environmental issues to worry about. Since both sides are magnetically coupled, they are immune to vibrations. And, yes, since there is no-contact between the base and the remote side, there are no worries about bending or breaking of the pins.

Inductive coupling with IO-Link technology adds more benefits besides replacing the pin coupling. IO-Link enabled inductive couplers allow transferring up to 32 bytes of data in addition to power for actuation or sensors. When you connect IO-Link enabled I/O hubs or valve connectors to the remote side, (as shown in the picture below) you can also store identification data on the IO-Link hub or valve. When the connection is establish the controller can request the identification data from the tool to ensure that robot or system is utilizing the correct tool for the upcoming process. You might say, “wait a minute– this identification is also possible with pin-based coupling, so what is so great about inductive coupling?” Great question! With pin based coupling you first need to engage the tool to mate the two ends of the pin couplers and then request the identification. Up to 4-5 seconds are wasted before you realize it is a wrong tool. With inductive coupling, just the base need to be brought closer to the remote so that you could quickly couple and identify the tool before engaging the tool– saving you precious seconds. Coupling usually takes less than a second and most importantly the base and remote do not need to be well aligned to couple misalignment up to 15-20 degrees of angular offset or 2-4mm of axial offset still provides functionality.

Robot

So, you may ask, what are the limitations with Inductive coupling? The most important factor is how much energy your tool’s smarts require. Generally speaking 24W-48W is probably the most commonly available inductive couplers. If your tool requires any more than that then pin based coupling is the way to go. Another deciding factor is – metal dust in the environment. In the presence of metal dust on the surface of the couplers may cause interruptions in the communication as the basis of the communication is magnetic induction.

I hope this blog helps you decide the right coupler for your next application. In the next blog of this series we will review how inductive coupling can simplify automation along the assembly lines.

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The Often Overlooked Proximity Sensor

If someone says proximity sensor, what is the first thing that comes to mind?  My guess is inductive and justly so because they are the most used sensor in automation today.  There are other sensing technologies that use the term proximity in describing the sensing mode.  These include diffuse or proximity photo electric sensors that use the reflectivity of the object to change states and proximity mode of ultrasonic sensors that use high frequency sound waves to detect objects.  All of these sensors detect objects that are in close proximity of the sensor without making physical contact.

One of the most overlooked or forgotten proximity sensors on the market today is the capacitive sensor.  Why?  Perhaps it is because they have a bad reputation from when they were released years ago as they were more susceptible to noise than most sensors.  I recently heard someone say that they don’t discuss capacitive sensors with their customers because they had this bad experience almost 10 years ago, however, with the advancements of technology this is no longer the case.

CapacitiveFlushCapacitive sensors are versatile in solving numerous applications.  These sensors can be used to detect objects such as glass, wood, and paper, plastic, ceramic, the list goes on and on.  The capacitive sensors used to detect objects are easily identified by the flush mounting or shielded face of the sensor.  Shielding causes the electrostatic field to be short conical shaped much like the shielded version of the inductive proximity sensor.

Capacitive Non-FlushJust as there are non-flush or unshielded inductive sensors there are non-flush capacitive sensors, and the mounting and housing looks the same.  The non-flush capacitive sensors have a large spherical field which allows them to be used in level detection.  Since capacitive sensors can detect virtually anything, they can detect levels of liquids including water, oil, glue and so forth and the can detect levels of solids like plastic granules, soap powder, sand and just about anything else.  Levels can be detected either directly, the sensor touches the medium or indirectly where the sensor senses the medium through a non-metallic container wall.

SmartLevelWith improvements in capacitive technology sensors have been designed that can compensate for foaming, material build-up and filming of water based highly conductive liquids.  Since these capacitive sensors are based on the conductivity of liquids they can reliably actuate when sensing aggressive acids such as hydrochloric, sulfuric and hydrofluoric acids.  In addition, these sensors can detect liquids through glass or plastic walls up to 10mm thick are not affected by moisture and require little or no cleaning these applications.

The sensing distance of a capacitive sensor is determined by several factors including the sensing face area, the larger the better.  The next factor is the material property of the object or dielectric strength, the higher the dielectric constant the greater the sensing distance.  Lastly the size of the target affects the sensing range.  Just like an inductive sensor you want the target to be equal to or larger than the sensor.

Most capacitive sensors have a potentiometer to allow adjustment of the sensitivity of the sensor to reliably detect the target.  The maximum sensing distance of a capacitive sensor is based on a metal target thus there is a reduction factor for non-metal targets.

Although capacitive sensors can detect metal inductive sensors should be used for these applications.  Capacitive sensors are ideal for detecting non-metallic objects at close ranges, usually less than 30mm and for detecting hidden or inaccessible materials or features.

Just remember, there is one more proximity sensor…the capacitive one!

To learn more about Balluff capacitive sensors visit www.balluff.us/capacitive.

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Eliminating Manufacturing Errors Begins with Identifying Trouble Spots

We have all gotten that dreaded phone call or email…the customer received their order, but there was a significant problem:

  • ErrorProofingTagsMissing part
  • Wrong color
  • Leaking seal
  • Improper assembly
  • Too lose…or too tight
  • Incomplete processing, e.g. missing threads
  • Something is damaged
  • Missing fluids or fluids at wrong level
  • …and so on

Assuming that we have reliable suppliers delivering quality parts that meet the required specifications…everything else that can (and often does) go wrong happens inside our own facilities. That means that solving the issues is our responsibility, but it also means that the solutions are completely under our control.

During the initial quality response meetings, at some point the subjects of “better worker training” and “more attention to detail and self-inspection” may come up. They are valid subjects that need to be addressed, but let’s face it: not every manufacturing and assembly problem can be solved by increased worker vigilance and dedication to workmanship. Nor, for that matter, is there the luxury of time or capacity for each worker to spend the extra time needed to ensure zero defects through inspection.

It is often more effective to eliminate errors at their source before they occur, so that further human intervention isn’t required or expected.

Some things to look for when searching for manufacturing trouble spots:

  • Are all fasteners present and properly tightened, in the proper torque sequence
  • Correct machine setup: is the right tool or fixture in place for the product being produced?
  • Manual data entry: does the process rely on human accuracy to input machine or product data?
  • Incorrect part: is it simply too hard to determine small differences by visual means alone?
  • Sequencing error: were the parts correct but came together in the wrong sequence?
  • Mislabeled component: would the operator realize that part is wrong if it was labeled incorrectly in the first place? Sometimes where the error has impact and where it actually occurred are in two different places.
  • Part not seated correctly: is everything is correct, but sometimes the part doesn’t sit properly in the assembly fixture?
  • Critical fluids: is the right fluid installed? Is it filled to the proper level?

Once the trouble spots have been identified, the next step is to implement a detection and/or prevention strategy. More information on the error proofing process is available on the Balluff website at www.balluff.us/errorproofing

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How can I convince my boss to send me to training?

trainingWith responsibilities expanding, resources declining, and margins narrowing, companies today must scrutinize every dollar spent. Bad decisions are often based on bad data. An informed decision, on the other hand, can be defended in the light of the facts. In this article, we examine three misconceptions –  misconceptions which too often lead to poor decisions about training.

  1. If I train my people, they will leave.

In today’s companies where people change positions frequently, training is seen as a risky investment.  The correct perspective is seeing the risk involved in NOT training your people.  Do you really want your people making costly mistakes by the trial-and-error method of on-the-job training? Lack of training does not just affect the untrained person. Those that have been trained and are doing the job correctly often get pulled aside to explain procedures to the untrained. The bottom line is that people are going to be trained one way or another. What is the most efficient way to do this?

  1. I can’t afford the downtime to send my people to training.

Tools need to be sharpened.  This means they can’t be “productive” 100% of the time.  “Productivity” needs to be seen as a totally different thing from being “busy.”   Once a tool is sharpened, it is far more productive.  A dull tool can be “busy” 100 % of the time accomplishing nothing of value.  The correct perspective then is that you can’t afford the loss of productivity caused by a lack of training.

  1. All training offered out there is basically the same, so just take the cheapest one.

Training is not a one-way dump of information.  Training means that a change has taken place in a cognitive domain, an affective domain, or a psychomotor domain.  For automation companies, these three domains are intricately linked.  For example, it is not enough to just sit through a safety presentation:  you need to know the safety regulations (cognitive), you need to be passionate about why these are important (affective), and you need the skill necessary to implement these regulations by specifying, configuring, and integrating systems (psychomotor).

The best way to train in the psychomotor domain is through hands-on training.  Students learn skills best by practicing those skills.  For many companies who offer training, training is just a presentation of ideas without the necessary opportunity for participants to try anything for themselves. At Balluff, we have made a substantial investment in equipment, an investment in writing courseware properly, and an investment in training those who conduct the training with platform skills, adult learning skills, and teaching skills.  These investments make world-class, performance-based training available to our customers.

To see all that Balluff has to offer in Automation Training, click on our training web page link:  http://www.balluff.com/balluff/MUS/en/service/standard-training.jsp

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Direct vs Indirect Mounting of Capacitive Sensors

Direct sensing mount

Figure 1: Direct sensing mount

In liquid level sensing applications, capacitive sensors can be mounted directly in contact with the medium or indirectly with no contact to the medium.

Containers made of metal or very thick non-metallic tank walls (more than 1″) typically require mounting the sensor in direct contact with the medium (Fig. 1). In some instances, a by-pass tube or a sights glass is used, and the senor detects the level through the wall of the non-metallic tube (Fig. 2).

Indirect sensing mount

Figure 2: Indirect sensing mount

The direct mounting method could simplify sensor selection and setup since the sensor only has to sense the medium or target material properties. Nonetheless, this approach imposes certain drawbacks, such as costs for mounting and sealing the sensor as well as the need to consider the material compatibility between the sensor and the medium. Corrosive acids, for example, might require a more expensive exotic housing material.

ChemicalCompatibilityChart

The preferred approach is indirectly mounting the capacitive sensor flush against the non-metallic wall to detect the target material non-invasively through the container wall.  The advantages for this approach are obvious and represent a major influence to specify capacitive sensors.  The container wall does not have to be penetrated, which leaves the level sensor flexible and interchangeable in the application.  Avoiding direct contact with the target material also reduces the chances of product contamination, leaks, and other sources of risk to personnel and the environment.

The target material also has relevance in the sensor selection process.  Medical and semiconductor applications involve mostly water-based reagents, process fluids, acids, as well as different bodily fluids.  Fortunately, high conductivity levels and therefore high relative dielectric constants are common characteristics among all these liquids.  This is why the primary advantages of capacitive sensors lies in non-invasive liquid level detection, namely by creating a large measurement delta between the low dielectric container walls and the target material with high dielectric properties.

At the same time, highly conductivity liquids could impose a threat to the application.  This is because smaller physical amounts of material have a larger impact on the capacitive sensor with increasing conductivity values, increasing the risk of false triggering on foam or adherence to the inside or outside wall.  SMARTLEVEL sensors offered by Balluff will ignore foaming, filming and material build-up in these applications.

Learn more about Balluff’s capacitive solutions on our website at www.balluff.us.

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