In-Cylinder Position Sensing in Electrically Conductive Hydraulic Fluids

The standard for hydraulic fluid in the industry is mineral oil, which is a dielectric medium that does not conduct electricity. Yet environmental concerns have led to the search for alternatives that are less harmful in case of leaks and spills. One development is biodegradable oils, typically with biological origins, often called “bio-oils” for short. They behave in many ways like mineral oil with a key difference in that they can be electrically conductive.

Another alternative hydraulic fluid is water-glycol mixtures, commonly known as the anti-freeze found in your liquid-cooled automobile engine. Water-glycol solutions are used for several reasons, including environmental concerns but more often conditions of extreme heat or extreme cold. They have much lower viscosity than oil, and there are several fluid power application considerations as a result, but water-glycol mixtures, like bio-oils, are electrically conductive.

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So, when it comes to cylinder position sensing, why should we care whether or not the hydraulic fluid is electrically conductive? Well, because it could come back to bite us if we put an incompatible position sensing technology into a cylinder that is filled with a conductive fluid.

I recently met an engineer who’d run into this exact situation. A hydraulic cylinder was ordered from the manufacturer with an “integrated position feedback sensor.” The feedback sensor turned out to be a resistive potentiometric type, in other words, a linear potentiometer or “pot.” The entire length of the resistive material is “wetted” inside the cylinder, along with the traveling “wiper” that moves with the piston. In typical applications with non-conductive, mineral-based hydraulic fluid, this works fine (although linear pots do tend to be somewhat fragile and do wear out over time). However, when the resistive material and wiper is wetted in a conductive liquid, all kinds of wrong start happening. The signal becomes very erratic, unstable, and lacks resolution and repeatability. This is because the fluid is basically short-circuiting the operation of the open-element linear potentiometer.

This caused quite a headache for the engineer’s customer and subsequently for the engineer. Fortunately, a replacement cylinder was ordered, this time with a non-contact magnetostrictive linear position sensor. The magnetostrictive sensor is supplied with a pressure-rated, protective stainless steel tube that isolates the electrical sensing element from the hydraulic medium. The position marker is a magnet instead of a wiper, which the sensor can detect through the walls of the stainless steel pressure tube. So, a magnetostrictive sensor is absolutely unaffected by the electrical properties of the hydraulic medium.

A magnetostrictive linear position sensor carries a lot of performance and application advantages over linear pots that make them a superior technology in most applications, but when it comes to conductive hydraulic fluids they are definitely the preferred choice.

To learn more about linear position sensors visit www.balluff.com.

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Who Has Access to Your Machine Controls?

If you can provide a list of people who have authorized access to your machine controls, then you are ahead of the game. If you can truly ensure that only the people on that list are accessing the machine and not sharing their credentials, then you are way ahead of the game.

Limiting access to the controls of a machine is certainly not a new concept. I see many organizations still using a mechanical key system for override or start up.  According to multiple controls engineers, the main issue with that is people share, copy, and misplace these keys on a regular basis. In this case, just about everyone on the plant floor would have access to the controls of any machine.

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Just about all of us carry a device that allows us to enter and exit our buildings. Whether it be a badge or a key fob, the technology is the same. RFID adds accountability to machine access control.  For example: Jane, the team lead, has full authority to make changes in the control system. The production line comes to a screeching halt and needs to be restarted. In order to restart the machine, Jane has to present her RFID badge to a reader near the controls and she is then given access to make some adjustments within the machine. When Jane authenticates into the machine, the date, time, and Jane’s ID can be recorded. This adds full accountability to the controls and deters Jane from giving John her badge to let him restart the machine.  If John makes unauthorized changes he makes them in Jane’s name.

Access control has become a popular solution in the last few years as machines have become more critical to operation.  Like most RFID applications there are multiple ways to address this.  The key is to select a vendor who has a core competency in the industrial space with knowledge of industrial control systems.

To learn more about how RFID technology controls machine access click here or visit www.balluff.com.

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Demystifying Class A and Class B Type IO-Link Ports

Since the inception of the Class (or Type) A and Class (or Type) B ports in the IO-Link specifications, there have been several new IO-Link devices and IO-Link masters introduced to the market. This has caused a lot of confusion about when and where to use Class A and Class B IO-Link masters and devices.

Before getting into the details of Class A vs. Class B, I would like to address one question that I get asked quite often: are Class B master ports safety-rated? The answer is no. Just like any other network I/O modules (with the exception of the Safety I/O modules), any type of IO-Link master (whether it is Class A, Class B or mixed) is not safety rated. If the block is safety-rated, I am certain that the manufacturers of these blocks will kindly let you know. So, we just busted the first myth about Class B ports. Side note: the IO-Link Consortium just released a specification for IO-Link Safety. At the time of this posting (Oct. 2017), there are no IO-Link masters on the market that are safety rated, even when the IO-Link master ports exist alongside Safety I/O parts on the same block.

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For IO-Link communication, only pins 1, 3 and 4 have significance. The implementations of pin 2 and 5 is where Class A and Class B ports differ and with that, the advantages and disadvantages of the uses for these ports.

Clearly, with the wiring diagrams above, a Class A port offers more flexibility in terms of additional I/O count and in some cases high-amperage outputs to drive high-current devices such as valves.  We will discuss the detailed power routing and application flexibility of Class A ports in a later blog.

With Class B ports, Pin 2 and Pin 5 are tied to a separate power source and cannot really be used as I/O.  Pin 5, the ground for output power, is separated from pin 3, the ground for device power. Actuation devices, such as valve banks, that are now offered on IO-Link could utilize separate output power that can be turned off through safety relays. Technically, this separation of power is possible with Class A ports as well, but it is inherent with Class B ports.

A word of caution when implementing I/O architectures with Class B masters: since the commons for device power and output power are isolated at the master, the power fed to this device should be isolated at the source as well to keep the isolation intact. That means, the power supplies feeding the power to these devices should be isolated.

Another question that I get asked frequently reveals another myth about Class B master ports: do Class B master ports offer any extra power than Class A ports? Again the answer is no. Class B does not mean extra power or the ability to provide more power. It simply means output power with isolated commons. What leads to that thinking is that on several IO-Link masters in the market, the outputs available on pin 2 of Type A ports have lower amperage ratings, because in most cases the output power is shared or drawn from the same source that feeds device power.  There will be more discussion about this in my next blog!

A third interesting question is, can you plug Class A IO-Link devices into Class B master ports? In most cases there is no problem doing this as a true IO-Link Class A device is only a 3 pin device using pins 1,3, and 4 shown above. So as long as pin 2 of the device does not exist or is not being used for any purpose, it is possible to use Class A devices with Class B ports. Caution: several manufacturers make sensors that can be used in IO-Link mode as well as analog or digital mode and the implementation may have more than 3 pins. In these circumstances, you will need to use a 3-pole cable to keep the device unharmed or the pin 2 of the type B port that always has +24V going through may damage or disrupt the sensor.

Meanwhile, I hope this blog helped provide some clarity on Class A and Class B ports.

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5 Ways Flexible Manufacturing has Never Been Easier

Flexible manufacturing has never been easier or more cost effective to implement, even down to lot-size-one, now that IO-Link has become an accepted standard. Fixed control and buried information is no longer acceptable. Driven by the needs of IIoT and Industry 4.0, IO-Link provides the additional data that unlocks the flexibility in modern automation equipment, and it’s here now!  As evidence, here are the top five examples of IO-Link enabled flexibility:

#5. Quick Change Tooling: The technology of inductive coupling connects standard IO-Link devices through an airgap. Change parts and End of Arm (EOA) tooling can quickly and reliably be changed and verified while maintaining connection with sensors and pneumatic valves. This is really cool technology…power through the air!

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#4. On-the-fly Sensors Programming: Many sensor applications require new settings when the target changes, and the targets seem to always change. IO-Link enables this at minimal cost and very little time investment. It’s just built in.

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#3. Flexible Indicator Lights: Detailed communication with the operators no long requires a traditional HMI. In our flexible world, information such as variable process data, timing indication, machine status, run states and change over verification can be displayed at the point of use. This represents endless creativity possibilities.

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#2. Low cost RFID: Radio Frequency Identification (RFID) has been around for a while. But with the cost point of IO-Link, the applications have been rapidly climbing. From traditional manufacturing pallets to change-part tracking, the ease and cost effectiveness of RFID is at a record level. If you have ever thought about RFID, now is the time.

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#1. Move Away from Discrete to Continuously Variable Sensors: Moving from discrete, on-off sensors to continuously variable sensors (like analog but better) opens up tremendous flexibility. This eliminates multiple discrete sensors or re-positioning of sensors. One sensor can handle multiple types and sizes of products with no cost penalty. IO-Link makes this more economical than traditional analog with much more information available. This could be the best technology shift since the move to Ethernet based I/O networks.

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So #1 was the move to Continuously Variable sensors using IO-Link. But the term, “Continuously Variable” doesn’t just roll off the tongue. We have discrete and analog sensors, but what should we call these sensors? Let me know your thoughts!

To learn more about RFID and IO-Link technology, visit www.balluff.com.

 

 

 

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RFID in the Manufacturing Process: A Must-Have for Continuous Improvement

There is quite an abundance of continuous improvement methodologies implemented in manufacturing processes around the globe. Whether it’s Lean, Six Sigma, Kaizen, etc., there is one thing that all of these methodologies have in common, they all require actionable data in order to make an improvement.  So, the question becomes: How do I get my hands on actionable data?

All data begins its life as raw data, which has to be manipulated to produce actionable data. Fortunately, there are devices that help automate this process. Automatic data collection (ADC), which includes barcode and RFID technology, provides visibility into the process. RFID has evolved to become the more advanced method of data collection because it doesn’t require a centralized database to store the data like barcode technology. RFID stores the data directly on the product or pallet in the process, which allows for much more in-depth data collection.

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RFID’s greatest impact on the process tends to be improving overall quality and efficiency. For example, Company X is creating widgets and there are thirty-five work cells required to make a widget. Between every work cell there is a quality check with a vision system that looks for imperfections created in the prior station. When a quality issue is identified, it is automatically written to the tag.  In the following work cell the RFID tag is read as soon as it enters the station. This is where the raw data becomes actionable data. As soon as a quality issue has been identified, someone or something will need to take action. At this point the data becomes actionable because it has a detailed story to tell. While the error code written to the tag might just be a “10”, the real story is: Between cells five and six the system found a widget was non-conforming. The action that can be taken now is much more focused. The process at cell five can be studied and fixed immediately, opposed to waiting until an entire batch of widgets are manufactured with a quality issue.

Ultimately, flawless execution is what brings success to organizations.  However, in order to execute with efficiency and precision the company must first have access to not only data, but actionable data. Actionable data is derived from the raw data that RFID systems automatically collect.

Learn more about RFID technology at www.balluff.com.

 

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The Evolving Technology of Capacitive Sensors

In my last blog post, Sensing Types of Capacitive Sensors, I discussed the basic types of capacitive sensors; flush versions for object detection and non-flush for level detection of liquids or bulk materials.  In this blog post, I would like to discuss how the technology for capacitive sensors has changed over the past few years.

The basic technology of most capacitive sensors on the market was discussed in the blog post “What is a Capacitive Sensor”.  The sensors determine the presence of an object based on the dielectric constant of the object being detected.  If you are trying to detect a hidden object, then the hidden object must have a higher dielectric constant than what you are trying to “see through”.

Conductive targets present an interesting challenge to capacitive sensors as these targets have a greater capacitance and a targets dielectric constant is immaterial.  Conductive targets include metal, water, blood, acids, bases, and salt water.  Any capacitive sensor will detect the presence of these targets. However, the challenge is for the sensor to turn off once the conductive material is no longer present.  This is especially true when dealing with acids or liquids, such as blood, that adheres to the container wall as the level drops below the sensor face.

Today, enhanced sensing technology helps the sensors effectively distinguish between true liquid levels and possible interference caused by condensation, material build-up, or foaming fluids.  While ignoring these interferences, the sensors would still detect the relative change in capacitance caused by the target object, but use additional factors to evaluate the validity of the measurement taken before changing state.

These sensors are fundamentally insensitive to any non-conductive material like plastic or glass, which allows them to be utilized in level applications.  The only limitation of enhanced capacitive sensors is they require electrically conductive fluid materials with a dipole characteristic, such as water, to operate properly.

Enhanced or hybrid technology capacitive sensors work with a high-frequency oscillator whose amplitude is directly correlated with the capacitance change between the two independently acting sensing electrodes.  Each electrode independently tries to force itself into a balanced state.  That is the reason why the sensor independently measures  the capacitance of the container wall without ground reference and the capacitance of the conductivity of the liquid with ground reference (contrary to standard capacitive sensors).

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Up to this point, capacitive sensors have only been able to provide a discrete output, or if used in level applications for a point level indication.  Another innovative change to capacitive sensor technology is the ability to use a remote amplifier.  Not only does this configuration allow for capacitive sensors to be smaller, for instance 4mm in diameter, since the electronics are remote, they can provide additional functionality.

The remote sensor heads are available in a number of configurations including versions image2that can withstand temperature ranges of -180°C up to 250°C.  The amplifiers can now provide the ability to not only have discrete outputs but communicate over an IO-Link network or provide an analog output.  Now imagine the ability to have an adhesive strip sensor that can provide an analog output based on a non-metallic tanks level.

For additional information on the industry’s leading portfolio of capacitive products visit www.balluff.com.

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Hydraulic Valves – Customize your Feedback

Hydraulic actuators can be used to open and close a valve’s position.  In automation architectures, a linear position sensor is used within the hydraulic actuator to provide continuous position feedback.

The linear position sensor is installed into the back end of the cylinder.  The sensing element resides in a cavity that has been gun-drilled through the piston and cylinder rod, Image1extending the full length of the mechanical stroke. A magnet ring is used as a position marker and mounted on the face of the piston.  As the piston (and the position marker) move, the linear position sensor provides a continuous absolute position by way of an analog or digital signal.

In some applications, a cylinder’s position may only be moving across a small portion of the overall stroke or a specific portion of the stroke.  The end user could benefit from altering the transducer’s signal based on the application’s specific stroke requirements instead of the entire cylinder’s stroke, thereby maximizing available position resolution.  When this situation arises, most transducer manufacturers offer the ability to customize or “teach” a modified output of the stroke via push buttons or from wiring inputs.  When this is done, the process does require the cylinder (and position marker) to move to these defined locations for a “teach”.

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A more user-friendly and repeatable approach for customized stroke lengths with linear position sensors is to use a graphical software package. The software can be connected
from a PC via USB to a compatible linear position sensor. Starting and ending stroke values can be precisely entered into the software and a graphical representation of the output curve is created.  For a more straightforward approach, you can also drag and drop these stroke points by a click of a cursor. The file can be saved on a PC and downloaded to the transducer. In either case, the cylinder’s piston doesn’t need to be actuated.

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In projects where multiple, identical actuators and linear position sensors need to be customized, the setup would only need to be done once, the file saved, and simply uploaded to all the sensors for the project.  A great time-saver over manually teaching each and every sensor.

Another benefit to using software with linear position sensors is to be able to upload programs for replacement units in a safe user environment (e.g. lab station or office) and shipping them to various job sites.  These different locations (or locales) can be in harsh environmental conditions (extreme cold or heat) or areas that contain ignitable or explosive gases or dusts which may be difficult to work in.

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Other software features include inverting the output curves, offering position or velocity outputs, and more.

For more information on Balluff’s Magnetostrictive Linear Position Sensors, visit www.balluff.com.

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The Benefits of using RFID or Barcode for E-Kanban or Automatic Replenishment

Electronic Kanban (E-Kanban) is a messaging system that uses a mix of technology to trigger the movement of components and materials within a manufacturing facility. Electronic Kanban differs from traditional Kanban in that it uses technology to replace traditional elements, such as Kanban cards with barcodes and RFID.

A typical electronic Kanban system will see inventory marked with barcodes or RFID. The inventory is scanned at various steps in the manufacturing process to signal usage levels that are sent back to an ERP system for replenishment. This method ensures a constant flow of material while keeping inventories to a minimum.

An additional benefit of E-Kanban is the integration of outside suppliers through an ERP system. By relaying this information, the entire supply chain can be optimized for Just-In-Time inventory flow.

Benefits include:

  1. Reduce inventory levels, carrying cost
  2. Savings in material transfer, labor cost
  3. Increase in inventory replenishment, decrease down time and line stoppage due to stock out

Automatic replenishment, Ekanban, and end-to-end pull, are all names that describe a system in which parts and sub-components are automatically replenished in a manufacturing environment. While most manufacturing organizations have some form of replenishment system in place, I have found that just about every company does it differently. While some are more effective than others, the ones that truly want to automate the process utilize automatic identification.

For more information, visit www.balluff.com.

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How to Develop and Qualify Sensors for Arctic Conditions

The climatic conditions in the arctic are characterized by cold winters and short summers. There is a large variability in climate and weather: Some regions face permafrost and are ice covered year-round with temperatures down to -40°C / -40°F (and lower), other land areas face the extremes of solar radiation up to +30°C / +86°F in summer.

As oil and gas exploration, as well as renewable energy (e.g. cold climate versions of wind turbines) move into arctic areas, the need grows for sensors designed to deal with the extreme conditions and to perform reliably over their whole life cycle.

One option is the implementation of a Highly Accelerated Life Test (abbreviation HALT) in the development process. The basic idea of HALT is the accelerated aging of electronic products (including sealing gaskets, potting compound, housing etc.) with the aim of detecting their possible weak spots as early as possible and to correct them at the development stage.

Example of a sensor in the HALT test facility (Balluff magnetostrictive linear position sensor BTL)

The item under test is subjected to higher and higher thermal and mechanical stress in order to cause failures. The limits where the product will fail functionally or be destroyed are determined in order to push these limits as far out as possible, and so achieve a higher reliability for the product.

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Product operational specs = data sheet values

The HALT procedure – in brief:

a) Analysis of weaknesses already known, definition of failure criteria, establishing the stress factors

b) Stressing the test specimen beyond the specification to find the “upper and lower operating limits”, and the “upper and lower destruct limit” for temperature, rapid change of temperature, vibration, combined vibration and temperature stress

c) Determination of the causes of failure

d) Devising a solution to eliminate the weaknesses

e) Repeating of steps b) to c)

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Example: Temperature step test – cold and hot

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Example: Combined vibration test and rapid temperature changes

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Example: Cowan Dynamics E2H Electro-Hydraulic valve actuator Photo: Cowan Dynamics (Canada)

In contrast to other environmental tests, HALT is not qualification testing according to specific technical standards (as  ISO/IEC etc.), but it applies stimuli to the items under test until they fail, so weak spots will be revealed. A HALT test is not an exam you can pass!

However, if sensors are implemented into more complex automation systems that will be operated in remote areas, this method may help to prevent major faults in the field and is therefore also used in the aircraft and automotive industry.

For more information about Balluff testing methods and the laboratory, please visit www.balluff.com or download our brochure “The Balluff Testing Laboratory”.

 

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Capture vs Control – The Hidden Value of True IIoT Solutions

A few months ago a customer and I met to discuss their Industry 4.0 & IIoT pilot project.  We discussed technology options and ways to collect data from the existing manufacturing process.  Options like reading the data directly from the PLC or setting up an OPC service to request machine data were discussed; however these weren’t preferable as it required modifying the existing PLC code to make the solution effective.  “What I really want is the ability to capture the data from the devices directly and not impact the control of my existing automation equipment.”  Whether his reason was because of machine warranty conflicts or the old adage, “don’t fix what ain’t broke” the general opinion makes sense.

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This concept really stuck with me months after our visit that day.  This is really one of the core demands we have from the data generation part of the IIoT equation; how can we get information without negatively impacting our automated production systems?  This is where the convergence of the operational OT and network IT becomes critical.  I’ve now had to build an IT understanding of the fundamentals of how data is transferred in Ethernet; and build an understanding of new-to-me data protocols like JSON (JavaScript Object Notation) and MQTT.  The value of these protocols allows for a direct request from the device-that-has-the-data to the device-that-needs-the-data without a middleman.  These IT based protocols eliminate the need for a control-based data-transport solution!

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So then truly connected IIoT automation solutions that are “Ready for IIoT” need to support this basic concept of “Capture versus Control.”  We have a strong portfolio of products with Industrial Internet of Things capabilities, check them out at www.balluff.com.

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