Changing the Paradigm from Safety vs. Productivity to Safety & Productivity

In a previous blog, we discussed how “Safety Over IO-Link Helps Enable Human-Robot Collaboration”. It was a fairly narrow discussion of collaborative robot modes and how sensors and networks can make it easier to implement these modes and applications. This new blog takes a broader look at the critical role safety plays in the intersection between the machine and the user.

In the past, the machine guarding philosophy was to completely separate the human from the machine or robot.  Unfortunately, this resulted in the paradigm of “safety vs. productivity” — you either had safety or productivity, but you couldn’t have both. This paradigm is now shifting to “safety & productivity”, driven by a combination of updated standards and new technologies which allow closer human-machine interaction and new modes of collaborative operation.

Tom_Safety1.pngThe typical machine/robot guarding scheme of the past used fences or hard guards to separate the human from the machine.  Doors were controlled with safety interlock switches, which required the machine to stop on access, such as to load/unload parts or to perform maintenance or service, and this reduced productivity.  It was also not 100% effective because workers inside a machine area or work cell might not be detected if another worker restarted the stopped machine.  Other drawbacks included the cost of space, guarding, installation, and difficultly changing the work cell layout once hard guarding had been installed.

We’ve now come to an era when our technology and standards allow improved human access to the machine and robot cell.  We’re starting to think about the human working near or even with the machine/robot. The robot and machinery standards have undergone several changes in recent years and now allow new modes of operation.  These have combined with new safety technologies to create a wave of robot and automation suppliers offering new robots, controllers, safety and other accessories.

Standards
Machine and robot safety standards have undergone rapid change in recent years. Standard IEC 61508, and the related machinery standards EN/ISO 13849-1 and EN/IEC 62061, take a functional approach to safety and define new safety performance levels. This means they focus more on the functions needed to reduce each risk and the level of performance required for each function, and less on selection of safety components. These standards helped define, and made it simpler and more beneficial, to apply safety PLCs and advanced safety components. There have also been developments in standards related to safe motion (61800-5-2) which now allow more flexible modes of motion under closely controlled conditions. And the robot standards (10218, ANSI RIA 15.06, TS15066) have made major advances to allow safety-rated soft axes, space limiting and collaborative modes of operation.

Technology
On the technology side, innovations in sensors, controllers and drives have changed the way humans interact with machines and enabled much closer, more coordinated and safer operation. Advanced sensors, such as safety laser scanners and 3D safety cameras, allow creation of work cells with zones, which makes it possible for an operator to be allowed in one zone while the robot performs tasks in a different zone nearby. Controllers now integrate PLC, safety, motion control and other functions, allowing fast and precise control of the process. And drives/motion systems now operate in various modes which can limit speed, torque, direction, etc. in certain modes or if someone is detected nearby.

Sensors and Networks
The monitoring of these robots, machines and “spaces” requires many standard and safety sensors, both inside and outside the machine or robot. But having a lot of sensors does not necessarily allow the shift from “productivity vs. safety” to “productivity & safety” — this requires a closely coordinated and integrated system, including the ability to monitor and link the “restricted space” and “safeguarded space.” This is where field busses and device-level networks can enable tight integration of devices with the control system. IO-Link masters and Safety Over IO-Link hubs allow the connection of a large number of devices to higher level field busses (ProfiNet/ProfiSafe) with effortless device connection using off-the-shelf, non-shielded cables and connectors.

Balluff offers a wide range of solutions for robot and machine monitoring, including a broad safety device portfolio which includes safety light curtains, safety switches, inductive safety sensors, an emergency stop device and a safety hub. Our sensors and networks support the shift to include safety without sacrificing productivity.

Back to the Basics – Measuring

In the last post about the Basics of Automation, we discussed how objects can be detected, collected and positioned with the help of sensors. Now, let’s take a closer look at how non-contact measurement – both linear and rotary – works to measure distance, travel, angles, and pressure.

Measuring travel, distance, position, angle and pressure are common tasks in automation. The measuring principles used are as varied as the different tasks.

Sensor Technologies

  • Magnetostrictive enables simultaneous measurement of multiple positions and can be used in challenging environments.
  • Magnet coded enables the highest accuracy and real-time measurement.
  • Inductive is used for integration in extremely tight spaces and is suitable for short distances.
  • Photoelectric features flexible range and is unaffected by the color or surface properties of the target object.

Different Sensors for Different Applications

Distance measurement

Janni1Disc brakes are used at various locations
in wind power plants. With their durability and precise measurement, inductive distance sensors monitor these brake discs continuously and provide a timely warning if the brake linings need to be changed.

In winding and unwinding equipment, a photoelectric sensor continuously measures the increasing or decreasing roll diameter. This means the rolls can be changed with

minimal stoppages.

Linear position measurement

Janni4Workpieces are precisely positioned on the

slide of a linear axis. This allows minimal loss of production time while ensuring quality. Magnetic encoders installed along the linear axis report the actual slide position to the controller (PLC) continuously and in real time — even when the slide is moving at a speed of up to 10 m/s.

In a machine tool the clamping state
of a spindle must be continuously monitored during machining. This improves results on the workpiece and increases the reliability of the overall system. Inductive positioning systems provide continuous feedback to the controller: whether the spindle is unclamped, clamped with a tool or clamped without a tool.

Rotational position measurement

Janni5Workpieces such as a metal plate are printed, engraved or cut on a cut/print machine. This demands special accuracy in positioning it on the machine. Magnetic encoders on both rotating axes of the machine measure the position of the workpiece and ensure an even feed rate.

In a parabolic trough system,
sunlight is concentrated on parabolic troughs using parabolic mirrors allowing the heat energy to be stored. To achieve the optimal energy efficiency, the position of the parabolic mirror must be guided to match the sun’s path. Inclination sensors report the actual position of the parabolic mirror to the controller, which then adjusts as needed.

Pressure and Level Measurement

Janni7Consistently high surface quality of the machined workpiece must be ensured in a machine tool. This requires continuous monitoring of the coolant feed system pressure. Pressure sensors can reliably monitor the pressure and shut down the machine within a few milliseconds when the defined pressure range is violated.

Janni8In many tanks and vats, the fill height of the liquid must be continually measured. This is accomplished using ultrasonic sensors, which note levels regardless of color, transparency or surface composition of the medium. These sensors detect objects made of virtually any material (even sound-absorbing) including liquids, granulates and powders.

Stay tuned for future posts that will cover the essentials of automation. To learn more about the Basics of Automation in the meantime, visit www.balluff.com.

Where Discrete Position Sensing Belongs in the Manufacturing Process

Unlike continuous position sensors which provide near real-time position feedback throughout the stroke of the cylinder, discrete position sensors are equipped with a switching functionality at one or more designated positions along the cylinder’s stroke. Typically, these positions are set to detect fully retracted and extended positions but one can also be used to detect mid-stroke position.

To determine which is right for you requires a review of your application and a determination of how precisely the movement of the cylinder needs to be controlled. Some hydraulic cylinder applications require no position sensing at all. These applications simply use the cylinder to move a load, and position control is either done manually or by some other external switch or stop. Moving up a step, many applications require only that the beginning and end of the cylinder stroke be detected so that the cylinder can be commanded to reverse direction. These applications are ideal for discrete position sensing.

Several types of sensors are used for discrete position detection, but one of the most common is high-pressure inductive proximity sensors, which are installed into the end caps of the cylinder. The sensors detect the piston as it reaches the end of the cylinder stroke in either direction.

These sensors are designed to withstand the full pressure of the hydraulic system. Inductive sensors are extremely reliable because they operate without any form of mechanical contact and are completely unaffected by changes in oil temperature or viscosity.

High-pressure
High-pressure inductive sensors installed in hydraulic cylinder

Discrete position sensors are used in applications such as hydraulic clamps, detection of open/closed position in welding operations, and in hydraulic compactors and balers for compacting materials until end of cylinder stroke is reached, at which point the cylinder retracts.

Additionally, it is quite common for pneumatically-actuated clamps and grippers to use discrete sensors to indicate fully extended and fully retracted positions, and in many cases, in-between positions as well. There are even applications where multiple discrete sensors are used in grippers for gauging and sizing work pieces.

By far, the most common method of providing discrete position in an air cylinder is to use externally-mounted switches that react to a magnet installed around the circumference of the piston. These magnetically-actuated switches can sense the field of a magnet embedded in the cylinder’s piston through the aluminum body of the cylinder.

magnetically actuated
Magnetically actuated sensor installed into cylinder C-slot

There are several different operating principles used in these magnetically-actuated switches, ranging from simple, low-cost reed switches and Hall-effect switches to significantly more reliable sensors that use magnetoresistive technology. One of the big advantages of magnetoresistive sensors is that they will reliably detect both radial and axial magnetic fields, making them ideal replacements for reed or Hall-effect switches.

Check out our previous blog to learn more about continuous position sensors.

IO-Link Master Differences – Part 3

In the first part of this series “Demystifying Class A and Class B Type IO-Link Ports” we discussed the two different types of IO-Link master ports and pointed out how they differ in operation and applications. The point of that blog was to ensure that when we choose one over the other, what is the opportunity cost of that decision.

In my recent blog, part #2 in this series, “Not all IO-Link Masters are Born Equal!“, we explored that even when multiple vendors provide or call out their IO-Link master, they are different in the implementation of features and functions they offer. IO-Link is IO-Link! It is a standard for communication but other features that accompany the communication differentiates how they behave; for example- sensor only master, hybrid master, and architecture backbone master.

In this blog, we will focus on various implementations of Port Type A (or Class A) and how they add varying degrees of value to your applications.

Implementation #1: Figure 1 below depicts the guts (electrical connections) of one of the three implementations of the IO-Link Class A master port. Two key things to notice here:

  • The power coming into the IO-Link master port is only device power. There is no output power with this implementation. The reason that it is designed like this is to only integrate sensor inputs.
  • Pin 1 and Pin 3 provide the device power and ground (common) to the IO-Link device, pin 4 is IO-Link communication. Pin 2 works as an input only for digital sensors like photo-eyes or prox switches. Basically, this port can be split to use one IO-Link sensor (pins 1, 3 and 4) and one standard ON/OFF sensor (pins 1,3, and 2).
Figure 1
Figure 1: Implementation 1 of Class-A IO-Link Master Port (The electrical drawings shown here are simplified for illustration only, the actual implementation drawings may be different)

Another alternate of this implementation is that some vendors may have another IO-Link connection on Pin 2. So, it serves to add 2 IO-Link devices off the same port. Unfortunately, I am not an expert to say whether this is according to the specification or not.

The Prso: Low power consumption and simplifies integrating smart sensors.

The Cons: By definition, a control system has both inputs and outputs – controlling “something” based on sensory inputs and logic. This implementation provides semi-standard implementation to the controls architecture. IO-Link promises unified communication across the plant floor not half of the plant floor. Characteristics of this type of master port would be max output current of about 250-300mA per port and about 2A per module (rated for up to 4A, if its carries UL).

Implementation #2: This implementation is a slight variation of the sensor only port (Implementation #1 above). It is achieved by adding an output capability for pin 2 on each port- shown in figure 2 below. It is important to note that although each port has output capability on pin 2, the output power is shared with the device power for the port. It implies that, in case of E-stop situations, where shutting off power to the valves/solenoids connected to pin 2 or an IO-Link device that requires an output power, the entire device power will be shut-off.  Basically, the state of the device connected to pin 2 and state of IO-Link devices connected on pin 4 will be lost or requires more elaborate approach (programming, testing and validation) in the controls side to handling these types of safety situations.

Figure 2
Figure 2: Implementation 2 of Class-A IO-Link Master Port (The electrical drawings shown here are simplified for illustration only, the actual implementation drawings may be different)

This type of implementation is commonly found on hybrid IO-Link master’s Class A (type A) port implementation.

The Pros: Flexibility to use pin 2 for input or output – standardized approach to all devices.

The Cons: Lack of ability to control the output power separate from the device power – causing variety of controls approaches (lots of precautions) when incorporating machine safety.

Implementation #3: This implementation offers the most flexibility in designing the controls architecture that utilizes IO-Link. Figure 3 depicts the implementation below.  In this case, the device power, as prior approaches, comes from pin 1 and pin 3 but pin 2 uses a separate power for output. The pin 2 on each of these ports can be used for input, output or to provide separate output power to the IO-Link devices. It is important to note that although pin 2 offers output power separate from the device power, the common/ground for this power is still tied to pin 3. The output power is separate but not isolated, like in the Class B port implementation discussed in the blog “Demystifying Class A and Class B Type IO-Link Ports“.

Figure 3
Figure 3: Implementation 3 of Class-A IO-Link Master Port (The electrical drawings shown here are simplified for illustration only, the actual implementation drawings may be different)

The two key advantages with this approach are: 1) High amperage output can be used from pin 2 to control valves or solenoids by splitting the port, and 2) IO-Link devices such as valve terminals or configurable I/O hubs that require output power can be connected with standard 4 pole cables without needing additional power cables or connectors.

This does appear very similar to implementation 2 where output power can be provided as well. The key difference is that since the output power comes from a different power line, it is not shared with the device power — as you know, amperage reduces when you have parallel circuits, so implementation 2 is subject to that principle whereas implementation #3 is not.

Another benefit with this approach is that a safety relay can be placed on the power going to pin 2 because the output power for the entire module is separate. That means in case of E-stop situations, the output power can be shut off without harming the device power. This eliminates the need for elaborated controls planning as the device state is maintained throughout the operation. After recovering from an E-stop, the valves and all other outputs go back to their original state. This significantly simplifies your controls architecture, offers standardized approach to cabling and provides unified interface for all devices.

To learn more about Balluff’s implementation of IO-Link masters please visit www.balluff.com.

How RFID Can Push Your Automotive Production Into the Fast Lane

The automotive industry is one of the technological trendsetters in the manufacturing industry. In 1913 Henry Ford invented the assembly line and forever changed automotive production. Now a bit more than a century later the automotive industry is again facing one the biggest innovations in its history.

The complexity of different models and the variety of equipment variations are enormous. This individuality comes with great challenges. The workers in the assembly process are confronted with countless, almost identical components. This requires accurate tracking of all items to avoid mistakes. Safety-relevant components are, therefore, often provided with a barcode that has to be scanned manually.

The major advantages of RFID over barcodes in automotive production

Another technology could relieve employees of this routine task and give them the security of having installed the right parts through automatic testing: RFID. These are the big advantages of RFID over barcodes:

  • While the barcode only contains the information about which type of product it is, the RFID tag provides additional information, such as in which vehicle the car seat is to be installed.
  • While the barcodes have to be read out manually one after the other with a handheld scanner, the RFID tags can all be detected simultaneously and without contact via a scanner – even if the parts are already installed.
  • RFID tags can be used to retrieve information in seconds at any time. During the production process, it can already be checked whether all the required components are installed –  provided they are all equipped with an RFID tag. Without RFID, this was only recorded in the final inspection, using visual inspection and paper list.
  • Additionally, nowadays it is indispensable for the automotive industry to make the production parts traceable and thereby assign them a unique identity. RFID has the advantage that without visual contact or even after a repainting of the component, the information can be easily retrieved. The function is not lost with dirt or oil coverage. Furthermore, tags with special encapsulation can retain their function even under high mechanical, thermal or chemical loads.

How does RFID work?

RFID is the identification of objects by electromagnetic waves.  A reader generates a high-frequency electromagnetic field. If a data carrier (also called “tag”) is brought into the vicinity of the reader, the specific structure of the tag ensures a change in the field and thus transmits individual information about itself – contactless.

RFID Tag and Reader
Functional principle of an RFID system

Increase process reliability and profitability with RFID

Several thousand parts are needed to build a car. But only those parts that are safety, environmentally or testing relevant get an RFID tag. For example, the motor cabling would get a tag that can be read out automatically. Without RFID a worker would have to manually enter the label in a database and errors can easily arise. RFID detects the part automatically and you don’t have to look for labels in transport boxes, etc.

With RFID you know exactly where a component is located at any time – from the moment of delivery until the belt run of the car. With this information you can react flexibly to changes in the process, such as delays in certain areas, and can reschedule at short notice. In addition, you can always retrieve the current stock and know whether the right component is mounted on the right vehicle. So it can significantly increase process reliability and efficiency. An RFID solution eliminates several manual steps in the documentation per vehicle, and it brings more transparency to the logistics and production processes. That means the effort is reduced and the profitability increases.

The implementation starts with the suppliers

Ideally, the implementation of RFID starts with the automotive suppliers. They attach the RFID tags to their components what allows them to use the technology within their own logistics and manufacturing facilities. On arrival to the car manufacturer, the parts are driven through an RFID gate that reads out the tags automatically and adds the parts to the inventory. If the car leaves the assembly hall after manufacturing you can screen again by the RFID gate. At the push of a button it can show which parts are under the hood.

Automatic configuration with UHF for your convenience

The processes in the automotive industry are versatile, but a broad selection of innovative RFID products can push your automotive production into the fast lane.

For more information on RFID, visit www.balluff.com.

Basics of 3-Wire DC Sensor Output Protection

Most sensors offered today by reputable manufacturers include some type of electrical output protection that prevents sensor damage in the event of a wiring fault. There are a variety of protection methods and functions available, so let’s take a quick look at some of the most commonly found types.

Polarity Reversal Protection

This one is fairly straightforward and does just what its name implies. In case of accidentally reversed positive and common power leads, a series diode prevents any reverse flow of current that could damage the internal sensor electronics.

Miswiring Protection

This takes polarity reversal protection to the next logical step. Any of the three sensor wires can be misconnected in any combination and the sensor will not be damaged. For example, output to positive, common to load, and positive to common. Or, output and common to positive, and positive to load … you get the idea. Regardless, the sensor will be protected and will function normally once it is properly connected.

In either case of reversed polarity or other miswiring, although the sensor won’t be damaged, the sensor still represents a system fault and will require troubleshooting. This is why more and more machine builders and plant operators are moving away from hand-terminated sensor cables and toward double-ended quick-disconnect cordsets and distributed modular I/O over IO-Link.

Short-Circuit Protection (SCP)

This protects the output of the sensor from damage if it is connected to a dead short. Left unprotected, the sensor’s output becomes a fuse and “blows”, permanently destroying the sensor.

There are three types of short-circuit protection in use:

  • Thermal
  • Latching solid state
  • Pulsing solid state

Thermal SCP utilizes series device called a thermistor. As current through it rises, its resistance increases, which acts to throttle the current to a safe level. When the short circuit is removed, the sensor requires a cool down period before it can resume normal function. This is a crude form of short-circuit protection; modern 3-wire sensors no longer employ this method but some older types or some from lesser-known manufacturers may still be using it. One potential advantage for thermal SCP is that it has an inherent time delay that allows for a slightly longer, larger inrush current. This may be helpful in starting some high inrush loads like larger relays or incandescent lamps. However, in most cases today there is no need for a sensor to directly pilot loads like this. Most sensors today have a PLC input as a load.

Thermal Short-Circuit Protection

Latching solid state SCP was common in the past but today is less widely used. When the output current exceeds a defined threshold, the output circuit opens, stopping the flow of current. To reset the sensor after the fault, power to the sensor must be cycled (interrupted and re-applied). This can create a nuisance if the fault is intermittent, because someone has to disconnect and reconnect the sensor to reset it. However, at least the fault condition is captured every time it occurs.

Latching Short-Circuit Protection.JPG

Pulsing solid state SCP is used in most of today’s high-performance sensor designs. The sensor monitors the output for a short circuit and interrupts it the moment the current exceeds the design threshold. Subsequently, the electronics will start to continuously attempt to close the output to see if the fault has been removed. If not, it keeps removing and reapplying power to the output in a “pulsing” manner. If there is an intermittent fault, the sensor will resume normal function when the fault goes away. Sometimes this is called “automatic reset” (as opposed to latching SCP, which is manual reset). Automatic reset can be helpful, or it can be a nuisance. Because the fault isn’t latched, it may be hard to track down which sensor is being shorted if the fault is intermittent. On the plus side, if the fault was one-and-done, the sensor resumes normal function and production continues without further interruption.

Pulsing Short-Circuit Protection

The need to capture short-circuit events is one of the reasons more and more control systems are going with distributed modular I/O blocks using IO-Link. The input port of the block will detect the short circuit and will begin pulsing power to protect the sensor. Although it will automatically reset if the fault is removed, the block will send a fault message to the controller indicating which port was faulted. Note, however, that not all I/O blocks can interrupt a short circuit only at the port level. Many blocks will fault the entire block when only one port is affected. Be sure to ask any potential block supplier how their blocks behave during short-circuit events.

Overload Protection

This circuit monitors the length of time that higher-than-normal (but not short-circuit) load current is flowing. Over time, this can cause overheating of the sensor and subsequent damage. Overload Protection will detect this excessive-current condition and — depending on the type of SCP employed —either reduce current to a safe level (thermal SCP), turn the output off (latching SCP), or pulse the output (pulsing SCP).

Surge Protection

Also sometimes called Overvoltage Protection, this circuit monitors the incoming power supply voltage. When it exceeds the safe threshold, an internal circuit shunts the excessive voltage and clamps the applied voltage to the sensor at a safe level.

Inductive Overvoltage Protection

This circuit prevents sensor output damage from high voltages generated by “back EMF” (Electromotive Force) when an inductive load (like a relay coil) is switched off. Sometimes this is referred to as “inductive kickback”. Since current through an inductor tries to remain constant, the voltage across the inductor rises as the current falls to try to keep it flowing at the same level. The voltage can rise to very high levels, hundreds or thousands of volts, and will appear on the sensor’s output line. (In fact, this generation of high voltage from the collapse of current through an inductor is exactly how automotive spark ignition coils operate.)

So, how does inductive overvoltage protection work? Inside the sensor, a shunt device called a “freewheeling diode” allows the current to continue circulating harmlessly through the inductive load while it decays, preventing the buildup of damaging high voltage.

What Exactly is Safety Over IO-Link?

Users of IO-Link have long been in search of a solution for implementing the demands for functional safety using IO-Link. As a first step, the only possibility was to turn the actuators off using a separate power supply (Port class “B”, Pins 2, 5), which powers down the entire module. Today there is a better answer: Safety hub with IO-Link!

Automation Pyramid.png

This integrated safety concept is the logical continuation of the IO-Link philosophy. It is the only globally available technology to build on the proven IO-Link standards and profisafe. This means it uses the essential IO-Link benefits such as simple data transport and information exchange, high flexibility and universal applicability for safety signals as well. Safety over IO-Link combines automation and safety and represents efficient safety concepts in one system. Best of all, the functionality of the overall system remains unchanged. Safety is provided nearly as an add-on.

In the center of this safety concept is the new safety hub, which is connected to an available port on an IO-Link master. The safety components are connected to it using M12 standard cable. The safety profisafe signals are then tunneled to the controller through an IO-Link master. This has the advantage of allowing existing infrastructure to still be used without any changes. Parameters are configured centrally through the user interface of the controller.

Safety Hub

The safety hub has four 2-channel safe inputs for collecting safety signals, two safe outputs for turning off safety actuators, and two multi-channel ports for connecting things like safety interlocks which require both input and output signals to be processed simultaneously. The system is TÜV- and PNO-certified and can be used up to PLe/SIL 3. Safety components from all manufacturers can be connected to the safe I/O module.

Like IO-Link in general, Safety over IO-Link is characterized by simple system construction, time-and cost-saving wiring using M12 connectors, reduction in control cabinet volume and leaner system concepts. Virtually any network topology can be simply scaled with Safety over IO-Link, whereby the relative share of automation and safety can be varied as desired. Safety over IO-Link also means unlimited flexibility. Thanks to varying port configuration and simple configuration systems, it can be changed even at the last minute. All of this helps reduce costs. Additional savings come from the simple duplication of (PLC-) projects, prewiring of machine segments and short downtimes made possible by ease of component replacement.

Capture

To learn more about Safety over IO-Link, visit www.balluff.com.

 

When and Where to Use Continuous Cylinder Position Sensing

The role of smart cylinders — hydraulic or pneumatic cylinders with integrated position detection capability — has increased as manufacturers constantly strive to improve efficiency through automation. Smart cylinders can use either continuous or discrete position sensing, providing manufacturers with options, but possibly leaving them with questions on which is best for their application.

In this post we will review the benefits of continuous position sensors and list the applications where this is the best fit.

Continuous position sensors provide near real-time position feedback throughout the entire stroke of the cylinder making them the ideal choice for applications at the higher end of the control spectrum. Closed-loop servohydraulic systems can achieve sophisticated, dynamic control of motion across the entire cylinder stroke.

Continuous position sensors are commonly used when the application calls for closed-loop servo control, where the position, speed, acceleration, and deceleration of the cylinder must be controlled. Closed-loop servohydraulics have been widely used in industrial applications, such as sawmills, steel processing and tire manufacturing, and more recently in cylinders in off-highway equipment.

Magnetostrictive linear position sensors are the most commonly used continuous position sensors in hydraulic cylinders. These sensors are installed into the back end of the cylinder. The sensor detects the position of a magnet attached to the piston and provides a continuous, absolute position signal.

Blog
Magnetostrictive linear position sensor installed in hydraulic cylinder

The sensor is rated to withstand the full pressure of the hydraulic system. Magnetostrictive technology offers the advantage of being completely non-contact, meaning it requires no mechanical contact between the sensor and the moving cylinder and is not subject to wear and performance degradation. In addition, numerous electrical interface options are available, from simple analog (0 to 10V or 4-20mA) to high-performance industrial fieldbus interfaces that offer advanced functionality.

Continuous position sensors can also be used in pneumatic cylinders. While closed-loop servo control with pneumatics is not as common as it is with hydraulics, there are situations where pneumatic cylinders require continuous position sensing capability. For example, low-pressure pneumatic cylinders are sometimes used as measurement probes, or touch probes, where the cylinder rod is extended until it touches a part to be measured or gaged. In these situations, it is beneficial to be able to get continuous position feedback, especially when there is variability in the measured part.

To learn more about cylinder position sensing, visit www.balluff.com.

Flexibility Through Automated Format Changes on Packaging Machines

Digitalization does not stop at the packaging industry. There is a clear trend toward more individual packaging and special formats. What does this mean for packers and packaging machine manufacturers? The variants increase for every single packer, and this leads to a decreased batch size. The packer needs highly flexible machines, which he can easily adjust to the different formats and special variants. The machine manufacturer, in turn, must make these flexible machines available. What does this format change look like? Which technologies can support the packer optimally?

There are two different format adjustment tasks to perform. One is the adjustment of guide rails, side belts or link chains so that they can be adapted to the new format. The other is the changing of parts when a new format is to be produced.

Both tasks have different demands concerning automation technology and therefore there are different solutions available.

Format adjustment

Format adjustment is the adjustment of guide rails, side belts or link chains. In order to carry out this adjustment quickly, safely and error-free, precise position information is required. This recorded position information can then be used to support manual adjustment on the display unit or it can be transferred to the PLC for fully automatic adjustment. One possible solution is to use different position measuring systems. Various standardized interfaces are available as transmission formats, including IO-Link.

Fast format changes in secondary packaging.png
Fast format changes in secondary packaging

IO-Link has ideal features that are predestined for format adjustment: sufficient speed, full access to all parameters, automatic configuration, and absolute transmission of measured values. This eliminates the need for time-consuming reference runs. Since the machine control remains permanently traceable, the effort for error-prone written paper documentation is also saved.

One example for a non-contact absolute position measuring system

BML SL1, IO-Link

A magnetic encoded position measuring system is ideally suited for position detection during format adjustment. It is insensitive to dust, dirt and moisture, offers high accuracy and a measuring length of up to 8,190 mm. Therefore, the position determination and the speed control during the change of guide rails, sidebands or link chains are no problem.

For more information read our previous blog post “Boost Size-Change Efficiency with IO-Link Magnetic Encoders and Visualization”.

Changeable part detection

When changing to a different format size, it is often necessary to not only adjust guide rails but to also replace changeable parts. Machines are becoming more and more flexible, which means that the number of changeable parts per machine is growing.  It is becoming increasingly difficult for the machine operator to find the right part and even more difficult to find the correct mounting position. This conceals some avoidable sources of error. If the replacement part is installed incorrectly, it can cause machine damage, which can lead to downtime.

Therefore, a fast recognition of changeable parts is all about reliably detecting the changeable part at the correct position in the machine. It is also important to make it as easy as possible for the operator to detect possible faults before they happen via a visualization system.

One way of identifying exchangeable parts is industrial identification with RFID.

The right part at the right position

When changing a machine over to a new format you can use RFID data carriers or barcodes to ensure that the correct new parts are being used. Vision sensors also detect whether the part was installed correctly or incorrectly. These solutions help you prevent errors and machine damage, which in turn increases throughput and reduces production costs.

Implement predictive maintenance

With RFID data carriers, the operating times of each change part can be documented directly on the part itself. If a part needs to be cleaned, replaced or reworked, a notification or alarm is issued in the machine controller before fault conditions can arise. RFID data carriers also allow regular cleaning cycles to be logged.

Automate machine settings

Since you can store the individual setting parameters for the change part on the data carrier, the part itself also provides the information to the machine controller. Thus, the change part can trigger a format change in the PLC and change the production process. This is an important step toward intelligent production in the Industry 4.0 concept.

Simple visualization enables expert free operation

With an LED signal lamp, the operator can recognize the operating status of the machine quickly, easily and at a glance. Among other things, it serves to monitor the operating windows and signals whether all settings have been made correctly. The segments of the signal lamp can be configured so that one machine lamp meets a wide range of requirements.

Summary

Format adjustment involves changing guide rails, sidebands or link chains due to a new format. This can be semi-automated or fully automated on the machines. It requires displacement measuring systems whose sensors provide feedback on the respective position.

If format parts on the machine have to be replaced, it must be ensured that the correct changeable part is installed at the correct position in the machine. Industrial identification systems such as RFID are suitable for this purpose. Each changeable part is equipped with a tag and, with the help of the read/write heads, it recognizes whether the correct changeable part is installed in the correct place.

Both automation options offer the following advantages:

  • Short set-up times and increased system productivity
  • Efficient error prevention
  • Increased machine flexibility
  • Avoidance of machine damage due to wrong parts when starting up the machine
  • Simple visualization for the operator

To learn more about format change visit www.balluff.com.

Distance Measurement with Inductive Sensors

When we think about inductive sensors we automatically refer to discrete output offerings that detect the presence of ferrous materials. This can be a production part or an integrated part of the machine to simply determine position. Inductive sensors have been around for a long time, and there will always be a need for them in automated assembly lines, weld cells and stamping presses.

We often come across applications where we need an analog output at short range that needs to detect ferrous materials. This is an ideal application for an analog inductive proximity sensor that can offer an analog voltage or analog current output. This can reliably measure or error proof different product features such as varying shapes and sizes. Analog inductive sensors are pure analog devices that maintain a very good resolution with a high repeat accuracy. Similar to standard inductive sensors, they deal very well with vibration, commonly found in robust applications. Analog inductive proximity sensors are also offered in many form factors from M12-M30 tubular housings, rectangular block style and flat housings. They can also be selected to have flush or non-flush mounting features to accommodate specific operating distances needed in various applications.

Application Examples:

Shawn_1.png

Shawn_2

For more specific information on analog inductive sensors visit www.balluff.com.