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Focusing on Machine Safety

Machine safety refers to the measures taken to ensure the safety of operators, workers, and other individuals who may come into contact with or work in the vicinity of machinery. Safety categories and performance levels are two important concepts to evaluate and design safety systems for machines. A risk assessment is a process to identify, evaluate, and prioritize potential hazards and risks associated with a particular activity, process, or system. The goal of a risk assessment is to identify potential hazards and risks and to take steps to prevent or mitigate those risks. The hierarchy of controls can determine the best way to mitigate or eliminate risk. We can use this hierarchy, including elimination, substitution, engineering, and administrative controls, and personal protective equipment (PPE), to properly mitigate risk. Our focus here is on engineering controls and how they relate to categories and performance levels.

Performance level

The performance level (PL) of machine safety components is a measure of the reliability and effectiveness of safety systems. Defined as EN ISO 13849-1 standard by the International Organization for Standardization (ISO), it is based on the probability of a safety system failing to perform its intended function. Performance levels are designated by the letters “a” through “e” with PLa being the lowest level of safety and PLe being the highest. Assessing the safety function of the machinery and evaluating the likelihood of a dangerous failure occurring determines the performance level.

Four levels of protection

The categories of machine safety components refer to the four levels of protection required to ensure the safe operation of machinery, as defined by the ISO. Figure 1 below shows how the measured risk determines the performance level and category of circuit performance.

    • Category 1: The occurrence of a fault can lead to loss of the safety function. Single channel safety circuit.
    • Category 2: The occurrence of a fault can lead to loss of the safety function between checks. Single channel safety circuit with monitoring.
    • Category 3: When a single fault occurs, the safety function is always performed. Some faults, but not all, can be detected, but the accumulation of those undetected faults can lead to the loss of the safety function. This category can be implemented using control reliable devices in a dual channel redundant safety circuit that includes monitoring.
    • Category 4: When a fault occurs, the safety function is always performed. Faults will be detected in time to prevent a loss of the safety function and is implemented using control reliable devices in a dual channel redundant safety circuit that includes monitoring.

Using control reliable devices is crucial in Category 3 and 4 safety circuits. One example of a control reliable device is a safety relay that mechanically interlocks the control contacts to the auxiliary contacts. Being mechanically interlocked means when the relay changes states the auxiliary contact will also changes states. Another example of a control reliable device is a safety PLC. A standard PLC is not rated to control safety functions because it is not control reliable and a malfunction could lead to the loss of a safety function.

 

The selection of the appropriate category and performance level for devices used to mitigate a risk in a machine is crucial for ensuring the safety of operators and other individuals. While it is important to note that the purpose of this blog is to provide information, it is not enough to qualify individuals to design or test safety systems. In summary, the category of machine safety defines the level of protection required for safe operation, while the performance level measures the reliability and effectiveness of safety systems.

Now let us go automate with a focus on safety!

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IO-Link Safety: What It Is and Isn’t

Comparing “IO-Link” and “Safety” to “IO-Link Safety”

There are many I/O blocks that have “IO-Link” and “Safety” in their descriptions, which can cause some confusion about which safety features they include. Here’s an overview of different safety-named blocks and how they compare to IO-Link Safety.

Safety Network Blocks

These blocks have I/O ports that use Pin 4 and Pin 2 as OSSD signals (safety ports). OSSD—output switching signal devices—send 24-volt signals over two wires to confirm that a device is operating in a safe condition. If 0 volts are detected in either signal, besides their safety-checking 0-volt pulses, it’s read as a safety event that signals the machine to go into a safe state. Safety network blocks are only for standard (non-network) safety devices. These blocks communicate directly back to a Safety Controller over safety protocols like CIP Safety, PROFIsafe, etc. These blocks typically can monitor between 8-16 standard safety devices. There is no intelligence built into the safety devices.

Safety Network Blocks with IO-Link

Blocks in this category usually have a mixture of I/O ports on them. The ports can range from standard I/O to standard IO-Link communication, and in addition, include ports that use Pin 4 and Pin 2 as OSSD signals (safety ports). These blocks communicate over the safety protocols with only a few ports to connect standard (non-network) safety devices. There is some versatility with these blocks since you can wire standard sensors, IO-Link devices, and safety devices to it. The drawback is, you will always run short of the port style you need and, in the end, use more blocks to cover either the safety or IO-Link needs of the application. There is no intelligence built into the safety devices.

Safety over IO-Link Blocks

In this system/architecture, there are standard IO-Link Masters communicating to the Safety PLCs/Controllers over standard protocols like EtherNet/IP, PROFINET, etc. Connected to the IO-Link Ports of these Masters are Safety over IO-Link devices, currently limited to only Safety over IO-Link hubs. The Safety PLCs/Controllers communicate via safety protocols like PROFIsafe to the standard IO-Link Master, and then using the IO-Link communication channel, they bridge the gap to the Safety over the IO-Link hub via the “black channel.” These Safety over IO-Link hub’s ports use Pin 4 and Pin 2 as OSSD signals (safety ports), so standard (non-network) safety devices can be connected. This system provided a “gap filler” while IO-Link Safety was being developed. In this system/architecture, the standard IO-Link Masters allowed standard IO-Link devices and Safety over IO-Link hubs to be connected to any ports. This brought even more versatility to an application and the beginnings of the benefits of IO-Link. Still, there is no intelligence built into the safety devices.

IO-Link Safety

IO-Link Safety adds a safety communication layer to IO-Link. The difference between this and Safety over IO-Link is that this safety layer applies to both the IO-Link Master and IO-Link Safety devices. Within a CIP Safety or PROFIsafe network, the safety communication protocol has top priority over standard EtherNet/IP or PRIFONET data if both are existing on the same physical network. The same is true for IO-Link Safety: both standard and safety IO-Link protocols can exist on the same physical cable between the IO-Link Master ports and IO-Link Safety devices, with IO-Link Safety carrying the top priority. For a deep dive into the IO-Link Safety protocol, I suggest visiting the IO-Link Consortium’s website at io-link.com. In this system/architecture, you have IO-Link Safety Masters, which communicate to the Safety PLCs/Controllers over safety protocols like CIP Safety, PROFIsafe, etc. The ports on the Masters can utilize Pin 4 and Pin 2 as OSSD signals (safety ports), so standard (non-network) safety devices can be connected. Pin 4 can also be used to carry standard IO-Link and IO-Link Safety communication to standard IO-Link devices and IO-Link Safety devices, respectively. This allows for the most versatile safety solution in the market–IO-Link Safety Masters that can accept standard (non-network) safety devices, standard IO-Link devices, and IO-Link Safety devices. Intelligence in the IO-Link Safety devices is now available.

Benefits of IO-Link Safety

    • IO-Link Safety devices are fieldbus neutral: you just need to specify the IO-Link Safety Master to match the Safety PLCs/Controllers protocol.
    • IO-Link Safety Master port versatility: standard (non-network) safety devices, standard IO-Link devices, and IO-Link Safety devices can be connected.
    • Parameter storage: standard IO-Link and IO-Link Safety device’s parameters can be stored for ease of device replacement.
    • Smart IO-Link Safety device data: more data available, like internal temperature, humidity, number of cycles, power consumption, diagnostics, etc.
    • Simplified wiring: IO-Link Safety devices are still connected to the IO-Link Master port with a standard 3 to 4 conductor cable.
    • IIoT fit: IO-Link Safety gives more visibility to upper-level systems like SCADA, allowing safety device-level monitoring.

I am looking forward to seeing how quickly IO-Link Safety will be accepted, with how IO-Link numbers have skyrocketed over the last few years. The future looks great for IO-Link with IO-Link Safety, IO-Link Wireless and in the future, Single-Pair Ethernet (SPE). With all these new capabilities, what application can’t IO-Link support?

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Weld Immune vs. Weld Field Immune: What’s the difference? 

In today’s automotive plants and their tier suppliers, the weld cell is known to be one of the most hostile environments for sensors. Weld slag accumulation, elevated ambient temperatures, impacts by moving parts, and strong electromagnetic fields can all degrade sensor performance and cause false triggering. It is widely accepted that sensors will have a limited life span in most plants.

Poor sensor selection does mean higher failure rates which cause welders in all industries increased downtime, unnecessary maintenance, lost profits, and delayed delivery. There are many sensor features designed specifically to withstand these harsh welding environments and the problems that come along with them to combat this.

In the search for a suitable sensor for your welding application, you are sure to come across the terms weld immune and weld field immune. What do these words mean? Are they the same thing? And will they last in my weld cell?

Weld Immune ≠ Weld Field Immune

At first glance, it is easy to understand why someone may confuse these two terms or assume they are one and the same.

Weld field immune is a specific term referring to sensors designed to withstand strong electromagnetic fields. In some welding areas, especially very close to the weld gun, welders can generate strong magnetic fields. When this magnetic field is present, it can cause a standard sensor to perform intermittently, like flickering and false outputs.

Weld field immune sensors have special filtering and robust circuitry that withstand the influence of strong magnetic fields and avoid false triggers. This is also called magnetic field immune since they also perform well in any area with high magnetic noise.

On the other hand, weld immune is a broad term used to describe a sensor designed with any features that increase its performance in a welding application. It could refer to one or multiple sensor features, including:

    • Weld spatter resistant coatings
    • High-temperature resistance
    • Different housing or sensor face materials
    • Magnetic field immunity

A weld field immune sensor might be listed with the numerous weld immune sensors with special coatings and features, but that does not necessarily mean any of those other sensors are immune to weld fields. This is why it is always important to check the individual sensor specifications to ensure it is suitable for your application.

In an application where a sensor is failing due to impact damage or weld slag spatter, a steel face sensor with a weld resistant coating could be a great solution. If this sensor isn’t close to the weld gun and isn’t exposed to any strong magnetic fields, there is really no need for it to be weld field immune. The important features are the steel face and coating that can protect it against impact and weld slag sticking to it. This sensor would be classified as weld immune.

In another application where a sensor near the weld gun side of the welding procedure where MIG welding is performed, this location is subject to arc blow that can create a strong magnetic field at the weld wire tip location. In this situation, having a weld field immune sensor would be important to avoid false triggers that the magnetic field may cause. Additionally, being close to a MIG weld gun, it would also be wise to consider a sensor with other weld immune properties, like a weld slag resistant coating and a thermal barrier, to protect against high heat and weld slag.

Weld field immunity is just one of many features you can select when picking the best sensor for your application. Whether the issue is weld slag accumulation, elevated ambient temperatures, part impact, or strong electromagnetic fields, there are many weld immune solutions to consider. Check the placement and conditions of the sensors you’re using to decide which weld-immune features are needed for each sensor.

Click here for more on choosing the right sensor for your welding application.

 

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Does Your Stamping Department Need a Checkup? Try a Die-Protection Risk Assessment

If you have ever walked through a stamping department at a metal forming facility, you have heard the rhythmic sound of the press stamping out parts, thump, thump. The stamping department is the heart manufacturing facility, and the noise you hear is the heartbeat of the plant. If it stops, the whole plant comes to a halt. With increasing demands for higher production rates, less downtime, and reduction in bad parts, stamping departments are under ever-increasing pressure to optimize the press department through die protection and error-proofing programs.

The die-protection risk assessment team

The first step in implementing or optimizing a die protection program is to perform a die-protection risk assessment. This is much like risk assessments conducted for safety applications, except they are done for each die set. To do this, build a team of people from various positions in the press department like tool makers, operators, and set-up teams.

Once this team is formed, they can help identify any incidents that could occur during the stamping operations for each die set and determine the likelihood and the severity of possible harm. With this information, they can identify which events have a higher risk/severity and determine what additional measures they should implement to prevent these incidents. An audit is possible even if there are already some die protection sensors in place to determine if there are more that should be added and verify the ones in place are appropriate and effective.

The top 4 die processes to check

The majority of quality and die protection problems occur in one of these three areas: material feed, material progression, and part- and slug-out detections. It’s important to monitor these areas carefully with various sensor technologies.

Material feed

Material feed is perhaps the most critical area to monitor. You need to ensure the material is in the press, in the correct location, and feeding properly before cycling the press. The material could be feeding as a steel blank, or it could come off a roll of steel. Several errors can prevent the material from advancing to the next stage or out of the press: the feed can slip, the stock material feeding in can buckle, or scrap can fail to drop and block the strip from advancing, to name a few. Inductive proximity sensors, which detect iron-based metals at short distances, are commonly used to check material feeds.

Material progression

Material progression is the next area to monitor. When using a progressive die, you will want to monitor the stripper to make sure it is functioning and the material is moving through the die properly. With a transfer die, you want to make sure the sheet of material is nesting correctly before cycling the press. Inductive proximity sensors are the most common sensor used in these applications, as well.

Here is an example of using two inductive proximity sensors to determine if the part is feeding properly or if there is a short or long feed. In this application, both proximity sensors must detect the edge of the metal. If the alignment is off by just a few millimeters, one sensor won’t detect the metal. You can use this information to prevent the press from cycling to the next step.

Short feed, long feed, perfect alignment

Part-out detection

The third critical area that stamping departments typically monitor is part-out detection, which makes sure the finished part has come out of the stamping

area after the cycle is complete. Cycling the press and closing the tooling on a formed part that failed to eject can result in a number of undesirable events, like blowing out an entire die section or sending metal shards flying into the room. Optical sensors are typically used to check for part-out, though the type of photoelectric needed depends on the situation. If the part consistently comes out of the press at the same position every time, a through-beam photo-eye would be a good choice. If the part is falling at different angles and locations, you might choose a non-safety rated light grid.

Slug-ejection detection

The last event to monitor is slug ejection. A slug is a piece of scrap metal punched out of the material. For example, if you needed to punch some holes in metal, the slug would be the center part that is knocked out. You need to verify that the scrap has exited the press before the next cycle. Sometimes the scrap will stick together and fail to exit the die with each stroke. Failure to make sure the scrap material leaves the die could affect product quality or cause significant damage to the press, die, or both. Various sensor types can ensure proper scrap ejection and prevent crashes. The picture below shows a die with inductive ring sensors mounted in it to detect slugs as they fall out of the die.

Just like it is important to get regular checkups at the doctor, performing regular die-protection assessments can help you make continuous improvements that can increase production rates and reduce downtime. Material feed, material progression, part-out and slug-out detection are the first steps to optimize, but you can expand your assessments to include areas like auxiliary equipment. You can also consider smart factory solutions like intelligent sensors, condition monitoring, and diagnostics over networks to give you more data for preventative maintenance or more advanced error-proofing. The key to a successful program is to assemble the right team, start with the critical areas listed above, and learn about new technologies and concepts that are becoming available to help you plan ways to improve your stamping processes.

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Add Automation to Gain Safety and Control in Manufacturing

Industry automation not only has a positive effect on the improvement of production processes, it also significantly improves employee safety. New technologies can minimize the need for employees to work in dangerous situations by replacing them all together or by working cooperatively alongside them.

Overcoming fears of automation
Many workers fear technological progress due to the generally accepted view that robots will replace people in their workplaces. But their fears are conjecture. According to a study published in 2017 by scientists at the Universities of Oxford and Yale, AI experts predict a 50% chance of AI outperforming humans at all tasks within 45 years. But, instead of replacing all workers, there is a stronger chance AI will eliminate dangerous manual labor and evolve other roles. Following are a few examples.

    • Automation in palletizing systems
      Before automation-based solutions entered factories, laborers had to do most work by hand. A work system based on the strength of the human body, however, does not bring good results. Workers tire quickly, causing a decrease in their productivity. And with time, health problems related to regularly carrying heavy daily loads also begin to appear. Until recently, employees of the palletizing departments struggled with these problems. But today, robots are carrying out the work of moving, stacking, and transporting products on pallets.
    • Automation forging processes
      Also, until recently, forging processes in the metallurgical industry were performed with the help of human workers. There are still factories today in which blacksmiths are responsible for putting the hot metal element under the hammer to form the final shape of the product. Such a device hits with a force of several dozen tons, several times a minute. Being at the hammer is therefore extremely dangerous and may cause permanent damage to the worker’s health. Elevated temperatures in the workplace can also have negative effects on the body.

      At       most businesses, forging processes are now fully automated. Robots specially prepared for such work feed the elements to the automatic hammer with their grippers. And sensory solutions help make the job safer by detecting the presence of people or undesirable elements within the working machine. The quality control of manufactured products is also extremely important and more easily controlled with an automated system.
    • Automation in welding processes
      Welding processes are another dangerous activity in which automation is starting to play a key role. During welding work, toxic fumes are released from the gas lagging, which the welder regularly inhales. This can result in serious poisoning or chronic respiratory diseases. Welding also produces sparks which can lead to severe burns and worker blindness.

      Again, automation makes the process safer. High-class welding machines exist on the market that can work continuously, under human control. With such solutions, it is necessary to use appropriate protection systems to protect employees against possible contact with machines during work. Automation in this situation eliminates a dangerous role, and creates a new, safer, and, some would say, better work role.

Skillful design of automation systems
While factory automation eliminates some threats to workers, others often arise, creating the need for strict design plans prepared by specialists in this field. It is necessary to prepare the automation system in such a way that it not only ensures safety, it does so without reducing productivity or creating downtime which can cause the employee to bypass security systems. The systems blocking the working space of the machine should not interfere with the worker and the worker should not interfere with the system. Where possible, instead of a mechanical lock, an optical curtain at the feeding point should be used to stop the machine’s operation if a foreign object breaks the curtain’s beam of the light. Mechanical locks blocking access to the working space should be in places where it is not necessary to open the door frequently.

Successful human-machine collaboration
When designing automation systems in production companies, it is also necessary to remember that often a human is working alongside the robot. In palletizing systems, for example, a person is responsible for preparing the place for packing and cleaning the working area. For the work to go smoothly, it may be worth creating two positions next to each other. Mechanisms on the market today allow you to control the work of robots at a given position, assigning them to the workspace. Special security scanners prevent the robots from moving to positions where someone is working.

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Zoning in on Explosive Atmospheres

Everybody wants to wake up in the morning and know they’re going to a safe workplace. A major safety concern among certain industries is the occurrence of fires and explosions. This makes for some of the most expansive safety codes and standards. This article is aimed at explaining hazardous area classification in simple terms for easy comprehension. Before we begin to classify hazardous areas, it is crucial to define what they are.

What is a hazardous area?

A hazardous area is a place in which an explosive atmosphere may occur in quantities requiring the implementation of special precautions to protect the health and safety of workers. Hazardous areas are classified into two major categories: gases/vapors and dusts.

Classification of hazardous areas

Both categories are further divided into three ATEX Zones, as directed by the European Union for protection against explosive atmospheres. Each zone indicates the frequency and duration an explosive atmosphere may be present. Hazardous areas involving gases/vapors are classified as follows:

    • Zone 0 is an area where an explosive atmosphere consisting of a mixture of air with flammable substances in the form of gas, vapor, or mist is present continuously for long periods or frequently (continuous hazard)
    • Zone 1 is an area where an explosive atmosphere is likely to occur in normal operation occasionally (intermittent hazard)
    • Zone 2 is an area where an explosive atmosphere is unlikely to occur in normal operating conditions, and if it does occur, it is likely to do so for a short period only (possible hazard)

Similarly, dusts classify into three different zones: Zones 20,  21, and  22, each representing identical meanings as their gas/vapor code counterparts, respectively. The gas station example below offers a real-world picture of these hazardous zones.

Gas station hazard zonesThe vessels containing the fuel underground and on the truck are classified as Zone 0 because these areas are continuously holding flammable substances. The gas pumps and any valve or opening into the gas containers are classified as Zone 1 because gas will be passing through intermittently — when a customer uses the pump or an employee fills the tanks. Zone 2 is the natural space or the natural environment. While fuel should not be exposed to the natural environment under normal operating conditions, it is possible. Spills, for example, can create a possible hazard for a short duration.

It’s important to note the European Union ATEX directive is not compliant with OSHA standards in the United States. While similar, the U.S. has its own classification system for identifying hazardous zones called the NEC Zone Classification System. See how the two systems compare here.

Safety

The more frequent an explosive gas or dust cloud is present, the more dangerous the zone. Therefore, companies practice ATEX zone reduction by implementing safety measures.

In areas with risk of explosion, accurate and reliable position detection is often relied on to complete tasks. Examples include monitoring hydraulic and pneumatic cylinders, checking hydraulically and pneumatically controlled valves, and level detection.

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Robust Cylinder Feedback Adds Safety to Mobile Equipment Applications

Adding position feedback to a hydraulic cylinder provides several benefits which include increasing the efficiency of a process, automating a function, and adding safety to a machine. Most manufacturers of cylinder sensing products offer both discrete and proportional outputs to achieve the cylinder feedback required of the application. Of the proportional types, there’s been a few technologies utilized through the years which include resistive potentiometers, glass scales, linear Hall effect, optical readers, linear variable displacement transducers (LVDT’s), and magnetostrictive transducers. Of these many technologies, magnetostriction continues to be the technology of choice for many absolute position feedback applications due to its non-contact sensing, repeat accuracies, linearities within a few micrometers, and robust mechanical assemblies.

The phenomenon of magnetostriction was first discovered by James Joule in 1842. Joule found that a ferromagnetic material, such as an iron rod, would change dimensions slightly when subjected to a magnetic field. Today’s magnetostrictive transducers use special ferromagnetic alloys and utilize Joule’s effect as a position marker. Additional electronics, including time-of-flight circuitry, are then used to define the position and/or velocity of the marker. While the technology of the magnetostrictive transducer is sophisticated today, the general principal remains the same and is well proven.

Magnetostrictive transducers are widely used in steel mills, sawmills, tire manufacturers and many other industrial processes. They are also widely used in mobile equipment in industries such as construction, agriculture, and rail maintenance of way vehicles.

One strong application for cylinder feedback in mobile equipment is for operator safety. Large mobile elevated work platforms (MEWPs, aka boom lifts, man lifts, cherry pickers, etc.) do not utilize outriggers to stabilize the machine due to the machine’s ability to drive while the basket (and operator) are at height. These machines are also likely to be rented, leaving the skill of the operator in question. A quality cylinder transducer provides precise position feedback to the electronic control module which determines if the operator is approaching an unsafe working condition. One such scenario is when the boom is at 45 degrees and telescoping further out from the side of the machine. In this case, the joystick controls will limit the operator inputs to keep the machine from extending any further out, keeping the machine within a predetermined working “envelope.” Another popular application would be as a memory function. A good magnetostrictive transducer will allow the operator to “teach” a specific position. The operator can return to the programmed position automatically. Memory functions are useful for repeat actions such as returning a bucket to a specific height. If trucks to be filled are all the same height, the memory function can save time and reduce mishaps, allowing the operator to concentrate on other functions such as turning and driving. In the rail industry, maintenance of way machines uses magnetostrictive transducers to determine the depth of hydraulic tines that are used to compact ballast, or to raise the track to a specific height.

No matter what the application, when reliable feedback of a cylinder is needed, magnetostrictive transducers provide reassuring feedback on mobile machines, even in harsh conditions.

But not all magnetostrictive transducers are found within a cylinder housing. Some manufacturers offer both internal and external products. The arguments for an internal approach center around added protection for the transducer from rocks, dirt, heat, etc., while advocates for an external approach speak of less downtime in the event of a transducer mishap, and the reduced costs and delivery times of using a standard cylinder. A reputable manufacturer with technical experts can help guide your choice.

Whether internal or external, industrial or mobile, the phenomenon of magnetostriction will continue to be the technology chosen for reliable, accurate detection of hydraulic cylinders.

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RFID for Improved Operator Accountability

One of the most fascinating parts of my job is making site visits to manufacturing plants across the country. Getting a first-hand look at how things are made in a modern manufacturing facility is nothing short of amazing. Robots whirling, automatic guided vehicles (AGV’s) navigating the floor, overhead cranes and gantries lifting tons of material over-head, flames shooting from ovens, and metal chips flying create an exciting, but sometimes dangerous, work environment. To some people this may seem like a good reason to avoid these places, but if you are fitted with the appropriate personal protective equipment (PPE) the chances for injury are minimal.

The safety of every human in the plant is the top priority.  This is why there are requirements to wear PPE that is suitable for the environment and the hazards within. The challenge is confirming that everyone is aware of the required equipment, and that they indeed are wearing that equipment.

This can be accomplished with a simple RFID kiosk system. When an operator scans their ID they are asked a series of questions to ensure they are wearing the correct PPE. If the operator confirms they are wearing all the required gear, they can begin work in the area they are assigned. If not, a supervisor will be notified so the correct equipment can be obtained. This method can serve as a daily reminder for what needs to be worn while holding the operator accountable.

Ultimately, it is up to the plant and occupational safety organizations to define what needs to be worn and where it should be worn, but it is the responsibility of the operator to actually wear it. The same system can be used for vendors, visitors or anyone else who ventures out on the plant floor.

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Sensor and Device Connectivity Solutions For Collaborative Robots

Sensors and peripheral devices are a critical part of any robot system, including collaborative applications. A wide variety of sensors and devices are used on and around robots along with actuation and signaling devices. Integrating these and connecting them to the robot control system and network can present challenges due to multiple/long cables, slip rings, many terminations, high costs to connect, inflexible configurations and difficult troubleshooting. But device level protocols, such as IO-Link, provide simpler, cost-effective and “open” ways to connect these sensors to the control system.

Just as the human body requires eyes, ears, skin, nose and tongue to sense the environment around it so that action can be taken, a collaborative robot needs sensors to complete its programmed tasks. We’ve discussed the four modes of collaborative operation in previous blogs, detailing how each mode has special safety/sensing needs, but they have common needs to detect work material, fixtures, gripper position, force, quality and other aspects of the manufacturing process. This is where sensors come in.

Typical collaborative robot sensors include inductive, photoelectric, capacitive, vision, magnetic, safety and other types of sensors. These sensors help the robot detect the position, orientation, type of objects, and it’s own position, and move accurately and safely within its surroundings. Other devices around a robot include valves, RFID readers/writers, indicator lights, actuators, power supplies and more.

The table, below, considers the four collaborative modes and the use of different types of sensors in these modes:

Table 1.JPG

But how can users easily and cost-effectively connect this many sensors and devices to the robot control system? One solution is IO-Link. In the past, robot users would run cables from each sensor to the control system, resulting in long cable runs, wiring difficulties (cutting, stripping, terminating, labeling) and challenges with troubleshooting. IO-Link solves these issues through simple point-to-point wiring using off-the-shelf cables.

Table 2.png

Collaborative (and traditional) robot users face many challenges when connecting sensors and peripheral devices to their control systems. IO-Link addresses many of these issues and can offer significant benefits:

  • Reduced wiring through a single field network connection to hubs
  • Simple connectivity using off-the-shelf cables with plug connectors
  • Compatible will all major industrial Ethernet-based protocols
  • Easy tool change with Inductive Couplers
  • Advanced data/diagnostics
  • Parametarization of field devices
  • Faster/simpler troubleshooting
  • Support for implementation of IIoT/Industry 4.0 solutions

IO-Link: an excellent solution for simple, easy, fast and cost-effective device connection to collaborative robots.

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Power & Force Limiting Cobots for Dull, Dirty and Dangerous Applications

Collaborative robots, or cobots, is currently one of the most exciting topics in automation. But what do people mean when they say “collaborative robot”? Generally, they are talking about robots which can safely work near and together with humans. The goal of a collaborative robot system is to optimize the use of humans and robots, building on the capabilities of each.

There are four modes of robot collaborative operation defined by the global standard ISO/TS 15066. We discussed these modes in a previous blog, Robot Collaborative Operation.

This post will go more deeply into the most commonly used mode: power & force limiting. Robots in this category include ones made by Universal Robots, as well as FANUC’s green robots and ABB’s Yumi.

What is power & force limiting?

Power & force limiting robots are designed with limited power and force, along with physical features to avoid or reduce injury or damage in case of contact. These robots are generally smaller, slower and less powerful than traditional robots but also more flexible and able to work near or with humans — assuming a risk assessment determines it is safe to do so.

The standards define the creation of a shared or collaborative work space for the robot and human, and define how they may interact in this space. In a power & force limiting application, the robot and operator can be in the shared/collaborative work space at the same time and there may be contact or collision between the operator and the collaborative robot system (which includes the robot, gripper/tool and work piece). Under the proper conditions the features built into the power & force limiting robot allow this close interaction and contact to occur without danger to the operator.

What technologies allow these robots to work closely with humans?

The limiting of the robot’s force can be implemented in several ways. Internal torque/feedback sensors in the joints, external sensors or “skins” and/or elastic joints are some of the methods robot suppliers use to assure low force or low impact. They also design possible contact areas to avoid injury or damage by using rounded edges, padding, large surface areas, etc. to soften contact. Grippers, tools and work pieces also need to be considered and designed to avoid injury or damage to people and equipment.

Peripherally, additional sensors in the robots, grippers, tools, work holders and surrounding work stations are critical parts of high performance robot applications. Connecting these sensors through protocols such as IO-Link and PROFISafe Over IO-Link allows more tightly integrated, better performing, and safer collaborative robot systems.

Where are power & force limiting robots typically applied?

Similar to traditional robots, power & force limiting robots are best applied in applications which are dull, dirty and/or dangerous (the 3 Ds of robotics). They are especially well suited to applications where the danger is ergonomic — repetitive tasks which cause strain on an operator. In many cases, power & force limiting robots are being applied to cooperate closely with people: the robots take on the repetitive tasks, while the humans take on the tasks which require more cognitive skills.

A large number of the customers for power & force limiting robots are small or medium-sized enterprises which can not afford the investment and time to implement a traditional robot, but find that power & force limiting robots fit within their budget and technical capabilities.

What are some of the benefits and drawbacks to power & force limiting robots?

Benefits:

  • Low cost
  • Fast, simple programming and set up; often does not require special knowledge or training
  • Small and lightweight
  • Easy to deploy and redeploy
  • Can be fenceless
  • Low power usage
  • Close human-robot interaction

Drawbacks:

  • Slow
  • Small payload
  • Low force
  • Low precision (not always the case, and improving)

Final Thoughts

Buying a power & force limiting robot does not necessarily mean that fences or other safeguards can be removed; a risk assessment must be completed in order to ensure the application is appropriately safeguarded. The benefits, however, can be significant, especially for smaller firms with limited resources. These firms will find that power & force limiting robots are very good at cost-effectively solving many of their dull, dirty and dangerous applications.