Every time I enter tier 1 and tier 2 suppliers, there seems to be a common theme of extreme sensor and cable abuse. It is not uncommon to see a box or bin of damaged sensors along with connection cables that have extreme burn-through due to extreme heat usually generated by weld spatter. This abuse is going to happen and is unavoidable in most cases. The only option to combat these hostile environments is to select the correct components, such as bunker blocks, protective mounts, and high temperature cable materials that can withstand hot welding applications.
In many cases I have seen standard sensors and cables installed in a weld cell with essentially zero protection of the sensor. This results in a very non-productive application that simply cannot meet production demands due to excessive downtime. At the root of this downtime you will typically find sensor and cable failure. These problems can only go on for so long before a culture change must happen throughout a manufacturing or production plant as there is too much overtime resulting in added cost and less efficiency. I call this the “pay me now or pay me later” analogy.
Below are some simple yet effective ways to improve sensor and cable life:
Whether it’s through preventative maintenance or during planned machine downtime, reducing downtime is a common goal for manufacturers. Difficult environments create challenges for not just machines, but also the components like sensors or cables. Below are three tips to help protect these components and reduce your downtime.
Cables don’t last forever. However, they are important for operations and keeping them functional is vital. An easy way to help reduce downtime and save money is by implementing a “sacrificial cable” in unforgiving environments. A sacrificial cable is any cable less than two meters in length and placed in situations where there is high turnover of cables. This sacrificial cable does not have to be a specialty cable with a custom jacket. It can be a simple 1 meter PVC cable that will get changed out often. The idea is to place a sacrificial cable in a problematic area and connect it to a longer length cable, or a home-run cable. The benefits of this method include: less downtime for maintenance when changing out failures, reduced expenses since shorter cables are less expensive, and there is less travel for the cable around a cell.
A second way to help reduce downtime is consider your application conditions up front. We discussed some of the application conditions to consider in a previous blog post, but how can we address these challenges? Not only is it important to choose the correct sensor for the environment, but remember, cables don’t last forever. Choosing the appropriate cable is also key to reducing downtime. Welding environments demand a cable that weld beads will not stick to and fuse the cable to the sensor. There are a variety of jacket types like silicone, silicone tube, or PTFE that prevent weld debris from accumulating on the cable. I’ve also seen applications where there is a lot of debris cutting through cables. In this case, a stainless steel braid cable would be a better solution than a traditional cable. Fitting the right protection to the right application is crucial..
A third tip to help reduce your machine downtime is to simply add protection to your existing components. Adding protection, whether it is a protective bracket or a silicone product, will help keep components running longer. This type of protection can be added before or after the cell is operational. One example of sensor protection is adding a ceramic cap to protect the face of a sensor. You can also protect the connection by adding tubing to the cable out version of the sensor to shield it from debris. Mounting sensors in a robust bracket helps protect the sensor from being hit, or having debris cover the sensor. There are different degrees of changes that help prolong operations.
Metalforming expert, Dave Bird, explains some of these solutions in the video below. To learn more you can also visit our website at www.balluff.us.
When working in harsh environments and in heavy duty applications like welding, it is important to take a multi-angle approach to designing the application. When you are working with existing sensor installations, it is important to consider all the reasons for the sensor’s failure before determining a winning solution. An important step in any application is to protect the connection between the controller and the sensor. In a welding environment, whether the sensor cable fails from weld slag buildup or from physical damage from contact with a part, the cable can be the key to a successful weld-sensing application.
That being said, the number of options available to protect the connection can be overwhelming and at times even confusing. For example, silicone cables vs silicone tube cables. Silicone cables have a jacket that is made out of silicone material over the conductors. This usually allows for a smaller diameter and more variety with the cordsets i.e. length and connector types. On the other hand, a silicone tube cable is a standard sensor cable with a silicone pulled over the cable then over-molded. The silicone tube is a second jacket and the air is a good insulator, prolonging the life of the sensor cable.
Another important consideration is how to even connect your sensor. One option is to install a sensor with a connector. This allows for a quick disconnect from the cable. In this case, it may be better to use a right angle connector, so the bend radius of the cable is not hanging loose. A second option is to install a sensor with cable out. This can have flying leads or a connector added to the end. At times, when there is not enough room to add a cordset, the cable out gives extra space.
In any continuous manufacturing process such as steel production, increased throughput is the path to higher profits through maximum utilization of fixed capital investments. In order to achieve increased throughput, more sophisticated control systems are being deployed. These systems enable ever-higher levels of automation but can present new challenges in terms of managing system reliability. Maintenance of profit margins depends on the line remaining in production with minimal unexpected downtime.
It is essential that control components, such as sensors, be selected in accordance with the rigorous demands of steel industry applications. Standard sensors intended for use in more benign manufacturing environments are often not suitable for the steel industry and may not deliver dependable service life.
When specifying sensors for steel production applications, some environmental conditions to consider include:
High temperatures exist in many areas of the steel-making process, such as the coke oven battery, blast furnace, electric arc furnace, oxygen converter, continuous casting line, and hot rolling line. Electronic components are stressed by elevated temperatures and can fail at much higher rates than they would at room temperature. Heat can affect sensors through conduction (direct transfer from the mounting), convection (circulating hot air), or radiation (line-of-sight infrared heating at a distance). The first strategy is to install sensors in ways that minimize exposure to these three thermal mechanisms. The second line of defense is to select sensors with extended temperature ratings. Many standard sensors can operate up to 185° F (85° C) but high temperature versions can operate to 212° F (100° C) or higher. Extreme temperature sensors can operate to 320° F (160° C) or even 356° F (180° C).
Don’t forget to consider the temperature rating of any quick-disconnect cables that will be used with the sensors. Many standard cable materials will melt or break down quickly at higher temperatures. Fiberglass-jacketed cables, for example, are rated to 752° F (400° C).
Shock and Vibration
Steel making involves large forces and heavy loads that generate substantial amounts of shock under normal and/or abnormal conditions. Vibration is also ever-present from motors, rollers, and moving materials. As with heat, look for sensors with enhanced specifications for shock and vibration. For sensors with fixed mountings, look for shock ratings of at least 30 G. For sensors mounted to equipment that is moving (for example, position sensors on hydraulic cylinders), consider sensors with shock ratings of 100 to 150 G. For vibration, the statement of specifications can vary. For example, it may be stated as a frequency and amplitude, such as 55 Hz @ 1 mm or as acceleration over a frequency range, such as 20 G from 10…2000 Hz.
Don’t forget that the quick-disconnect connector can sometimes be a vulnerability under severe shock. Combat broken connectors with so-called “pigtail” or “inline” connectors that have a flexible cable coming out of the sensor that goes to a quick-disconnect a few inches or feet away.
The best way to protect sensors from mechanical impact is to install them in protective mounting brackets (a.k.a. “bunker blocks”) or to provide heavy-duty covers over them. When direct contact with the sensor cannot be avoided, choose sensors specifically designed to handle impact.
Another strategy is to use remote sensor actuation to detect objects without making physical contact with the sensor itself.
Corrosion and Liquid Ingress
In areas with water spray and steam, such as the scale cracker on a hot strip line, corrosion and liquid ingress can lead to sensor failure. Look for stainless steel construction (aluminum can corrode) and enhanced ingress protection ratings such as IP68 or IP69K.
When All Else Fails…Rapid Replacement
If and when a sensor failure inevitably occurs, choose products and accessories that can minimize the downtime by speeding up the time required for replacement.
Strategies include quick-change sensor mounts, rapid-replacement sensor modules, and redundant sensor outputs.
In the case of redundant sensor outputs, if the primary output fails, the system can continue to operate from the secondary or even tertiary output.
In industrial automation we put our products through a lot. Extreme temperatures, harsh environments, and the demands of high performance can put a strain on the components of any machine. This led me to wonder, if our products could talk, what would they say?
Cordset: Cables have certain limpness which makes installing the cordset in automation easier to fit in tight spaces. Most cable installers prefer to have the least amount of slack in cable to prevent the cable being snagged or pulled during operations. Cables need to have a bend radius to prevent kinking of the conductors and a continuous flow of power. The bend radius is “the smallest radius of curvature into which a material can be bent without damage” (McGraw-Hill Dictionary of Architecture and Construction). Typically in a fixed (stationary) application, an unshielded sensor cable has a minimum bending radius of 8 times the outer diameter of the cable.
Power Supply: Everyone wants a friend. When a load is too much for one power supply, adding another power supply helps increase the voltage or current output. “The simplest method to create higher current is to connect the power supplies in parallel and leave only one supply in constant voltage mode. Some power supplies are equipped with analog control signals that allow auto-parallel or auto-tracking, a more elegant way to control multiple power supplies. Auto-parallel supplies can be controlled with a single master supply; a second advantage is that all of the master power supplies features can be used.” (Keysight Technologies) By stringing together power supplies, it allows more voltage or current but also keeps operations up and running.
There are many different types of cable jackets and each jacket works well in a specific application. The three main sensor cable jackets are PVC (Polyvinyl Chloride), PUR (polyurethane) and TPE (thermoplastic elastomer). Each jacket type has different benefits like washdown, abrasion resistant or high flexing applications. Finding the correct jacket type for your application can extend the life of the cable.
PVC is a general purpose cable and is widely available. It is a common cable, and typically has the best price point. PVC has a high moisture resistance, which makes it a good choice for wash-down applications.
PUR is found mostly in Asia and Europe. This cable jacket type has good resistance against abrasion, oil and ozone. PUR is known for being Halogen free, not containing: chlorine, iodine, fluorine, bromine or astatine. This jacket type does have limited temperature range compared to the other jacket types, -40…80⁰C.
TPE is flexible, recyclable and has excellent cold temperature characteristics, -50…125⁰C. This cable is resistant against aging in the sunlight, UV and ozone. TPE has a high-flex rating, typically 10 million.
The table below details the resistance to different conditions. Note that these relative ratings are based on average performance. Special selective compounding of the jacket can improve performance.
Choosing the right jacket type can help reduce failures in the field, reducing downtime and costs. Please visit www.balluff.us to see Balluff’s offering of sensor cables in PVC, PUR and TPE.
Inductive coupling is not new to automation. The concept in various forms has been around for over few decades. It was not actively used, and my guess is that more than form factor or functionality of couplers, it has to do with automation technology relying on mechanical and hard wired components. With growing complexity and ever evolving technology, the inductive coupling has also evolved. Nowadays, you can charge your smart phones or tablets using the charging pad that uses the very same technology.
In industrial automation space, inductive sensors are very popular and commonly used for detecting proximity of metal objects such as food cans, or machine parts. Inductive coupling also known as non-contact connectors, use magnetic induction to transfers power and data over an air gap. Yes, it is a kind of very short range wireless technology that also enables power transfer.
In this series of blogs on Inductive coupling, we can explore various use cases of Inductive coupling in complex automation. Today, let’s see how inductive coupling compares with traditional slip-ring mechanism. That’s right, it is the same technology used in the motor starters.
Slip-rings also known as rotary connectors are typically used in areas of the machine where one part rotates and other part of the machine remains stationary. For example, indexing table or turn table where stations on the indexing table need power and I/O but the table rotates through full 360°, hence standard cable solutions are ineffective. A slip ring could be installed at the base of the table.
Since, slip rings are electromechanical devices, in a long term they are subject to wear out. Unfortunately, the signs for wearing are not evident unless one day there is no power to the table. Inductive coupling solution eliminates all the hassle of the mechanical parts. With non-contact inductive coupling base of coupler could be mounted at the base of the table and the remote end could be mounted on the rotating part of the table. Slip rings are susceptible to noise and vibration — because they are electromechanical devices, whereas inductive couplers are not because there is no contact between the base and the remote. In fact, the turn table shown above uses an inductive coupler.
Inductive coupler, typically have IP67 rating for the housing are not affected by dirt or water, immune to vibrations and most important they are contact free so no maintenance unless you hammer one out. Learn more about Balluff inductive couplers www.balluff.us.
Example of a Flexible EOA Tool with 8 sensors connected with an Inductive Coupling System.
Over the years I’ve interviewed many customers regarding End-Of-Arm (EOA) tooling. Most of the improvements revolve around making the EOA tooling smarter. Smarter tools mean more reliability, faster change out and more in-tool error proofing.
#5: Go Analog…in flexible manufacturing environments, discrete information just does not provide an adequate solution. Analog sensors can change set points based on the product currently being manufactured.
#4: Lose the weight…look at the connectors and cables. M8 and M5 connectorized sensors and cables are readily available. Use field installable connectors to help keep cable runs as short as possible. We see too many long cables simply bundled up.
#3: Go Small…use miniature, precision sensors that do not require separate amplifiers. These miniature sensors not only cut down on size but also have increased precision. With these sensors, you’ll know if a part is not completely seated in the gripper.
#2: Monitor those pneumatic cylinders…monitoring air pressure in one way, but as speeds increase and size is reduced, you really need to know cylinder end of travel position. The best technology for EOA tooling is magnetoresistive such as Balluff’s BMF line. Avoid hall-effects and definitely avoid reed switches. Also, consider dual sensor styles such as Balluff’s V-Twin line.
#1: Go with Couplers…with interchangeable tooling, sensors should be connected with a solid-state, inductive coupling system such as Balluff’s Inductive Coupler (BIC). Avoid the use of pin-based connector systems for low power sensors. They create reliability problems over time.
While originally a mixed reviewed 1994 console video game, the recently published report by The Boston Consulting Group titled “The Rise of Robotics” really made me realize how important it is that we embrace robotics in our manufacturing processes. And I strongly agree with this statement: “Because robots can sharply improve productivity and offset regional differences in labor costs and availability, they’ll likely have a major impact on the competitiveness of companies and countries alike.” They studied the growth of the usage of robots in personal, commercial, military and industrial use and the numbers were quite powerful. Of interest to me is the rise in industrial robotics; doubling in 5 years from $5.8b to $11.0b in 2015. And the growth is expected to more than double again by 2025 to $24.4b in the industrial space.
What this means for manufacturers, machine builders and component suppliers is we need to make sure our people are trained to support this growth and that we we have strong peripheral technologies to support robots as they grow and expand. Even today there are some great technologies available in sensors and controls that make robotic integration easier for manufacturing companies.
So here are the three ways to make sure you are your robot’s ally.
Maximize Their Payload!
No one wants to be treated like they can’t help… especially your robots, they want you to utilize them and feel appreciated. For most robotics right now, payload size & payload weight is a limiting factor. Mini sensing products with precision switch points, small form factors and low mass allow for the design of low weight, compact payloads without limiting the functionality or speed of the robot.
Keep them Working!
A working robot is a happy robot. By adding flexible tooling or quick-change tooling to the end-effector of a robot you can have one arm perform multiple functions and keep idle arms to a minimum, increasing their value and “happiness.” Multiple products are out there to allow for this, however there is a technology that allows for sensor connections through inductive coupling that dramatically decreases repair issues and downtime due to tool changer pins.
Remove the Chains!
What’s the deal with cable dress packs… they look like really bad suspenders sometimes… you see them, you don’t like how they look, but you need it to keep your pants on… I guarantee that robots don’t like these things either… And with all that flexing something in there will fail regularly. There are some great technologies to reduce the sensor cables running on the arm and add flexibility and they are supported by the open standard IO-Link (discussed in other posts here!).
So as you integrate robots more and more into the manufacturing we are doing, please start thinking how to align yourself as a robot’s ally. Because I know I want to be on this guy’s team…
Environments with debris and caustic agents, wear down equipment exponentially. When a cell goes down, every minute counts to get production up and running. An accessory like a cordset is important for operations, and can frustrate technicians when it fails. Cordsets do not last forever in this environment and to help save money, time and work, we came up with the concept of a “sacrificial cable.” The basic idea is to install a double-ended cable under 2 meters to help in situations where cables are placed in surroundings which will destroy the cable. A sacrificial cable’s main function is to save time reducing cable replacement downtime and money.
Sacrifice Cordset Solution: Used in extremely rugged applications to reduce cordset replacement downtime
A sacrificial cable does not have to be a specialty cable with a custom jacket; it could just be a 1 meter PVC cable that will get changed out often. The idea is that by placing a sacrificial cable in a problematic area and connecting it to a longer length cable this will allow maintenance to have a shorter down time when changing out failures less. This is accomplished with travel around the cell following a cable run and less maintenance expense in labor.