Looking Into & Through Transparent Material With Photoelectric Sensors

Advance automated manufacturing relies on sensor equipment to ensure each step of the process is done correctly, reliably, and effectively. For many standard applications, inductive, capacitive, or basic photoelectric sensors can do a fine job of monitoring and maintaining the automated manufacturing process. However, when transparent materials are the target, you need a different type of sensor, and maybe even need to think differently about how you will use it.

What are transparent materials?

When I think of transparent materials, water, glass, plexiglass, polymers, soaps, cooling agents, and packaging all come to mind. Because transparent material absorbs very little of the emitted red LED light, standard photoelectric sensors struggle on this type of application. If light can make its way back to the receiver, how can you tell if the beam was broken or not? By measuring the amount of light returned, instead of just if it is there or not, we can detect a transparent material and learn how transparent it is.

Imagine being able to determine proper mixes or thicknesses of liquid based on a transparency scale associated to a value of returned light. Another application that I believe a transparent material photoelectric senor would be ideal for is the thickness of a clear bottle. Imagine the wall thickness being crucial to the integrity of the bottle. Again, we would measure the amount of light allowed back to the receiver instead of an expensive measurement laser or even worse, a time-draining manual caliper.

Transparent material sensor vs. standard photoelectric sensor

So how does a transparent material sensor differ from a standard photoelectric sensor? Usually, the type of light is key. UV light is absorbed much greater than other wavelengths, like red or blue LEDs you find in standard photoelectric sensors. To add another level, you polarize that UV light to better control the light back into the receiver. Polarized UV light with a polarized reflector is the best combination. This can be done on a large or micro scale based on the sensor head size and build.

Uses for transparent material sensor include packaging trays, level tubes, medical tests, adhesive extrusion, and bottle fill levels, just to name a few. Transparent materials are everywhere, and the technology has matured. Make sure you are looking into specialized sensor technologies and working through best set-up practices to ensure reliable detection of transparent materials.

The 5 Most Common Types of Fixed Industrial Robots

The International Federation of Robotics (IFR) defines five types of fixed industrial robots: Cartesian/Gantry, SCARA, Articulated, Parallel/Delta and Cylindrical (mobile robots are not included in the “fixed” robot category). These types are generally classified by their mechanical structure, which dictates the ways they can move.

Based on the current market situation and trends, we have modified this list by removing Cylindrical robots and adding Power & Force Limited Collaborative robots. Cylindrical robots have a small, declining share of the market and some industry analysts predict that they will be completely replaced by SCARA robots, which can cover similar applications at higher speed and performance. On the other hand, use of collaborative robots has grown rapidly since their first commercial sale by Universal Robots in 2008. This is why collaborative robots are on our list and cylindrical/spherical robots are not.

Therefore, our list of the top five industrial robot types includes:

    • Articulated
    • Cartesian/Gantry
    • Parallel/Delta
    • SCARA
    • Power & Force Limited Collaborative robots

These five common types of robots have emerged to address different applications, though there is now some overlap in the applications they serve. And range of industries where they are used is now very wide. The IFR’s 2021 report ranks electronics/electrical, automotive, metal & machinery, plastic and chemical products and food as the industries most commonly using fixed industrial robots. And the top applications identified in the report are material/parts handling and machine loading/unloading, welding, assembling, cleanrooms, dispensing/painting and processing/machining.

Articulated robots

Articulated robots most closely resemble a human arm and have multiple rotary joints–the most common versions have six axes. These can be large, powerful robots, capable of moving heavy loads precisely at moderate speeds. Smaller versions are available for precise movement of lighter loads. These robots have the largest market share (≈60%) and are growing between 5–10% per year.

Articulated robots are used across many industries and applications. Automotive has the biggest user base, but they are also used in other industries such as packaging, metalworking, plastics and electronics. Applications include material & parts handling (including machine loading & unloading, picking & placing and palletizing), assembling (ranging from small to large parts), welding, painting, and processing (machining, grinding, polishing).

SCARA robots

A SCARA robot is a “Selective Compliance Assembly Robot Arm,” also known as a “Selective Compliance Articulated Robot Arm.” They are compliant in the X-Y direction but rigid in the Z direction. These robots are fairly common, with around 15% market share and a 5-10% per year growth rate.

SCARA robots are most often applied in the Life Sciences, Semiconductor and Electronics industries. They are used in applications requiring high speed and high accuracy such as assembling, handling or picking & placing of lightweight parts, but also in 3D printing and dispensing.

Cartesian/Gantry robots

Cartesian robots, also known as gantry or linear robots, move along multiple linear axes. Since these axes are very rigid, they can precisely move heavy payloads, though this also means they require a lot of space. They have about 15% market share and a 5-10% per year growth rate.

Cartesian robots are often used in handling, loading/unloading, sorting & storing and picking & placing applications, but also in welding, assembling and machining. Industries using these robots include automotive, packaging, food & beverage, aerospace, heavy engineering and semiconductor.

Delta/Parallel robots

Delta robots (also known as parallel robots) are lightweight, high-speed robots, usually for fast handling of small and lightweight products or parts. They have a unique configuration with three or four lightweight arms arranged in parallelograms. These robots have 5% market share and a 3–5% growth rate.

They are often used in food or small part handling and/or packaging. Typical applications are assembling, picking & placing and packaging. Industries include food & beverage, cosmetics, packaging, electronics/ semiconductor, consumer goods, pharmaceutical and medical.

Power & Force Limiting Collaborative robots

We add the term “Power & Force Limiting” to our Collaborative robot category because the standards actually define four collaborative robot application modes, and we want to focus on this, the most well-known mode. Click here to read a blog on the different collaborative modes. Power & Force Limiting robots include models from Universal Robots, the FANUC CR green robots and the YuMi from ABB. Collaborative robots have become popular due to their ease of use, flexibility and “built-in” safety and ability to be used in close proximity to humans. They are most often an articulated robot with special features to limit power and force exerted by the axes to allow close, safe operation near humans or other machines. Larger, faster and stronger robots can also be used in collaborative applications with the addition of safety sensors and special programming.

Power & Force Limiting Collaborative robots have about 5% market share and sales are growing rapidly at 20%+ per year. They are a big success with small and mid-size enterprises, but also with more traditional robot users in a very broad range of industries including automotive and electronics. Typical applications include machine loading/unloading, assembling, handling, dispensing, picking & placing, palletizing, and welding.

Summary­

The robot market is one of the most rapidly growing segments of the industrial automation industry. The need for more automation and robots is driven by factors such as supply chain issues, changing workforce, cost pressures, digitalization and mass customization (highly flexible manufacturing). A broad range of robot types, capabilities and price points have emerged to address these factors and satisfy the needs of applications and industries ranging from automotive to food & beverage to life sciences.

Note: Market share and growth rate estimates in this blog are based on public data published by the International Federation of Robotics, Loup Ventures, NIST and Interact Analysis.

Protecting photoelectric and capacitive sensors

Supply chain and labor shortages are putting extra pressure on automation solutions to keep manufacturing lines running. Even though sensors are designed to work in harsh environments, one good knock can put a sensor out of alignment or even out of condition. Keep reading for tips on ways to protect photoelectric and capacitive sensors.

Mounting solutions for photoelectric sensors

Photoelectric sensors are sensitive to environmental factors that can cloud their view, like dust, debris, and splashing liquids, or damage them with physical impact. One of the best things to do from the beginning is to protect them by mounting them in locations that keep them out of harm’s way. Adjustable mounting solutions make it easier to set up sensors a little further away from the action. Mounts that can be adjusted on three axes like ball joints or rod-and-mount combinations should lock firmly into position so that vibration or weight will not cause sensors to move out of alignment. And mounting materials like stainless steel or plastic can be chosen to meet factors like temperature, accessibility, susceptibility to impact, and contact with other materials.

When using retroreflective sensors, reflectors and reflective foils need similar attention. Consider whether the application involves heat or chemicals that might contact reflectors. Reflectors come in versions, especially for use with red, white, infrared, and laser lights, or especially for polarized or non-polarized light. And there are mounting solutions for reflectors as well.

Considering the material and design of capacitive sensors

Capacitive sensors must also be protected based on their working environment, the material they detect, and where they are installed. Particularly, is the sensor in contact with the material it is sensing or not?

If there is contact, pay special attention to the sensor’s material and design. Foods, beverages, chemicals, viscous substances, powders, or bulk materials can degrade a sensor constructed of the wrong material. And to switch perspectives, a sensor can affect the quality of the material it contacts, like changing the taste of a food product. If resistance to chemicals is needed, housings made of stainless steel, PTFE, and PEEK are available.

While the sensor’s material is important to its functionality, the physical design of the sensor is also important. A working environment can involve washdown processes or hygienic requirements. If that is the case, the sensor’s design should allow water and cleaning agents to easily run off, while hygienic requirements demand that the sensor not have gaps or crevices where material may accumulate and harbor bacteria. Consider capacitive sensors that hold FDA, Ecolab, and CIP certifications to work safely in these conditions.

Non-contact capacitive sensors can have their own special set of requirements. They can detect material through the walls of a tank, depending on the tank wall’s material type and thickness. Plastic walls and non-metallic packaging present a smaller challenge. Different housing styles – flat cylindrical, discs, and block styles – have different sensing capabilities.

Newer capacitive technology is designed as an adhesive tape to measure the material inside a tank or vessel continuously. Available with stainless steel, plastic, or PTFF housing, it works particularly well when there is little space available to detect through a plastic or glass wall of 8mm or less. When installing the tape, the user can cut it with scissors to adjust the length.

Whatever the setting, environmental factors and installation factors can affect the functionality of photoelectric and capacitive sensors, sometimes bringing them to an untimely end. Details like mounting systems and sensor materials may not be the first requirements you look for, but they are important features that can extend the life of your sensors.

 

Detecting Liquid Media and Bubbles Using Optical Sensors

In my line of work in Life Sciences, we often deal with liquid media and bubble detection evaluation through a vessel or a tube. This can be done by using the absorption principle or the refraction principle with through-beam-configured optical sensors. These are commonly embedded in medical devices or lab instruments.

This configuration provides strong benefits:

    • Precise sensing
    • Ability to evaluate liquid media
    • Detect multiple events
    • High reliability

How does it work?

The refraction principle is based on the media’s refraction index. It uses an emitted light source (Tx) that is angled to limit the light falling on the receiver (Rx, Figure 1). When the light passes through a liquid, refraction causes the light to focus on the receiver as a beam (known as a “beam-make” configuration). All liquids and common vessel materials (silicon, plastic, glass, etc.) have a known refraction index. These sensors will detect those refraction differences and output a signal.

The absorption principle is preferred when a media’s absorption index is high. First, a beam is established through a vessel or tube (Figure 2). Light sources in the 1500nm range work best for aqueous-based media such as water. As a high absorption index liquid enters the tube, it will block the light (known as a beam-break configuration). The sensor detects this loss of light.

Discrete on-off signals are easily used by a control system. However, by using the actual light value information (commonly analog), more data can be extracted. This is becoming more popular now and can be done with either sensing principle. By using this light-value information, you can differentiate between types of media, measure concentrations, identify multiple objects (e.g., filter in an IV and the media) and much more.

There is a lot to know about through-beam sensors, so please leave a comment below if you have questions on how you can benefit from this technology.

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.

The Right Mix of Products for Recipe-Driven Machine Change Over

The filling of medical vials requires flexible automation equipment that can adapt to different vial sizes, colors and capping types. People are often deployed to make those equipment changes, which is also known as a recipe change. But by nature, people are inconsistent, and that inconsistency will cause errors and delay during change over.

Here’s a simple recipe to deliver consistency through operator-guided/verified recipe change. The following ingredients provide a solid recipe-driven change over:

Incoming Components: Barcode

Fixed mount and hand-held barcode scanners at the point-of-loading ensure correct parts are loaded.

Change Parts: RFID

Any machine part that must be replaced during a changeover can have a simple RFID tag installed. A read head reads the tag in ensure it’s the correct part.

Feed Systems: Position Measurement

Some feed systems require only millimeters of adjustment. Position sensor ensure the feed system is set to the correct recipe and is ready to run.

Conveyors Size Change: Rotary Position Indicator

Guide rails and larger sections are adjusted with the use of hand cranks. Digital position indicators show the intended position based on the recipes. The operators adjust to the desired position and then acknowledgment is sent to the control system.

Vial Detection: Array Sensor

Sensor arrays can capture more information, even with the vial variations. In addition to vial presence detection, the size of the vial and stopper/cap is verified as well. No physical changes are required. The recipe will dictate the sensor values required for the vial type.

Final Inspection: Vision

For label placement and defect detection, vision is the go-to product. The recipe will call up the label parameters to be verified.

Traceability: Vision

Often used in conjunction with final inspection, traceability requires capturing the barcode data from the final vials. There are often multiple 1D and 2D barcodes that must be read. A powerful vision system with a larger field of view is ideal for the changing recipes.

All of these ingredients are best when tied together with IO-Link. This ensures easy implantation with class-leading products. With all these ingredients, it has never been easier to implement operator-guided/verified size change.

Using MicroSpot LEDs for Precise Evaluations in Life Science

Handling microfluidics and evaluating samples based on light is a precise science. And that precision comes from the light source, not the actual detection method. But too many times we see standard LEDs being used in these sensing and evaluation applications. Standard LEDs are typically developed for lighting and illumination applications and require too many ancillary components to achieve a minimum level of acceptability. Fortunately, there is an alternate technology.

First, let’s look at a standard LED. Figure 1 shows a typical red LED. You can see the light emission surface is cluttered with the anode pad (square in the middle) and its bond wire. These elements are fine for applications like long-range sensing, lighting and indications, but for precise, up-close applications they cause disturbances.

Figure 1: Typical red LED showing the intrusion of the anode and bond wire into the light emission

Most notable is the square hole in the middle of the emission pattern. There are two typical methods to reduce the effect of the hole: lensing and apertures. An aperture essentially restricts the emitted light to a corner of the die, substantially reducing the light energy causing difficulties with low-contrast detections. Using a lens only will maintain the light energy, but the beam will have a fixed focused point that is not acceptable for many applications. But even the bond wire produces reflections and causes spurious emissions. These cannot be tolerated with microfluidics as adjacent channels will become involved in the measurement. An additional aperture is typically used to suppress the spurious emissions.

Fortunately, there is an alternative with MicroSpot LEDs. Basically, the anode and emission areas are inverted as shown in the Figure 2 comparison.

2
Figure 2: Comparison of the typical LED with the MicroSpot’s clean, powerful and collimated emission

This eliminates the need for the anode and bond wire to interfere with the emitted light. This produces a clean, powerful and collimated emission that will produce consistent results without additional components. This level of beam control is typically reserved for lasers. However, lasers also require more components, are much larger and cost more. The MicroSpot LED is the best choice for demanding life science applications.

Try the MicroSpot for yourself in select Balluff MICROmote miniature photoelectric sensors.

Learn more at www.balluff.com.