Eliminating Manufacturing Errors Begins with Identifying Trouble Spots

We have all gotten that dreaded phone call or email…the customer received their order, but there was a significant problem:

  • ErrorProofingTagsMissing part
  • Wrong color
  • Leaking seal
  • Improper assembly
  • Too lose…or too tight
  • Incomplete processing, e.g. missing threads
  • Something is damaged
  • Missing fluids or fluids at wrong level
  • …and so on

Assuming that we have reliable suppliers delivering quality parts that meet the required specifications…everything else that can (and often does) go wrong happens inside our own facilities. That means that solving the issues is our responsibility, but it also means that the solutions are completely under our control.

During the initial quality response meetings, at some point the subjects of “better worker training” and “more attention to detail and self-inspection” may come up. They are valid subjects that need to be addressed, but let’s face it: not every manufacturing and assembly problem can be solved by increased worker vigilance and dedication to workmanship. Nor, for that matter, is there the luxury of time or capacity for each worker to spend the extra time needed to ensure zero defects through inspection.

It is often more effective to eliminate errors at their source before they occur, so that further human intervention isn’t required or expected.

Some things to look for when searching for manufacturing trouble spots:

  • Are all fasteners present and properly tightened, in the proper torque sequence
  • Correct machine setup: is the right tool or fixture in place for the product being produced?
  • Manual data entry: does the process rely on human accuracy to input machine or product data?
  • Incorrect part: is it simply too hard to determine small differences by visual means alone?
  • Sequencing error: were the parts correct but came together in the wrong sequence?
  • Mislabeled component: would the operator realize that part is wrong if it was labeled incorrectly in the first place? Sometimes where the error has impact and where it actually occurred are in two different places.
  • Part not seated correctly: is everything is correct, but sometimes the part doesn’t sit properly in the assembly fixture?
  • Critical fluids: is the right fluid installed? Is it filled to the proper level?

Once the trouble spots have been identified, the next step is to implement a detection and/or prevention strategy. More information on the error proofing process is available on the Balluff website at www.balluff.us/errorproofing

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How can I convince my boss to send me to training?

trainingWith responsibilities expanding, resources declining, and margins narrowing, companies today must scrutinize every dollar spent. Bad decisions are often based on bad data. An informed decision, on the other hand, can be defended in the light of the facts. In this article, we examine three misconceptions –  misconceptions which too often lead to poor decisions about training.

  1. If I train my people, they will leave.

In today’s companies where people change positions frequently, training is seen as a risky investment.  The correct perspective is seeing the risk involved in NOT training your people.  Do you really want your people making costly mistakes by the trial-and-error method of on-the-job training? Lack of training does not just affect the untrained person. Those that have been trained and are doing the job correctly often get pulled aside to explain procedures to the untrained. The bottom line is that people are going to be trained one way or another. What is the most efficient way to do this?

  1. I can’t afford the downtime to send my people to training.

Tools need to be sharpened.  This means they can’t be “productive” 100% of the time.  “Productivity” needs to be seen as a totally different thing from being “busy.”   Once a tool is sharpened, it is far more productive.  A dull tool can be “busy” 100 % of the time accomplishing nothing of value.  The correct perspective then is that you can’t afford the loss of productivity caused by a lack of training.

  1. All training offered out there is basically the same, so just take the cheapest one.

Training is not a one-way dump of information.  Training means that a change has taken place in a cognitive domain, an affective domain, or a psychomotor domain.  For automation companies, these three domains are intricately linked.  For example, it is not enough to just sit through a safety presentation:  you need to know the safety regulations (cognitive), you need to be passionate about why these are important (affective), and you need the skill necessary to implement these regulations by specifying, configuring, and integrating systems (psychomotor).

The best way to train in the psychomotor domain is through hands-on training.  Students learn skills best by practicing those skills.  For many companies who offer training, training is just a presentation of ideas without the necessary opportunity for participants to try anything for themselves. At Balluff, we have made a substantial investment in equipment, an investment in writing courseware properly, and an investment in training those who conduct the training with platform skills, adult learning skills, and teaching skills.  These investments make world-class, performance-based training available to our customers.

To see all that Balluff has to offer in Automation Training, click on our training web page link:  http://www.balluff.com/balluff/MUS/en/service/standard-training.jsp

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Direct vs Indirect Mounting of Capacitive Sensors

Direct sensing mount

Figure 1: Direct sensing mount

In liquid level sensing applications, capacitive sensors can be mounted directly in contact with the medium or indirectly with no contact to the medium.

Containers made of metal or very thick non-metallic tank walls (more than 1″) typically require mounting the sensor in direct contact with the medium (Fig. 1). In some instances, a by-pass tube or a sights glass is used, and the senor detects the level through the wall of the non-metallic tube (Fig. 2).

Indirect sensing mount

Figure 2: Indirect sensing mount

The direct mounting method could simplify sensor selection and setup since the sensor only has to sense the medium or target material properties. Nonetheless, this approach imposes certain drawbacks, such as costs for mounting and sealing the sensor as well as the need to consider the material compatibility between the sensor and the medium. Corrosive acids, for example, might require a more expensive exotic housing material.


The preferred approach is indirectly mounting the capacitive sensor flush against the non-metallic wall to detect the target material non-invasively through the container wall.  The advantages for this approach are obvious and represent a major influence to specify capacitive sensors.  The container wall does not have to be penetrated, which leaves the level sensor flexible and interchangeable in the application.  Avoiding direct contact with the target material also reduces the chances of product contamination, leaks, and other sources of risk to personnel and the environment.

The target material also has relevance in the sensor selection process.  Medical and semiconductor applications involve mostly water-based reagents, process fluids, acids, as well as different bodily fluids.  Fortunately, high conductivity levels and therefore high relative dielectric constants are common characteristics among all these liquids.  This is why the primary advantages of capacitive sensors lies in non-invasive liquid level detection, namely by creating a large measurement delta between the low dielectric container walls and the target material with high dielectric properties.

At the same time, highly conductivity liquids could impose a threat to the application.  This is because smaller physical amounts of material have a larger impact on the capacitive sensor with increasing conductivity values, increasing the risk of false triggering on foam or adherence to the inside or outside wall.  SMARTLEVEL sensors offered by Balluff will ignore foaming, filming and material build-up in these applications.

Learn more about Balluff’s capacitive solutions on our website at www.balluff.us.

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Inductive coupling – simple concept for complex automation

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.


Figure 1: Inductive coupling for power and data exchange

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. To learn more about this technology see our Balluff Basics.


Figure 2: Slip ring example

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.


Figure 3: Inductive coupling replacing the slip-ring

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/inductive-couplers.

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RFID ROI – Don’t forget the payback!

traceability_1Just recently, while visiting a customer wanting to implement an RFID asset tracking solution, it occurred to me that ROI (return-on-investment) should always be the ultimate goal for most uses of RFID. What brought this to mind? It was because we were discussing technology before understanding what the ultimate ROI goal was. I’m sure you could say this was failure from a sales perspective, but I’m sure at some point you have also found yourself caught up in the technology seeming so promising and exciting in terms of its benefits, that you lost track of why you were there in the first place. Also, many times, the technology stage is where equipment suppliers and/or integrators are brought in.

As with most projects of this nature, they get started because someone says something like “why don’t we do XXX, it will save us money, time, trouble, loss or get us in compliance” or all of the above and likely more. But this same thought can get lost going through execution. RFID projects are no exception. Many successful RFID implementations show it can bring large benefits in short and long-term ROI not just in asset tracking, but manufacturing, warehousing, supply chain and so on. But the implementor must always keep track of the ROI goal and be willing to share this with their internal stakeholders, supplier and integration partners to be sure everything stays on track and technology does not take over for technologies sake.

Unfortunately the ROI is not always calculated the same for applications. Typically ROI can simply be measured in time period until the investment is paid back or the money saved over a given period of time. The most simplistic way of calculating payback or ROI is: Cost of Project (calculated at the beginning) / Annual Cash Revenues (expected savings) = Payback Period. Unfortunately the rub comes in when calculating the detail in the two factors. This can be because the cost of the project is not totally encompassing and/or revenue does not take into consideration factors like interest costs or variations in production, for example. As this will ultimately become the measure of successful projects, really understanding ROI is critical.

Factors in Annual Cash Revenues are factors the implementer needs to understand and grasp as the reasons for undertaking a project. These factors will typically involve several aspects of their business, including savings from greater efficiency, lower cost in storage or inventory, less scrap, higher quality standards (less failure returns), compliance benefits, etc. In fact, this part is difficult to encompass here in this forum. But Cost of Project has some factors I can point out. In the example I raised in the beginning, the customer needed to not only address the read/write equipment and tags (including handheld’s), but also the cost of installing all the possible variations in tag types used during manufacture, common database/software needed, bringing distributors and field service on board, integration providers costs (internal also), training needs, software licensing, start-up and support cost, and so on. So in a manufacturing line, it starts with the new equipment, but must include the PLC/database programming, pallet modifications, station installation, spare parts, start-up and training for example. In warehousing, it might include new equipment, loss of facility equipment like forklifts or warehouse area, facility modification like electrical for example, ERP and WMS implementation or integration, commissioning and training.

One thing to consider toward understanding these factors before implementing a total enterprise solution, whether in warehousing, supply chain or manufacturing is to consider a pilot or test/trail program to determine as many factors as possible and test the results before committing to the full investment of the complete project.

So in your next project, remember to include your stakeholders and partners in your end goals, try to encompass all the factors and don’t forget the payback!

To learn more about RFID visit us at www.balluff.us/rfid.

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Let’s Get Small: The Drive Toward Miniaturization

minisensorGoing about our hectic daily lives, we tend to just take the modern cycle of innovation for granted. But when we stop to think about it, the changes we have seen in the products we buy are astonishing. This is especially true with regard to electronics. Not only are today’s products more feature-laden, more reliable, and more functional…they are also unbelievably small.

I remember our family’s first “cell phone” back in the ’90s. It was bolted to the floor of the car, required a rooftop antenna, and was connected to the car’s electrical system for power. All it did was place and receive phone calls. Today we are all carrying around miniature pocket computers we call “smartphones,” where the telephone functionality is – in reality – just another “app”.

Again going back two decades, we had a 32″ CRT analog television that displayed standard definition and weighed over 200 pounds; it took two strong people to move it around the house. Today it’s common to find 55″ LCD high-definition digital televisions that weigh only 50 pounds and can be moved around by one person with relative ease.

LabPhotoThese are just a couple of examples from the consumer world. Similar changes are taking place in the industrial and commercial world. Motors, controllers, actuators, and drives are shrinking. Today’s industrial actuators and motion systems offer either the same speed and power with less size and weight, or are simply more compact and efficient than ever before possible.

The advent of all this product miniaturization is driving a need for equally miniaturized manufacturing and assembly processes. And that means rising demand for miniaturized industrial sensors such as inductive proximity sensors, photoelectric presence sensors, and capacitive proximity sensors.

Another thing about assembling small things: the manufacturing tolerances also get small. The demand for sensor precision increases in direct proportion to manufacturing size reduction. Fortunately, miniature sensors are also inherently precision sensors. As sensors shrink in size, their sensing behavior typically becomes more precise. In absolute terms, things like repeatability, temperature drift, and hysteresis all improve markedly as sensor size diminishes. Miniature sensors can deliver the precise, repeatable, and consistent sensing performance demanded by the field of micro-manufacturing.

For your next compact assembly project, be sure to think about the challenges of your precision sensing applications, and how you plan to deploy miniature sensors to achieve consistent and reliable operation from your process.

For more information on precision sensing visit balluff.us/minis.

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When to use IO-Link RFID

IO-Link logoAt this point it is pretty clear that RFID is a fairly simple identification solution that involves a tag, antenna, and processor. The tag holds the information that is critical to the application. That information could be a very brief identifying number, sometimes called a license plate, and usually consists of 4 to 12 Bytes of data. Or, the application may require the tag to hold all the information about the product being manufactured such as build data, process data, or lineage data. In this case, there are tags with up to 128 Kilobytes of available storage. The scenarios above help to answer the question: “when do I use IO-Link RFID?”

Simply put, IO-Link makes life on the manufacturing floor much easier. It eliminates the mess in the cabinet, it is plug and play, it allows connection to any major controller, etc. etc. etc. So, why not just do away with everything not IO-Link and call it a day? For RFID there is 1 major question that needs to be answered to determine whether or not IO-Link is the right solution: How much data needs to be read from the tag?

IO-link specializes in transferring smaller amounts of data. When required to transfer large amounts the speed is greatly reduced. Here is a very simple way to look at it: IO-Link RFID comes in two different versions- 10Bytes or 32Bytes. The 10 Bytes or 32 Bytes refer to the size of the buffer or container that transfers the data. Imagine this as two semi-trucks carrying a load in a trailer (buffer). Of course, the 32 Byte trailer can carry a larger load (Data) than the 10Byte trailer. Therefore, we can conclude that the 10Byte trailer has to make more trips to carry larger amounts of data. More trips take more time therefore slowing down the process. If there are only 8Bytes of data that need to be read from the tag then the 10Byte version is fine, but if there are 28 bytes then it makes sense to us the 32 Byte version. However, as mentioned above there are applications where the tag may hold up to 8KB, 32KB, or even 128KB of data and IO-Link should not be considered. As a general rule IO-link should not be used to read anything over 96 Bytes due to speed being greatly reduced.

Need For Speed?

As a rule of thumb it takes about .2 seconds for IO-Link RFID readers to read 16Bytes of data and about .5 seconds to read 96Bytes. Reading anything above 96Bytes increases the read time dramatically. As a comparison, the latest and greatest Balluff RFID processor, the BIS V can read 256Bytes of data in about .2 seconds.

Ultimately, the amount of data that needs to be read from the tag and the time required to read that data should be the deciding factors of whether or not IO-Link RFID is right for the job or not.

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Anatomy of a High Pressure Inductive Proximity Sensor

Some industrial applications will require a sensor with special properties. This type of sensor offering is needed especially when pressure comes to play. In a wide range of hydraulic cylinder and valve applications high pressure sensors are exposed to hostile environments and are subject to pressure that a standard sensor simply cannot hold up in. For example 350 bar of pressure can be detrimental to a standard sensor as it is not designed for a pressure application.

High pressure inductive sensors are designed to withstand the severe duty of a high pressure application with product features like corrosion – resistant housing materials, high strength ceramic sensing faces and special sealing techniques such as undercut housings with sealing and support rings. This is very important because not only do we need to have a sensor that can withstand pressure on the face of the sensor without damage we also need to make sure we can keep the hydraulic fluid inside the cylinder or valve where it belongs.

In the photo below you will notice the undercut area at the sensing face of the sensor along with an O-ring and supporting backing ring to make sure the application is sealed tight.

installation instruction Installation Photo

There are several common sizes for different types of cylinder and valves however the same principle applies. Below is an example of a flange mount style offering. This type of sensor takes a different design approach that is bolted to the top side of a cylinder with a sealing O-ring under the mounting point.

Strokemaster Diagram

strokemaster photo

It’s also important to know what form factor is needed when specifying a high pressure inductive sensor. Typically you will see pressure options from 50 up to 500 bar. The dimensions of the cylinder or valve will determine what type of high pressure sensor is needed.


For more information on high pressure Inductive Sensor click here.

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DC Does Have Its Benefits

My blog this time was supposed to be about photoelectric basics, however, I recently had a discussion with an individual who asked why the market does not offer more AC sensors.  In thinking about our discussion I thought this would make an interesting blog and perhaps would spark (no pun intended) some comments from our readers.

 Why DC control circuits are more common than AC and what benefits do they provide? 
minifamilyWith machines getting smaller and faster, and costs becoming more of a concern DC sensors and components solve these issues.  The circuit boards are smaller which means the sensors can be smaller and lighter thus the machines can move faster due to lighter loads.  DC sensors are typically less expensive and a larger selection of products exists to solve more of the demanding applications seen today.

Some regulations go into effect at the 50 – 60 volt threshold and since a vast majority of DC control circuits are 24 volt these regulations can be avoided.  DC control circuits are more universally accepted than AC plus the fact DC power supplies are getting less expensive.  Today’s newly designed DC circuits consume less power which means smaller power supplies can be used.  Another advantage of the DC power supply is if there is a short circuit the power supply folds back and will resume full power when the short is removed.

Not only are there more sensor options available there are more and faster interface cards for the most common control device used today, the PLC.  DC sensors and components do not have the current leakage that their AC counterparts have.  That being said, when using an AC sensor with the higher leakage, frequently pull down resistors are required to prevent the leakage current from causing false inputs to the PLC.

In addition to the PLC interface, more and more manufacturers use DC interfaces to their electronic devices.  With AC controls you have to use relays for interface which can add to cycle times.  A real money saver is being able to run instrumentation and communication cables with DC controls in the same conduit or cable tray.

DC is inherently faster than AC which means faster response.  With more and more cycle times being reduced to achieve faster processes milliseconds can really add up.  An AC signal introduces approximately an 8 msec delay in actuation of a device, however, this delay time is very unpredictable.

Typically, AC is used on the outputs of PLC’s to turn on motor control starters, larger solenoid valves, and higher current devices.  Also, AC circuits are going to be more immune to noise that would cause problems on DC circuits.  In some cases it makes sense to use an AC sensor especially if there is a long run of conduit down a conveyor with one motor and one sensor.  Those wires can be run together saving installation time and money.

When it comes to speed, size, and costs DC controls seem to provide more benefits than AC.  What are your thoughts?

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Back to the Basics: How Do I Wire a DC 2-wire Sensor?

In one of my previous post we covered “How do I wire my 3-wire sensors“. This topic has had a lot of interest so I thought to myself, this would be a great opportunity to add to that subject and talk about DC 2-wire sensors. Typically in factory automation applications 2 or 3 wire sensors are implemented within the process, and as you know from my prior post a 3 wire sensor has the following 3 wires; a power wire, a ground wire and a switch wire.

A 2-wire sensor of course only has 2 wires including a power wire and ground wire with connection options of Polarized and Non-Polarized. A Polarized option requires the power wire to be connected to the positive (+) side and the ground wire to be connected to the negative side (-) of the power supply. The Non-Polarized versions can be wired just as a Polarized sensor however they also have the ability to be wired with the ground wire (-) to the positive side and the power wire (+) to the negative side of the power supply making this a more versatile option as the sensor can be wired with the wires in a non – specific location within the power supply and controls.

In the wiring diagrams below you will notice the different call outs for the Polarized vs. Non-Polarized offerings.

PolarizedDiagramsnon-polarized diagramsNote: (-) Indication of Non-Polarized wiring.

While 3-wire sensors are a more common option as they offer very low leakage current, 2 wire offerings do have their advantages per application. They can be wired in a sinking (NPN) or sourcing (PNP) configuration depending on the selected load location. Also keep in mind they only have 2 wires simplifying connection processes.

For more information on DC 2- Wire sensors click here.

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