Roughly four sensing-related processes occur in a welding cell with regards to parts that are to be joined by MIG, TIG and resistance welding by specialized robotic /automated equipment:
Nesting…usually, inductive proximity sensors with special Weld Field Resistance properties and hopefully, heavy duty mechanical properties (coatings to resist weld debris accumulation, hardened faces to resist parts loading impact and well-guarded cabling) are used to validate the presence of properly seated or “nested” metal components to ensure perfectly assembled products for end customers.
Poke-Yoke Sensing (Feature Validation)…tabs, holes, flanges and other essential details are generally confirmed by photoelectric, inductive proximity or electromechanical sensing devices.
Pneumatic and Hydraulic cylinder clamping indication is vital for proper positioning before the welding occurs. Improper clamping before welding can lead to finished goods that are out of tolerance and ultimately leads to scrap, a costly item in an already profit-tight, volume dependent business.
Connectivity…all peripheral sensing devices mentioned above are ultimately wired back to the controls architecture of the welding apparatus, by means of junction boxes, passive MIB’s (multiport interface boxes) or bus networked systems. It is important to mention that all of these components and more (valve banks, manifolds, etc.) and must be protected to ensure optimum performance against the extremely hostile rigors of the weld process.
Magnetoresistive (MR), and Giant Magnetoresistive (GMR) sensing technologies provide some very positive attributes in welding cell environments in that they provide exceptionally accurate switching points, have form factors that adapt to all popular “C” slot, “T” slot, band mount, tie rod, trapezoid and cylindrical pneumatic cylinder body shapes regardless of manufacturer. One model family combines two separate sensing elements tied to a common connector, eliminating one wire back to the host control. One or two separate cylinders can be controlled from one set if only one sensor is required for position sensing.
Unlike reed switches that are very inexpensive (up front purchase price; these generally come from cylinder manufacturers attached to their products) but are prone to premature failure. Hall Effect switches are solid state, yet generally have their own set of weaknesses such as a tendency to drift over time and are generally not short circuit protected or reverse polarity protected, something to consider when a performance-oriented cylinder sensing device is desired. VERY GOOD MR and GMR cylinder position sensors are guaranteed for lifetime performance, something of significance as well when unparalleled performance is expected in high production welding operations.
But!!!!! Yes, there is indeed a caveat in that aluminum bodied cylinders (they must be aluminum in order for its piston-attached magnet must permit magnetic gauss to pass through the non-ferrous cylinder body in order to be detected by the sensor to recognize position) are prone to weld hostility as well. And connection wires on ALL of these devices are prone to welding hostilities such as weld spatter (especially MIG or Resistance welding), heat, over flex, cable cuts made by sharp metal components and impact from direct parts impact. Some inexpensive, effective, off-the-shelf protective silicone cable cover tubing, self-fusing Weld Repel Wrap and silicone sheet material cut to fit particular protective needs go far in protecting all of these components and guarantees positive sensor performance, machine up-time and significantly reduces nuisance maintenance issues.
The article touches on different lingo between flexible, high-flex and high-flex-life. Flexible and high-flex mean the same thing. Google’s definition of flexible is the capability of bending easily without breaking. High-flex-life is described by Northwire as a cable designed to survive 10 million to 20 million flexing cycles. Those are just the common terms used to describe flexing of a cable, but there are manufacturers that use their own flexing name to describe their cables.
Teschler also describes the feel of a cable, whether the cable bends easily or not, based on different degrees of limpness or stiffness. “All in all, cable makers say the stiffness or limpness of the cable has nothing to do with its flex life.” The article goes on to describe a limp cable as a jacket that is made from soft materials, or finely stranded conductors, that allow the cable to move easily but is not meant to be used in applications with repeated flexing.
The last part of the article mentions how cables are tested for flexing. There is not a standard in the industry so different manufacturers can use differernt tests. The 3 most common tests are twist and flex test, tick-tock cable test, and UL test setup. Teschler pointed out the main focus for UL and CSA is to test for fire safety and UL test the cables for runs of 15,000 cycles.
Overall, I really enjoyed the article and highly suggest giving it a read to understand more about raw cable and testing requirements.
To see Balluff’s offering of UL listed cables click here.
It’s the worst when a network goes down on a piece of equipment. No diagnostics are available to help troubleshooting and all communication is dead. The only way to find the problem is to physically and visually inspect the hardware on the network until you can find the culprit. Many manufacturers have told me over the past few months about experiences they’ve had with down networks and how a simple cable or connector is to blame for hours of downtime.
By utilizing IO-Link, which has been discussed in these earlier blogs, and by changing the physical routing of the network hardware, you can now eliminate the loss of communication. The expandable architecture of IO-Link allows the master to communicate over the industrial network and be mounted in a “worry-free” zone away from any hostile environments. Then the IO-Link device is mounted in the hostile environment like a weld cell and it is exposed to the slag debris and damage. If the IO-Link device fails due to damage, the network remains connected and the IO-Link master reports detailed diagnostics on the failure and which device to replace. This can dramatically reduce the amount of time production is down. In addition the IO-Link device utilizes a simple sensor cable for communication and can use protection devices designed for these types of cables. The best part of this is that the network keeps communicating the whole time.
If you are interested in learning more about the benefits that IO-Link can provide to manufacturers visit www.balluff.us.
From The Free dictionary by Farlex, a receptacle is defined as “A fitting connected to a power supply and equipped to receive a plug.” I like this definition it describes both halves of the receptacle. In the automotive industry, the back half of a receptacle has threading on the nut with leads that could possibly connect a power supply. The front half describes which kind of cordset is needed. Typically, receptacles are used in a control cabinet, where there is easy access and out of the movement of machinery. Inside a control cabinet is a power source and/or programmable logic controller (PLC) which a receptacle would be wired to in the configuration of the controller. Receptacles used on a control box normally have a tight seal to keep out moisture and dust.
When looking at a receptacle there are two ends with different kinds of threading. In the front of the receptacle has a connection for a cable to connect to the outside environment, cells, and machinery, to the control box. The different cables could have diameter widths of M8, M12, 7/8”, 1” and more. From the picture, we see the front side of the receptacle calls for the M12x1 which would use a M12 cable. The first number is always the diameter of the outer threads. The other end of the receptacle, ½”-14NPT, where the leads come out, has another diameter referred as to the mounting type. There are many different kinds of mounting: Metric, PG, NPT, front mount, back mount, panel mount, etc. The two mounts types being explained here are Metric and NPT.
Normally the sensor experts here at SensorTech blog chose topics that we think will interest our readers. But this week we’re asking our readers to send us their top questions about sensors and connectivity. Got a question about how sensors work? How to select them? How to hook them up to a network? How to properly install and set them up? Some nagging problem with an application that’s driving you crazy? We’d like to hear from you!
Please enter your question (or questions) in the comment box below. We’re looking forward to doing our best to help you out!
Everyone likes things on demand right? Movies, TV shows, chocolate, you name it. My good friend, John Harmon, has prepared a YouTube video so that you have at your fingertips an on-demand presentation on Distributed Modular I/O. It is a great overview of the available functionality of Distributed Modular I/O and what kinds of control products that are available utilizing this technology. I realize the video is seven and a half minutes, which is pretty long for a web video, but I think he does an excellent job of keeping your attention and demonstrating the value of this technology. Grab a soda and your favorite chocolate bar, put your phone on silent, and hit play on this excellent presentation.
I’ve been talking pneumatic systems (valves, cylinders, actuators, etc.) recently with my customers and I’m finding among these engineers some common pains coming out of the system design. It seems that many people are researching networked valve islands with I/O built-in. These seem to be a great way to consolidate lots of I/O into one IP address, but there are some new issues cropping up similar to the above photo:
When assembling these at a machine builder the routing of cables with piping is more cumbersome with cables hanging off the valves, larger cable tray installations and large amounts of piping all running to the same spot.
For machine builders, with all of the valves centralized in one place, the pneumatic lines have to be longer. This causes many issues such as slower responsiveness due to air volume, air inertia, and lower air quality.
When trying to perform maintenance at an end-user, it becomes a nightmare to troubleshoot with a cluster of cables and pipes. The zip-tied and clean runs installed by the machine builder are cut, tangled and re-routed as the machine ages and becomes more difficult to troubleshoot.
Also at end users, if the manifold needs to be expanded, updated, retrofitted with new valves or I/O, there are big hurdles to jump when doing this: re-piping the valve due to mounting position shifting or even having to edit and repair code in the PLC to adapt to new bitmaps generated by the new valve manifold configuration.
When closing the loop with magnetic field sensors mounted on the cylinders, typically reed switches are used which are prone to failure. In addition, these switches typically have two sensors & cables per actuator to give extend or retract position, these cables cause larger cable trays and long cable runs back to the centralized manifold and I/O.
In April, Jim Montague of Control Design wrote an interesting article on Machine Mount I/O entitled “Machine-Mount I/O Go Everywhere.” I think the article makes some very good points as to the value of why someone wants to move from inside an enclosure, or controls cabinet, to mounting I/O products directly on the machine.
He summarizes, with the help of a number of industry experts, the below points:
Valve manifolds, or islands or banks, are used by many automation engineers in their machine design. They are a great way to easily implement a large number of pneumatic motion applications while keeping the air infrastructure minimal. Recent demand in the market has driven manifold manufacturers to reluctantly embed network interfaces and remote I/O into their products. Customers tell me while manufacturer’s expertise may lie with the pneumatic side of the product; there is usually less knowledge with-in their organizations to work on the Ethernet side of the product.