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:
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 automated manufacturing, part quality issues are a weekly discussion and this continues to be true in most weld shops across North America. One of the more common issues that I encounter in discussions with customers involves nuts being welded to a part.
Nut problems seem to come in a variety of frustrations:
no nut present
There are many different sensing technologies that have been applied or attempted over the years for weld nut detection and each has its pros and cons. In my travels I have personally encountered technologies like machine vision, mechanical plungers, inductive proximity sensors, photoelectric sensors, specially designed “nut sensors” and linear position sensors, to name a few. The biggest complaints I hear about different technologies is either they are unreliable/unrepeatable or they aren’t rugged enough to survive a hit from big metal parts or they can’t take the heat of close proximity to welding.
Repeatedly we have found two technologies are finding success for tough weld nut detection applications in two different parts of the production process.
Post Process Check Stations – Mechanical Contact with PlungerProx sensor. This sensor uses a spring loaded pin sized for the proper nut to detect presence, is easily repairable (if necessary) and has the ability to adapt to a wide range of nut threads and diameters.
In-Process Check on Pedestal Welders – Linear position feedback on the height of the weld gun can provide exact measurements and feedback on the status of the weld nut from presence to orientation of the nut.
I acknowledge that every nut and every application are different. I regularly see the key to success is to test and discuss with your local sensor guy about the best technology for the situation. If you are interested in discussing a particularly difficult application please connect with me on Linked-In or Twitter @WillAutomate.
When the topic of welding comes up we know that our application is going to be more challenging for sensor selection. Today’s weld cells typically found in tier 1 and tier 2 automotive plants are known to have hostile environments that the standard sensor cannot withstand and can fail regularly. There are many sensor offerings that are designed for welding including special features like Weld Field Immune Circuitry, High Temperature Weld Spatter Coatings and SteelFace Housings.
For this SENSORTECH topic I would like to review Weld Field Immune (WFI) sensors. Many welding application areas can generate strong magnetic fields. When this magnetic field is present a typical standard sensor cannot tolerate the magnetic field and is subject to intermittent behavior that can cause unnecessary downtime by providing a false signal when there is no target present. WFI sensors have special filtering properties with robust circuitry that will enable them to withstand the influence of strong magnetic fields.
WFI sensors are typically needed at the weld gun side of the welding procedure when MIG welding is performed. This location is subject to Arc Blow that can cause a strong magnetic field at the weld wire tip location. This is the hottest location in the weld cell and typically there is an Inductive Sensor located at the end of this weld tooling.
So as you can see if a WFI sensor is not selected where there is a magnetic field present it can cause multiple cycle time problems and unnecessary downtime. For more information on WFI sensors 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.
Sensors in welding cells are subject to failure because, although they are intended to be non-contact devices, they tend to be located directly in the middle of the welding process. Conditions such as damage by direct mechanical impact, erosion by hot welding slag, false tripping by accumulated slag, and high intermittent heat cause conventional sensors to fail at an excessive rate. In a previous blog post we discussed our three-step protection process.
Properly bunkering and protecting sensors will prolong their service life and reduce downtime. Ideally, this strategy is implemented during the design and construction of the weld cell by the equipment builder in response to buyer demands for increased process reliability. But what about currently existing production equipment that originally was built to a lower standard that is plagued with issues? It can be very difficult for a plant to find the time and personnel resources to go back and address problematic applications with better sensor mounting solutions. The job of retrofitting an entire weld cell with proper sensor protection can take two experienced people up to eight hours or more.
Plural of Giz-mo. A noun. Defined as a gadget, one whose name the speaker does not know. Customers call us and ask for this or that “gizmo” all the time! I think we should consider creating a product category simply called “GIZMOS”.
I like to call these things “Enablers” because these devices are very much helping hands that optimize the function of sensors. A sensor of any brand and manufacturer performs only as well as it’s mounted, matching the fixture to the demands of the application at hand. But how often does this happen in a price-driven world? They often end up in below-par mounting that fails with regularity, in both pristine environments as well as in hostile environments. Some examples:
Here’s one example below. These inductive proximity sensors in plastic brackets, showing an exposed coil on one, with corroded mounts on the sensor caused by being beaten to death during parts loading and heat.
With a few “Gizmos” like an application-specific quick change mount, some care in gapping the sensor and guarding the cable/connector system, it could look much different. Check out the examples below.
Photoelectric sensors can suffer the same fate. In this case, a plastic bodied photoelectric sensor, originally used to replace a fiber optic thru beam pair also suffered abuse. With a little extra beefy mounting, these photoelectric sensors can be expected to last a long time without failure.