Little problems on a large scale become big problems. Let’s do some math:
You figured it out! Or cheated….it doesn’t really matter. Because the next problem is the most important one:
Congratulations! You figured this one out, too. Now the only thing you have to figure out is what you’re going to tell Congress when they ask why you shipped out 10,000 defective pacemakers. Your insurance provider and your company’s legal team will probably have a few questions for you, too. An error rate of 1% may seem reasonable, but when you operate an automated assembly process at scale, one percent can be enormous. For assembling products with threaded fasteners—like pacemakers, circuit boards, and disc brakes—torque control and calibration help you lower your product defect rate from one to none.
Torque Control in Automated Assembly Processes
Torque is what tightens fasteners, the radial force that screws in screws. As you apply torque to a screw or bolt, that radial force turns into tension that clamps the threads of the fastener against its receptacle. So if you don’t apply enough torque, the threads won’t clamp all the way and the screw or bolt can come loose under stress or over time. If you apply too much torque, you can overload the fastener’s shaft or threads, or the assembly itself.
Over- or under-tightening can cause the fastener or assembly to fail under stress, either immediately or later. When a fastener fails, it can have serious repercussions, including overloading other parts and creating a cascading failure or rattling free in a moving assembly like an engine. As they say, loose screws sink ships.
To prevent over- or under-torquing fasteners, it’s important to use tools which can reliably detect and limit the amount of torque they deliver, such as torque control electric screwdrivers. For complex assemblies, control systems that can handle different torque values for different fasteners in one or more passes over a product are difficult to do without. The added benefit of these control systems is that they track each screw their tools fasten, which means that even if a mistake is made, the system will detect it, flag it, and prevent the product from moving further down the line. These tools and systems significantly reduce the chance of fastening errors.
Calibrating Torque Tools for Automated Assembly
Electric screwdrivers and automated torque control systems, however, are only as good as their calibration. Over time, even the best tools can slip out of alignment and start to deliver inaccurate results. To prevent this, it’s necessary to frequently test the calibration of your torque tools. The longer each tool goes between calibration tests, the greater the chance that it will start fastening products incorrectly and undetectably.
Fortunately, torque testing can be a simple, in-house affair. Benchtop torque testers can give each tool the green or red light in a matter of minutes, allowing torque testing to become a weekly or daily routine. In order to be sure you’re testing your tools for the right level of torque, use a rotary torque sensor to test the tool in actual production conditions. Once you’ve determined the actual, not estimated, torque value for the joints your tool will be fastening, you can program this value into the torque tester for quick, frequent calibration checkups.
The speed and volume of automated assembly can turn minor fastening errors into major concerns for your company. To greatly reduce the risk of error, use torque tools and controllers which can accurately limit the amount of torque each fastener receives. Frequent calibration checks ensure that tools always deliver the amount of torque they intend to. Using the right tools and keeping them calibrated is an effective way to error-proof the automated assembly process.