In the manufacturing and assembly world, tightening, controlling, and measuring torque are imperative for production efficiency and reducing manufacturing costs. A fastener inadequately tightened can vibrate or work loose: conversely, if the tension is too high, the fastener can snap or strip its threads. Faced with these problems, manufacturers are realizing that precise torque control can spell the difference between a safe, reliable, and economical product and complete disaster. A quality torque program helps increase productivity, reduce rejection rates and make the assembly worker’s jobs easier.
Anybody who has to tighten a threaded fastener and needs to control, monitor, or measure torque needs sophisticated torque tools. If manufacturers want to save money, make their workplace safer, enhance product quality, or reduce their exposure to liability; only specialized high-quality torque tools will get the job done properly.
1. The Importance of Torque Control
The reliability of machine parts subjected to fluctuating loads and stress depends on the fatigue strength of the materials. A threaded fastener, however, relies upon an elastic interaction between the mating components. Its objective is to clamp parts together with a tension greater than any external force trying to separate them. The bolt then remains under almost constant stress and is immune to fatigue. If the initial bolt tension is too low, the fluctuating load in the shank in much greater and it will quickly fail. Reliability, therefore, depends on correct initial tension and is ensured by specifying and controlling the tightening torque.
2. Selecting the Proper Torque Tool
A wide variety of torque tools are available to control or measure the torque applied to fasteners, from electric screwdrivers to large industrial torque wrenches, pneumatic tools and torque multipliers. These tools utilize calibrated torque setting mechanisms that may be factory pre-set or user-definable. When the specified setting is reached, the tool gives a visual, audible, or tactile signal. The anticipated production output, the type of materials being joined, the amount of torque required, and the specified fasteners determine the selection of tools for a given application. Lighter materials such as aluminum or plastic may require only lightweight tools; likewise, heavy materials such as steel may require stronger or larger tools.
Selecting the proper torque tool for your fastening application may seem like an overwhelming process. Take time to educate yourself and understand the various torque tool options that are available. If you need assistance, don’t hesitate to ask for help. Call in a torque expert. Request a product demonstration to ensure you are selecting the proper torque equipment that fits your assembly or torque measurement needs.
3. Ergonomics & Safety
Power tools, both electric and pneumatic type, generally produce unwanted torque reaction that transfers over to an operator’s hand. After a while, the daily fastening process will expose your operators to repetitive stress injuries, which can impact him or her anywhere from the neck down to the fingers. The results of work related injuries effect productivity, employee absenteeism, as well as costly workers’ compensation claims and litigation expenses.
Making the assembly station more ergonomic and protecting employees is a vital objective for any manufacturing organization. The goal is to minimize strain and stress on the assemblers’ bodies. Following good ergonomic practices will contribute to the overall safety, comfort and health of employees. Ergonomics should be a team effort. Actively having the assembly operators involved in the ergonomic discussion will allow them to help identify any areas of concern and improvement.
Ergonomic torque arms are designed to absorb any torque transfer from the tool to the operator. The torque reaction arms are ideal for assembly lines like automotive, aerospace, appliance and electronics, where space is a premium and operator safety is mandatory.
4. Measuring Torque
Testing torque should occur in three facets of the manufacturing phases – prior, during and after the assembly process. Torque measurement is paramount for many manufacturers. Simply running a fastener or bolt down until it’s snug and tight and assuming the torque control process is complete, is no longer sufficient. Measuring torque doesn’t stop once the assembly process is complete. As part of the overall quality control process, manufactures should include a “Torque Auditing” program. A method to detect loose fasteners or any signs of joint relaxation. Torque auditing validates the fastening process, the torque tool, the product design and the materials used for the application.
Daily, weekly and monthly, assembly torque tools are used to tighten fasteners with precision torque control. Overtime, all torque tools start to drift out of tolerance. How do you know when a tool starts to drift out of tolerance? One solution is to have a torque analyzer system be used as a line checker. Have the torque tester placed in the production area and have the torque tools verified daily or weekly to ensure the tools aren’t falling out of calibration. Other options to consider is using a hand held portable torque meter system or have the torque testing system placed on a mobile cart. Then, your quality team can travel around to test and verify the torque output. Checking the tools more frequently with a simple torque tester, ensures assembly tools aren’t falling out of calibration, which will increase productivity and decrease product defects or rework costs.
5. Preventive Maintenance
To maintain consistent accuracy, torque tools must be checked periodically for wear or defective parts. Regular maintenance and torque calibration ensures repeatable performance and accuracy, as well as adherence to international standards. A properly structured preventive maintenance program optimizes tool performance and reduces unexpected downtime, thereby saving time and money in the long run.
When implementing torque equipment into your assembly process, it’s important to also create a maintenance schedule and budget for each tool. Planning a maintenance schedule for a tool requires you to evaluate the fastening application as well as the frequency of use. Monitoring the number of cycles per day and total hours that a tool is used is the most accurate way to establish proper maintenance intervals.
Make sure you know how to properly operate the equipment. Ensure your staff is trained to properly operate the torque tool. Learn the requirements needed to maintain the equipment. Improper use and irregular maintenance are key ingredients for a tool failure. With proper care, a quality torque tool will continue operate for many years with precision torque control.
6. Establish a Torque Calibration Program
Calibration is fine-tuning the torque control process in a production environment. A torque tool is a precision device and should be treated and maintained like a measuring instrument. In order to maintain accuracy, it is crucial that a torque tool and measuring equipment be calibrated regularly. A regularly scheduled calibration program enables quality control personnel to correct divergence from proper settings, whether it’s because of normal slippage over time or because of adjustments to the tool. Begin by setting a calibration interval initially based on severity of the application and the tool manufacturer’s recommendations. Some organizations may recommend six (6) month calibration intervals, while others may schedule it at twelve (12) months. However, it is the organization that owns the tool that must determine a suitable calibration frequency that meets their needs based upon many factors, such as history of equipment performance, application, degree of usage, and management objectives.
Using a quality torque control process makes a safer world through accuracy and precision. Controlling torque is essential for companies to ensure their product’s quality, safety and reliability isn’t compromised. The failure of a three-cent fastener that isn’t properly tightened can lead to catastrophic or latent failures. Fasteners that are insufficiently fastened can vibrate loose and excessive torque can strip threaded fasteners. Torque measurement should occur in all three facets of the assembly process.
Contact us with any questions you may have with establishing a quality torque control program.