You don’t have to be Einstein to know that for every action, there is an equal and opposite reaction (though you might have to have been Newton to figure it out). It’s a fundamental fact of our reality; if you bang a gong, as it wobbles and rings, so do your wrists. Applied to the assembly line, this concept means that each time your employees tighten a fastener with a power tool, they’re pushing against the inertia of the tool to hold it in place. When the tool suddenly cuts out as it reaches the max torque, the sudden lack of inertia affects the operator’s wrists.

Newton figured out something else that influences operators of torque tools: gravity. Simply put, the heavier the tool, the harder an operator has to fight against the tool’s weight to raise and lower it for each new fastener. No matter how tough your operators are, even if they used to walk twelve miles to school in a raging blizzard uphill both ways, over time, the effects of repeated unassisted power tool use will take their toll. While not everybody is affected, the toll often takes the form of carpal tunnel syndrome and other repetitive motion injuries which cause musculoskeletal disorders. Musculoskeletal disorders affect soft tissue, including muscles, tendons, ligaments, joints, and cartilage, as well as the nervous system. So, what steps can you take to prevent these sorts of repetitive motion injuries on your assembly line?

Ergonomics and Preventing Repetitive Motion Injuries

It is incumbent on the designers and owners of assembly lines to prevent these injuries in their workers for two reasons: good financial sense and a sense of moral responsibility. In regards to the financial part, investing in preventative measures will require a capital outlay. However, this initial investment will generate a return by preventing workers’ compensation claims, doctor’s visits, human resources consultations and insurance payments while increasing productivity and lowering training costs. A little good can go a long way. As regards responsibility, taking care of workers means taking care of families, the community, and your own company. It’s usually a good idea.

Fortunately, an entire science has been pursued in the exploration of knowledge about work; work habits, work motions, and preventing work injuries. This science is known as ergonomics. Through the engineered application of ergonomic principles, it is possible to prevent long-term injuries caused by the reaction and weight of torque tools. Simple devices known as torque arms and torque balancers are capable of eliminating the effects of tool weight and reaction. Quality ergonomic devices for factory usage are sturdy, dependable, easily mounted, and appropriately rated for the tools they will be used with.

Torque Arms Counter Tool Weight and Reaction

Torque arms can counteract the effects of both weight and reaction. They are rigid structures mounted to your assembly area. Depending on the needs of your assembly, you may be best suited by linear, articulated, telescoping, or position control torque arms, or some combination thereof. Torque arms counteract weight by suspending the tool so the operator doesn’t have to take the load. They counteract reaction by absorbing the kinetic energy generated by a tool’s sudden lack of inertia. Typically, some form of reaction control is called for above 15-20 lbf.in when using an inline tool, ranging higher for pistol grip and right-angle tools.

Because they absorb reaction so well, torque arms are also useful for applications with minute amounts of torque, measured in oz.in. In this range, the amount of torque an operator absorbs when stopping a tool can cause a deviation from the standard. By remaining rigid when the tool stops, the torque arm keeps delivery true to the predetermined torque.

Linear Torque Arm:

Linear torque arms move along a single axis. Usually, this means they go two directions: up and down. However, they can be mounted horizontally or at other angles as needed. Linear torque arms can handle large amounts of torque, up to 73.7 lbf.ft, rendering them useful for all but the heaviest applications. Ideally, they are suited for usage in single-motion assembly line tasks. Their horizontal arm can be adjusted, allowing the same torque arm to be used for many different product runs. In addition to protecting their operator, linear torque arms improve efficiency by reducing cross-threading, side loads, and other fastening errors.

Articulated Torque Arm:

Articulated torque arms allow their operator to move the tool along two axes, the horizontal and the vertical, within the boundaries of a cylinder defined by the reach of the tool. The horizontal arm’s elbow joint can be set at multiple angles—such as 0°, 22.5°, and 45°—to allow the operator to reach different fasteners. In addition to counteracting weight and reaction in the same manner as linear torque arms, articular torque arms allow operators to tighten multiple fasteners in sequence.  Due to this versatility, they are better suited for cell manufacturing and complex line manufacturing. Articulated torque arms also prevent cross-threading and side-loading. Capable of handling heavier tools, articulated torque arms are rated for up to 73.7 lbf.ft.

Telescoping Torque Arm:

Telescoping torque arms take up very little space and allow for a broad range of motion. Operators using telescoping torque arms will be able to perform complex sequences in cell and line manufacturing, even in close quarters. Like linear and articulated torque arms, telescoping torque arms counteract weight and reaction while preventing cross-threading and side-loading. However, while telescoping torque arms have a greater range of motion than the other options, not all models can handle as much weight. Still, some telescoping arm designs can handle up to 147.5 lbf.ft.

Position Control Torque Arm:

Position control torque arms are smarter than your average torque arm. Connected to a processor and storage, position control arms track and time their own movements in sequence, then compare them to programmable standards. Both articulated and telescoping torque arms are built with position control capabilities. These capabilities allow operators to verifiably ensure that each fastener has been tightened in the right sequence, to the right torque. Further, they are able to detect cross-threads, omissions, unfinished rundowns, and, preferably, cycle complete. Compatible with DC control tools, position control torque arms allow for total visibility of the assembly process.

Depending on your assembly setup, different torque arms will suit your needs best. If you reliably perform simple assemblies of high-torque fasteners, linear arms may be called for. If your operators fasten multiple small screws in complex sequences in close quarters, telescoping position control arms may be best. If your process involves multiple stages or you regularly reconfigure to meet the needs of new clients, some combination will likely solve your needs. In cases where you’re more concerned about the weight of the tool than its reaction, employing a torque balancer may be best.

Torque Balancers Take the Load Off Operators

Torque balancers, in contrast to torque arms, can counter the weight of a tool effectively but not its reaction force. Unlike torque arms, torque balancers are not rigid constructions. Rather, they are lines suspended from hard points above an assembly area, which hold the weight of their attached tool. Most torque balancers are spring loaded, causing their lines and attached tools to automatically recoil. However, some are truly neutral, holding their attached tool at whatever height it is left at without retracting. Typically, tool balancers are used for lightweight tools, ranging up to 11 points. The zero gravity balancer stands as a significant exception, holding up to 264 lbs in a true neutral suspension.

Because torque balancers aren’t rigid, they allow their operators an unencumbered range of motion, enabling them to torque fasteners in complex sequences and at multiple angles. Naturally, they are correspondingly less effective at preventing cross-threading and side-loads than rigid torque arms. Still, attaching tools to torque balancers not only takes the weight off the operators, but it also prevents the chance of accidental damage from dropping a tool or leaving it on a bench. Torque balancers are ideal for lightweight manufacturing environments where the reaction is lower than the 15-20 lbf.in threshold but higher than the oz-in range where operator absorption can throw off torque value.

The simplest and most common type of tool balancer is the retractor, which suspends a tool on a spring-loaded line. These are useful in most fastening applications within the right weight range, particularly for electric tools. For pneumatic tools, including pulse tools, hose reel tool balancers use the tool’s own air supply hose as a retractable suspension line. Zero gravity balancers suspend even heavy tools, and by holding their position mid-air, they ensure operators are not working against either gravity or their own spring.

To recap, investing in ergonomic devices such as torque arms and torque balancers yields gains in worker safety and productivity. Depending on the needs of your assembly, different torque arms or torque balancers will be best suited for your process. Regardless of application, quality ergonomic devices will be compact, built to withstand the stresses of your factory, and backed by a reliable manufacturer.

At Mountz, we believe taking care of employees is just good business. After all, we’re a proud employee-owned company. We build our ergonomic devices with care and attention, making us a leading name in torque products and accessories for over fifty years. If you have questions about ergonomics, feel free to ask. To see our full line of products, download a catalog. If you’re interested in ergonomic or other torque products, request a quote or schedule an appointment with one of our experts.