Proper Ergonomics Improve Welding Productivity, Protect Welders

By Jack Kester, senior VP, Marsh Risk Consulting and Andy Monk, product manager, Bernard

What is ergonomics? While this term has several definitions, its practical meaning is “to adapt a task and work environment to a human.”

Despite what some think, the importance of ergonomics far surpasses comfort. A workplace environment or task that causes a welding operator to repetitively reach, move, grip or twist in an unnatural way — or even stay in a static posture for an extended time without proper rest — can do much more than become a literal pain in the neck. Over time, it can lead to repetitive stress injuries with life-long impacts that may even prevent the welding operator from working.

People are built with certain limitations, and when the design of work exceeds normal limitations, excessive wear and tear on the body occurs, accelerating damage that can lead to Work-Related Musculoskeletal Disorders (WMSDs) — injury to the muscles, tendons, ligaments, joints, nerves and/or spinal discs.

Although many welding operators may start with a dull pain that they dismiss as “just getting conditioned” or “tweaking something that will go away,” it can become more intense — and more expensive — and difficult to treat as time goes on. For example, early treatment for pain may require only ice, heat or some anti-inflammatories, and it might cost $200. However, waiting months or years to address the problem could result in invasive treatment and cost thousands of dollars. That is especially true with wrist and shoulder injuries that require surgery.

Ergonomics not only protects welding operators from injuries, but it can also improve the productivity and profitability of a welding operation. Stressful postures and motions tend to be inefficient. Lifting boxes from floor level or reaching outward beyond arm’s length, for example, takes extra time. These posture and motions repeated throughout the year by multiple employees can have a significant impact on earnings for the company.

By proactively reducing the risk of injury, companies can improve productivity, while also reducing employee absences and eliminating overtime pay for replacement workers who may not be as efficient or proficient. Eliminating stressful postures and motions can also help reduce employee turnover and training costs for replacing welding operators who quickly decide “this job isn’t for me.”

According to the Bureau of Labor statistics, WMSDs account for 29 percent of all lost workday injuries and for about 34 percent of all workers’ compensation claims — and they cost employers $20 billion each year in workers’ compensation.

Welding-related musculoskeletal disorders

Injuries ranging from mild and short-term to serious and chronic can result when the demands of a task do not naturally align with the capabilities of the welding operator. Most WMSDs develop when repetitive micro-traumas occur to the body over time.

WMSDs include strains or sprains, which can result in pain, decreased productivity, disability, medical treatment, financial stress and even a change in the quality of life for those affected. The most common symptoms among welding operators are shoulder pain, range of motion loss and reduced muscle strength. The most common injuries for welding operators include back and shoulder injuries, wrist injuries (such as tendinitis) and various knee joint disorders.

Today WMSDs are the fastest-growing disorder in the aging workforce because these illnesses have developed over time, before welding operations were as aware of them as they are today. As a result, there is the potential for an increase in claims costs in the coming 10 years as welding operators seek treatment.

The risk factors

There are three primary risk factors that increase the likelihood of developing WMSD injuries:

1) Highly repetitive tasks that keep an operator in a static posture for too long or use the same motion over and over, such as pulling a MIG gun trigger.

2) Tasks that require an operator to apply significant force or pressure, such as pushing, pulling or heavy lifting.

3) Poor or awkward postures, such as bent wrists or necks tilted backward.

In addition, environmental conditions such as extreme temperatures can also contribute to the development of WMSDs. Personal risk factors that increase the likelihood of incurring WMSDs include physical conditioning, pre-existing health problems, gender, age, work techniques and stressful hobbies.

Some common welding postures that are considered awkward and stressful include kneeling, squatting, torso twisting, leaning on a hard surface, holding the arms away from the body or above shoulder height for long periods of time, hunching or bending over, and looking upward too long.

In general, the best postures are those that are as close to neutral as possible — a natural position that the body would rest in if it were not doing anything.

Ergonomic solutions

The use of proven ergonomic principles can dramatically improve the way a welding operator performs a task, thereby reducing the exposure to risk factors and simultaneously increasing productivity. A simple work station adjustment or the use of different tools can make a big difference on an operator’s long-term health and wellbeing, as well as on the company’s bottom line.

For example, operators who weld with pistol grip tools, such as a welding gun, and use their finger to apply pressure for an extended length of time can develop “trigger finger.” This problem can be easily resolved by using a welding gun with a locking trigger.

Welding operators should position their work between the waist and shoulders, whenever possible, to ensure they are working in a close to a neutral posture. Achieving this posture may mean using work stools or height-adjustable chairs, as well as lifting tables and rotational clamps or other material-positioning equipment. All these solutions can reduce awkward postures and allow employees to work in more neutral positions.

Welding guns with rear swivels on the power cable can help reduce the stress of repetitive motions. Different combinations of handle angles, neck angles and neck lengths can also keep an operator’s wrists in a neutral position. In some cases, a welding gun with a rotatable neck can help the welding operator more easily reach a joint, with less strain on the body. Manipulators, lighter-weight welding guns, lighter power cables with low stiffness and cable supporting balancers can also be invaluable.

Remember, the working height of a welding operator’s hands should typically be at elbow height or slightly below.

The engineering controls described above are effective because they reduce or eliminate risk factors in the workplace. Administrative control measures, such as job rotation and stretching programs, can also be used to reduce the exposure time for welding operators or at least prepare their bodies for the work-related stress.

The keys to an effective ergonomics program

An effective and sustainable ergonomics process provides a structured approach to reducing risk in the workplace and preventing WMDs over the long-term. It typically includes:

1) A formal ergonomics risk assessment process to identify and prioritize high- risk work.

2) A structured task analysis process to define the causes of the risk factors, leading to the development of practical engineering controls.

3) An action plan developed by management stakeholders to set expectations and allocate resources for ergonomics in the workplace.

4) An ergonomics team trained to implement the ergonomics process and empowered to implement the action plan.

5) A formal process for developing, implementing and validating ergonomics solutions for high-risk tasks.

6) Ergonomics training for management, supervisors, the ergonomics team and other production staff members.

Once an ergonomics solution has been implemented, it is important to provide frequent reinforcement to the welding operators to ensure that the solution is utilized effectively. It can be difficult, initially, for a welding operator to get comfortable with new work practices if the job has been done a specific way for years. Therefore, it is important for welding operators to use any new welding gun and implement new best practices for at least 30 days. At that point, they can provide valid feedback on how well the new equipment or practices work for them. After all, gaining the benefits of proper ergonomics is only possible if they are used and the welding operator also sees the results.

In the end, the goal is to secure the safety of the welding operator, which requires an active commitment on the part of both the individual and management. Gaining the benefit of ergonomics is a team effort — one that ultimately provides a comfortable work environment, leads to a more productive and profitable welding operation, and provides for the long-term health of the welding operator.

Tips to Optimize the Robotic Weld Cell

Companies invest in robotic welding systems to improve productivity and gain efficiencies in their operation. But if the weld cell layout is not optimized, it can negatively impact those goals — along with the quality of the completed welds.

Poor cell layout can create a bottleneck in the process or result in parts not being properly welded —problems that cost time and money in the long term. 

When considering proper layout for a robotic weld cell — whether it’s a pre-engineered cell or a custom cell —gun and consumable selection, robot reach, parts flow in and out of the cell, and weld sequencing are all important.

Pre-engineered or custom welding cell?

Proper weld cell layout is important for both pre-engineered robotic welding systems or a custom-designed system. Determining which option is right hinges on several factors.

A pre-engineered robotic welding cell is designed for welding specific parts in a certain size range. Pre-engineered cells offer benefits for easy and fast installation and a much lower first cost, but they do have their limitations regarding the type and size of parts that can be welded. Part size is often the key determining factor when choosing between the two systems. 

If there isn’t a pre-engineered weld cell available to fit the parts — perhaps there is a reach or weight capacity issue — then a custom robotic weld cell is the better option. Custom cells have a higher initial cost and typically a longer lead time for design and installation, but the upside is they can be customized to meet specific needs.

When installing either type of robotic weld cell, the system integrator should be involved in planning and testing to ensure cell layout is optimized for the application.

Choosing the right gun and nozzle 

Having the right gun is a critical factor that can help reduce or eliminate the sources of common problems in the weld cell. Gun choice should not be an afterthought in robotic welding applications. The gun must have proper access and be able to maneuver around fixturing in the weld cell. Different choices in gun types and in consumables can help in achieving this.

Robotic welding systems are available in two styles: through-arm or conventional. Through-arm systems are gaining popularity, and most through-arm robots allow for mounting either type of gun — providing more options and flexibility depending upon the needs of the application.

As the name suggests, the power cable assembly of a through-arm MIG gun runs through the arm of the robot as opposed to over the top of it like in a conventional gun. Because of this design, the through-arm gun style is often more durable, since the power cable is protected. However, because conventional guns can be used on either type of system — a through-arm or a conventional robot — they can sometimes offer greater flexibility, and can be used with more robot makes and models. Consider which type of gun provides the best access to the welds when making the selection.

With conventional robotic welding systems especially, proper cable management is important. Once the hardware is installed and the system is set up — but before full production begins — be sure to do a test run or two through the welding sequence to determine how the gun cable moves and if it gets caught on tooling.

Another choice in selecting a gun is air-cooled versus water-cooled. This essentially comes down to the required duty cycle. The base material thickness, weld length and wire size all help determine the necessary duty cycle. Water-cooled guns are typically used in manufacturing heavy equipment and in the case of long cycle times and large wire diameters.

Once the system type and gun is chosen, it’s all about proper fit and function of the gun. It’s critical to ensure the robot arm can access all the welds — ideally in one position with one neck if possible. If not, different neck sizes, lengths and angles — and even custom necks — as well as different consumables or mounting arms can be used to improve weld access.

The choice of nozzle is another important consideration, since it can greatly hinder or improve access to the weld in a robotic cell. If a standard nozzle is not providing the necessary access, consider making a change. Nozzles are available in varying diameters, lengths and tapers to improve joint access.

While many companies like to choose a nozzle with the smallest outside diameter available, it may be necessary to size the nozzle up to avoid spatter buildup and loss of shielding gas coverage. A nozzle with a 5/8-inch bore or larger is recommended because it allows the most access. 

Key considerations for proper layout

Choosing the right gun is tied closely to proper weld cell layout — since different sizes and lengths of guns and nozzles can improve or hinder reach to the welds. However, there are also many other factors involved in proper weld cell layout. Think of weld cell layout as the footprint of the entire process. Some important issues to keep in mind:

• Robot reach: It’s critical to match the size of the part being welded with the reach of the robot. A small robot welding on a very large part won’t work well, and a large robot shouldn’t be welding on a very small part. The robot must have the capability and position to reach all the areas on the part that require welding. If there is a weld on the edge of the reach envelope, for example, it might force a company to sacrifice optimal gun angle or work angle to reach that weld. This can impact weld quality, resulting in potential rework and added costs. It can also lead to premature gun or cable failure, if the robot is constantly trying to access a weld that isn’t accessible in the configuration. Many robotic welding cells mount the robot on a riser for better access to the part. Pay attention to proper riser height to optimize the access of the arm to the welds.
• Size and weight capacity: To ensure proper operation, the size and weight capacity of the positioners in the robotic weld cell must factor in not only the weight of the part, but also the weight of the tooling. Undersizing the positioner or weight capacity of the cell is a common mistake. To address this, design the cell for the heaviest part to be welded. Consider the project scope to ensure the welding system always has the capacity to handle the heaviest part in the operation.
• Material flow: The flow of material in and out of the weld cell, in addition to the sequencing of the welding process, are key in determining the right layout and positioning. Understand the material flow to the robot, how the material will be presented to the robot, and then how that welded component will be removed from the cell and moved to the next step in the operation. The weld sequence should be planned in advance, to ensure the robot can reach all the welds with the gun configuration being used.
• Test it with modeling: Software programs that allow virtual modeling or simulation of the weld cell provide the ability to test the many factors involved in proper robotic weld cell layout — from gun and nozzle choice to material flow. Take the time to simulate the weld cell layout and welding process during development. This helps determine which product and positions are needed — and helps avoid issues that could arise later once the weld cell is installed and running. In modeling, consider the components, gun, positioner, tooling, arm movements and the part itself. All these pieces must fit together and work properly to ensure the desired results. The beauty of offline programming and 3D modeling is that these components and factors can be tested virtually, without wasting materials or consumables. It’s better to prepare and prevent problems — rather than face repairs later.

The right choices enhance productivity and quality

Weld cell layout and the chosen components that fit inside have a significant impact on productivity, efficiency and quality of the finished welds. Weld cell layout that is not optimized can even harm the tooling or consumables, and result in increased time and money spent on maintenance and repair.

Protect the robotic weld cell investment by taking the time at the start of the process to test proper cell layout and equipment — to help ensure the end results and productivity gains being sought.