Guide to Welding Automation

Types of welding robots 

Robotic welding options are available in pre-engineered cells and custom-designed systems. Determining the right option hinges on several factors, including the space available, throughput goals, part repeatability and cost.

Companies can drop pre-engineered robotic welding systems into existing workflows and put them into operation with training and much of the basic tooling that manual welders are already using. These cells are designed for welding specific parts in a certain size range. Among their benefits are easy and fast installation and a much lower first cost. However, pre-engineered robotic welding cells do have limitations regarding the type and size of parts they can weld. 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 that operations can customize them to meet specific needs.

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

Choosing a robotic gun and nozzle 

The right welding gun is a critical factor that can help reduce or eliminate common problems in the weld cell. Gun choice should not be an afterthought; welding guns must have proper access and be able to maneuver around fixturing in the cell.

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 arm protects the power cable. 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 you install the hardware and set up the system — but before full production begins — conduct a test run or two through the welding sequence. This will help 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 you choose the system type and gun, it’s all about proper fit and function of the gun. 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.

Nozzle choice is also important 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.

Robotic weld cell design

Think of weld cell layout as the footprint for the entire welding automation process. Poor cell layout can create a bottleneck or result in weld defects. These problems cost time and money in the long term.

When considering proper layout for a robotic weld cell, gun and consumable selection, robot reach, parts flow in and out of the cell, and weld sequencing are all important.

Key considerations for proper weld cell layout:

• Robot reach: It’s critical to match the size of the welded part 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. Also keep in mind that weld gun type (thru-arm vs. conventional) and neck angle can affect overall robot reach.
• 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. Plan the weld sequence in advance to ensure the robot can reach all welds with the gun configuration in use.
• 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. With offline programming and 3D modeling, you can test these components and factors virtually, without wasting materials or consumables. It’s better to prepare and prevent problems — rather than face repairs later.
  
  

  Poor weld cell design is one factor that can contribute to secondary circuit wear in robotic welding. Read this article to learn how to prevent it.

Operator training 

When implementing welding automation, don’t underestimate the importance of training. Investing in the people who are responsible for overseeing the robotic welding system is just as important the equipment itself.

For the sake of continuous improvement, companies should invest in the personnel and training necessary to make the process easier, faster and more efficient. After all, robotic welding systems don’t operate autonomously — the human element is still a significant factor and one that is integral to creating proper workflow, implementing effective maintenance programs and creating parts designs that can lead to the best performance and profitability.

Employees need to clearly understand the operation of the system and undergo the proper up-front training before taking on the responsibility of working with the robotic welding system — loading and unloading parts, programming the robot or overseeing its maintenance, for example. Typically, robotic integrators can offer OEM-based training, as can robot manufacturers. Beyond this training, it is critical that the employees involved with the system commit to continuous improvement of the operation and truly understand the welding process.

Best practices for welding automation 

Gaining the desired results from welding automation doesn’t happen by chance. It is important to follow best practices to gain the best efficiencies and a desirable return on the investment. Consider these five robotic welding best practices to optimize results:

1. Manage workflow
   The most efficiently programmed robotic welding system means nothing if the parts it needs to weld don’t reach or leave the cell in a consistent manner. Bottlenecks upstream or downstream can negate the benefits of automation. Companies should always look carefully at the steps involved with bringing the parts to the robotic welding cell and determine the best course of action for handling them after the robot finishes welding. In some cases, it may be necessary to reconfigure an existing operation or change the way parts are fabricated upstream and completed downstream (e.g., finishing, painting, etc.). Companies may also need to assess how employees supply parts to the robot to ensure they can match its cycle time. The goal when establishing a good workflow is to eliminate any non-value-added activities including unnecessary transporting, lifting or handling of parts. Omitting these activities can be as simple as changing the way an employee removes the parts from the tooling or minimizing the distance they walk to place them on the pallet.
2. Pay attention to part design and fit-up 
   Designing parts up front is critical, as is ensuring proper part fit-up. Complex parts or those with large gaps or fit-up or access challenges do not lend themselves well to robotic welding. Leave these parts to a manual weld operator. Make certain that parts intended for the robotic system are simple and repeatable. If there is a mature part that was originally welded manually, look for ways to change the part design to make it easier and faster to weld with a robotic welding system while still preserving its function. For parts that are new to automation, look for ways to build efficiencies into the design from the ground up. A careful assessment of a part’s blueprint or electronic CAD drawing is a good start. In addition to ensuring proper part fit-up when first implementing welding automation, continue to assess it in the days, weeks and months following. Normal wear on a die, for example, can lead to slight variations in the parts produced and affect how the parts fit together. Ultimately, if a company doesn’t take the time to address poor part fit-up, it can lead to poor weld quality and/or overwelding — sources of unnecessary costs.
3. Use appropriate welding cell tooling 
   Using weld cell tooling suited to the volume and variation of the produced parts is essential to ensuring good quality and high productivity. In addition to securing the parts so the robotic system can execute consistent welds, the proper tooling can also have a measurable impact on the comfort and efficiency of operators overseeing the loading and unloading of parts. Job shops and small manufacturers tend to have a low volume and high mixture of parts, which typically means that tooling with basic manual clamps will be adequate. For companies that weld a higher volume, lower variety of parts, more sophisticated tooling with automatic clamping capabilities can bring significant benefits. Automatic clamping can minimize downtime for manually clamping what could be thousands of parts over a relatively short period of time. It also minimizes fatigue and ergonomic problems for operators that can result in potential mistakes. 
4. Implement weld management program 
   Weld management programs are an excellent way to get results from a robotic welding system. These programs allow companies to track the parameters of individual welds, determine the cause of weld defects and identify general inefficiencies in order to rectify those problems and optimize the process for quality and productivity. Most often — and producing the most effective results — weld management programs are integrated into the power source. In some cases, companies can utilize this software by way of third-party integration. The basic goal of any weld management program is to provide actionable data — information that can help the company predict and rectify potential problems that could cause downtime and added costs. Additionally, weld data management can track consumable usage so companies can implement changeovers during routine pauses in production and help companies address overwelding, which adds costs.
5. Don’t neglect maintenance 
   Implementing a preventive maintenance program is among the easiest and most important best practices to protect the investment in welding automation. These programs should cover the robot and the robotic MIG gun, consumables, cables and peripherals. Scheduling time to check connections, clean fixturing (to prevent debris that may affect part fit-up) and confirm tool center point, for instance, helps ensure that the system continues to operate within its proper parameters. Usually, it’s possible to schedule maintenance during routine pauses in production.

Optimize results with welding automation 

Implementing welding automation can be a daunting task, especially for first-time purchasers. From justifying the expenditure to determining space requirements for the robotic welding cell and ensuring parts are suitable for the operation, every detail is critical. When done properly, these steps can lead to drastic improvements in productivity, quality and cost savings compared to manual welding. Following some key best practices can go far in establishing high weld quality and productivity, as well as a solid return on the investment in welding automation.