Setting realistic goals for robotic welding projects

WWW.THEFABRICATOR.COM NOVEMBER 2001

November 15, 2001

By:

Expecting a robot to solve all of your production problems can inflict the cruel irony of ceating more. If you want your robots to speed up your operation, know what they can and can't do from the start.

Companies interested in purchasing robotic weldingequipment often expect robots to solve all their productivity and quality problems. After installation, the actual results often do not meet the end user's high expectations. The natural conclusion is that the robot company dropped the ball; but very often, the problem is unrealistic expectations that are created either by the robot seller or the end users themselves.

Therefore, an important step is to abide by a realistic set of expectations for those who are specifying, purchasing, and installing robotic welding equipment. These guidelines not only can prevent disappointments resulting from false expectations, but also can help make your robotic welding project more profitable and dependable.

Define the Project

The exact requirements of your robotic welding system need to be defined clearly before the system is designed. Will parts be pretacked, or will loose parts be clamped into fixtures? Is the primary goal increased quality, operator safety, increased productivity, or some combination of these? Are you just playing with the idea of robotic welding, or are you serious about it and convinced that this technology is something you need? Do you need robots because you can't find qualified welders to hire?

Be clear about the reasons you're interested in robotic welding. This will help guide the project along a predictable path.

When it comes time to specify and purchase a system, be involved in its design and functionality. This does not mean that you, the end user, are responsible for the actual design, but you must become intimately familiar with the system before it's built and stay on top of design changes as they happen. This will prevent surprises and disappointments in the future-for instance, in case the system becomes too big to fit into the floor space you have provided for it or cannot reach certain weld spots.

What Robots Can Do, Can't Do

Do not expect your robot to compensate for quality problems such as poor component tolerances or fit-up.

In the early days of robotic welding (the late '70s and early '80s), a lot of robotic welding projects failed. Robot companies didn't understand all the requirements of making a project successful, and end users thought robots were the magic cure-all for their production woes.

To prevent such exercises in futility, do a lot of homework before you purchase your first robotic welding system. Production controls and quality systems should be put in place before you consider automated welding.

Many companies already may have put these systems in place, perhaps simply to improve the quality of their manually welded products. In such cases, the foundation for a successful robot installation already has been laid. However, most manufacturing facilities that still are welding their products manually and doing things the same way they did 20 years ago need to put some basic quality controls in place to ensure the repeatability of component parts.

Robots have a hard time dealing with gaps between component parts, and they don't like welding on parts that are not repeatable. Although part-to-part variations in the weld joint can be detected-seam finding and tracking are common robot options-these things consume cycle time and also have their limitations.

The best solution is to strive toward producing consistent piece parts with little or no gaps between parts. Smart part design and fixture design are crucial elements here. Do the homework, and don't expect the robot to compensate for poor preparation. If necessary, buy good press brakes or laser cutting machinery or new tooling for existing presses and punches to optimize component part quality.

Taking Some Welding Away From Robots

At times it may make more sense to have the robot do less welding. Most end users are highly disappointed to learn that the expensive robot they bought can reach only 90 percent of the welds on a particular assembly. Or they approach a project assuming that the more welding the robot does, the more justified the cost of the project is. These assumptions may not necessarily be true. Consider the following:

1. Improve quality by taking welds away from the robot. Some welds just are not suited for robots. For instance, the complicated contours created when welds wrap around corners sometimes are difficult for robots to do.

For cases in which gaps simply cannot be avoided at any cost, it may be necessary for an operator to weld a stringer bead in the gap before presenting the parts to the robot. These are a couple instances in which quality actually can improve by giving certain welds to operators.

2. Improve throughput by taking welds away from the robot. If the fixture load/unload time is significantly less than the robot cycle time, operators may be idle for long periods of time. Sometimes you can give other tasks to operators to take advantage of this slack time, but in many cases, it may make sense to give some of the robot welds to the operator to do.

By giving 10 percent of the more difficult welds to the operator, the robot cycle time will be shortened, and what may have been unproductive time for the operator becomes productive. The overall effect is better utilization of the operator's time, improved throughput due to decreased cycle times, and possibly higher quality because you chose the most difficult robot welds to hand off to the operator.

3. Improve justification by taking welds away from the robot. Since throughput is improved with what could essentially be the same amount of labor, the return on investment is improved. Also, increased quality can reduce the amount of rework, thus reducing overall cost.

Plan for and Implement Proper Training

Planning for proper training up-front and actually making it happen can be opposite sides of the same coin.

It's easy to envision which training courses are necessary, to plan for a gradual startup, and to purchase various levels of training. But when it comes time to implement all of this, it can seem far too time-consuming and unproductive. Production, after all, is the biggest priority, and proper training often is neglected.

Don't give in to this mentality. The type and extent of training provided can make or break an automated welding project. Certain things just cannot be rushed. For example, an important part of training is learning to troubleshoot, whether you're talking about robotic programs, welding data, or hardware problems (electrical or mechanical). The problem with troubleshooting, though, is that it usually is needed for uncommon or intermittent problems. Therefore, gaining the proper knowledge and experience can take time, maybe even weeks or months.

In general, the type of training most commonly discussed deals with learning the robot's language, how to operate the machinery and recover from errors, and how to adjust the characteristics of the machine to operate in different circumstances. Robot suppliers have developed effective training courses, and it is essential at least to take the basic language course. But any time an advanced course is offered, whether it focuses on advanced language functions or optional equipment and devices such as seam tracking, participation should be considered mandatory.

There is a direct correlation between an operator or programmer's depth of training and an ability to troubleshoot problems quickly and keep the robot producing.

Service Support and Preventive Maintenance

First, a preventive maintenance (PM) plan that actually is implemented (not just given lip service) is crucial to the dependable performance of a robotic welding cell.

Few people would neglect to change the oil in their cars, but many robot purchasers think it is unnecessary to perform any PM on their equipment. Good prevention certainly pays for itself in increased uptime and productivity. In many cases, good PM programs also can improve quality by, for instance, requiring new or serviced contact tips, liners, nozzles, and wire feed rollers on a regular basis. All of these items contribute to a stable welding arc, which translates into better quality and process reliability.

Maintenance training also is critical, because warranty periods are limited. It makes sense to train your own maintenance and service personnel thoroughly, to get repairs done more quickly, and get back into production as soon as possible. Many robot companies provide separate classes for mechanical service (lubricating, replacing motors and gearboxes) and electrical service (troubleshooting circuit boards, tracking down failed components). Both are necessary, though each class may involve different people in your facility.

Having taken the preparations to properly train personnel in the operation, programming, preventive maintenance, and troubleshooting of the equipment, you will be faced with fewer surprises and will be able to keep the equipment in production-which is why robots are purchased in the first place.

Conclusions

Realistic expectations begin at the concept stage of a robot project. If the system is conceptualized and designed properly, there is a better chance it will work as expected.

The next step is to take pains with homework and prepare the upstream processes (and, in some cases, the downstream processes) to be compatible with robotic welding. A realistic expectation about how much of the welding the robot will do on a particular assembly can prevent unpleasant surprises about the robot's productivity.

Proper training in programming, operation, maintenance, and troubleshooting can and will contribute to a robotic welding system that works as expected.



Berge Robotics

Jim Berge

Contributing Writer
Berge Robotics
Sherveport, LA
Phone: 970-222-1753

More in Automation and Robotics from TheFabricator.com

Published In...

www.thefabricator.com

Read more from this issue

comments powered by Disqus