Selecting equipment for a robotic welding workcell

PRACTICAL WELDING TODAY® JULY/AUGUST 2003

August 14, 2003

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So you've decided to automate your welding process. Now it's time to select the equipment that performs the robotic welding. It's critical to take care choosing the appropriate equipment and an integration partner.

Keep the end result—the product that the robotic workcell is turning out —as your primary focus when you select automation equipment. The entire workcell, no one part of it, is crucial for successful integration and an expedient return on investment.

A robot is repeatable and makes welds consistently. If the programming is done correctly by an experienced application engineer, you should be able to program the robot to perform the welding to the required product specifications.

Overwelding an assembly to prevent product failure and ensure the assembly passes a quality inspection is common in manual welding. However, overwelding can substantially impact the bottom line.

Successful application programming can reduce overwelding and its unnecessary consumable and labor costs. These costs may be reduced by up to 100 percent or more by welding to specifications instead of overwelding the assembly.

All robotic systems have features that allow you to weld your assemblies, but focusing on other critical issues, such as material flow and part staging, cycle time, and mix of production requirements, will allow you to select the workcell that seamlessly integrates into your manufacturing environment while performing to established requirements.

Requirements

The first step in selecting an appropriate workcell for your manufacturing process is to identify the range of products to be welded in the workcell. Are your requirements a high-volume, low-mix? Or are your production requirements better described as low-volume, high-mix?

Some manufacturers, such as OEMs and automotive suppliers, weld one product for a long period of time with few manufacturing changeovers. A job shop, however, might have several products to utilize its machine to full capacity and justify its investment.

Understanding volume, cycle time, and material flow helps drive the concept and layout of your workcell to fit your manufacturing requirements.

The next step is to consider the physical characteristics of the parts and assemblies being welded. Knowing part variables such as height, weight, length, and depth will help you size the machine for your applications.

Some manufacturers base their automation equipment decisions on their most complicated part. However, by choosing a less complicated part, you present an opportunity for immediate impact, quicker success, corporate approval, and employee acceptance. Other, more complicated parts may be handled differently down the road. Remember to crawl before you walk.

Configuration

Many automation options are available. Determining which system is right for you hinges on how you answer questions about product size, material flow, and cycle time.

  • Does the workcell have to be installed in a particular area of the plant?

  • How much space is available for the system, staging of the piece parts, routing of the final assemblies, and other integral operations?

  • Is the applications mix to be considered low-volume, high-mix or high-volume, low-mix?

  • What are the estimated cycle times, and how do they affect operator movement and activities?

Think about the three primary workcell configurations when choosing your equipment:

  1. Single-station. A single-station configuration is used most commonly for assemblies that have long cycle times and are produced in lower volumes.
  2. Single-point multistation. This is one of two multistation configurations. It allows the operator to be in one area while the positioner indexes the assemblies in and out to the robot to be welded.
  3. Multipoint load/unload station. The second multistation configuration is a multipoint operator load/unload. In this configuration, the operator travels from one station to another. The robot welds in one station while the operator loads and unloads the assemblies in the opposite station.

Support

Reducing downtime and ensuring machine availability from the vendor often are overlooked during the buying process. During the initial decision-making phase, you selected the appropriate robot arm, torch, power supply, positioner hardware, and process consumables that are well-supported and proven performers.

However, during the order fulfillment process—and before you receive your system—you should focus on your manufacturing and support needs before you integrate the system into your plant.

By determining the level of spare parts and support your organization requires during the start-up phase and training period, you are better prepared to handle any hidden or unforeseen circumstances.

Ask yourself how much downtime is acceptable based on your production requirements, and ask your supplier to recommend a spare-parts package to match these expectations. Begin with the equipment with the quickest failure rate, such as the torch and consumables, and design a spare-parts inventory.

In addition to the spare-parts inventory, discuss with your integrator the support process and how it works. Learn what the quickest way is to get support and who the key contact people are.

Does the integrator have the right people to answer your questions at the right time? If your workcell is down, simply having somebody answer the call is not enough; the person who answers your call for help should be qualified to get your workcell operating again. Your robotic integrator should be concerned with your company's success when its representative isn't on-site. This is why training is critical: Your workcell should perform at its best even when the integrator isn't there.

Finally, make sure you take time to check into the integrator's company history. Will your integrator and part suppliers be around tomorrow?

When investing in robotic automation, you have to consider the overall return on investment. Don't be afraid, shocked, or turned off by the initial cost. When correctly applied, robotic systems can offer quick payback and other intangible benefits.

Of course, everyone wants nearby support, but don't assume that local support is available. Focus primarily on having access to the right person at the right time to support your production needs. By understanding your supplier's support process and how the support network is organized, you will be better equipped to get help when you need it.

System Features

A robotic system may be equipped with advanced features, such as touch sensing, seam tracking, automatic tool realignment, and coordinated motion. These features add cost to a workcell, and some features may lengthen the overall production cycle time for your assembly because the robot isn't welding while these activities take place. If sensing is required, you can confine it to critical areas.

However, these features can impact the quality, consistency, and reliability of your product. You might not need such advanced features initially, but you should consider purchasing them with an eye toward future robotic welding needs.

Also remember to consider variables that affect the outcome of robotically welding a part, such as tooling. The tooling available today is so diverse that every tool is like a custom piece. Determine what the ergonomic considerations are and what controls may be needed to close a clamp. And if tooling is needed, what is needed to load the part.

The Human Aspect

Too often in a robotic welding integration, people are given secondary consideration. Remember that you are automating the welding process to achieve an end result, and it helps to have buy-in from everyone involved in the automation project. The people who have welded these parts manually or worked on the shop floor and the folks running the workcell should have ownership in the integration. Their practical experience might help fend off potential problems before they happen.

Brainstorm with these people. Ask why your company is choosing to integrate. Decide what challenge you are hoping to solve. Is your hope to increase productivity or improve quality? Then be sure to give your robotic integrator the answers to these questions.

Ideally, someone will champion the integration, rally co-workers, and take the lead on the project. A workcell can't be set up on the shop floor and then left alone to run: The operators and maintenance people are perhaps more important to the integration's success than the robotic equipment itself.



Darl Osborne

Sales Engineer
Genesis Systems Group
8900 Harrison St.
Davenport, IA 52806
Phone: 563-445-5600

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