Welding Automation: Flexible Or Fixed?

How to determine the best approach for the job

By Brad Benfield

Automatic welding is an ever-increasing segment of the welding market, providing increased production and repeatability, and a means to compensate for the lack of skilled welders. After deciding to automate, however, the manufacturer must choose the most appropriate application: Flexible or Fixed Welding Automation.

Fixed Automation dual torch welding lathe cell simultaneously welding two flanges onto an automotive catalytic converter

Definitions
Flexible Automation generally applies to welding Robots programmed to weld just about any joint configuration, then called up to weld a completely different weld joint. Fixed Automation generally applies to machines performing a more dedicated movement on a weld joint that has a highly repeatable geometric shape, i.e., circles, arcs and straight line seams. While the machine may be highly flexible and adapted to an extremely wide and differing range of applications, its operation is normally fixed to perform a basic geometric function.

Welding automation encompasses everything from high production, completely automated transfer lines to machines welding low volume heavy fabrications or pressure vessel weldments where a high degree of loading alignment and set up is required before the part is automatically welded. This article focuses on the most popular approach in automatic welding, the welding cell, where one operator loads or oversees the operation of one or more stand-alone machines. Several cells may be linked together as part of a larger line, but the welding cell can usually stand alone and be operated as an independent system. They are geared toward parts the operator can load into the tooling alone without an assist device and require production rates of from 60 to 400 parts per hour.

How to Decide
Because of the programmable flexibility of the average welding Robot, deciding which form of automation to use should be simple. Just put a Robot on it because it can be programmed to weld anything. After all, its multi-axis arm and wrist movements can duplicate the motions of a man holding a welding gun with more accuracy and repeatability. However, reproducing the movements of an arm holding a welding gun is not always the most efficient approach to performing a weld joint that has a simpler geometric shape, or has several welds that, to meet the production rate, must be made simultaneously.

Weld Joint and Design
When deciding between a Robot and a Fixed Automation System, consider the weld joint and the design of the welded assembly. If numerous contours, welding gun positions and parameter changes are required, the Robot is the only way to automate. If, however, the assembly has end caps or fittings being welded to a cylinder, or hubs onto a pulley, or straight line brackets onto plates, Fixed Automation may be the best solution.

Requirements
Regardless of the approach, Flexible and Fixed Automation both require accurate tooling to hold the parts together and good joint fit to achieve good welding results. Robotics has the edge in total flexibility and is the only way to go for complex or lower volume fabrications, but for higher volume repeatable applications, Fixed Automation achieves higher production rates at less cost, with a lower learning curve in terms of set-up.

Fixed Automation Applications
Just about any part that requires partial or complete OD or ID circumferential welds, various straight-line continuous or skip welds, or multiple GMAW spot welds and/or any combination is a good candidate for Fixed Automation. These parts include many cylinder applications, pulleys, hubs, sprockets, end caps, ports and fittings onto tanks, exhaust system components, automotive and non-automotive seat components, metal furniture sub-assemblies and all types of small to mid-size brackets and plates.

Flexible Automation robotic cell welding automotive engine cradle assembly

The machines and systems at the backbone of Fixed Automation usually include high quality welding lathes, turntables, orbital torch welders and straight-line linear seam welders. Many of these systems are available directly from the machine manufacturers as components as well as complete standard line systems that can be purchased as a turnkey cell just as you would purchase a Robotic cell. They can then be equipped with interchangeable tooling so that one machine can do a variety of different parts.

End customers may tool the system themselves on some applications. Other times, a system integrator may produce tooling or integrate the welding components into a machine that incorporates multiple station index tables with automatic clamping and automatic ejection for high production applications.

Fixed Automation welding cells also produce two or more welds at the same time at a relatively low cost. For example, if you are welding a flange onto either end of a tube on a welding lathe, add the cost of the second welding system and the items that support the second torch to produce two simultaneous welds. The cost of the basic lathe remains the same. This cuts the welding time in half.

Speed and simplicity are two other considerations. If you want to weld a hub to a sprocket or a round tube to a plate, send a torch mounted to a high speed pneumatic slide into the joint and rotate the part (or rotate the torch around the part), breaking the motion required into its two most basic elements. The simplicity of most Fixed Automation Systems makes them easy to understand and operate, and because they use basic mechanical, pneumatic and electrical components, provide years of trouble-free operation when maintained properly.

Best ROI
Ultimately, the decision to automate a project and whether to use Fixed or Flexible Automation breaks down to some very basic questions: What is the budget? Will it meet the production rate? Will it provide the payback the customer is looking for? If the customer has complex fabrications, low quantity runs or many different parts that have no commonality to one another and you have the resources to retool and reprogram the system, then Flexible Automation may give the best return on investment.

If, however, the customer's business involves welding higher production runs of similar types of parts, a fixed automation cell may be the most efficient for the application.

Fixed Automation has been around a long time, and though it often doesn't get as much of the glory, it represents a major portion of how parts are automatically welded. This is, after all, how all welding automation was done prior to the introduction of welding Robots. Flexible Automation has expanded welding into areas that could not have been easily or inexpensively done with Fixed Automation.

Like any tool, it's best to use the right one for the job. Keep in mind that the best approach may not be to reinvent the wheel, but to simply use it.