Offline Programming and Simulation in Robotic Welding Applications Speeds Up Programming Time, Reduces Robot Downtime
Software solutions substantially reduce the time it takes to program a part in robotic welding applications and doesn’t tie up weld cells with non-productive activity.
As manufacturers look for new ways to compete globally, it’s important to look holistically at the manufacturing process. There is one great truth: parts — and money — are not made when equipment sits idle. While robotic welding cells have helped manufacturers speed up productivity, even the latest and greatest robots sit idle during the programming process. Programming robots — the practice of teaching a robot its various points, trajectories and joints on a workpiece(s) — can take days or weeks, depending on the size and scope of the workpiece and cell.
In this article we’ll examine offline programming and simulation technology, such as Desktop Programming and Simulation (DTPS) software from Miller, and how it allows fabricators and manufacturers of all sizes to program parts faster and more consistently, become more competitive through improved and accurate costing, and provide operational flexibility. An overview of the technology is first, followed by some pivotal points of interest. Finally, we will look at the type of operations the technology may be best suited for.
How Does Offline Programming/Desktop Simulation Work?
Offline programming and simulation software allows you to program your robot from a computer rather than on the robot itself. In order to work with this type of software, you will require 3D CAD models of both your parts and fixtures that will be used in the cell (created in a program such as Solidworks®). From there, your software options will vary depending on the manufacturer of the robots in your robotic welding cells. For instance, most OEM robot manufacturers offer specific in-house developed offline programming software that features proprietary 3D CAD models of their robots. If your operation features a multi-brand robotic fleet, there are software solutions that offer 3D CAD models of numerous manufacturers. It is crucial to note the in-house robot software programs tend to be customized with more brand-specific functionality and finer control over the programming.
When the 3D CAD models of your part(s) and tooling/fixtures are imported, the software will then match that with the 3D CAD model of the robot, creating a virtual replica of the system on the shop floor. With the click and drag of a mouse, you will then begin to build the program on your PC instead of using a teaching pendant in the weld cell. Upon completing all of the weld sequences, the system lets you to run the welding program as a simulation, where the software will detect possible collisions (discussed later), identify areas where weld procedure angles could be difficult to achieve and provide the time it would take for the cell to make a complete part. After simulation and testing, the program is then exported from the computer to the robot via Ethernet. Manually touching-up your program with a teaching pendant in the cell is next, as the software typically gets the robot to within a quarter of an inch of its final path. In the not-too-distant future, however, automating the polishing process through external sensing technology on the end of the robot will become a reality.
Even with the current manual touch up, offline programming and simulation software drastically reduces the time it takes to create programs. While each application is different, it is not unheard of to program a part in one-quarter of the time it previously would have taken to program the robot at the cell. Considering that weeks are sometimes spent by heavy equipment manufacturers programming large weldments, the time savings add up. Yet the greatest benefit is that the vast majority of programming occurs while the cell is still welding other parts, ensuring optimal uptime.
Getting Fixtures and Tooling Right the First Time
Having the ability to verify the type of fixtures you need to build in a 3D scenario is a major advantage of this type of software. Designers hope to get the tooling right the first time, but any number of variables can change during the planning stages, requiring the tooling to be reworked. This software allows you to review the workspace, ensuring the robots can actually reach each point sans interference. Before testing the robot in a real-world scenario, which requires time and money to set up, you can verify the program in the computer to make sure you have the proper equipment to accomplish its intended goals. Most of the software presents actual robot kinematics, the trajectory between each point, and allows the tooling/fixture architect to guarantee that their design will maintain the required tolerances while also accommodating the welding system.
Calibrating Imperfection to Improve Accuracy
The virtual world is perfect. On a computer, a right angle is precisely 90 degrees, 1,000 millimeters exactly 1,000 millimeters. No more, no less. The real world, on the other hand, is entirely imperfect. So, how do you translate the slight blemishes of a real weld cell into a computer-generated program? Through mastering and calibration tools in the software, users can teach the robot a small number of real points in the physical system, incorporate that back into the computer program and ultimately achieve greater accuracy than if you relied on the “perfect” world of the computer.
For instance, simply teach the real robot system a few key points, such as the location of the worktable, where one rotational axis is located, and the starting point of a weld. Import those points back into the program, and the software will reconcile any differences between the real world and the virtual world. This reconciliation is only performed once per system and typically gets total program accuracy to within a quarter of an inch. This acquired level of accuracy requires considerably less touch-up time once the final program has been downloaded to the robot.
One of the most efficient features of this technology is the copy/paste/mirror function, extremely useful for manufacturers who may weld many of the same or similar parts on a single fixture. If the user has two identical parts next to each other, there is a simple way within the software to take the program for the first part and copy/paste it over the to second. Should the two parts exist on the same fixture, but as reflective opposites of each other, the software mirrors that program on the first part directly onto the second. This simplifies programming in the computer and is substantially easier than manually teaching each individual part in the cell. Even if parts have similar yet non-identical features, the software facilitates growing or moving taught paths. As with constructing a real-life assembly component, the robot program transforms into a series of shorter sections that were copied/pasted/shrunk/moved to create the whole.
A solid, albeit extreme, example stems from a recent customer who had to weld 24 iterations of the same part. Working with an integrator and based off the original program for one part, the rough program for all 24 pieces was finished in about two hours. Manually teaching each individual iteration may have taken days, perhaps weeks.
Easily Transfer Programs from Cell to Cell
A manufacturer can easily transfer a program from one robotic cell to another with this technology. After creating a program in Miller Welding Automation’s DTPS software, you can seamlessly transfer that program to any other Panasonic robotic welding cell or PerformArc™ pre-engineered weld cell. Minor adjustments are inevitable, such as if you transfer from a larger system to a smaller cell or robot (the smaller robot may not be able to reach all of the points on the same program), but the process is substantially simplified. This is particularly helpful if a manufacturer is upgrading to a new robotic system. It allows us to take the legacy programs, run them through the software and tweak them a bit to function in the new cell, ensuring you don’t lose your old programming work and allowing you to return to welding your production parts as soon as possible.
Applications Best-Suited for Offline Programming and Simulation
While this software presents excellent benefits for most robotic welding applications, it provides differentiating benefits to different customers. There are also robotic applications it may not suit.
Low-Volume, High-Variety Shops Requiring Minimal Downtime: Fab shops and manufacturers that move a lower volume of differing parts through the shop are prime candidates. The software allows the user to constantly implement new parts into the system with no downtime. It also acts as an optimal quoting tool for this type of shop, letting the user determine if a job will fit their robotic system, whether or not they’ll be able to reach it and if they possess the proper tooling/fixtures. The simulation also helps determine cycle times and wire consumption for more accurate quoting, providing companies the ability to grow more efficiently, tighten their cost structure and bid more aggressively due to data-based intelligence rather than just instinct.
Big Parts with Many Welds: Especially pertinent for heavy equipment manufacturers and others who weld extremely large components with many welds, programming on a computer is infinitely easier than slowly jogging a robot around the part in a weld cell and trying to gain access to every joint. The software can cut weeks off the programming and implementation times.
Short Start-Up Times: A recent customer had a new robotic system that took months to build and they wanted to be up and running as soon as the system was complete. The system featured two robots that moved along a gantry-style structure to weld an extremely large part. The customer was able to offline program the system as it was being constructed and, upon completion, dropped in its programs, touched them up and began welding. Manually programming these parts would have been difficult, and would have required the user to spend extensive time in and out of a hoist to access each weld. The software cut what could have been four weeks of programming down to one, allowing the user to perform the bulk of it from the comfort of his/her office.
Value-Added Manufacturing and Diversification: If you’re a manufacturer who makes millions of one part and very little else, or if you make many similar parts with very few welds, this software is probably not worth your investment. However, due in part to today’s economic uncertainty, many manufacturers are diversifying their offerings. These cookie-cutter parts are now becoming customizable as a value-added enticement for the customer and require the manufacturer to be more flexible in their programming. As this type of manufacturer continues to diversify, this software will become more appropriate.
When viewed comprehensively, offline programming and simulation software is a tool that helps you program robots faster, reduce robotic cell downtime, achieve faster project implementation on new cells, quote new jobs more accurately, ease the transition of programs from one cell to another and simplify upgrading to new robotic systems. As more and more companies turn to robotics to stay competitive amid a skilled labor shortage and aggressive bidding from other manufacturers, this software is another important tool that keeps you a step ahead of the competition.
For large, complicated systems, offline programming allows manufacturers to program the part during the construction of the cell, shortening the start-up time once completed.
Weld joints and robot movements can be programmed with a simple click of the mouse.
Offline programming helps keep robots on the floor working and not tied up with programming.
Using real world points, the computer system is able to reconcile differences between the computer generated cell and the real world cell, helping improve programming accuracy.