Demystifying Robot Offline Programming
| By: Tanya M. Anandan, Contributing Editor
‘It’s too complicated. You need a PhD to use it. Only big companies with deep pockets have that kind of time. There are too many variables; the software can’t possibly handle all of them. This is how we’ve always done it.’
We’ve heard the excuses. The misconceptions still linger, even though offline programming (OLP) has come a long way.
The old-school mindset is one of skepticism, that offline programming is not up to the task. A lot of robot programming in the welding industry is still done manually, point by tedious point with a teach pendant. Many still remember the ole days of robotics that overpromised and under delivered. This time around, the dreamers and doers have been working double time to exceed your expectations.
Simulation and offline programming software has evolved. It’s smarter, faster, more flexible and reliable. We’ve reached a new era in ease of use. Today, we bring together third-party OLP software suppliers to help us demystify the softer side of robotics.
OLP vs. Simulation
Most simulation and OLP solution providers will tell you that it’s not one or the other. Simulation and offline programming go hand in hand. Oftentimes, the terms are used interchangeably. But there is a difference. You can have simulation without offline programming, but you cannot have offline programming without simulation.
Simulation has been around for many years. Robot simulation is the 3D representation of a robotic cell or production line. It visually demonstrates how a robot moves along a path or trajectory from one XYZ coordinate to another XYZ coordinate. It can include multiple robots mounted on external axes working with multi-axis workpiece positioners, or coordinating on an assembly line.
All this movement can get complicated. That’s why we have mathematicians and engineers, the brains behind the software.
“A lot of customers purchase a robot thinking it will behave like a CNC. This is not the case,” says Albert Nubiola, CEO of RoboDK Inc. in Montreal, Canada. “CNCs are easy to program. The workspace is properly defined. It’s like a cube. However, robots have a spherical workspace, and because of joint limits and robot singularities (points at which a robot movement is not mathematically predictable), there are certain types of movements you cannot do. Offline programming helps avoid these errors when programming a robot.
“In robotic machining, there could be hundreds to thousands of points,” continues Nubiola. “Nobody would ever be able to program that point by point using a teach pendant. You definitely need software to be able to do that offline.”
Simulation can be used for proof of concept, as a robot integrator’s sales tool to demonstrate how a robotic system will perform. With simulation, you can detect possible collisions between the robot, tooling, fixtures and any safety fences. It can analyze joint limits, singularities, and reach issues. Plus, simulation can reveal a host of eye-opening issues that save time and money down the line.
Offline programming then uses that simulation to output robot-specific code you load onto your physical robot controller and run the program. Post processors turn programming code into a language the robot can understand. Different robot manufacturers each have their own proprietary programming languages. Third-party software solutions must be multilingual to tame even the most feisty robot brands.
When OLP Makes Sense
Our industry experts say the main impetus for offline programming is robot downtime, the time required to manually program a robot point by point with a teach pendant. There’s also the costs associated with that machine downtime and the programmer’s labor.
“If an end user is manually programming a robot on the teach pendant (online), they have to shut down production in order to program the part,” says Rob House, Director of Sales at OCTOPUZ Inc. in Waterloo, Canada. “The benefit of using offline programming is you can be running production and you can program your next two, three or five parts offline in the software and then once you’re ready to start a new job, you can just switch over the program and then start your production again.”
Offline programming is best suited for complex path planning applications that require a lot of points, such as welding, trimming, laser cutting, deburring, thermal spraying, painting, laser cladding and additive manufacturing. OLP is least suited for simple pick-and-place applications, assembly, packaging and palletizing. These applications can still be programmed using offline software solutions, but users may not realize their ROI. For processes with only four or five points, it’s more cost-effective to program manually.
“If you’re spending as much time programming in software as you do with a teach pendant every single time you have a new part, you’re not any better off,” says Garen Cakmak, Senior Director at Hypertherm Robotic Software Inc. in Montreal, Canada. “For robots to be utilized in a high-mix, low-volume environment, software needs to be easy.”
Improving ease of use is top priority for these software developers. But simulation and OLP are pointless if they don’t accurately reflect reality.
Calibrate, Don’t Deviate
For OLP to work, the virtual world must match the real world. The simulation must accurately represent the physical robotic cell. Don’t let deviations or discrepancies trip you up.
“The virtual environment in OLP software has to be an exact replication of the actual workcell on the shop floor, which is not the case in most situations,” says Helmut Ziewers, Vice President Digital Factory Solutions for CENIT North America, Inc. in Auburn Hills, Michigan. “The deviations between a CAD model and the physical part associated with that CAD model can be minor or significant, especially in conjunction with less than perfect tooling. We still see major issues and people saying we can’t do this offline, because of those deviations.”
Those deviations are not insurmountable, however. Calibration is critical.
“If we are off just a few millimeters or centimeters, you can create as many offline programs as you wish,” says Ziewers, “they will never fit. We have to know exactly how that robot was set up on the shop floor, and there must not be any deviations or else the OLP won’t work. The toolpath, the trajectory will always be off. This was the case with Crown.”
Crown Equipment Corporation is one of the largest manufacturers of powered forklift trucks in the world. Their facility in Roding, Germany, has several complex robotic welding systems with external axes and multi-axis workpiece positioners, some totaling up to 13 axes per cell. Faced with production bottlenecks caused by time-consuming manual robot programming, Crown Roding Germany decided to explore the feasibility of offline programming. Their journey was not without a few hiccups along the way.
At first, some members of the Crown team were skeptical of OLP’s ability to handle cell complexity while maintaining ease of use. Others were eager to give it a try.
CENIT was one of two suppliers brought into participate in a benchmarking study. Ziewers says they took CAD drawings provided by Crown’s automation integrator and created the virtual robotic workcell in their FASTSUITE Edition 2 software. Based on those drawings, they created the robot program and ran it on the physical workcell. But something was off.
“The customer said this is exactly what we thought, offline programming is impossible. The last OLP software provider was not able to get it going and it looks like your software can’t do this either,” recalls Ziewers. “What they didn’t know is that the drawing from the integration company no longer matched how the integrator set up that cell.”
CENIT engineers arrived on site to physically calibrate Crown’s workcell.
“We found out what the differences were, dimensionally,” says Ziewers. “We applied those differences in our FASTSUITE Edition 2 software and then adjusted the offline program based on the new setup in the virtual world. This matched exactly the physical setup from the shop floor, and the robot program worked perfectly.”
Watch CENIT’s 3D simulations and the Crown welding cells in action.
CENIT’s software coordinates the Reis arc welding robot on an external axis with the movements of a multi-axis workpiece positioner. What used to take several days to manually program a new part, now takes just a few hours. Production interruptions and downtime were significantly reduced. Welding quality consistently meets the customer’s high standards. Get the full story.
Ziewers says Crown’s top management has taken notice: “They’re not only happy with the smooth transition from hand-teach to offline programming and simulation, but the customer also uses our FASTSUITE Edition 2 software for pre-production feasibility studies. They actually detected tooling flaws and process flaws during simulation and provided feedback to their engineering for repair before they started producing tooling. Instead of finding out last-minute during physical runoff, they were able to identify those engineering flaws way ahead of time before any money was wasted.”
He credits the calibration process for contributing to the application’s success. It’s important to consider the CAD model in relation to the physical part being processed.
“The part as it comes out of a press or die never has the same shape it’s supposed to have based on the 3D CAD model. There’s always a difference between manufacturing and the CAD model. In sheet metal applications, for example, there’s springback.”
CENIT has calibration tools in FASTSUITE Edition 2 such as three-point transformation, multipoint best-fit calibration, and in-process probing capability that help address issues related to springback and other variables that cause the physical part to differ from the CAD model. For example, the multipoint best-fit calibration tool picks 10 to 15 random points on a part and then feeds them back into the OLP system, which calibrates the part into the robot’s work envelope in the virtual cell.
These calibration tools stem from CENIT’s years of practical experience in the manufacturing space, working with large aerospace customers. From big OEM players, to small laser job shops in Detroit serving the automotive industry, CENIT has worked with a wide range of companies. That breadth of knowledge goes into software development.
At this year’s IMTS show, CENIT unveiled the latest version of FASTSUITE Edition 2. The software expands on their OLP offering for complex robotic applications to include cell layout planning, PLC validation, and virtual commissioning.
“The ultimate goal of a 3D simulation platform like FASTSUITE Edition 2 is to provide a software environment for the manufacturing automation controls engineer to validate their PLC, ladder logic, the HMI and OLP, and debug them in the virtual world before the actual workcell is built,” says Ziewers.
When properly calibrated, the virtual world is like a crystal ball into the physical world. Check your deviations at the door.
Easier to Use, No Expertise Required
Another myth about offline programming is that it is too complicated, difficult to use, and requires specialized expertise. Suppliers of simulation and OLP software are working hard to prove those assumptions wrong.
“People think that because a robot is a complex device, that offline programming is a complex tool as well,” says Hypertherm’s Cakmak. “That’s one of the biggest misconceptions. For people to adopt more robotics, we have to provide tools that make that end-user experience very easy and flexible at the same time.”
Hypertherm strives to make robot programming as easy as possible for the user with their “task-based programming” approach to simulation and OLP software.
“A welder is a process expert. He’s not necessarily a CAD/CAM programming expert, or a robotician,” says Cakmak. “Task-based programming takes away all that complexity of robot programming, the CAD/CAM and robotics expertise, and really empowers the process expert.”
Empowering process experts through task-based programming is the foundation of Hypertherm’s Robotmaster offline programming software. The company released the latest version, Robotmaster V7, at Automatica in June. An entirely new architecture built from the ground up makes the OLP software even easier to use and paves the way for increased functionality and flexibility.
Cakmak says Robotmaster dramatically reduces offline programming time and effort by optimizing robot trajectories and automatically resolving robotic errors and collisions. It works with a simple but powerful, intuitive user interface and includes tools to optimize part placement, tool tilting, and effective control of external axes. It allows the end user and integrator to maximize the robot’s capabilities.
In a recent case study, Robotmaster software takes on a tedious process for programming hundreds of points, an application that if programmed manually would have taken months. The backdrop is northern Germany where high-speed trains routinely traverse the cityscape. Keeping up with rail maintenance is an ongoing issue for all worldwide rail and transport services, but the frequency of trains in this region is a growing traffic problem. Rolling contact fatigue is a major issue where the train’s wheels meet the rails.
To help remedy the signs of rail wear, German companies NSI CAD/CAM Technik and Mevert Maschinenbau collaboratively developed a rail milling technology to smooth and re-profile the rail surfaces. The reversible rail plates have to be turned almost daily, or else be replaced. That was done manually by four maintenance workers. Now that process has been automated with a robot.
The robot unfastens and fastens dozens of threaded bolts on each rail plate. Programming the 720 start-up positions was done with Robotmaster software.
“You have hundreds of holes that you have to go into with this robot,” explains Cakmak. “Using our software (and a CAD model of the rail plate), you can very quickly program the process. It automatically detects the holes, creates the screwing cycle, takes the bolts and threads them into the correct locations, while always checking for robotic errors and collisions. It validates the process and then outputs an error-free robot program.”
Using Robotmaster OLP software allows personnel to focus on other maintenance work, while the robot makes sure it doesn’t miss any bolts. Instead of the original four, only two maintenance workers are required for the new robotic process, saving Mevert significant costs.
On the job is a collaborative robot, or cobot, from Universal Robots. These power and force limiting robots allow operators to work in close proximity without the need for elaborate safety fencing. More on these cage-free cobots later, and why they also benefit from offline programming.
High-Mix Low-Volume, No Problem
Making offline programming easier for users helps facilitate wider adoption of robotic processes. Robots are no longer the exclusive domain of megacorporations with deep pockets and high-volume production. Small and midsized enterprises (SME), even mom-and-pop job shops, can get in on the action. High-mix, low-volume production is no longer a constraint when you have the latest simulation and offline programming tools at the ready.
“We have some customers that have robot engineers who are running the robot and are very capable of programming it manually. They are also very capable with the software,” says OCTOPUZ’ Director of Sales. “We have other companies that are just starting to automate. They don’t have a robot engineer on their staff. They can be hard to find and they can be expensive. They may be promoting a manual welder to now work with the robot and he may not have much experience.
“We take the approach that anyone should be able to program a robot,” continues House. “We have worked with people that have never touched a robot in their life and do not use software that often. It requires a little bit more training, but we can definitely get them to the point where they are comfortable programming a robot.”
Accumetal Manufacturing Inc. is a producer of high-mix fabricated components for the off-road equipment industry, including subassemblies for mining equipment. The Canadian company has less than 100 employees, with welding proficiency at the heart of their success.
After many years of manually programming their Panasonic robot, the volume of work increased to the level where Accumetal needed to take some pressure off of their welders. They acquired a new robotic welding cell in early 2018 and sought out OCTOPUZ for a simulation and OLP software solution.
The new cell consists of a six-axis Panasonic welding robot and a single-axis headstock/tailstock workpiece positioner. House says this type of cell is very popular in the welding industry. See Accumetal’s new arc welding cell in action.
“Our software handles all seven axes easily,” says House. “We can either index the part in position and weld it, or we can support coordinated motion where the robot and positioner are moving at the same time.”
OCTOPUZ added support for Panasonic robots expressly for Accumetal. The software easily converts the programming code into Panasonic robot-specific code.
“That’s one of the benefits of using our software. We program every robot in exactly the same way,” says House. “You could be programming three different robots to do the same process and the software would convert it to each robot code.”
This also allows for application flexibility. House says it allows the user to grow with automation. A company may be using the software for welding right now. If for example they want to do a trimming application in the future, they can use their same seat of software to program that application.
“It also allows them to work on more jobs,” says House. “Many companies will have a welding robot, but they are only comfortable running one or two parts on that robot. Everything else might be manually welded, because they’re not sure the robot can handle it. But with offline programming, you can do things like R&D and testing to make sure you can weld a new part. You’re doing all this from the comfort of your office and your computer. This allows you to start opening new jobs for your robot.”
In addition to helping Accumetal reduce programming time, OCTOPUZ was able to help their new customer reduce robot downtime and meet production demand. The customer reports that their initial programming time was cut in half. Check out the full case study.
Accumetal’s cell also uses through-arc seam tracking (TAST) for real-time tracking of the weld joint. This is in case the robot needs to adjust its trajectory on the fly, like when the CAD model and the actual part don’t match, as mentioned in the earlier discussion on calibration.
“We do a lot in the welding industry,” says House. Welding is notorious for having parts that are not exact, especially for the CAD. There can be quite a bit of discrepancy. Lasers are very popular. You create a path in our software and then using a laser seam tracker, if the part is not perfect, it will modify our path to follow that seam. Same thing with touch sensing. The robot will touch the welding wire to the part at different positions to locate that part. Then, based on any discrepancies between our program and the physical part, it will modify that welding path to match the part.”
House says they have in-depth support for welding, with over 200 different variables for welding applications alone. You can modify variables like your torch tilt, torch twist, push/pull angle, and touch sensing.
“Rather than going in and changing all of those things for each one of your welds, which is obviously time-consuming, we have something called Quick Weld,” he says. “You can basically save a recipe. Most of our power users will save maybe 10 or 12 recipes and never go back into those variables. Then they just click on Quick Weld and pick their recipe. When they click on the seam, it will automatically use all the variables they’ve saved. It’s a very quick way to create a lot of welds.”
Also common in the latest OLP and simulation tools is drag-and-drop functionality. Everything is very visual and designed to be intuitive, further facilitating ease of use.
“Rather than plugging in numbers to position components, you can simply drag from the catalog and snap it onto something like a robot pedestal,” says House. “You can drag which tool you want to use and it will automatically snap to the end of the robot. You can even hover over a part and it will highlight an entire toolpath around that part for something like trimming. Then you can click once and it develops that entire path.”
In early 2018, the software developer launched OCTOPUZ 2.0, which introduces a completely new engine and interface. House says it includes a significant graphic upgrade from previous versions. It’s also able to work with much larger CAD geometry and larger files. The powerful new architecture supports a number of new features, including automatic path solving, cable wrapping simulation, and virtual reality support.
One OLP Tool, Multiple Robot Brands
A key advantage of third-party simulation and offline programming software is its universality. Most can manage multiple robot brands. This is in sharp contrast to the OLP solutions offered by robot manufacturers. Robot OEM software is proprietary and specific only to that brand.
OCTOPUZ has an online catalog of components included in their software. House says there are thousands of components in their library, including all the major robot brands and their various models.
“We support around 15 different brands at this time,” says House. “Programming an ABB, to a FANUC to a KUKA, there’s no difference in the programming process to do that. Many integrators we work with have multiple robot brands. Rather than learning a number of different tools to program each one, they find it beneficial to have one tool to program all of them.”
Even Easier, Cobots and OLP Collaborate
Cobots aren’t out in the cold either. OLP software supports these robotic rebels, too. Cobots can often be “taught” an intended path via a lead-through teach feature common to these types of robots, where you simply push the arm to the desired position and record the points. However, complex edge-following tasks often call for a more sophisticated programming solution than the standard platform that comes with some of these cobots. Our third-party OLP providers once again come to the rescue.
OCTOPUZ and RoboDK are both part of the Universal Robots UR+ Solutions Program that certifies products for plug-and-play compatibility with UR cobots.
House says they have a number of customers using UR cobots. Glue dispensing is a popular application for these lightweight, power and force limiting robots that can work in tight spaces near their human coworkers typically without safety cages. He says OCTOPUZ also works with FANUC CR Series collaborative robots and the KUKA LBR iiwa cobot.
“It all comes down to the application, not the robot,” says House. “For a pick-and-place application with only four or five points, you can drag the robot arm manually from point to point. But if you have a complex edge-following dispensing program you want to do with a UR robot, you can program it manually, but it’s going to be very time-consuming. That’s where software will help.”
RoboDK simulation and OLP software helps researchers at NASA Langley Research Center automate a novel aircraft inspection method using collaborative robots. The UR10 cobots are equipped with FLIR infrared inspection cameras. These thermal sensors can detect material or structural defects in composite aircraft fuselages without damaging them by analyzing the flow of heat through the structure.
The inspection system is bulky and heavy, and must be moved across the entire exterior and interior surfaces of the fuselage. So while the UR cobots handle the heavy lifting, RoboDK software simulates and programs the inspection pattern, ensuring the robots don’t miss any areas.
But why offline programming when cobots are supposed to be easy to program?
“Their user interface is made very simple, but it’s made for people that have never programmed a robot,” explains RoboDK’s Nubiola. “If you want to move the robot from point A to point B, that’s very easy. Probably a 10-year-old can do it. But as soon as you want to do something more sophisticated, Universal Robots may be more complicated than other robot brands.”
For a complex process like NASA’s inspection system, where the thermal sensors are analyzing hundreds of points, OLP software is a no-brainer. Manual operation or even point-to-point robotic programming would be tedious, and it would take three or four people to do the same thing one robot and one operator can achieve.
Using calibrated 3D CAD models of the robot, fuselage and inspection tool, NASA uses RoboDK software to not only generate the robot paths, but also test for the most efficient path. Automating the process with a robot also creates digital data of the inspection that can remain with the vehicle record. Subsequent test results on the exact same areas can reveal structural and material changes over time.
See NASA’s robotic inspection system and the RoboDK interface in action.
The inspection system using one cobot on a wheeled base has been in testing at NASA for about a year. Nubiola says a new version of the system, which uses two UR10 cobots working together on the same linear rail has been in testing for a few months. This speeds inspection time and saves the operator from having to repeatedly wheel the robot from one section of the fuselage to another. The movements of the two cobots are coordinated in the RoboDK simulation and subsequent program. The new setup brings this system one step closer to a production scenario.
Less Time Programming, More Time Producing
In a perfect world, a state that is rarely attainable, a virtual solution should replicate the physical world. But part and process variances, or deviations, can throw a monkey wrench into your simulation and offline programming setup. That’s where calibration is critical. Complex robotic processes and sophisticated software are no longer the exclusive domain of megacorporations. High-mix, low-volume job shops can join the OLP party. So can collaborative robots.
Yes, there are growing pains. But offline programming software has come of age, with better functionality, ease of use and reliability. Spend less time programming and more time producing. OLP is up to the task! Are you?