Cobot Welding: From Science Project to Mainstream Automation

Gen 3 & 4 Software Features Drive Productivity and Quality Gains

Universal Robots shipped the world’s first commercially viable collaborative robot in 2008, three years after being founded in Odense, Denmark. The early years of UR’s cobot market were dominated by machine tending, assembly, packaging and palletizing – all applications that relied on the accurate picking and placing of parts and boxes. However, arc welding is a different type of application, far more demanding than the typical machine tending project.

It took nine long years for the first UR cobot based arc welding system to hit the market in 2017, and that transition accelerated in 2018 with the introduction of the e-Series family of controllers and related versions of PolyScope, the UR operating system and programming & development environment. This combination supported the precise path following performance, tool tip attitude & speed control and advanced process controls that welding applications required.

Cobot welders brought immediate benefits versus traditional robot welders to fab shops of all sizes. Automation investments to boost productivity are not new – arc welding robots have been on the market since the late 1970’s.

The traditional robot approach to automated welding has very real limitations, including:

  • Floor space – safety guarding required by traditional automation consumes large chunks of manufacturing floor space.
  • Complexity – traditional robots are difficult to program, operate and maintain. Small shops just don’t have the skilled resources to dedicate to traditional automation, and large shops don’t want the expense.
  • Lead times – traditional automation lead times are typically 3-5 months, an eternity for a shop fighting labor challenges day to day.
  • Limited flexibility – traditional robots are difficult to move to a new location, and to re-program for new parts, limiting the overall efficiency.
  • Total cost – given all the above points, traditional robot welding is an expensive investment that is difficult to justify.

Cobot welding has significant advantages over traditional robotic welding:

  • Floor space is not an issue. With a proper risk assessment and operator PPE, cobot welders can be deployed throughout manual weld lines with no safety fences, interlock or barriers.
  • UR based cobot welding solutions can be programmed and operated by welders, not robot engineers.
  • Long lead times are in the past. UR cobot welding solutions can be in production in weeks, not months.
  • Simple programming delivers maximum flexibility. The old saying “I can weld it before you can program it” is no more. New parts can be programmed in minutes, maximizing flexibility.
  • Total cost is typically third to half that of traditional automation. And with short lead times, UR cobot welding solutions deliver ROI in record time.
TIG Welding at Raymath Manufacturing by CSI THG Automation
TIG Welding at Raymath Manufacturing by CSI THG Automation

The initial development was focused on ease-of-use, bringing the unique UR user interface and ease-of-use to welding. Gen 1 cobot welding software addressed only the basics: MIG weld in a straight line with control of the wire feed rate and output from the power source/supply. The scope expanded in Gen 2, to include more geometric options, welding functions such as weaving and additional weld process types such as TIG.

Gen 3 and Gen 4 welding software saw the introduction of more advanced features that enabled additional programming productivity, and improved weld quality. While many of these features are available in traditional welding robots, it is worth noting that all have been developed in just the past five to six years. And more importantly, the advanced features have been implemented from the viewpoint of a skilled welder, not just an engineered product.

We have simply removed the complexity of a robot and let the welder with his skills program the robot with his actions. The welder must be good at his craft. Then our program helps make the cobot as good as him

Ahmad Gheit, lead software developer at Smooth Robotics

New Cobot Welding Features Push Productivity, Increase Quality

Multi-pass | Programming Productivity

Multi-pass is a valuable feature in heavy welding / high deposition applications. The old school option is to teach every pass manually – start, finish and process. The more efficient approach is to teach a single root pass, followed by a series of offset passes to build up the required size of the weld.

Reference Frames | Programming Productivity

While Reference Frames have been part of PolyScope from the outset, the application in welding required a full six dof implementation. The reference frame feature allows a complete program to be shifted to properly align with the physical parts. This required the teaching of a few points, versus touching up a complete program. Reference frames are particularly helpful in applications with multiple fixtures, or multiple parts within a fixture. It is also common on large parts in agricultural, mining, off-road and construction equipment, where precise fixturing is not practical.

Thru Arc Seam Track | Quality

Thru Arc Seam Tracking is a real-time tool that monitors the electrical characteristics of the arc to measure location relative to the weld path and makes program adjustments to properly follow the seam. It is particularly helpful on large parts with fit up and tolerance issues, component parts that were flame (oxy fuel) cut, and large weldments that suffer dimensional distortion from heat buildup during welding. The real time nature of Thru Arc Seam Tracking makes it a good fit in heavy duty welding applications.

Hi Mix / Low Volume customer MT Solar leverages multiple programming tools on their system from Vectis Automation
Hi Mix / Low Volume customer MT Solar leverages multiple programming tools on their system from Vectis Automation

Touch Sense | Quality

Touch Sense, also called Wire Touch, uses a low voltage electrical current (note: not available on all power sources) passed through the weld wire or torch nozzle to locate parts. Prior to welding, the robot probes along the vector of a seam, adjusting the pre-programmed weld path. Touch Sense is good for large parts with fit-up variations, but not thin materials, and not for cycle time intensive parts as it is a two-step process.

The built in 6DOF force sensor in the e-series and UR20 can provide the same functionality, at a reduced cycle time.

Pattern | Programming Productivity

A Pattern tool allows a programmer to copy and paste complex moves / welds in a program. It is very effective in programming multiple parts in a single fixture.

Tack | Programming Productivity

The Tack Tool is similar to a pattern tool but focused on short tack welds to hold individual parts together prior to welding.

Stitch | Programming Productivity

Stitch welding is the intermittent welding along a joint. It is used when a continuous weld is not required for strength or would put too much heat into a part and thereby distort the original geometry. Stitch welds can be done straight line or curved, and the best stitch weld tools allow the programmer to define start and stop points and the number of welds or the centerline length of the weld.

Manually positioning the weld torch on a UR20 Migatronic System
Manually positioning the weld torch on a UR20 Migatronic System

What’s next?  Multiple AI and Machine Learning based products are under development by UR+, OEM and CSI partners. Stay tuned, as UR OEM partner Hirebotics continues to develop an Industry 5.0 Cloud based program to help set weld parameters the first time, based on data collected from past programming and set up sessions.

Touch-to-Teach | Programming Productivity

Overriding all the above features is the unique Touch-to-Teach feature as implemented by various UR partners. Also commonly called Lead Through Teach, it involves the programmer’s ability to interact with the UR cobot manually, using Free Drive to position the torch precisely as a welder would. Conservative estimates show Touch-to-Teach improves complex weld path programming by a factor of 5x.

Joe Campbell

Joe Campbell is a 40+ year veteran of the robotics and automation industry. After executive assignments in sales, marketing, operations and customer service with industry leading robot, system integrator and engineering companies, Joe recently retired as head of strategic marketing for Universal Robots North America. He is a regular speaker, lecturer and author on manufacturing labor issues, and the technology and economic benefits of robots and factory automation.

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