Zane Michael isClick image to enlargeby Zane Michael

Best practices will help you achieve a maximum ROI on your investment

 

While the purchase of a robotic weld system has the potential to set a company apart from the competition, maximum ROI and optimum operational success happen when organizational leaders plan and promote best practices for robotic welding. Steps taken to educate operators and protect the system before implementation provide a strong foundation for fast and efficient robotic welding operation. And adherence to key programming guidelines, once the system is up and running, helps ensure maximum productivity for corporate success.

Operator training
Hiring or investing in the correct people to operate a robotic weld system is key to overall success. Unless an employee is already proficient in the type of robotic system being implemented, it is best for designated system operators to attend a series of robot programming classes. Training courses offered by the system supplier are ideal and will provide comprehensive teaching.

The majority of robotic OEMs are equipped with classrooms, equipment and instructors to provide workers with the most complete and applicable training experience. A classroom environment like this can provide selected robot programmers the chance to interact with other students and knowledgeable trainers in a dedicated learning environment, apart from on-site interruptions. 

When selecting the proper employees to invest in for this type of training, it is important for company management to choose individuals with strong welding capabilities. While there is nothing wrong with sending a mechanical engineer or an electrical engineer to training, organizational leaders need to understand that workers with these skill sets most likely will not be able to fix welding defects. It is easy for most people to learn how to program a robot, but not everyone has the patience or experience for solving welding issues such as undercut, lack of penetration and burn-thru.

 

5 best practices for robotic weld system performance

1) The golden weld torch neck

For consistent and optimum weld quality, it is important that the tip of the weld wire is physically at the correct tool center point (TCP), as a slight variation in wire position can lead to poor weld quality. The TCP includes dimensions that are loaded into the robot’s controller and represent the tip of the weld wire, including the electrical stick out of the GMAW process. The robot path and speed are all “driven” at the tool centre point, so if an operator programs the robot to weld around a four-inch diameter pipe at 40 ipm (1,016 mm/min), all calculations are done at the TCP.

On a new system, the robot supplier will set the robot’s TCP to physically match the weld wire, typically with a half-inch (12.7 mm) stick out. The issue becomes, what do you do when you crash the torch into the part or fixture?

Many programmers step thru the program and edit the point (i.e., get the weld wire back in the joint), however, this is a huge mistake. Before editing, an operator should remove the torch neck, before placing it into the torch alignment jig. If the torch neck does not line up correctly, the operator should physically bend the torch neck to align it with the original dimensions. Doing this procedure accurately can greatly reduce editing time.

2.) Weld contact tip replacement frequency

An operator should determine the life of the contact tip by monitoring the overall weld quality. Once the life of the tip has been decided upon, the operator should set a counter in the robot program that gives an alert for future contact tip change.

 

3.) Weld cable liner service

The weld liner on a robotic weld system will need to be serviced (blown out, cleaned or replaced) more frequently than a manual welding system. Operators would be wise to add this to a weekly preventive maintenance check list to ensure optimal system performance.

 

4.) Robot programming guidelines

Regardless if an operator is utilizing offline programming or a traditional approach (via a teach pendant), adherence to certain guidelines is suggested. 

Proper Electrical Stick Out and Torch Angle: For the GMAW process, maintaining the proper electrical stick out and torch angles are paramount to the weld quality. If your stick out and angles are varying, so will the weld quality.

Clamp Clearance: Operators should program the robot path to not only clear closed clamps, but the robot should also be able to clear open clamps. This could save you from a robot crash, especially with manual clamps. 

Speed: If a robot has the ability to move at very high speeds, it does not necessarily mean it needs to operate that fast. Moreover, if a robot is sitting idle at the end of the weld cycle, the speed of the “air cut” moves can be reduced without impacting weld quality. This alleviates some of the wear and tear on the robot arm.

Editing Rights: Once the robot system is programmed and making good parts, it is a good idea to evaluate who should be allowed to perform edits. The pitfall of running different programs on each shift due to operator preference should be avoided. Password levels for different operators authorized to run the cell should be established and set up. Each operator should be trained to understand how and why edit should take place. A useful hint is to remember tracking the weld quality will help determine if a robot needs to be edited or if a part needs to be fixed.

Backing Up the Controller: Operators should set up the robotic weld system to back up the robot controller on a frequent basis. Most controllers allow an operator to connect the system to a network, providing for easy backups and retrieval when needed.

 

5.) Weld Fixture

The main purpose of the weld fixture is to locate and hold the weld joint repeatably with minimal to no gaps for the robot. Some basic steps to help monitor how well the robotic weld fixture is performing are as follows:

  • Step 1: For repeatability of the same part with the same operator, load and unload the same set of parts using the same operator. Then bring in the robot and check the weld wire position across the weld joints.
  • Step 2: For repeatability of different parts with the same operator, change parts and repeat Step #1.
  • Step 3: For repeatability of the same part with different operators, change the operator and repeat.

No matter how large or small a company, the implementation of a robotic welding workcell has the potential to provide transformative productivity gains, consistent weld quality and reduced operational costs. These results will only happen, however, if the robotic weld system is operating as efficiently as possible. While the criteria given are not an all-inclusive list, adhering to these guidelines has the potential to help companies achieve ROI and optimum results at a more rapid pace. SMT

Zane Michael is director, Thermal Business Development at Yaskawa America, Inc., Motoman Robotics Division.

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