Coordinate Systems
The robot's coordinate systems provide multiple means of jogging the robot. Thereby using different frames of reference to determine how the robot will move in 3D space.
The user can move the robot via the Jogging Panel, or by using the buttons on the right side of the pendant. Changing the coordinate system will dictate how the robot will move and react with each button press.
The following coordinate systems are available:
- Smart Frame:
Move the robot relative to the orientation of the Smart Pendant. Rotate the pendant or face a different direction to influence the relative jogging direction. - Joint:
Move each axis of the robot independently. - World:
Move the robot in cartesian space relative to the robot's base frame. - Tool:
Move the robot in cartesian space relative to the robot's current tool frame. Changing the active tool will update the reference frame.
Note that the Z-axis is often flipped, where Z+ is down, due to how the tool axes are defined. - User:
Move the robot in cartesian space relative to some user defined reference frame. - Hand Guiding:
Move the robot via the Direct Teach (DT) buttons on the end of a collaborative arm. Drag and reorient the robot by hand.
To change the robot coordinate system, press on the shown button, and select the desired option.
Tool Control Point (TCP)
The TCP refers to the specific position and orientation of a robot's tool or end-effector where the robot's actions are focused. In welding applications, the TCP is positioned at the tip of the welding wire. This is commonly programmed with approximately 3/4in or 19mm stick out. The +Z-axis generally points in the direction of wire feeding.
When using Weld Builder it is necessary to ensure that the following conditions are met:
- The selected tool corresponds to the actual tool being used by the robot.
- The tool is properly calibrated.
- Move the TCP to an external reference point.
- Select the tool motion frame.
- Rotate the TCP in several directions.
- If the TCP has moved away from the reference point, the TCP needs to be calibrated.
Note: Some Weld Builder features may not work as expected if the TCP is inaccurate.
TCP Calibration
- Open Tools under Robot Settings main menu.
- Select the tool to calibrate from the list.
- If the tool coordinates are known, enter them manually. If they are unknown, press the [ESTIMATE] button.
- Use an external reference point and follow the instructions to register 5 robot joint configurations that place the tool tip on the reference point to calulate the TCP position.
- Make sure the TCP is properly calibrated.
Motion Types
During programmed robot motion the manipulator will move using one of several interpolation types to reach the destination. These interpolation types dictate how the robot will to the taught position.
Joint Motion:
Optimizes the robot motion in such a manner that all joints reach their final destination at the same time. This is useful when the travel time is more important than the exact path to get to the taught position.
Best used when there is no danger of collision.
Linear Motion:
Moves the robot's tool along a linear path from the current to the taught position, ensuring precise control of the tool's path.
Used to approach the welding start position, and to weld straight lines.
Circular Motion:
Moves the tool along an arc passing through at least 3 points. Useful for tasks like welding arcs or cutting curves.
Spline Motion:
The spline interpolation makes the teaching for workpieces with irregular shapes easier. The motion path creates a parabola passing through three programmed points.
Note: This motion type is not yet available in Weld Builder.
Positioning Level (PL)
The PL can be added to move instructions to set the degree of approximation in which the robot will reach a taught position.
If PL is not set, the accuracy depends on the operation speed. In which a higher speed will further approximate and round the corner.
GMAW / MIG Welding Processes
MIG (Metal Inert Gas) and GMAW (Gas Metal Arc Welding), are two widely used welding processes that combine a continuous feed of welding wire with shielding gas.
These processes can be classified in:
Standard MIG
In standard MIG welding, a solid wire electrode is continuously fed through a welding gun and into the weld pool.
Standard MIG leads to high heat input, it is then typically used on thick materials, when high travel speeds and low wire feed speeds are used.
Pulse MIG
Pulse MIG welding alternates between high and low current levels, creating a pulsing effect.
This process enhances control over heat input, making it particularly useful for thin materials, when low travel speeds and high wire feed speeds are used.
Torch Angle
The torch angle refers to the orientation of the welding torch relative to the workpiece. It influences how heat and filler material are applied to the joint, affecting the overall quality.
There are two types of torch angles to control during robotic welding:
- Work Angle: The angle of the torch relative to the axis perpendicular to the joint.
- Travel Angle: The angle of the torch in relation to the direction of welding.
Appropriate Work Angle
The correct work angle depends on the type of joint being welded. The recommended values for each joint type are:
| Joint Type | Work Angle Recommendation |
|---|---|
| Fillet Joint (T-Joint) | 45° |
| Lap Joint | 60° |
| Edge Joint | 90° |
| Corner Joint | 45° |
| Butt Joint | 90° |
Appropriate Travel Angle
The travel angle can be up to 10° to 15°. Depending on the intentions, the user might want to incline the torch in this direction.
- Leading (Push) Angle: The torch is tilted forward, in the direction of welding. Use a leading angle for deeper penetration, thicker materials, better arc stability and faster travel speeds.
- Trailing (Pull) Angle: The torch is tilted backward, opposite the direction of welding. Use a trailing angle this angle for thinner materials, to reduce spatter, to control heat input, and when working with overlapping joints.
Wire Stick-Out Requirements
Wire stick-out refers to the portion of the unmelted wire coming out from the contact tip to the arc. The length of the wire stick-out affects several aspects of the welding process, including arc stability, heat input, and weld penetration.
The ideal wire stick-out length varies depending on the welding process and the material being used.
Weld process considerations:
- In Standard GMAW processes, 10 to 15 mm (3/8" to 5/8") are typically used.
- For Pulse GMAW processes, 12 to 20 mm (1/2" to 3/4") are typically used. The stick-out range is slightly longer than conventional GMAW to accommodate the pulsed arc.
Material considerations:
- For thin materials, stick-out should be kept shorter to avoid overheating and excessive burn-through.
- For thicker materials, a slightly longer stick-out can help reduce heat input while still achieving good penetration.
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