Once the control is removed as a source of variation, spot welding operations can still face problems from variations such as:
Problem: Material surface variations
- Monitoring can detect problems from surface contamination and material coating variations, and alert the operator, to keep these poor-quality and inconsistent welds from leaving the factory.
- Adaptive features can prevent these problem welds from being made in the first place by automatically making adjustments to burn through the coating or contamination in a controlled fashion, and completing the weld to specifications.
Problem: Poor part fit-up
- Monitoring can detect welding problems from parts that were fit together poorly, and alert the operator, to keep these poor-quality and inconsistent welds from leaving the factory.
- Adaptive features can prevent these problem welds by automatically making adjustments to squeeze the parts together, and completing the weld to specifications. This reduces the variations on the welded result to levels approaching what it would be if no part fit-up problem existed.
Problem: Undersized weld created by:
- Flattening electrodes. As the electrodes gradually become flattened during production, the programmed current becomes less concentrated at the site of the weld. This causes the welds to become smaller.
- Shunting. A weld made in close proximity to a previously produced weld is often undersized because a portion of the programmed current gets diverted through the electrical path that was created by the existing weld.
- Monitoring will recognize that an undersized weld was produced and alert the operator, preventing the undersized weld from leaving the factory. In the case of flattening electrodes, the operator can also respond by changing the electrodes.
- Adaptive features can be added to detect these types of problems as the weld is taking place, automatically adjust the heat by the right amount to compensate for the condition, and produce a consistent weld. In addition to improving weld consistency and preventing problem welds from occurring, the adaptive control extends the number of welds that can be produced before the electrodes have to be changed.
- This occurs when the electrodes lose their ability to contain the molten nugget during weld formation. Expulsion can result in excessive surface indentation as well as cracks and porosity inside the weld. When expulsions occur, welds that are X-ray tested often don’t pass.
- Monitoring can detect these expulsions and allow the operator to reject the part, without having to X-ray the part to detect that the expulsions took place.
- Adaptive features allow you to detect expulsion the instant it occurs during the weld, instantly cut off the heat to minimize damage, then perform a repair operation in place. These actions, which take place automatically, have been demonstrated to effectively mediate the effects of expulsion, and produce welds that consistently pass X-ray testing.