The Often-Overlooked Dynamic Performance Requirements Crucial for Machines to Produce Repeatable, High-Quality Welds

In the world of resistance welding, maintaining high-quality and consistent welds is paramount, yet, it’s astonishing how often the dynamic performance requirements of welding machines are overlooked, leading to erratic performance and compromised weld integrity.

Unfortunately, these issues often stem primarily from the mechanical sources of inconsistency within the welding machine itself. For those that have the funds, the first solution considered is often to procure a new machine which should, in theory, eliminate the problem. But too often we’ve found that resistance welding operations look to solve their issues by purchasing a new machine.

Manufacturers specify requirements such as current, force, throat depth, and electrode stroke for their resistance welding machines. However, they often overlook dynamic performance requirements essential for consistently producing high-quality welds.

There’s often a difference between the performance intended and the terms described in the contract.  Making a list of requirements for your machine doesn’t automatically guarantee the machine will perform up to your required specifications. There’s a significant difference between a luxury car and one that simply has four wheels, an engine, and a trunk.

In his most recent article published in the Welding Journal, resistance welding expert, Bob Cohen, describes the often-overlooked dynamic performance requirements crucial for producing repeatable, high-quality welds.

By addressing these performance needs, we ensure reliable and repeatable results, enhancing the overall efficiency and quality of your welding operations. Knowing what to look for — including focusing on the ram’s mechanical responsiveness — these problems can be significantly mitigated.

Understanding the Ram’s Role in Welding Performance

The ram (ram/cylinder) of a resistance welding machine plays a crucial role in ensuring the repeatability and quality of welds. Ideally, the ram should have low friction to minimize lower arm deflection and the potential energy build-up required to initiate movement. It should not require more force to start moving than to keep moving. This consistency is essential in managing the thermally expanding and contracting part during welding.

The Problem with High Friction

High static and kinetic friction within the ram can lead to increased breakaway force, which results in an inconsistent and erratic ram motion response. This inconsistency translates directly into welding performance, causing variability and defects. When the breakaway force is too high, the ram’s initial movement can cause a disturbance that affects the stability of the weld.

Inconsistent ram motion leads to several issues:

• Expulsions: Mechanical disturbances during nugget formation can breach the containment field produced by the force of the electrode surfaces against the part, causing molten material to escape.
• Weld Variability: Variations in ram motion result in inconsistent weld sizes and strengths.
• Process Instability: The lack of uniform motion can excite machine resonances, further destabilizing the welding process.

How to Identify and Address Mechanical Issues

The easiest way to diagnose these mechanical issues is by equipping the machine with a WeldComputer® control. This system can compare the actual motion pattern of the ram to the expected temperature rise pattern of the material. Any deviation indicates a problem with the ram’s mechanical responsiveness.

Practical Steps for Ensuring Consistency

1. Use a Low-Friction Ram:

• Ensure that the ram moves smoothly with minimal friction.
• Check that it does not require excessive force to start moving compared to maintaining motion.

2. Monitor Ram Motion Patterns:

• Use tools like WeldComputer controls to compare actual ram motion with expected patterns.
• Look for inconsistencies in the force required to keep the ram in motion.
  

3. Assess the Electrode Force:

• Ensure that mechanical disturbances during welding do not introduce sudden changes to the electrode force.
• Maintain a repeatable force to prevent fluctuations in current density and temperature rise rate from weld to weld.

Real-World Application

A resistance welding machine is a large investment and is mission critical to the manufacturing operation. Consider a scenario where a company invested $1 million in a new resistance welding machine. Without proper assessment of the ram’s mechanical performance to identify if there’s a problem prior to deploying in production, this manufacturer risks being plagued with ongoing quality issues over the capital life of the installation.

This exact example happens more often than you’d think. The best practice in this situation is to ensure the machine is free from mechanical issues before you take it home. 

We’ve  encountered buyers with existing contracts, with enough concern about potential issues that they call their machine suppliers to put in a change order for WeldComputer controls. Specifying a WeldComputer control is a reliable way to protect your investment and get the most out of the equipment.

Additionally, individuals with a current machine can seamlessly swap their existing control for a WeldComputer control to promptly detect any maintenance issues. This switch offers similar advantages, optimizing the performance of any machine.

Conclusion

Mechanical sources of inconsistent welding performance can be effectively reduced by ensuring the ram’s mechanical responsiveness is consistent. A low-friction ram minimizes lower arm deflection and the potential energy build-up required to initiate movement. By using a WeldComputer system to compare the ram’s actual motion pattern to the expected temperature rise pattern, manufacturers can ensure the machine is capable of producing welds with consistent quality and strength.

Investing in the right resistance welding machines and accompanying control systems from WeldComputer, not only prevents costly errors but also ensures the longevity and reliability of the machine. Whether prior to or after release of a contract to build or rebuild a machine, a WeldComputer system can be specified to provide peace-of-mind and significantly improve welding outcomes.

You can read Bob’s full article in the Welding Journal here. For more information on how to enhance your welding processes and ensure consistent high-quality welds, contact our team at WeldComputer. Let’s work together to achieve excellence in every weld.