Weld Monitor -Welding Applications

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Weld Monitor Applications

The Weld Monitoring Unit delivers effective quality weld monitoring to the many applications that simply cannot afford or justify the expense of conventional and typically digital capture based solutions.

Regardless of the type and/or sophistication of any welding power supply, the need for real time Quality Checking in a manufacturing process is a highly desirable modern day requirement to give assurance that a process is under control.

External Weld Monitors INDEPENDENTLY check that all is well with a Power Supply, Weld Head, Operator and Material process combination, essentially auditing each and every weld to declare whether or not it was created within a pre-defined process window. Those welds that fall within the process window are essentially verified, while those outside of the window can be rejected.

Independent Weld Monitoring significantly increases Quality and decreases product rejects and faults.

Capacitor Discharge DC Resistance Welders - a new era for weld monitoring

Capacitor Discharge Welding Power Supplies are common place the world over and with their simple design and operation, they provide highly effective micro joining / spot welding solutions, especially where conductive materials necessitate higher welding currents.

Ironically, the relatively low purchase cost of such power supplies is often less than the cost of a conventional weld monitoring system and hence many Cap Discharge applications exist without external Quality weld monitoring.

The Weld Monitoring Unit offers a simple, low cost monitoring solution for Capacitor Discharge users.

Since the capacitor discharge process is electrically uncontrolled, overall product quality relies heavily upon well trained operators and well configured weld heads and consistent materials to maintain a stable process.

The Weld Monitoring Unit readily measures the heat energy delivered to the weld by measuring the discharge current.

If the power supply output changes, or the electrodes wear, or the materials change, or the operator varies what they do, then the electrical resistance characteristics of the joint will be dynamically affected and hence the discharge current will be modified and detected as an erroneous change to the normal process.

Power Supplies with a “Built In” Weld Monitor - The Pros & Cons

Graphical interfaces with “monitoring capabilities” add cost and functionality to a welding power supply. Internal power supply monitors can be a useful operational feature BUT from a Quality Control standpoint, it is important to consider and understand the true level of “independent checking” that such monitors offer.

Typically internal monitors will use the same signal sensors and referencing electronics for monitoring as are also used to derive the power supply output. This is fine with all being well, but an important consideration is to understand what happens if one or more of those items goes wrong or becomes inaccurate ?

In view of this, well controlled environments production environments such as aerospace, medical, automotive etc.. often deploy external weld monitors in applications where high end power supplies have an internal weld monitor. This ensures that something is checking the internal checker and that an independent Quality verification is taking place.

The Weld Monitoring Unit is designed specifically to deliver low cost, truly independent real time weld checking.

Controlled Linear, HFDC & Hybrid DC Resistance Welding Power Supplies

Controlled power supplies regulate their output in accordance with real-time feedback measurements. Typical operational modes will include Constant (Regulated) Current, Constant Voltage & Constant Power.

In all resistance welding applications, the heat energy at the weld is entirely proportional to the welding current and the dynamic resistance of the weld. Thus all modes of operation can and will suffer from process variability caused by changes in operators, materials, electrodes, weld head setups etc…

As with capacitor discharge applications, Quality Weld Monitoring will verify the welding process repeatability and detect changes in the delivered heat energy.

Controlled power supplies are more complex and generally more expensive than Capacitor Discharge units. The additional sophistication allows output currents and hence heating profiles to be programmed in terms of amplitude and time.

This capability provides greater flexibility when dealing with a wide range of material applications. The ability to control the rate at which current is applied to the weld can be beneficial in optimising electrode life and compensating for some material variations.