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Micro Welding Trials

Micro Welding Trials (or Design of Experiments (DoE) ) are an important part of any welding process.  

Bespoke Electronics is able to advise and assist with on-site training and process analysis to support clients who wish to carry out Welding Trials.

In order to establish the ideal weld process, Design of Experiments (DoE) techniques, or as we say in the U.K., Welding Trials should be carried out.  In a nut shell, this amounts to setting up laboratory conditions in which the welded joint is made using various welding equipment settings until such time as the welding engineer can statistically show that they have the best fit set of conditions.  To do this, measurement devices are needed to measure current, energy, weld head force and weld peel and pull strengths.

In order to do this statistically, one process variable at a time is adjusted, a small sample of welds made, and then the welded samples are analysed for appearance and strength, usually using destructive methods such as peel and pull tests to verify target strengths. Average and standard deviation values for force, current, energy and pull strength then provide an indication of the process mean and variance levels around it.

The welding engineer is aiming to statistically evaluate the effect of each process variable (Force, current, waveform shape etc..) on both the joint and usually also upon the electrode life.  As a broad and crude starting point, the engineer will want to minimise the overall energy put into the weld and minimise any potential sparking in order to achieve a particular weld strength.  Excessive joint strength can be a sign of excessive energy, so sensible target values need to be pre-defined in order to minimise energy, localised heating and electrode wear.

The analysis should statistically show that the particular set up conditions sit in the middle of the parametric range of possible adjustments, such that small changes in any parameter have the least effect.

For fine wire welding and more complex material joints, this process is considerably more detailed, complex and lengthy, but the principle remains the same - to define the ideal weld process conditions.

The most important thing to do once these conditions have been determined, is to properly and “accurately” record and reference the setup.

Micro Welding Trials: Hints and Tips

Having defined and recorded the ideal welding scenario, it’s a very good idea to repeat the methodology to define some welding process limits and fault scenarios.  

In other words, contrive conditions that constitute undesirable welding conditions and then take measurements to record the effect these have.  

Simple examples would include component misplacement or misalignment, incorrectly adjusted force settings, incorrect electrode dimensions etc..

These measurements and records are especially sensible if you intend to use a weld monitor of any kind and at the very least, they provide process records that can be referred to quickly should the production process change.  

If you intend using a weld monitor, then make sure that it is able to accurately discern the measurement differences needed to detect these undesirable conditions.  If not, then don’t use it and/or source another one !