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When Using A Spot Welding Machine, Uneven Weld Spots Frequently Occur. Is This A Problem with The Equipment Or The Operation?
Views: 0 Author: Site Editor Publish Time: 2025-12-15 Origin: Site
On the shop floor, spot-weld spatter that is now too big, now too small, joints whose strength swings from “pass” to “fail,” and weld marks of unpredictable diameter are the headaches that show up every single day.
The first reaction of many plants is “the machine must be no good,” yet in reality uneven welds are almost always the combined result of equipment, process, material and operator. To solve the problem once and for all you have to check every core link in a fixed order instead of blaming one suspect at random.
The common “equipment” culprits
In a resistance-spot set-up anything that makes current or electrode force wander will immediately change nugget size or strength.
a) Unstable welding-current output Ageing IGBT modules, drifting power-source parameters or a mis-behaving main control board all let the current pulse fluctuate, so joint strength changes from weld to weld.
b) Worn or oxidised electrodes Tips that are mushroomed, contaminated or out-of-round give a varying contact area and pressure footprint, so spot size scatters.
c) Cylinder / servo force drift Any change in forging force alters nugget diameter; the same schedule may now penetrate too little or too much.
d) Inadequate cooling
High cooling-water temperature or blocked circuits heat the electrodes and machine hardware, varying bulk resistance and giving erratic spots.
Operating or set-up faults are more frequent than you think
Many “bad” spots are not caused by a broken welder but by skipped details in procedure or handling.
a) Mismatched weld schedule Current, voltage, time or force that is off by even one step will scatter results—especially when sheet thickness or coating type changes and the schedule is not updated.
b) Electrodes not dressed or changed on cycle Operators often ignore tip maintenance, yet spot-weld repeatability depends almost entirely on tip shape and cleanliness.
c) Poor part fit-up Mis-located panels or gaps that close only under force change dynamic resistance and give non-repeatable nuggets.
d) Inconsistent operator rhythm
On manual guns, varying pre-squeeze time, hesitation or changing arm pressure all shift the weld.
Quick field test: whose fault is it?
Use these rules of thumb:
Fluctuation shows a clear periodic or on/off pattern → look first at power source or force system.
One station or one operator is always worse → suspect handling or fixture.
Spots improve the moment you swap electrodes → tip wear was the cause.
Trouble starts right after a new material lot → check sheet surface, coating or chemistry.
A universal road-map to stable spots
Scheduled machine checks: power-source repeatability, cooling-water flow, air or servo pressure.
Tip maintenance plan: written dressing interval and replacement criterion.
Optimised tooling: nests and clamps that guarantee identical part position and intimate contact.
Parameter matrix: one weld schedule for every material / thickness combination, documented and locked.
Operator training: standard pre-squeeze time, gun motion and rhythm.
Data trail: log current, voltage, force and nugget diameter; react the moment a trend drifts.
Closing note
Uneven spot welds are never a single-point disease; they are the visible symptom of variation somewhere in the welding system. Equipment, settings, tooling, material and operator all feed the same quality ledger. Replace guess-work with a fixed troubleshooting loop and spot consistency—and yield—will finally stay where they belong.
If you have welding machine requirements, please contact Ms. Zhao
Founded in 2006, PDKJ is a professional supplier of welding automation solutions. The company has passed the ISO9001 international quality management system certification, has more than 90 officially authorized and applied national patents, and a number of core technologies in the welding field fill the technical gap at home and abroad. It is a national high-tech enterprise.
