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Spot Welding Machine Producing Weak Welds Or Incomplete Welds? Here Are 4 Core Reasons And Their Solutions.
Views: 0 Author: Site Editor Publish Time: 2025-12-17 Origin: Site
In metal-working and high-volume manufacturing, spot-welding machines are everywhere—automotive, white goods, hardware. Yet almost every shop floor sooner or later sees joints that look good but peel apart with little force: cold welds, partial fusion, “false” welds. Rework soars, throughput falls and quality reputation suffers. The root causes are almost always the same four system-level factors. Below they are unpacked with field-proven fixes.
Welding current too low or unstable
Why it happens
Current is the energy source. If the value is marginal or the pulse wanders, the nugget never reaches full plastic range and the bond is only skin-deep. Typical sources are an ageing power source, loose kick-less cabling, or an inverter that can no longer compensate for line fluctuation.
What to do
Inspect the complete power circuit—source, bus bars, shunts, joints and tips—for corrosion or looseness; torque and clean as required.
Size the schedule to the stack-up; when in doubt raise the kA or switch to a mid-frequency inverter supply that can hold ±2 % repeatability.
Replace aged contactors, IGBT modules or welded relays before they become resistive and steal energy.
Electrode force too low or unbalanced
Why it happens
Force collapses the contact resistance and lets current flow through a predictable path. If one side is soft, the couple rocks, local resistance skyrockets and heating becomes patchy.
What to do
Calibrate the cylinder, hydraulic servo or pneumatic regulator; aim for < ±5 % force variation side-to-side.
Check electrode alignment, shank straightness and tip dress; a 2° tilt can cut effective force by 15 %.
On thin or soft alloys, lower force slightly to avoid expulsion, but never below the minimum that gives full facial contact.
Part surface or material issues
Why it happens
Oil, mill scale, rust, zinc crystals or an oxide film all raise and randomise contact resistance; aluminium or high-strength steels add their own metallurgical quirks.
What to do
Degrease, brush or lightly abrade the faying surfaces before the parts reach the fixture.
Store coils in a dry, clean area; keep zinc-coated blanks separated to prevent white-rust transfer.
For aluminium, use a weld schedule with upslope and forge time; for coated steels, increase current 5–15 % and shorten weld time to burn through the coating without over-heating.
Wrong weld schedule or sloppy handling
Why it happens
Even perfect hardware will cold-weld if current, time and force are mis-matched or if electrodes are mushroomed, fixtures loose and operators inconsistent.
What to do
Build a parameter matrix: “material → thickness → force → current → time → hold”. Lock it in the controller and password-protect.
Write a one-page SOP: tip dress every 250 welds, change tips at 500 µm mushroom, check fixture pins daily, verify part gap < 0.2 mm.
Use built-in monitors—current, voltage, displacement, dynamic resistance—to alarm the moment a weld falls outside the proven window.
Closing note
A cold weld is rarely a single fault; it is the intersection of shaky current, weak force, dirty material and loose discipline. Chase each vector systematically, document the winning recipe, and the line will deliver repeatable, finger-proof joints while scrap and rework fade into the cost baseline.
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.
