Troubleshooting guide › Process troubleshooting › Spot welding problems
A spot weld is made by three things in balance: current, time and electrode force. Nearly every spot welding fault is one of the three out of balance, or electrodes that are worn, dirty or misaligned. The test is simple: a peel test that tears a round button out of one sheet is a good weld. This page covers pedal, pneumatic and hanging spot welders on steel, stainless and coated sheet.
Reviewed by the Cruxweld technical team, October 2026. Settings are starting points to confirm on a test piece; acceptance is decided by the code or drawing the job is built to. Checks marked “call” are for our technical team.
| Setting | Too low | Too high |
|---|---|---|
| Current (tap switch or % heat) | Weak weld, no nugget, sheets peel apart | Expulsion (sparks), holes, deep indentation, electrodes stick |
| Weld time (cycles) | Weak weld | Indentation, burnt surface, electrode wear |
| Electrode force (spring or air pressure) | Expulsion, burnt marks, sticking, inconsistent welds | Deep indentation, weak weld because contact resistance is too low |
| Squeeze time | Weld starts before full force: sparks | Slow cycle, no other harm |
| Hold time | Nugget not forged, cracks and voids | Slow cycle; electrode marking |
Sequence: squeeze (force builds), weld (current flows), hold (force stays while the nugget freezes), off. If the machine has only a weld timer, give it a half-second of foot pressure before the switch point and hold the pedal down a moment after the weld.
Current too low, time too short, worn or mushroomed electrodes spreading the current over a bigger area, electrodes misaligned so only an edge touches, dirty or oily sheets, low supply voltage or a thin supply cable.
Current too high for the force, force too low, dirty sheets or scale, electrode face too small or badly shaped, sheets not in contact (gap), weld started before full force.
Tip too small, time too long, current or force too high.
Current too high, time too long, dirty tips, poor cooling.
Dirty or worn tips, no cooling, current too high for the force, coated (galvanised) sheet without extra force.
Electrode wear through the batch, supply voltage swinging as other machines start, sheets of mixed cleanliness.
Hold time too short so the nugget is not forged while it freezes, excessive current.
Tips not aligned; arm deflecting under force; one tip worn more.
| Symptom | Likely cause | What to do |
|---|---|---|
| Power lamp off | Supply, main switch, fuse | Check supply and fuse |
| Pedal down, electrodes closed, no weld, weld lamp off | Initiation switch not reached (force too low) or faulty; timer or its fuse | Increase spring tension so the switch point is reached; check the timer fuse |
| Weld lamp on, no weld | Oxidised arm seats or electrode tapers, loose secondary connection, tap switch contact | Clean seats and tapers with fine abrasive paper; tighten secondary bolts; check the tap switch |
| Electrodes, arms or transformer hot | No or low cooling water, blocked passages, blocked transformer vents, duty cycle exceeded | Open water and check flow; flush passages; clean vents; pause between welds |
| Weld weak on a hot day or long run | Transformer heating raises resistance; duty cycle exceeded | Check cooling; slow the rate |
| Pneumatic machine: slow or weak stroke | Air pressure low, FRL filter blocked, cylinder seal worn | Set pressure; drain and clean the FRL; service the cylinder |
| Weld only sometimes | Foot switch or initiation switch intermittent; loose control plug | Check switches and plugs |
| Sheets | Tip diameter | Tap / heat | Weld time |
|---|---|---|---|
| 0.3 + 0.3 mm | 3 mm | Tap 1 | 5 cycles |
| 0.5 + 0.5 mm | 4 mm | Tap 1-2 | 5-10 cycles |
| 1.0 + 1.0 mm | 5 mm | Tap 2-3 | 10-15 cycles |
| 1.5 + 1.5 mm | 6 mm | Tap 3-4 | 15-25 cycles |
| 2.0 + 2.0 mm | 7 mm | Tap 4-5 | 25-35 cycles |
| 3.0 + 3.0 mm | 8.5 mm | Tap 6 | 35-50 cycles |
Typical for a 10-15 kVA pedal spot welder with standard arms; 50 cycles = 1 second. Tap numbers are not equivalent between models: the same tap on a different machine or with longer arms gives a different current, so confirm every setting with a peel test on your own machine.
You cannot, fully. Peel-test a sample at the start of each batch and after each dressing; in production, a consistent small indentation with no sparks and no discoloration is the sign that the settings are still right.
Longer arms increase the secondary loop and its impedance, so less current flows at the same tap. Select a higher tap, or shorten the arms if the job allows.
Up to about 3:1 ratio. Put a larger tip on the thick sheet and a smaller one on the thin sheet so the nugget forms at the interface.
Lamps, fault codes and the checks an operator can do outside the cabinet, for the machines this page applies to.
The machine must deliver enough current for the sheet thickness with the arm length you use: longer arms mean less current at the same tap. A timer with separate squeeze, weld and hold settings (and for pneumatic machines a pressure regulator) is what allows a repeatable weld. Water cooling is not optional on production work. Made in India, with spares available.
Send a photo of the weld or cut, your machine model, consumable and plate thickness. Our technical team replies on WhatsApp with the likely causes and the next checks to make.
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