Squeeze Time: The Most Misunderstood Parameter
Why it's not "clamping time" and how to adjust it correctly
Squeeze Time is one of the most misunderstood parameters in resistance welding, starting with its translation into Spanish. It's not "tiempo de apriete" (clamping time), but "tiempo de cierre" or "tiempo de aproximación" — the time the electrodes take to close and stabilize before current flows. Insufficient squeeze time is a hidden cause of material expulsion and inconsistent welds.
Technical Definition
According to AWS standards, Squeeze Time is: "The time interval between the start of electrode movement to close and the start of welding current."
In simple terms: it's the pause the machine gives so the electrodes close, compress the material, expel surface oxides, and stabilize before starting to apply current. Without sufficient squeeze time, current starts flowing when electrodes are still moving or contact isn't uniform.
Visual Demonstration: Correct vs Incorrect Squeeze Time
These videos (recorded at ALCAVIL's Monterrey facility) clearly show the difference between a correct and incorrect squeeze time on 1.2mm low carbon steel:
✓ Correct Squeeze Time
Squeeze Time: 12 cycles — Clean weld, no expulsion, consistent nugget. Electrodes close completely before current flows.
❌ Insufficient Squeeze Time
Squeeze Time: 3 cycles — Material expulsion, sparks, crater on electrode face. Current started before electrodes were fully closed.
Typical Values per Application
Recommended Squeeze Time by Process (at 60Hz)
| Application | Squeeze Time (cycles) | Squeeze Time (ms) |
|---|---|---|
| Standard spot welding (low carbon steel) | 10-15 cycles | 170-250 ms |
| Coated steels (galvanized, Zintec) | 15-20 cycles | 250-330 ms |
| AHSS/UHSS (Advanced High-Strength) | 20-30 cycles | 330-500 ms |
| Projection welding (nuts/studs) | 15-25 cycles | 250-420 ms |
| Cross wire welding (tungsten electrodes) | 8-12 cycles | 130-200 ms |
Note: MFDC (DC inverter) equipment uses millisecond settings; AC equipment uses cycles. 1 cycle at 60Hz = 16.67ms.
Diagnostic Signs of Insufficient Squeeze Time
Metal "explodes" outward when current starts before electrodes fully close. This creates spatter and craters on electrode faces.
Weld quality varies from piece to piece because contact point changes with each cycle.
Characteristic "rings" of alloying with zinc (galvanized steel) or aluminum (aluminized steel) on electrode face.
Electrode face grows irregularly and requires more frequent tip dressing.
How to Adjust Squeeze Time
Step 1: Start with the minimum value in the table above for your application.
Step 2: Make test welds and observe if there's expulsion or sparks. If so, increase by 3-5 cycles.
Step 3: Perform destructive testing (peel test) to verify nugget size and penetration are correct.
Step 4: If weld is cold or undersized, don't reduce squeeze time — increase current or weld time.
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