Insights · Reference
Six different welders show up in a duct shop, each for a different joint. This reference compares them on model, material thickness, welding capacity and weight, with the figures taken verbatim from the SBKJ Product Catalog 2026. For the welding methods and standards behind them, see the welding methods guide; this page is the machine spec sheet.
What separates these machines is the joint they make and the gauge they reach. Resistance welders (seam, spot, elbow) are rated in KVA; the stitch welder in kW; the laser in watts. The table keeps each figure in the unit the catalog uses.
| Welder | What it welds | Model(s) | Material & thickness | Capacity / power | Weight |
|---|---|---|---|---|---|
| Seam welder | Continuous gas-tight lap seam (resistance roller) | SBFN-35 / 55 / 75 / 100 | 0.4–1.0 / 0.4–1.2 / 0.4–1.5 / 0.4–2.0 mm | 45 / 55 / 75 / 110 KVA | 328–478 kg |
| Stitch welder | Intermittent seam on round duct Φ100–Φ1000 mm | SBSW-30-2Z | 0.4–1.0 mm | 40 kW | 850 kg |
| Spot welder | Single spot / tack welds | SBDN-40 | 1.2 + 1.2 mm | 40 KVA | 236 kg |
| Elbow welder | Segment seams on elbows Φ80–Φ250 mm (45°/90°) | — | GI/CRS 0.4–1.0, SS 0.4–0.8 mm | 45 KVA | 950 kg |
| Medium-frequency welder | Heavy-gauge stainless, carbon, aluminium, GI | — | ≤3.0 mm SS/carbon · 2.5 Al · 2.0 GI | MF inverter | — |
| Handheld laser welder | Portable laser welds on fittings & thin sheet | — | Thin sheet | 2000 W (220 V) | Portable |
Source: SBKJ Product Catalog 2026, manufacturer nameplate specifications. Resistance welders rated in KVA; most machines run 380 V / 50 Hz / 3-phase (the handheld laser runs 220 V). Seam-welder thickness/KVA/weight are listed per model in the same SBFN-35/55/75/100 order.
Seam welder — the workhorse for a continuous, gas-tight longitudinal lap seam on rectangular and round duct. Pick the SBFN model by your heaviest gauge: SBFN-35 for light 1.0 mm work up to the SBFN-100 for 2.0 mm at 110 KVA.
Stitch welder — for round duct, the SBSW-30-2Z lays an intermittent seam from Φ100 to Φ1000 mm at about 2 m/min. Lighter and faster than continuous seam welding where a fully gas-tight seam is not required.
Spot welder — the SBDN-40 makes single tack welds (1.2 + 1.2 mm), used to hold panels and brackets before final joining.
Elbow welder — purpose-built to weld the segment seams of round elbows from Φ80 to Φ250 mm at 45° or 90°, at 3–9 m/min.
Medium-frequency welder — when you weld heavy gauge or stainless, the MF inverter reaches 3.0 mm stainless and carbon, 2.5 mm aluminium and 2.0 mm galvanised, with cleaner heat control than a mains-frequency machine.
Handheld laser welder — a portable 2000 W laser for fittings, repairs and stainless feature work where a fixed machine cannot reach. Runs on a 220 V supply.
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Six: seam (continuous gas-tight lap seam), stitch (intermittent seam on round duct), spot (tack welds), elbow (segmented elbows), medium-frequency (heavy gauge / stainless) and handheld laser (portable). SBKJ supplies all six.
The medium-frequency welder: up to 3.0 mm stainless or carbon, 2.5 mm aluminium, 2.0 mm galvanised. Among resistance seam welders the SBFN-100 reaches 0.4–2.0 mm at 110 KVA.
A seam welder makes a continuous, gas-tight resistance weld between copper rollers at 0.5–3 m/min. A stitch welder lays intermittent welds on round duct (Φ100–Φ1000 mm) at about 2 m/min — faster and lighter where a fully sealed seam is not needed.
Most run 380 V, three-phase, 50 Hz. Resistance welders are rated in KVA (seam 45–110, spot and elbow 40–45); the stitch welder draws 40 kW. The handheld laser is the exception: 220 V single-phase, 2000 W.
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