WM5050: the 5 m class, where deflection becomes the design driver
Column-and-boom manipulators scale badly. A boom that is stiff at 2.5 m of reach is a spring at 5 m, and the consequences are not cosmetic: the head drops, arc length changes, and the bead that was 10 mm wide at the near end of the seam is 14 mm at the far end. The WM5050 sits in the 5 m boom / 5 m column class, which is the size where the structure stops being a bracket and becomes a piece of machine-tool design.
That class is chosen for wide or tall work: large diameter vessels welded from the outside with the seam at 3–4 m height, box girders, wind tower cans, and pressure equipment where the joint is simply too far from the floor for a smaller machine.
What changes at 5 m
1. The boom is a box, and it is counterbalanced
Deflection of a cantilever goes with the cube of length, so doubling reach from 2.5 m to 5 m multiplies it by eight before any change in section. Two measures follow: the boom is built as a deep welded box rather than a tube, and it is counterbalanced so the column load does not swing from a compression to a tension case as the boom extends. A counterweighted boom keeps the column stress roughly constant through the stroke, which is what permits a lighter column.
2. The column needs restraint, or a second column
At full extension the moment applied to a single column is large. Two answers are used: a column of substantial section with a properly grouted and bolted base, or a portal arrangement with two columns and a bridge between them. The portal removes the cantilever moment entirely at the cost of floor space and of the ability to serve stations on both sides.
3. Travel becomes a tolerance problem
A WM5050 is normally a travelling machine — it moves along a rail to serve several stations. Every metre of rail adds an opportunity for the head to be somewhere other than where the programme expects. Rail straightness, level, and the rack-and-pinion or friction drive's repeatability all become weld-quality parameters. On a TIG or a narrow-groove SAW job, 2 mm of rail settlement is a defect generator.
Head packages at this scale
The machine's job is to hold the head steady; the head package at 5 m reach usually includes:
- Submerged-arc head with flux hopper — the standard for thick-wall vessels, with flux recovery mounted so the recovered flux returns without a manual step.
- Motorised cross-slide and oscillator — fine positioning without moving the boom, plus weave for wide caps.
- Power-driven head rotation — so the same head welds a girth seam looking down and a longitudinal seam looking sideways.
- Seam tracking or a weld camera — at this reach the operator cannot see the arc directly, so feedback is not optional.
- Cable and hose management — a festoon or cable chain rated for the full travel, because a snagged welding lead at 4 m height is how machines get damaged.
Choosing between WM12 and WM5050 class
| Factor | WM12 class (smaller) | WM5050 class |
|---|---|---|
| Seam height above floor | Moderate | High — needs 3–4 m working height |
| Boom reach | Shorter, stiffer per unit length | Long, requires box section and counterweight |
| Internal welding | Normally the primary duty | Possible, but boom section limits internal access |
| Stations served | One to two | Several, along a rail |
| Foundation | Standard slab | Engineered foundation and rail bed |
| Cost driver | Head package | Structure, rail and foundation |
The mistake in this class is buying reach that is never used. A machine sized for the largest vessel in the shop runs, for most of its life, at half extension with a fully counterweighted boom and a rail to maintain. Sizing on the actual seam envelope — the highest joint, the furthest joint, and the diameter range — keeps both the price and the maintenance burden down.
Technical data: WM5050 welding centre
The WM5050 is normally supplied as a complete welding centre rather than a bare manipulator — column and boom, seam tracker, submerged-arc system, flux handling and a matched rotator, specified together so the axes and the process are compatible.
| Item | Specification |
|---|---|
| Structure | Movable and revolving column-boom |
| Applicable vessel diameter | Φ630 – 5,000 mm |
| Boom travel stroke | 5,000 mm |
| Boom travel speed | 100 – 2,000 mm/min (inverter) |
| Boom elevation stroke | 5,000 mm |
| Boom elevation speed | 1,050 mm/min |
| Column revolve | ±180°, manual, on heavy-duty cross-roll bearing |
| Boom droop along horizontal travel | 2 mm/m |
| Trolley travel speed | 0.12 – 1.20 m/min |
| Operator platform | Fitted from WM5050 upward; not available on smaller models |
KB-10 seam tracker (optional)
| Parameter | Value |
|---|---|
| Detection range | 100 mm |
| Detection speed | 200 mm/min |
| Detection accuracy | ±0.3 mm |
| Load capacity | 100 kg (two welding guns mounted in parallel) |
| Power supply | AC 220 V |
DC-1000 submerged-arc system (optional)
| Parameter | Value |
|---|---|
| Rated welding current | 1,000 A |
| Idle voltage | 75 V |
| Duty cycle | 100% |
| Current range | 200 – 1,000 A |
| Wire diameter | 3 – 6 mm |
| Welding speed | 15 – 75 m/h |
FRU80 flux feeding and recovery system
| Parameter | Value |
|---|---|
| Recovery distance | ≤ 16 m |
| Recovery speed | 12 kg/min |
Matched SAR20 welding rotator
| Parameter | Value |
|---|---|
| Max load capacity | 20 t |
| Workpiece diameter range | Φ500 – 3,500 mm |
| Roller | Steel, all-roller, Φ350 × 120 mm |
| Rotation motor | 1.5 kW |
| Rotation speed | 0.1 – 1 m/min, adjustable |
| Trolley motor | 0.75 kW |
Structural details that explain the droop figure
The 2 mm/m droop is not a design target so much as a consequence of the construction, and it is worth knowing what produces it. Column and boom are rectangular-section, double-rail beams, welded, stress-relieved and then machined — the stress relief is what stops the beam moving after machining. Eight sets of control rollers on the saddle, three rollers per set in an eccentric adjustable arrangement, contact the rails on three sides. That is what keeps the boom travelling without shudder at the 100 mm/min end of the speed range, where stick-slip is otherwise unavoidable. Boom elevation runs on an A.C. braking motor through a chain and sprocket with counterbalance, and a ratchet-type anti-drop unit on the column protects against chain failure — the safe-load question on a manipulator is never the drive, it is what happens when the drive fails.
Specifying a WM5050
Send: the workpiece envelope (diameter, length, seam heights), the heaviest head package the machine must carry, the number and position of stations along the rail, welding process and whether flux recovery is needed, the operator's required access and platform arrangement, and the civil condition of the floor. From those we confirm boom and column stroke within the 3–12 m WM range, drive type, and the rail and foundation requirements.
Minimum order quantity is 1 set. Standard machines ship in 30–50 days after deposit; travelling and multi-station configurations are scheduled in the technical proposal. Payment terms are T/T; trade terms are FOB, FCA or CIF. Core ranges are CE compliant and supplied against a certificate of compliance.
Manipulators are supplied under the BIQEE brand by DESAN ELECTRIC LTD, with turning rolls under DESAN and combination welding machines under ZAULUX. DESAN ELECTRIC LTD has served 1,000+ customers in 20+ countries over 20+ years, with welding engineering experience since 1997. For the general selection criteria, see welding boom selection; for the internal-welding configuration, see WM12.