Welding positioners

01

Check load and torque at your part's centre of gravity

Schweiss's POS TW welding positioner data sheet gives each model a load capacity together with the centre-of-gravity distances at which it applies: for example the POS-1TW carries 1 t with a centric load distance of 300 mm and an eccentric load distance of 200 mm, with a maximum rotating torque of 2,000 N·m and a maximum tilting torque of 3,000 N·m; the POS-10TW carries 10 t at 400 mm and 200 mm with 20,000 N·m and 40,000 N·m. Separate charts reduce the permitted load as centric or eccentric distance grows. [1]

Editorial calculation: the ratings are consistent with load × distance. For the POS-1TW, 1,000 kg × 9.81 m/s² × 0.2 m ≈ 1,960 N·m, matching its 2,000 N·m rotating torque at 200 mm eccentricity, and 1,000 kg × 9.81 × 0.3 m ≈ 2,940 N·m, matching its 3,000 N·m tilting torque at 300 mm. A 1 t part whose centre of gravity sat 400 mm off the axis would need about 3,900 N·m to rotate, nearly double the rating, so check your part and fixture's offsets against the torque figures, not just the weight. [1]

Give the supplier the heaviest part and fixture weight, the centre of gravity's distance from the table face and from the rotation axis, part dimensions and swing diameter, required rotation speed range and tilt angle, welding current, control type (pedal, remote, robot axis) and power supply.

02

Set rotation speed, tilt angle, table size and current

The POS TW range lists infinitely variable rotating speeds from 0.12–1.2 rpm on the 1 t model down to 0.02–0.2 rpm on the 8 t and 10 t models, a faster rewind speed, tilt angles of 0–135° (small models) or 0–130°, table diameters of 900–2,000 mm, maximum workpiece diameter at 90° tilt of 1,350–2,500 mm, and a welding current rating of 500 A, 700 A or 1,000 A. Features include a hand remote control and high-frequency protection. [1]

Editorial calculation: at 0.5 rpm a 1,000 mm diameter part moves π × 1,000 × 0.5 ≈ 1,570 mm per minute at its surface, so the slowest speed in the range sets the slowest travel speed achievable on small diameters and the fastest sets it on large ones.

Lemar, a supplier linked to this page, describes a 50 kg automatic positioner that replaced manual workpiece rotation to give stable low-speed rotation for precision parts. [2]

Robotic positioners are specified differently. Yaskawa India's sheet for the MOTOPOS PS500 single-axis servo positioner lists a 500 kg payload, 625 N·m torque, ±360° motion range, 125°/s maximum speed, repeatability of ±0.07 mm (1 arc minute), an allowable overhang of 308 mm, a 60 mm hollow shaft and a 185 kg weight, with motion coordinated with the robot so the part and torch hold their best posture at constant welding speed. It lists the sizing factors as inertia matching between motor, input and output drive, reducer backlash, motor torque curve and acceleration, and bearing loading. [3]

Editorial calculation: 125°/s is about 20.8 rpm (125 × 60 ÷ 360), more than ten times the 1.2 rpm top speed of Schweiss's 1 t manual-weld model, because a servo positioner also indexes the part between welds; and 1 arc minute equals 0.07 mm at about 240 mm radius (0.07 ÷ tan 1′), so ask at what radius a repeatability figure applies. [3] [1]

Koike Aronson's sizing guide gives the method behind both ratings. Its HD400 gear-driven positioner is rated for 40,000 lb (18,140 kg) with the centre of gravity 12 in (300 mm) from the table; tilt torque is the weldment weight times the distance from the table surface to its centre of gravity plus the positioner's inherent overhang, and rotation torque is the weight times the offset of the centre of gravity from the table axis, each to stay below the capacity plate values. It warns that swing clearance above the floor at full tilt is a frequent oversight, uses variable-frequency drives with dynamic braking to hold constant speed on eccentric loads such as an elbow on a pipe, and works an example: a 60 in (1,520 mm) part welded at 12 in/min (5 mm/s) needs 12 ÷ 188.5 ≈ 0.064 rpm, or 3.84 revolutions per hour. [4] Editorial calculation: 0.064 rpm is below the 0.12 rpm lowest speed of the 1 t Schweiss model above but within the 0.02–0.2 rpm range of its 8 t model, so the speed range, not only the load, decides the size for large-diameter work. [4] [1]

03

Compare what suppliers offer

The suppliers linked to this page list welding positioners; their cards link to the pages reviewed.

Ask any supplier for the load–distance chart for centric and eccentric loads, rotating and tilting torque, speed range and rewind speed, tilt angle and drive, table diameter and slotting, welding current rating, swing diameter at 90°, brakes, controls or robot-axis interface, and dimensions.

04

Trace the positioner parts

This is a functional reference built from the sources cited; it is not one maker's specification.

05

Fill the specification fields with values for your parts

A welding positioner quotation needs values for your parts and process. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the part, offsets and process data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Part: [weight with fixture; dimensions]
Offsets: [CG distance from table; eccentricity]
Motion: [rotation speed range; tilt angle]
Welding: [process; current]
Control: [pedal; remote; robot axis]
Site: [power; floor; anchoring]

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