Welding Positioner

Overview

A welding positioner exists because weld quality depends heavily on gravity. A weld made in the flat position, torch pointing down, molten pool held in the joint by gravity, is faster, cleaner, and easier to make sound than the same joint welded vertically or overhead. Rather than asking the welder or robot to chase a fixed joint around a workpiece, the positioner rotates and tilts the workpiece so each joint is presented flat.

The machine is two powered axes stacked on a Base Frame. The Tilt Drive tips the table from horizontal (0°) through vertical (90°) to 135°; the Rotation Drive spins the Faceplate Table continuously. With both axes, a pressure-vessel head, a pipe flange, or a fabricated bracket can be walked through all its welds without ever unclamping it.

How it works

Both axes use the same drive principle: an AC Servo Motor driving a Worm Gearset in an oil-filled Gearbox Housing. The worm geometry is the safety feature, the Worm Shaft's lead angle is below the friction angle against the bronze Worm Wheel, so the gearset cannot be back-driven. A tonne of workpiece tilted to 135° stays exactly where it is if power fails, with a Relay-controlled motor brake as a second layer. The table rides on a Slewing Bearing, a large-diameter bearing that takes thrust, radial load, and the overturning moment of an off-center workpiece in one element; the tilt axis pivots on a forged Tilt Trunnion in paired Ball Bearings.

The Faceplate is a T-slotted steel plate on a splined Table Hub. Fixtures, three-jaw chucks for pipe work, or the workpiece itself bolt to the slots with standard Fastener Set hardware. Capacity ratings always state a center-of-gravity offset, 1,000 kg at 150 mm CoG is a very different moment load from 1,000 kg at 400 mm, and exceeding the moment rating wears the worm wheel and slewing bearing long before anything visibly breaks.

Weld current return

The most commonly misunderstood subsystem is the Grounding System. Arc welding pushes hundreds of amps through the workpiece, and that current must return to the power source. If the return path is left to chance, it flows through the slewing bearing and gear mesh, micro-arcing across rolling contacts and destroying them within months. The positioner therefore provides a deliberate rotary return: a copper Ground Ring on the spindle, swept by spring-loaded Ground Brushes rated for 600 A, wired through a heavy Wire Bundle to the Ground Clamp where the welder's return cable lands.

Control

For manual welding, the operator works from the Control Pendant: a Speed Dial sets rotation speed, the Button Set handles jog, direction, and preset positions, and an Microcontroller in the pendant talks to the cabinet over the pendant cable. The Foot Switch matters most in practice, a circumferential pipe weld is made by holding the torch still and letting the part rotate, and the foot switch starts and stops rotation while both hands stay on the torch. Travel speed equals surface speed at the weld radius, so the dial is effectively the welder's travel-speed control.

In robot cells, the positioner becomes external axes of the robot controller. The two Servo Drives in the Electrical Cabinet, each an IGBT Power Module inverter with its own loop-control Microcontroller, accept position commands over the robot interface, and the absolute Encoders on both axes let the robot interpolate torch and table motion together. This coordinated motion is what allows a continuous weld around a saddle joint: the table rotates and tilts under the part while the torch barely moves, keeping the pool flat the whole way around. Repeatability of ±0.05° holds the joint within the arc-sensing window.

The cabinet itself is an IP54 Cabinet Enclosure, weld shops are full of conductive grinding dust that destroys open electronics, with a 24 V Power Supply for logic and Terminal Blocks for field wiring.

Installation

The Base Weldment anchors to the floor through four Leveling Foot points. Anchoring is not optional at rated load: a 1,000 kg part tilted past 90° puts its full weight ahead of the base footprint, and the anchor bolts are what keep the machine on the floor.