Press Release
DRIVE CUTS COST OF ROTATIONAL WELDER
A specialist machine builder, was given a
tight time scale – and a tight budget – by Sheffield based heating
systems company, Trianco Heating Products Ltd, to come up
with a cost-effective solution for welding the ends of a tubular
heat exchanger. The solution, which required precision
control and two welding programmes, was only possible thanks to a
Commander SK variable speed AC drive from Control Techniques,
Emerson Industrial Automation at the heart of the machine.
“We were faced with a moderately complex task that required
different operating modes, but given a limited budget,” explained
Alex Wilson, managing director of Telford-based Automatic
Technologies International. “The two welding speeds required
dictated that a variable speed drive was required as well as
overall process control. However, the extra cost of even a
small PLC with its associated power supply and larger control box
would have made the solution too expensive. The answer was
simple. We used the on-board PLC functionality within a
Control Techniques Commander SK to provide two drive programmes and
on/off control of the TIG welding torch.”
This particular task, to produce a heater assembly for a central
heating boiler, is to weld a 22-mm pipe to a blank tube end, weld
the tube end onto an 80-mm tube, then complete the task by welding
a flange to the other end of the tube.
The machine devised by ATI comprises two plates that act as a jig –
one fixed and the outer one free to rotate using slewing bearings
between the plates – with an 80-mm central hole through both.
The rotating plate is belt driven by an induction motor controlled
by a 0.25 kW Control Techniques Commander SK. After selecting
the correct programme, the operator simply presses one button that
initiates the sequence – clamps on the outer plate fixing the tube
base or flange into place and the tube is placed into position in
the centre; the plate is reversed to top-dead-centre (detected by a
proximity switch), then the TIG welding torch swings into position
and the welding sequence starts. A small initial delay allows
a small pool of metal to form and the drive then rotates the plate
through 360° at a selected speed, plus a 5° overlap, to ensure gas
tightness of the pressure vessel.
When welding the flange and vessel end, the motor speed is 80
Hz, but for welding the smaller 80-mm pipe in place, the rotation
speed is much slower at 20 Hz to give the same surface speed for
welding. >>>>>>
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