Bending beams in-house saves a week

A 2000kN bending machine has cut delivery lead time for each 20 tonne erectable package of steel to a building site by one week - the time it used to subcontract out the work.

Architects are increasingly specifying cambered steel members for buildings, as compared with straight girders they can support a greater load for a given cross section.

Recognising this trend, Billington Structures (part of the AMCO Group) has installed in its Wombwell, Barnsley factory a Swiss-built Stierli-Bieger 2000kN bending machine from Press and Shear Machinery.

By having this facility in-house, lead time for delivery of each 20 tonne erectable package of steel to the building site has been cut by one week - the time it used to take to send the relevant beams to a subcontract facility for cambering.

A further benefit to Billington is that instead of having to drill and cope the steelwork by hand after it comes back from the subcontractor, the company is able to machine the girders in one semi-automated process involving sawing, drilling and coping followed by cambering.

Additionally, shorter cambered sections may be produced by bending a full length beam and sawing it afterwards - a process that was impracticable when subcontracting out the cambering.

The hydraulic, horizontally-acting press was uprated in the UK by Billington, which manufactured an eight metre back beam to Stierli specifications to replace the standard five metre unit.

This is the part of the machine that carries the jacking points against which the steelwork is pressed by the ram to create the camber.

Being able to spread the jacking points as far apart as 7.9 metres allows larger section steel to be cambered.

Maximum dimensions of grade 335 steel I-beam that may now be processed are 762 x 267 x 197mm, up from 610 x 229 x 113mm when using the standard back beam.

Angle iron, channel and welded fabrications are processed in the Stierli 2000RP bender in addition to I-beams.

While cambering is the main task and the reason for investing in the machine, with payback now anticipated well inside the originally envisaged two years, straightening jobs are also regularly carried out.

The capability of the Swiss machine to perform the latter function set it apart from the other two shortlisted benders and the resulting flexibility was the reason for Billington choosing the Stierli option.

Previous straightening procedures involving the use of a jacking frame, or localised heating and the need to take and record temperature measurements, have consequently been eliminated.

A further application of the Stierli machine is the manufacture of bent plates, cleats and other attachments associated with the erection of steel buildings.

According to Billington's production director, Walt Bell, in the six months from the machine's June 2001 installation date, the Stierli 2000 RP cambered more than 650 beams for three major building projects at Kingfisher, Redditch; KeyMed, Southend; and BP Chemicals, Hull.

He describes the machine's performance as "very reliable".

Maximum camber so far produced has been 35mm in a 10 metre beam, a process that took seven minutes and required three bending points involving initial placement of the steel and two further movements.

Larger cambers may be achieved by choosing more bending points and / or pressing the beam in several passes.

Infinite adjustment of the ram stroke results in accurate cambering and minimises the risk of buckling the web and thus ruining a girder.

To support the beams, Billington has installed roller stands including one with an operator handle, so once the steel has been craned into position, use of the machine is single-handed.

This is a more economical approach than tying up the crane operator to move the beam between each successive pressing action.

Concluded Mr Bell, "Operation of the Stierli bender was taught to two of our people in a single day's training, and the machine has proved easy to use.

"A smaller Stierli bender has been installed at our Bristol factory for many years, straightening plates as they come off a plasma cutter, so we have high expectations of long service life from the 2000RP.

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