The invention discloses a method for manufacturing a double-spiral steel staircase without a middle standing pillar. The staircase is formed by
welding stairs, stair fixing
layers and a staircase platform. The method comprises the following steps: carrying out the three-dimensional
lofting by using a computer, so as to decompose the staircase into bent plate components; calculating the length, width, bending
radius and planar
cutting line position of each bent plate component; feeding and
cutting materials by a numerical-control
cutting machine; manufacturing the bent plate components; checking the bent plate components; manufacturing a jig; lifting the bent plate components onto the
assembly jig, to check and locate the bent plate components, and
welding the bent plate components into box-type components; lifting the stair fixing
layers onto the
assembly jig, so as to locate the stair fixing
layers, then, lifting the staircase platform onto the stair fixing layers to
mount and fix the staircase platform, and carrying out the integrity acceptance;
numbering the
stairs, the stair fixing layers and the staircase platform, then lifting the
stairs, the stair fixing layers and the staircase platform off the
assembly rig, sand-washing and
coating; and carrying out the integral installation. By using the method for 'breaking up the whole into parts', the invention increases the accuracy of the
single component, ensures the integrity of the double-spiral steel staircase and guarantees the overall quality.