Bullnosing Cranking and Curving for Roofing
Clotan Steel’s IBR, Corrugated, Wide-span and Craft-Lock® sheets can be bullnose, cranked, curved, smooth curved to customers’ requirements.
Bullnoses and Centre Cranks
Bullnosing and centre-cranking of a profiled sheet incorporate lateral rib indentations pressed in at a uniform distance of 25mm. Standard bullnoses are made with narrow flute uppermost and the bend away from the angular inclination. Reverse bullnoses are made with the bend into the narrow flute. Bullnoses and cranks can be at the end of a sheet or at any position along the length. Bullnoses and centre cranks can be manufactured in radii ranging from 350mm to 800mm for bullnoses which are bent through 0 – 135°. High tensile material can only be bull nosed and cranked to a minimum radius of 450mm.
Larger RADII will be Classified as a Forward Crank.
The maximum sheet length which can be bullnose is 15m, with a maximum height of 2m. The minimum run-out from the bullnose is 30mm on one side with a minimum of 500mm on the other side of the sheet. It is important to clearly identify the critical end of the bullnose in order to ensure that consistent lengths are supplied to the customer. The maximum height (after cranking) of centre and off-centre cranks which can be manufactured is 2m, with a limitation of 10m total sheet length, due to handling and transport limitations. (Height in this case is from ground level to highest point of bullnose sheet.)
Download Bullnosing and Cranking product brochure
IBR, Widespan and Corrugated material can be crank curved with the same process used for bullnosing, but with manual handling and with an increased distance between indentations in order to achieve the larger radius. In the case of pre-painting sheeting the colour can be specified on either side of the sheet. Due to the manual process involved, bullnoses will be priced as curves when the radius exceeds 800mm. The maximum height of curves which can be handled is 2m, with a maximum sheet length of 10m. (Height in this case is from ground level to highest point of bullnosed sheet.)
In addition to other processes described above, Corrugated sheets can be curved using a rolling process to achieve a smooth rolling finish on the sheet. High tensile material (550 MPA) is not suitable for curving due to the hardness of the material. It is therefore essential that only 0.58mm and 0.80mm material be used for smooth curving. The minimum radius for curving on 0.58mm ISQ300 material is 900mm and on 0.80mm ISQ230 material it is 600mm. When tight bend radii are specified edge ripple on the roof sheets might prevail. When only a part of the sheet is curved and bullnose slight crease marks on the sheets can be expected.
Sheet length is limited to 10m with a maximum height of 2m. (Height in this case is from ground level to highest point of bullnose sheet).