Rolling, forming and connections
Pillow plates are welded flat. After welding they can be rolled like plate, held flat, or formed as a cone or head. Inflation can be before or after rolling. Connections are a separate workshop step. Keppels trains this sequence with the machine.
Figure: pillow plate rolling
When to roll
Two common shop sequences. One: weld flat, inflate, then roll to the tank radius. Two: weld flat, roll the uninflated panel, build the tank, inflate after assembly so forming does not crush the pillows. Heads and cones follow the second idea: weld in the flat, leave an unwelded band if the press needs it, form, install, inflate. Published practice includes roll radii above about 100 mm (3.9 in). A trough can combine straight walls and a rounded bottom.
How hard you may roll
A pillow plate rolls like ordinary sheet if the pattern can take the shear. Heavy rolling wants stronger circles (often double-welded circles). If the roll is too aggressive the welds can tear. After inflation a light pass can flatten a panel that must sit flat. Do not over-inflate a single-embossed base or the thick side dishes. An inflation table holds flat work. A 45° or 90° edge fold can take remaining oil-canning out.
Shrink and extra clamp strip
The welded top sheet shortens a little along the weld path. Operators mark expected circle rows and correct transport on the machine. Many layouts add a tear-off clamp strip of about 40–50 mm (1.6–2.0 in) so the clamps hold the top sheet. That strip comes off after welding.
Connections and headers
A small inflation nipple is often welded on a hole in the top sheet, or the cavity is reached through the base. After inflation the process connection can be a tube on the pillow, a castle-piece at a spot, a tube in the plate edge, or a header that joins several plates. Headers are cut to the inflated shape and welded on. Castle-piece and header detail is workshop practice, not a laser-parameter setting.
