Maintaining tighter control of steel tubing tolerances
Controlling quality and cost with cross-section
optimization
Three constraints affect the cross-sectional
dimensions of as-welded tube:
-
Outside diameter (OD)
-
Gauge (wall thickness)
-
Inside diameter (ID)
Manufacturers can control only two of these three
parameters. There will be one degree of freedom causing one of the
parameters to be a result of the other two. For instance, if the OD
and gauge are held constant, the ID will be a result of these two
parameters. All three factors cannot be controlled simultaneously -
a concept statisticians refer to as "degrees of freedom."
To illustrate the significance of the constraints
imposed by the "degree of freedom" concept, suppose a fabricator of
steel tubing has to put a tube over a mandrel to punch a hole, roll
a bead, produce a bend, or perform some other fabrication operation
on the tube.
An as-welded tube manufacturer can control only the
OD and gauge of the tube. since the tube is manufactured from the
outside by a series of rolls that ultimately produces the final OD
size of the tube, the ID varies by the combination of the final OD
and gauge. The ideal situation in a punching operation is to have
sufficient clearance between the ID of the tube and the OD of the
mandrel to allow the tube to slide easily over the mandrel, yet have
the least amount of diametrical clearance to reduce burrs and
maintain sufficient dimensional stability during fabrication.
 Download
complete article (658 KB)
Source: The Tube & Pipe Journal
|
