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Equipment Differences
Difference between a flattener, straightener, and leveler
Flattener
Design characteristics:
- Work rolls supported by bearings on the ends of the rolls only
- Normally fewer number or rolls (4 to 7)
- Relatively large diameter rolls
- Typically capable of 10% to 20% of material in yield
Operational characteristics:
- Only capable of removing coil set and maybe reduce some cross bow
- Typically used for heavier gage materials
- When working the material hard a flattener can actually induce edge wave
Straightener
Design characteristics:
- Work rolls are supported by backup bearings along the full face
- Normally a larger number of rolls (10 to 20+)
- Close roll spacing with smaller diameter rolls
- Typically capable of 50% to 70% of material in yield
- Normally designed for narrow strip (less than 36") but can be designed for wider strip
- In general a much more precision machine than a flattener
Operational characteristics:
- Removes coil set and cross bow and maybe some edge wave and center buckle
- Typically used for lighter gage materials but can be designed for heavy gage
- Rolls stay straight no matter how hard you work the material (within the machine design limits)
Shape Correction Leveler
Design characteristics:
- Work rolls are supported by backup bearings along the full face of the work rolls
- Backup bearing rails either top or bottom can be adjusted up and down individually to bow or bend the work rolls
- Normally a larger number of rolls (10 to 20+)
- Close roll spacing with smaller diameter rolls
- Typically capable of 50% to 80% of material in yield
- Normally designed for wider strip (greater than 36")
- In general a much more precision Machine
Operational characteristics:
- Removes coil set, cross bow, edge wave, center buckle, and combinations
- Machines have been built for all gage materials but more common for .015" to .250"
- Requires operator expertise to set up and operate properly
How bending the work rolls can correct strip shape
By bending the work rolls you can selectively work some zones of the strip (from edge to edge) more than other zones causing elongation. The basic principle is to elongate the short zones to match the length of the long zones.
Elongation occurs due to working the material and differential path length thru the leveler.
Typical roll bending to eliminate center buckle. The short edges are worked harder than the long center.
Typical roll bending to eliminate edge wave. The short center is worked harder than the long edges.
Tension Leveler
Design characteristics:
- Work rolls are supported by backup bearings along the full face of the work rolls top and bottom to keep them straight. Normally intermediate rolls are used also.
- Spread center distance between rolls with fewer number of work rolls, typically five
- Bridle sections before and after leveler section to pull very high strip tension through leveler. All material is stretched beyond yield point
- Leveler section is normally very long with the bridles, takes a lot of space
- Very expensive equipment and high operating cost due to the very high tension requirements
- In general a much more precision machine
Operational characteristics:
- Removes coil set, cross bow, edge wave, center buckle, combinations of defects, and internal stress. Can also remove some camber as well.
- Typically built for light gage material only.
- Normally does not require much operator expertise to run
