In steel coil strip processing operations, improve surface finish of products in coil production can almost be tied directly to improving the profit margin in coil production. This makes improving final product surfaces, and being able to control coil surfaces precisely, strategically important for the overall performance of a steel processing company.
Coil surfaces that do not meet spec, even though dimensionally the entire product is perfect, represent a massive operational loss.
Non-Woven Rolls For Surface Preservation
While much of the coil surface for a final product will depend on the processing line, one also has to consider how the coil is handled before it reaches the processing line to ensure that the surfaces are not marred through material handling steps. The main method discussed here for surface presentation of steel coils is nonwoven rolls.
The nonwoven rolls refers to any type of random orientation of the fibers for the formation of a cover sheet including paper. A woven product would be something like cloth and that's because the fibers are formed into a pattern of threads and then woven into the overall material. The nonwoven rolls could be made of either different densities of fibers and resins all to hold the fibers in place.
Steps for Preserving Surface Finishes
Rolls are cut from a sheet of particular material and formed together into a tube or cover that is mounted on a shaft with the strength required to exert correct pressure on the metal for whatever process and line speed is required.
The disc can be made of a number of different materials for different applications and could be bonded with resin, or perhaps not, depending on the overall surface presentation needed.
The bonding helps provide a uniformity across the entire cover and helps resist any gouging or tearing or deformation at the edge. Unfortunately, the cost of these nonwoven covers tends to be fairly high and a significant percentage of material has to just be disposed of because of wear.
It also requires different shafts than those for rubber or urethane or other types of resin rolls. Nonwoven rolls nonetheless to provide a reasonable price to performance value in certain coil processing applications.
The key performance characteristics of the nonwoven product are dependent on how the fibers and voids line up. Product tends to collapse at the contact level when the voids in the material disappear.
So long as this features is properly controlled, it provides a sufficient contact area that adds to wringing capability. Unlike either rubber or urethane that are solid and bulge under pressure, steel rolls are solid without resiliency and there will be no enlargement at a pinch point so they may work better with the nonwovens.
Voids from nonwovens also serve to absorb liquid from the surface and have somewhat of a vacuuming effect. These features of nonwovens with the shock absorbing voids allows some of them to last for months or even years. The main drawback to nonwovens is that it is based on resins and resins have vulnerability to chemicals often used in strip metal coil processing.
There are different types of rolls that have different effects on the final production finish that are important to consider. The squeegee roll is often used for cleaning the sections of processing lines in order preserve solutions that may be used for cleaning or for water washing the surface prior to another process.
Non-woven rolls are fantastic for wringing off the solution of the strip. This will ultimately help chemical solutions down the line that will no longer be diluted because of the squeegee rolls process. Application pressures could be somewhere in the neighborhood of 35 on a 150 pounds per linear edge and are similar to rubber.
Oiling/Deoiling rolls are similar to squeegee rolls but apply higher pressures and densities up to 500 pounds per linear edge. Oiling will typically take place at the exit end of the line for applying a controlled coating of oil.
A backup roll wringer is used typically in the aluminium sheet metal strip coil processing plants for removing aluminium oxides that may pollute coolants and other kinds of things.
A deflector roll is used at the exit end of the line for maintaining the pass line through the mill and providing a deflection into the recoiler. Deflector rolls are under substantial pressures and often wear out quickly.
A non-woven roll can help here by controlling the coating for the coil and eliminating any marketing caused by a roll slippage. And last but not least, an ironing roll is on the recoiler for keeping the strip tight to the previous wrap for assuring a properly rerolled coil.
If any one of these rolls has worn nonwoven cover or surface that impacts the material going through the line, the net result is material wastage because it falls outside of surface finish specifications.
Maintaining the proper surface finishes is one of the higher order activities of a steel strip processing line. It requires more maintenance for changing out parts then most of the other functions of the line.
For this reason it is important to understand the types of technologies that can impact the final surface qualities of the material passing through your processing line.To return from this Improving Surface Finish page to the Strip Metal Coil Processing Home page, click here.
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