Can Prepainted Metals Be Formed Successfully?
CLEVELAND, OHIO — Many manufacturers may be aware of the cost saving and production time benefits of using prepainted metals in their manufacturing process, but fear that painted metal can not easily be formed without damaging the surface. The fact is, coil coated metal can be formed, even with extreme bends and folds, with no damage, loss in surface quality or beauty. The prepainted metal can be formed and shaped with a finish that is actually superior to post-paint.
The National Coil Coating Association (NCCA) offers insight into how to use prepainted metals and forming successfully.
Unlike post-painting processes, prepainting and forming work by first precleaning, pretreating, prepriming and prepainting the metal, then forming it after these processes have taken place. The paint layer is often more flexible than the underlying metal substrate and is more durable. This is because post-painted surfaces often suffer from dirt and oil residue, uneven application, and other imperfections.
Prepainted metal can be adapted to fit most product designs that currently use bare flat sheet or coil stock with only slight modifications. The three most important considerations are: flexibility, mar resistance, and dimensional fit with the production equipment.
Flexibility is determined by the combination of both the substrate and the coating system that is applied. Coaters conduct rigorous flexibility tests, called “T” bend tests, on the precoated metal to ensure the final product meets flexibility requirements. Often, the coating that is applied is more flexible and forgiving than the metal itself.
To avoid additional cost and the possibility of altering the performance, be careful not to over-specify the coating requirements. Marring of the finished surface during forming usually comes from rough dies that gouge and scratch, insufficient tooling clearance, or poor equipment alignment. These forming issues can be addressed with proper engineering.
Coil coated metal can usually be formed using the same tooling and production presses currently running in most production rooms, however it is important to ensure the prepainted product matches the dimensions of the production equipment. Dimensions for coils include width, thickness, weight, orientation, and inner and outer diameters. For sheets, measure the length, width, thickness and number of sheets. In both cases, keep in mind that the coating can add as much as 10% to the thickness of the bare substrate depending on the starting gauge.
Be sure to specify clearances and tolerances correctly, otherwise it could lead to a heavy burr scratching on the prepainted surface. It is essential to measure accurately, since the coating will add thickness to the bare substrate.
To avoid excessive deformation of the prepaint base, which can destroy the adhesion of the coating, the NCCA recommends multi-stage forming when producing rigorous bends. Warm forming at 125-160 degrees can help in cases of severe fabricating. The equipment supplier can provide expert advice on exact specs.
With some pre-planning and proper engineering, using prepainted metals, even on products which require heavy forming, can save manufactures the expense of manning an in-house paint shop and all the costs associated with adhering to environmental regulations. Incorporating prepainted metal also streamlines production and eliminates bottlenecks caused by waiting for post painted finishes to dry. Further, the end product has a more even and durable finish.
For more information about prepainted metal and forming, visit www.coilcoatinginstitute.org or call the NCCA at 216-241-7333.
