For flawless cosmetic finish, start at the head
A clean straightening head prevents debris damage during coil feeding
Stamping cosmetic parts in coil feed lines can be challenging. Cleaning the coil feeding head properly can eliminate waste or scrapped parts caused by debris and contamination.
To remain competitive and profitable in the face of rising energy and material costs and low-cost overseas labor, North American stampers are offsetting these higher costs by increasing pressroom efficiency. Stampers are investing in automation to reduce labor costs and to expand the use of existing machinery. Automation in a pressroom can include quick die change, die protection, press setup, and coil feed lines.
Reducing waste or scrapped parts that occur during the stamping process also can help increase profit margins by offsetting the material costs and reducing the labor required to produce them.
Scrap isn't just the material left over after a part is stamped; it's also unusable material from a coil or bad part. Rejected parts are costly, because they waste not only material, but they require labor to produce them.
Parts are rejected because they have cosmetic defects or they're out of tolerance. The time required to produce, identify, sort, and remove bad parts can greatly affect a job's profitability.
Stamping Cosmetic Parts
Producing a finished part is challenging, and it becomes even more challenging for applications that demand a perfect finish. Many secondary operations correct markings or blemishes created during the stamping process.
Stamping highly cosmetic parts also can create challenges for coil feed line manufacturers. Any surface that comes in contact with the material can cause marking. To combat this problem, some equipment has been developed with nonmarking surfaces to help stampers run cosmetic jobs. Some coil feed lines have been developed with ultrahigh-molecular-weight polyethylene and nylon-covered surfaces, as well as urethane-coated components to reduce marking.
Contamination and debris on a material's surface from the plant also can cause marking during the coil feeding process. Because the straightener is the first piece of equipment to come in contact with the material, any debris or contamination can stick to the surface of a straightener roll and cause marking. Keeping straightener rolls clean of debris or buildup is essential to successfully running cosmetic jobs.
Cleaning straightener rolls can be labor-intensive on a standard powered straightener. Getting access to the rolls' surfaces can be difficult because most straighteners are designed to open only one of two times the maximum material thickness. Because of this limited access, removing covers or components or completely disassembling a straightener head may be required to clean the straightener rolls adequately.
Disassembly and cleaning can take hours and require skilled maintenance technicians. Because most companies are minimizing their skilled labor staff, this can be challenging.
Some new features on powered straighteners have been developed to help eliminate buildup or debris on straightening rolls to reduce the roll-cleaning time.
One inexpensive feature that can be added to or included on any straightener is hard flash chrome plating on the surface of the straightener rolls. This smooth, hard finish helps keep debris from sticking to the rolls' surfaces. Chrome plating also makes cleaning easier.
Several designs can help reduce the time required for cleaning. The most basic design increases the access to the rolls on a standard straightener head. The head is spaced a few inches above the top of the cabinet base to allow access to the underside of the lower straightener and pinch rolls. The upper rolls are accessible through the topside of the straightener by reaching through the cross-shafts for cleaning. Removing covers or components may be required to gain full access to the rolls. Items like hinged covers or a pivoting curved stock support reduce cleaning times.
Another design allows for a larger opening of the straightener rolls for access for the entry and exit ends of the straightener head. The pinch and straightening rolls open 2 inches to 3 in., instead of the usual fraction of an inch, so surface rolls are reachable from either end of the straightener head. This design still may require the removal of covers or components for complete access. Because access is provided only at the entry and exit end, a ladder or climbing on the straightener cabinet may be necessary.
A quick-release or cartridge-type straightener head allows complete access to the surface of straightener rolls. Rolls may be removed, thoroughly cleaned, and then inspected without disassembling the complete head. Each roll is held by a retainer that, when removed, allows the rolls to be taken out from the side of the straightener.
Because the rolls are completely removed, an overhead crane, fork truck, or cart must be used, and sufficient space must be available. Spare rolls may be kept in stock and exchanged when needed, helping to reduce downtime. The removable-roll straightener type combined with flash chrome-plated rolls can be a good choice for running cosmetic materials.
A pivot-open powered straightener head allows access to the entire surface of each roll and does not require any disassembly or roll removal. With this design, the entire straightener head pivots open, allowing unobstructed access to the surface of each roll within seconds. Like the removable-roll-type straightener, the pivot-open head allows visual inspection of each roll—critical to the cleaning process.
The pivot-open head has two hydraulic cylinders that lift open one end of the bank of upper straightener rolls. The angle of the opening is approximately 62 degrees to provide access to the rolls. When the end of the bank is completely open, safety blocks are placed over the cylinder shafts. The opening of the head is push button-controlled by an operator station located on the straightener. While the end of the bank is opening, a warning light and alarm alert the operator that the head is in motion.
This type of powered straightener head can be cleaned without disassembly or special equipment, and press operators can correct a material marking problem without maintenance personnel. The pivot-open head also can be opened while the material is in the straightener. This helps operators troubleshoot which roll may be causing the marking problem, as well as saves them the time of removing the material and rethreading the tooling.
STAMPING Journal is the only industrial publication dedicated solely to serving the needs of the metal stamping market. In 1987 the American Metal Stamping Association broadened its horizons and renamed itself and its publication, known then as Metal Stamping.