Getting a great deal of non-specified quality aluminum foil master rolls is the same as building a house without a blueprint. You may receive a face value product, but you will have wrinkles and an hourglass when it is delivered. Variability in thickness, pinholes that are too many in number, surface oil disrupting lamination, and loading problems resulting from how the foil is wound cost you time and money to correct. Establishing quality standards before ordering, ensures that these problems do not occur and that the supplier and buyer know what to expect. Read how buyers can establish quality specifications for foil master rolls.
1. Start with the Application
The end use is where it all begins Hardness, dead-fold, food specifications, or thickness control? How will the foil be used? Do you need a soft foil for wrapping, or a hard foil for container use? Foil for flexible packaging lamination, or foil for food container manufacture? What's right for you? Specify the application, then specify the quality you need to fit that application. Quality standards can be written to meet the needs of one application, and be either an absolute overkill for another, or not enough for another. Clear communication at this stage is the difference that keeps everyone happy.
2. Define Thickness and Tolerance
Thickness is the most basic property and will be the first thing you need to set out when specifying a requirement. The buyer should state a target micron thickness (or range of thicknesses) and what the acceptable tolerance should be. Typical tolerance for aluminium foil is plus/minus 5 percent, but extremely tight tolerances may be necessary for high speed lamination and other thin-gauge applications. Thickness should be checked over several locations across the width and the length of the roll to check for uniformity. Thickness readings should be supplied by the manufacturer and checked where possible with a thickness gauge. Uneven foil thickness can lead to tension variations, inconsistent coating, and web breaks during converting. Clear standards for thickness will help keep production flowing.
3. Specify Pinhole Requirements
Pinhole control can be crucial to barrier performance, particularly when the end use is food or pharmaceutical packaging. Buyers should specify the maximum number of pinholes per square meter per product type and thickness. Typical maxima are less than 200 at 7 micron, less than 100 at 8 micron and less than 50 at 9 micron. For the thicker foils, more than 30 micron, the pinhole count becomes less critical but should still be controlled. Suppliers should have on-line laser pinhole detection systems that can scan the entire roll width at production speed. Buyers should ask for pinhole reports and check that testing is carried out across the entire roll.
4. Set Surface Cleanliness Standards
Surface cleanliness has an influence on adhesion, printing, coating and lamination. For lamination, residual oil of rolling oil should be less than 2 milligram/m2. For other application, maximum residual content of oil can be determined. Buyers should indicate the maximum residual oil content and a test method, which has to be used to measure the residual oil content. Surface wettability is another indication of surface cleanliness. A good surface should be fully wetted by the water; surface faults such as scratches, creases, black spots and dents should be specified. The limit values of these faults should be indicated by the buyer and the visual inspection report needs to be delivered.
5. Define Mechanical Properties
Mechanical properties are the quality standards for performance during converting. Elongation for lamination and deep drawing Tensile strength to resist web tension Hardness for container foil Buyers should require a minimum elongation, a tensile strength range, and a hardness to meet their particular converting process; these values should be tested for each run, and test reports should accompany the delivered order. Poor mechanical properties can result in web breaks, uneven forming, and lost production time.
6. Specify Winding and Roll Parameters
Winding Quality The quality of the winding determines how easily the master roll will run on the production line. Buyers can indicate the roll weight, outer diameter, core diameter, and winding tension specifications. Roll end faces should be smooth and level with no protrusions. The winding should be tight and uniform with no loose areas, telescoped rolls, or wandering edges. Core diameter is 76mm or 152mm. Roll weight can be between 200kg to 800kg depending on the application. Buyers should check these specs with their machinery and ask for samples for trials before production.
7. Document Standards in a Technical Agreement
All quality requirements should be included on a technical agreement or specification sheet countersigned by buyer and supplier. This document should specify alloy, temper, and for sheet, minimum thickness and tolerance, width and tolerance, pinhole limits, cleanliness of surface, mechanical properties, winding requirements, packaging, and inspection methods. It should also specify the acceptance criteria for each requirement, as well as the methods of acceptance for non-conforming material. A written agreement avoids confusion and acts as a reference should disagreements occur. Buyers should go over the agreement with production and quality personnel before countersigning.
8. Verify Through Inspection and Supplier Audits
The bottom line: Standards are only as good as they are verifiable. Buyers should create an incoming inspection system for shipments, including thickness tests, pinhole testing, surface inspections, and roll condition. In the case of large orders, it may make sense to engage in third-party testing. Buyers should also periodically audit a supplier to ensure they maintain the same level of process control and quality control. Henan Tendeli Metallurgical Materials Co., Ltd., developed in 2009, is able to produce 8011, 8079, 1235, 3003, 8006 aluminum foil master rolls with documented quality standards, food-grade certification and consistent batch assurance. HTMM has more than a decade of export experience, serving over 3,000 customers worldwide. Standards are there to protect both buyer and supplier.
