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The thinner sections solidify too quickly to permit liquid feed metal to pass from the riser to the thicker sections.Testing ensures that the material meets the requirements of the specification; consequently, testing may be mandatory. More frequent testing or other tests may be imposed, by use of supplementary requirements of material specifications or general requirement specifications. In addition to specifying test methods, acceptance criteria must be agreed upon between the purchaser and the foundry. The more testing and tighter the acceptance criteria the more expensive the product will be - without necessarily increasing quality or serviceability. Hence, the extent of testing and acceptance criteria should be based on the design and service requirements.It is impossible to produce a [http://www.edrfittings.it how to start outsourcing business] defect free casting, only castings with defects of varying degrees of acceptability. The acceptance and/or rejection of such castings can only be determined by examination and analysis of parts (in accordance with internationally recognized standards such as ASTM) based on customers' formal engineering requirements. A defect in one application may not be a defect in another application and it is impossible to make a casting without some kind of flaw. The size of flaw(s) can vary significantly, and what is acceptable and what is defined as a REJECTABLE defect depends on agreement between the supplier foundry and the client prior to production. Large cavities often exist in thick-section castings and can be perfectly acceptable depending on the application and the location within the casting. On the other hand, some applications are very critical and tiny flaws (or even micro-porosity - as defined by a specific NDT process and acceptance/rejection level) may be considered as defects that may be detrimental to the intended use of the product.Acceptance and rejection criteria for castings production must be determined at the time of quotation and certainly at the time of order, as such criteria affect the price of castings, as well as the production procedures and processes used to produce the castings.PatternsPattern equipment design and the resultant costs can constitute a major source of misunderstanding between customer and supplier foundry. The need to construct new pattern equipment when existing equipment is available, a requirement for a full split core box in place of a half core box, pattern material, and mounted or loose patterns are but a few of the many areas of discussion that effect the cost of the equipment. Invariably, the lowest casting cost and highest casting quality evolve from the more sophisticated pattern equipment, which generates the highest pattern cost.Patterns - Minimum Section ThicknessThe rigidity of a section often governs the minimum thickness to which a section can be designed. There are cases, however, when a very thin section will suffice, depending upon strength and rigidity calculations, and when castability becomes the governing factor. In these cases it is necessary that a limit of minimum section thickness per length be adopted in order that liquid metal will completely fill the mold cavity in these thinner sections.Molten steel cools rapidly as it enters a mold. In a thin section, close to the gate, which delivers the hot metal, the mold will fill readily. At a distance from the gate, the metal may be too cold to fill the same thin section.