Flash, also known as flashing, is excess material attached to a molded,

forged Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which it ...

, or

cast Cast may refer to: Music * Cast (band), an English alternative rock band * Cast (Mexican band), a progressive Mexican rock band * The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis * ''Cast'', a 2012 album by Trespassers William ...

product, which must usually be removed. This is typically caused by leakage of the material between the two surfaces of a mold (beginning along the

parting line A parting line, in industrial casting of molds, is the border line in which draft angles change direction. One can check the parting line in the mould or product which divides the two half, i.e; the core and the cavity of a molded part. It is so ...

) or between the base material and the mold in the case of

overmolding Injection moulding (U.S. spelling: injection molding) is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Injection moulding can be performed with a host of materials mainly including metals (for ...

Details

Molding flash is seen when the optimized parameter on cull height is not calibrated. Proper design of mold parting surfaces can reduce or eliminate flash. Molding flash can be caused from old or worn mold cavities that no longer fit tightly together. Other times, the complexity of the part requires so many mating pieces with such precise geometries that it is almost impossible to create a perfect fit on every impression. Most often, the type of material being molded, and its attendant viscosity in its liquid form, is the primary factor that leads to the creation of the unwanted mold flash.Bozzelli, Joh
"An Expert Tells How to Stop Flash"
''Plastics Technology'', July 2004, accessed May 9, 2011. The process of removing flash, known as deflashing, is commonly performed via cutting, breaking,

grinding Grind is the cross-sectional shape of a blade. Grind, grinds, or grinding may also refer to: Grinding action * Grinding (abrasive cutting), a method of crafting * Grinding (dance), suggestive club dancing * Grinding (video gaming), repetitive and ...

, or tumbling. Some foundries use robot autogrinders to remove this unwanted material. It is very typical for molders to have their operators trim flash with hand tools at the molding machine between cycles. Many molders and OEMs seek out the use of batch processes including vibratory tumbling, cryogenic deflashing or media blasting to remove unwanted flash from large batches of parts.

Witness mark

In plastic injection, a faint mark called a witness mark (or witness line) will occur along the parting line. This is unavoidable and is usually accepted despite the minor aesthetics issue. However, some part surfaces (e.g. when used for sealing) cannot tolerate witness marks, and thus either the marks must be removed post-molding or the mold redesigned.

References

{{DEFAULTSORT:Flash (Manufacturing) Plastics industry Metalworking terminology

Details

Witness mark

See also

References