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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
121:) 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.
94:. 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,
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Flash, center, on a molded plastic laundry basket. Plastic has filled an area that should be an empty space, probably by seeping through a gap where the molds were not clamped sufficiently close together.
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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.
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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.
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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
240:, Bernard, Edward Helmut, "Method and apparatus for eliminating a parting line witness mark from a molded part", issued 2005-09-06
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106:"Witness marks" redirects here. For the episode of The Haunting of Hill House TV series, see
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or media blasting to remove unwanted flash from large batches of parts.
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217:"Cryogenic Deflashing for Molded Plastic, Rubber & Silicone"
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Excess material attached to a molded, forged, or cast product
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219:. Nitrofreeze Cryogenic Solutions. 26 April 2012
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113:In plastic injection, a faint mark called a
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200:"An Expert Tells How to Stop Flash"
47:, is excess material attached to a
206:, July 2004, accessed May 9, 2011.
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144:Injection mold design engineering
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147:. Hanser Verlag. p. 70.
181:. Siemens PLM Software. 2007
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176:"NX I-deasVGX Core/Cavity"
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268:Metalworking terminology
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238:US patent 6939500
141:David Kazmer (2007).
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96:cryogenic deflashing
204:Plastics Technology
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263:Plastics industry
154:978-1-56990-417-6
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119:witness line
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115:witness mark
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102:Witness mark
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61:parting line
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65:overmolding
257:Categories
223:2014-04-03
185:2009-07-01
125:References
84:deflashing
160:15 April
92:tumbling
88:grinding
45:flashing
18:De-flash
71:Details
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53:forged
49:molded
179:(PDF)
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41:Flash
162:2011
149:ISBN
117:(or
57:cast
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