A parting line in moldmaking is the place where two or more parts of the mold meet. Parting lines occur due to minute inherit gaps between two mating faces of halves of the die. The material filling into these gaps is generally called molding flash or simply flashing. Parting lines generally show up as a raised line around the product (witness mark) on commodity products such as toys.
Many applications (seals, tight running molded parts) that require precision for shape control, call for removal of flashes. Secondary operations are thus employed, in addition to high precision molding dies to remove these flashes.
Flashes are known to improve sealing between mating faces in some instances (Fuel tank seals, hydraulic power steering gear, etc.), and thus flashes are permitted to some extent in special cases.
In engineering drawing, parting line is often abbrivated as PL. ASME's Y14.8 standard specifies a symbol for parting line.
Famous quotes containing the words parting and/or line:
“My Christian friends, in bonds of love, whose hearts in sweetest union join,
Your friendship’s like a drawing band, yet we must take the parting hand.
Your company’s sweet, your union dear; Your words delightful to my ear,
Yet when I see that we must part, You draw like cords around my heart.”
—John Blain (18th century)
“The line of separation was very distinct, and the Indian immediately remarked, “I guess you and I go there,—I guess there’s room for my canoe there.” This was his common expression instead of saying “we.” He never addressed us by our names, though curious to know how they were spelled and what they meant, while we called him Polis. He had already guessed very accurately at our ages, and said that he was forty-eight.”
—Henry David Thoreau (1817–1862)