Riser (casting)

"Underfeeder" redirects here. For the health problem, see Underfeeding.
A bronze casting showing the sprue and risers

A riser, also known as a feeder,[1] is a reservoir built into a metal casting mold to prevent cavities due to shrinkage. Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify. Risers prevent this by providing molten metal to the casting as it solidifies, so that the cavity forms in the riser and not the casting.[2] Risers are not effective on materials that have a large freezing range, because directional solidification is not possible. They are also not needed for casting processes that utilized pressure to fill the mold cavity.[3]

  1. ^ Ravi 2005, p. 63.
  2. ^ Degarmo, Black & Kohser 2003, p. 286.
  3. ^ Cite error: The named reference degarmo288 was invoked but never defined (see the help page).