The change in a unit of length of a material per unit change in temperature. Expressed in in/in-°F or cm/cm-°C. The CTE is not constant, but varies with temperature, so it is often expressed as an average over a temperature range. The ASTM test measuring the CTE in polymers is D696.
The surface where the two mold halves meet or part. Most parts can be formed by a mold with a flat parting surface. However, more complex parts may require a mold with an angled, stepped, or curved parting surface. More complex parting surfaces will increase the cost of the mold.
A turning operation in which a single-point tool, typically with a 60 degree pointed nose, moves axially, along the side of the workpiece, cutting threads into the outer surface. The threads can be cut to a specified length and pitch and may require multiple passes to be formed.
A feature on the exterior of a part that will not allow a mold that contains it to slide away along the parting direction. An external undercut can be either a protrusion or a depression (hole or pocket) and requires an additional mold piece called a side-core to form its shape.
The smallest box, sometimes called a bounding box, that is able to contain the part. The X-Y-Z dimensions of this box describe the maximum length, width, and height of the part. In molding processes, the Z-axis (describing the part's height) is the parting direction of the mold.
The time required for any tool movements that occur during an operation that do not engage the workpiece. This time includes approaching and retracting from the workpiece, moving between features, and changing tools. Most of these tool movements occur at the rapid travel rate.
The area of a part or feature that is projected onto the X-Y plane. In molding processes, this is the area projected onto the mold surface because the Z-axis is the parting direction. The projected area can be approximated by a percentage of the X-Y side of the envelope.
The material at the end of a piece of bar stock that will not be used. The bar end, or bar remnant, is typically the result of a device holding the bar while the stock is cut. The bar end is used in determining how many workpieces a single piece of bar stock will yield.
