ネックイン、ドローダウン（押出成形）

Neck-in（ネックイン）In extrusion of film, sheet and coatings, the difference between the width of the extruded web as it leaves the die and the final width of ... （グーグル検索）

For example, blow-up ratio (BUR)（無冠詞）used alone as a film-making parameter is meaningless.  BUR（無冠詞）must be related to draw-down（ドローダウン）ratio and die gap. In Figure 3, all three of these parameters are used to illustrate a theory of melt orientation, an important factor in extruding the high quality film required by customers. (How to solve blown film problems (PDF))

"Draw Down Ratio（引落、引き落とし比、率）is the ratio of the cross sectional area of the extruded plastic melt to the cross sectional area of the plastic in its final product form, be it a tube, hose or insulation on a core, such as a wire or cable. It is the
extent to which the plastic has been reduced in size to make the part." (Understanding and Communicating Draw Down Ratio Balance)