Tolerance Grades a Toolroom Signs under DIN 16742
DIN 16742 defines nine tolerance grades based on resin shrinkage variance, requiring toolmakers to split tool-bound and parting-line tolerances during sign-off.
Draft Angle Reference Plane
Meaning
Geometric design baselines define the primary reference orientation from which tapered sidewall angles are calculated to facilitate clean part ejection from mold cavities. Establishing a draft angle reference plane ensures that every vertical wall on a molded component tapers inward relative to the line of draw. Incorrect plane placement leads to undercut conditions and surface scuffing during part ejection.
Datasheet shrinkage factors must be applied outward from this plane during mold tool design.
Draw Vector
Tool ejection forces depend directly on wall inclination relative to the mold opening direction. Positioning the draft angle reference plane perpendicular to the main core pulling direction allows tool designers to apply uniform taper to cavity ribs and bosses. Insufficient draft causes excessive friction between plastic and steel surfaces, leading to part distortion or ejector pin push-through defects.
Textured surface finishes require additional taper depth measured from this plane.
Shrinkage Vector
Polymer cooling forces the plastic part to shrink onto core inserts while pulling away from cavity walls. Aligning the draft angle reference plane with the primary tooling split ensures that shrinkage stress assists rather than hinders part release. Semi-crystalline resins contract more aggressively toward core features, demanding larger draft angles than amorphous resins.
Variable wall thickness along the draw line disrupts uniform release mechanics.
Tooling Boundary
Complex tool constructions with side actions require multiple reference orientations for moving slides. Utilizing a primary draft angle reference plane prevents dimensional ambiguity when calculating side-core taper angles. Toolmakers cut mold steel to mirror these reference angles, leaving stock for fitting during tool tryout.
Part ejection performance validates the selected reference geometry.