Advertising in MoldMaking Technology offers
Issue link: https://mmt.epubxp.com/i/587376
Machining 22 MoldMaking Technology November 2015 The accuracy of jig boring and jig milling machines is such that some shops perform measuring operations with them in the same way they use coordinate measuring machines (CMMs). By Tom Dolan T he mold base assembly is the foundation of the mold and the molding process. A mold base positions and anchors the mold inserts, cavities and cores; incorporates cooling channels; and enables the mold to be opened and closed. The engineering and manufacturing quality of the mold base largely determines a mold's performance and durability. Hole making is a key manufacturing process, and any mold base will feature multiple high-tolerance bores for components such as guide pin bushings. The accuracy of those bores contributes to smooth and reliable mold operation. To maximize the quality of the critical bores, many shops that manufacture mold bases finish them with specialized jig boring and jig milling machines. Jig Types Jig boring machines were initially developed in the early 1900s to machine fixtures (jigs) used to guide tools in precision hole- making operations. Later, manufacturers began to use the jig bor- ing machines themselves to produce precision bores. The machining toleranc- es for bores in mold base applications can be less than 5 microns in location, roundness, perpendicular- ity and straightness. To meet those requirements, a jig borer must operate at even higher precision. Positioning tolerances for the machines of 1 micron are not uncommon. The machine accuracy is such that some shops perform measuring operations with them in the same way they use coordinate measuring machines (CMMs). Jig boring machines are available in two basic configura- tions. In gantry-style machines, a boring quill rides a bridge Mold performance and durability depends on mold base quality, and hole making is a crucial step in the process. JIG BORING for MOLD BASE ACCURACY As mold assemblies grow larger in size, the effects of deviations in mold base dimensions are magnified. Images courtesy of Mitsui Seiki USA Inc.