John Hart was commissioned by a world renowned supplier of suspension components to the global automotive industry to undertake a turnkey project for suspension knuckles in Shanghai, China.
During this very detailed project, John Hart undertook the following tasks: Fixture design and build, cutting tool interference checking, machine collision checking, CNC programming, first article sample cutting.
The project consisted of 4 individual parts, which included two front knuckles (left hand and right hand), and two rear knuckles (left hand and right hand), and included design of 6 fixtures with 8 units of fixtures being built.
The fixture consisted of base plate, main fixture plate, nest blocks, datums, arms, clamp points, guide blocks, imported hydraulic clamps and valves, and auxiliary pieces.
The fixtures were designed to suit horizontal machining centers with B axis tables and a vertical machining center, and adopted low pressure multi-action hydraulic sequence, operated under 7MPa system pressure with the clamping action and pressure controlled by a custom designed, intergral valve block on the fixture.
Each fixture had two nests or more, to make full use of machining envelope, and to reduce operator load-unload time. The process and CNC program were also planned carefully to achieve less tool changing time and tool path time. More parts were cut before changing another tool.
The fixtures had following characteristics:
- The fixtures were internally hydraulically ported.
- The fixture components were designed with high accuracy and interchangeability in mind so that the spare parts could be changed quickly, without requirement for additional adjustment.
- The fixtures had air sensing functionality (supported by machine side function), for error proofing, to prevent defect machining parts by incorrect loading.
- The fixtures were able to control and regulate the hydraulic pressure and sequence of each hydraulic line, which was convenient for adjustment of clamping force of fixtures during run-off, so as to control the part deformation.
The fixture was able to meet process capability (Cpk) within the strict and demanding timing and technical constraints that are applied to all high class automotive projects.