Grinding Process Model

7.3.2.1 Traditional Fundamental Requirements in Grinding

Manufacturing processes have to accomplish certain tasks depending on workpiece material, stock removal (finishing or roughing operation), availability of machines, batch size, form and dimension tolerances, achieved surface roughness and integ­rity, and more [LINK12c]. The following discussions focus on ductile material in finishing operations and the choice of the grinding tool, but the model can be easily adapted to other applications.

Dominant traditional functional requirements are creating part dimension and profile, i. e. the part’s macro properties, creating the part surface, i. e. the part’s micro properties, and being cost-effective (Fig. 7.11 top row). The first requirement for a given raw part can be achieved by several physical or chemical principles, such as material separation, evaporation, dissolvation, additive processes, etc. These prin­ciples underlie in fact all manufacturing processes as described by Todd, Allen and Alting [TODD94] or in the DIN8580 standard. In here, material separation is chosen (Fig. 7.11 left).

For the second requirement to create the part surface, the design parameters of part surface area and the surface integrity have to be considered (Fig. 7.11 middle). The third requirement for cost-effectiveness calls for high productivity, low scrap rate, and low tool costs (Fig. 7.11 right). Having more than one design parameter

Fig. 7.11 Main fundamental requirements
for one functional requirement does not follow the axiomatic design rules for a good design [SUH01, BROW11]. The system is overdetermined, but these conflicts highlight problems and could give hint at improvements for future grinding process designs.

The main mechanism of material separation depends on the workpiece material and is dominated by material shearing and chip formation for ductile material or fracture and crack propagation for brittle material. Either way, shear stresses have to be induced by forces applied to the material through cutting edges (Fig. 7.12 top). In grinding, abrasive particles and a track-bound principle are selected over of the alternatives shown in Fig. 7.12.

The abrasive grits have to be held together, which is done by a bonded tool in the shown axiomatic model. Alternatives are coated tools or polishing pads. The abrasive material separation generates chips, which have to be carried out of the contact zone. The grinding tool is chosen as transport mechanism to achieve this.