The most important setting parameters in creep grinding are cutting speed, vc, tangential feedrate, vft, and infeed, ae. Either up — or down-cut grinding can be set in creep feed grinding. The influence of the setting parameters on the work result will be explained below.
16.3.4.1 The Influence of Cutting Speed vc
Due to the large contact length and large infeed in creep feed grinding, grinding forces tend to be high, which, in turn, lead to high thermal stress in the working zone. High grinding forces lead to machine displacements and thus to dimensional inaccuracies on the workpiece. The grinding forces affecting the machine system can be reduced by minimizing the forces occurring at the single cutting edge during the grinding process. This can be realized by increasing the wheel speeds, which produces a smaller chip thickness and a lower number of active cutting edges. Furthermore, increasing the wheel speed generally results in a reduction of grinding wheel wear and in a lower surface roughness of the workpiece.
16.3.4.2 The Influence of Infeed, ae, and Feedrate, vft
Machining time in the grinding process is crucially influenced by the infeed, ae, and the feedrate, vft. An increase of the specific material removal rate by increasing the infeed or the feedrate involves higher grinding forces and elevated thermal stress due to a higher chip thickness [Uhlmann 1994a].
16.3.4.3 The Influence of Dressing Conditions
In the case of creep feed grinding, continuous conditioning may be required during the grinding process. Continuous dressing takes place by separate grinding and profiling devices on the grinding machine. This procedure ensures that the grinding wheel has the necessary sharpness over the whole engagement time, has the desired profile, and sufficient chip spaces are available [Spur, Uhlmann, and Brucher 1993]. A continuously dressed grinding wheel allows for low or constant grinding forces and process temperatures, and favorable wear behavior in the creep feed grinding process. The surface roughness and the condition of the subsurface of the workpiece are positively influenced with respect to the work result.
16.3.4.4 The Influence of Grinding Wheel Specification
Alongside the fully engaged cutting edges, there are additional grain tips engaged, situated deeper, which do not contribute to chip formation but only elastically and plastically deform the workpiece. In contrast to processes with small contact lengths, this occurrence must not be neglected in the case of creep feed grinding because of the large contact length. The friction in the working zone rises, causing higher thermal stress on the workpiece and the tool, as well as higher requirements on the tool drive. Influencing parameters for the number of active cutting edges are
• Cutting speed, vc
• Tangential feedrate, vft
• Infeed, ae
• Grinding agent concentration (grain number)
• Grinding agent geometry (grain size)
In order to avoid increasing the already high friction in creep feed grinding by additional friction and squeezing processes of the removed chips on workpiece and tool, the safe evacuation of the chips requires sufficient porosity of the bond structure (pores/chip spaces). This additionally counteracts the clogging of the grinding wheel. High thermal stress requires the transportation of sufficient cooling lubricant to the working zone, which is also aided by larger porosity in the grinding wheel bond. Grinding wheels for creep grinding should be softer than for reciprocating grinding for the same task.