## 3 Results
### Grinding Experiment
#### 3.2.2 Grinding Forces  
This section shows the results of the forces during the grinding process with different grinding process parameters (see Table 4) and different additively manufactured resin-bonded grinding wheels (see Table 2). Figure 6 displays the force values during the grinding operation on the Al workpiece with parameter set 1. In general, all GWs have a grinding-in phase after dressing. This was observed through the unstable and rapid changing forces at the beginning of the grinding process. This could be the result of the influence of the dressing parameter effect on the different bond properties. For example, in Figure 8, you can see that GW-2 has the highest force at the beginning. This could be due to protruding grains with better grain retention. In comparison, there is GW-1, where the grains detach more easily and fall out after making first contact with the workpiece. It was observed that after the initial phase of grinding, the GWs developed a fairly stable force level, indicating that the microstructure of the GWs finds a stable configuration. It was observed that the normal force (Fn) for all GWs reached roughly the same force after the removed material volume of 120 mm\({}^{3}\). The tangential (Ft) force varied for all GWs between 2 and 3 N. The fluctuating Ft indicates that there could be self-sharpening. To explain this phenomenon, when the grains become dull or drop out, the grinding forces begin to rise, leading to an increase in heat concentration and localized stress. In this state within the cutting zone, the bond starts to wear out and grain sharpening occurs, causing the forces to subsequently decrease. Figure 8: Grinding forces of the grinding experiment with parameter set 1. Figure 9 illustrates the grinding force for grinding with parameter set 2. In comparison to parameter set 1, the initial phase for all GWs was similar to the trend discussed earlier. The higher forces and larger contact area covered the differences in bond properties. The fluctuating tangential force of GW-1 indicates a constant flattening and sharpening of the wheel. In contrast, the force of GW-2, 3, and 4 stayed at the same level after roughly 250 mm\({}^{3}\), which indicates the start of the stable grinding region. Figure 10 illustrates the grinding force for grinding with parameter set 3. The grinding forces showed the most variation between the GWs compared to the other parameter sets. Additionally, the initial phase of grinding represents a significant force reduction since the higher depth of cut caused a smaller chip thickness, providing less frictional contact between the wheel and the workpiece. GW-1 has the lowest normal forces but high tangential forces, which could be indicative of higher tool wear and tool-workpiece frictional contact. GW-2 and 3 have low normal forces and fairly low tangential forces, which indicates a good balance between tool wear and material removal. GW-4 has the highest normal forces, which is attributed to the higher pressure and rubbing contact in the contact zone. Figure 9: Grinding forces of the grinding experiment with parameter set 2. In Figure 11, the average normal and tangential forces for the stable region of the grinding process for all grinding wheels are displayed. It can be seen that with the increase in the depth of cut, the cutting forces increase. For shallow grinding (parameter sets 1 and 2), GW-1 has the lowest average normal forces. For parameter set 3, GW-3 has the lowest forces. Although a higher depth of cut brings about smaller uncut chip thickness, it causes a higher material removal rate, creating higher thermal and mechanical stresses in the cutting zone. According to this explanation, the higher depth of cut could lessen the grinding force by reaching smaller uncut chip thickness and increase the force values by inducing higher material removal rates. On balance, the rise in force levels between the parameter sets in this study comes from the higher material removal rate resulting from the higher depth of cuts.