## 4 Discussion  
The dummy method was inserted into the SPIF by [PERSON] et al. [38]. The initial aim was to improve the surface finish of the manufactured metallic pieces by incremental deforming [29]. Later, the dummy method was used to deform welded sheets by means of friction stir welding [30]. In the present study, the dummy method has been used to conform, directly via SPIF, pre-coated molds rich in a PTFE resin.  
As well as presenting this novel method for directly manufacturing non-stick molds by incremental deforming, the present work has also studied the influence of both technological parameters (pitch and feed-rate) on the dimensional precision reached during the incremental forming of molds from pre-coated sheets using the dummy technique.  
After analyzing the results, we can affirm the following:  
* The minimum thickness appears to show no relation to any of the technological parameters studied (Figure 7). This result is coherent with the law of sine [47]. According to this law, the theoretical thickness can be calculated as a product of the initial thickness (1.20 mm) and the sine of the angle (45\({}^{\circ}\)). The theoretical value calculated (0.84 mm) coincides with the value measured experimentally.
* The differences between the theoretical profile and the real profile of the mold are minor, in general terms, when using low values of pitch and feed-rate (Figure 10). These results coincide with those obtained by [PERSON], [PERSON] & [PERSON] [48] (greater pitches provoke greater deviations), [PERSON] & [PERSON] [49] (lower pitches provoke lower geometrical accuracy) and [PERSON] & [PERSON] [50] (high values of the feed-rate lead to a low-dimensional accuracy).
* However, low values of pitch and feed-rate result in certain geometrical features (depth, height, angle #1, normalized springback, angle #2) moving away from the sought-after theoretical values:
* The depth and height approach the theoretical ones with high pitch and feed-rate values (Figure 8).
* Angle #1 approaches the sought-after value (45\({}^{\circ}\)) when high feed-rate values are programmed (Figure 5). Logically, the normalized springback shows the same behavior (Figure 9).
* Angle #2 (135\({}^{\circ}\)) approaches the sought-after value when greater pitch values are used (Figure 6).
* An increase in pitch increases the deformability (Figure 11). This result coincides with that presented by [PERSON] et al. [51].  
As can be appreciated, the test carried out with a greater pitch and feed-rate attains better results for the particular variables (height, depth, initial angle, maximum angle, minimum thickness). At the other end, the test carried out with a lower pitch and feed-rate manages to minimize the deviation area between the profile obtained and the expected theoretical one.  
To sum up, it can be affirmed that the results obtained relative to geometrical accuracy in the dummy method are similar to those obtained in the incremental deforming processes of a single sheet. To solve this problem, [PERSON], [PERSON] & [PERSON] [13] proposed a multistage strategy to improve geometrical accuracy. Following this idea, the authors are going to try a multi-stage strategy: firstly, high values of pitch and feed-rate will be used to get a good reproduction of the geometry details; secondly, lower values of pitch and feed-rate will be used to provide a lesser deviation in the real compared to the theoretical profile.