## 2 Materials and Methods
### Simulation  
To determine filling time, holding time, and holding pressure, a study was carried out based on the SolidWorks Plastics(r) software to verify if the points indicated as preferred by the customer were exactly those that best met the part filling needs. This study was carried out by avoiding possible conflicts between the local space of the runners and the space needed to place the new mechanisms involved in the movements. It should be noted that the mold will inject two parts per injection cycle, i.e., it will have two molding zones arranged in such a way to allow its subsequent extraction vertically, in relation to the engraving surface. To perform the simulation, the following characteristics were defined for the injection nozzles: channel diameter: 5 mm (both materials); nozzle diameter: 1.5 mm (both materials); submarine injection point diameter: 0.9 mm (PP) and 1.0 mm (HDPE). For the purposes of simulation, the properties of SABIC(r) PP PHC26 were considered, as this is the raw material provided for PP injections. When studying the Shear Rate vs. Viscosity, there is a clear perception that there is a maximum limit of 100,000/s to be met for the shear rate, since, from this value, the viscosity presents an unstable and unwanted behavior. This observation occurred from previous experience with this kind of polymer. After some simulations, it was possible to verify that the PP injection point should be changed, since the location proposed by the customer is not the most advisable, as it is susceptible to causing complications due to its positioning on the part. Whenever possible, the injection point should be close to one end, as it is more economical to produce and direct the injection flow in a more controlled manner. The new selected areas for injection can be seen in Figures 5 and 6, representing the progress of the material during the injection process. The simulation made it possible to establish a filling time of 1.23 s, a holding time of 5.5 s, and a holding pressure of 6.3 MPa.  
The simulation also made it possible to verify that the welding lines would be in the non-exposed points of the final part, which satisfies the customer's requirements. In addition, there is a gradient of about 20 \({}^{\circ}\)C in front of the injected material which, although not ideal, clearly does not represent problems for the welding line. The PP section of the part is subject to a shear rate of approximately 40,360/s, which is evidently below the maximum allowable rate: 100,000/s. The surface depressions in the part were also checked, and they did not exceed 0.2 mm in depth.  
Figure 5: Injection zones imposed by the end customer (red marks).  
The same study was carried out for the injection in HDPE. For this, the characteristics announced by REGIDEX(r) (provider) for the raw material with the reference HD 6070 EA were considered. The maximum permissible shear rate, as in the case of PP, is 100,000/s for HDPE. Figure 7 represents the progress of the material during the injection process. The simulation made it possible to calculate the filling time 0.49 s, for the holding time of 6.4 s and holding pressure of 7.8 MPa.  
The HDPE section of the part is subject to a shear rate of approximately 40,360/s, which is well below the maximum allowable rate: 100,000/s. The surface depressions in the part were also checked, and they did not exceed 0.08 mm in depth.