## 3 Results and Discussion
### Device Building  
The constructed prosthesis (Figure 19) took approximately 8 h to have all of its constructive polymeric components printed. For assembly and finishing the average time consumed was 3 h. The final weight of the fully assembled device was 263.90 g. The estimated cost of the device is $60.82, which is a low cost compared to the cost of conventional prostheses, with values ranging from $316.30 to $1408.75 [33; 34]. In addition, in the global market, there are upper limb prostheses with sophisticated operating systems that cost between $25,000 and $58,000 per unit [25; 35; 36].  
Regarding the weight achieved in the prosthesis (less than 270 g) developed in this project, it is essential for the user in the adaptation process, to have prosthetic devices that have the ability to combine mechanical strength and low weight, being extremely important factors in the rehabilitation process. Thus, having a polymeric raw material for use in the three-dimensional printing process, such as PETG, which, despite being a light input, has values for printing with 25% infill, having density of 1.27 g/cm\({}^{3}\), yield stress of 14.19 MPa, maximum tension of 20.68 MPa, and modulus of elasticity of 552.54 MPa.  
Since through significant properties the material stiffness can be evaluated through the value of its modulus of elasticity, the value of the initial strain of the plastic deformation can be evaluated by the stress or yield strength. Therefore, values that show that it is possible to use Fused Deposition  
Figure 19: Built-in device model: (**a**) view palmar region of device, (**b**) top view of device  
Figure 18: Software-generated images for initiating the three-dimensional printing process: (**a**) index finger phalanges and (**b**) wrist support.  
Modeling printing technology regarding the manufacture of hand prostheses, giving the orthopedic device good mechanical strength and lightness.  
After the prosthetic device is built, it can be placed over the region of the amputated limb, the prosthesis stabilization in the deficient region may be done through the use of Velcro stabilizers of firm padded foam (medical grade), protective stockings for the skin and tension adjustment executed by the fixed directional coupling (ratchet), so that the prosthesis can have a stable, comfortable, and functional use during the execution of daily activities. It is important to highlight that, with regard to the ratchet, once the prosthesis is placed on the patient's amputated region, it is possible to adjust the functional movement of the prosthesis, made by traction of the risers. High resistance lines the upper surface of the prosthesis, in order to allow the clamping and gripping movements performed by the device made from the angles 20\({}^{\circ}\)-30\({}^{\circ}\) degrees of the wrist flexion movement. This calibration can be done using an instrument capable of measuring angles called a goniometer, whose capacity allows to evaluate the angulations of the phalanxes and the wrist articulation.  
The operation and activation of the prosthetic device is possible, since high density orthodontic elastics are placed on the upper part of the interphalangeal regions, which allows passive extension of the finger. The flexion movement of the fingers is carried out through high resistance cords placed along the external palmar and phalangeal surface of the hand and fingers, being activated through the wrist flexion movement made at an angle between 20\({}^{\circ}\) and 30\({}^{\circ}\) degrees, resulting in a composite wrist with the ability to flex the fingers towards the palm of the hand.  
Thus, with this device it is possible through the handgrip movement, to pick up and hold objects with different geometries, such as a PET bottle with a volume of water equal to 500 mL, a Fuji apple with approximately 75 mm in diameter, a cubic body with 10 mm edge, cylindrical bases of different screwdrivers or screwdrivers, a marker brush for a whiteboard 125 mm long and 15 mm wide, among other items weighing no more than 1.5 kg.