## 1 Introduction  
The development of information technologies has caused data processing to be very difficult without the use of electronic devices in present times. Regardless of whether the data are edited, printed or transmitted, they take the form of electrical signals with various structures. These signals control the operation of various elements of electronic devices, and, consequently, the processed data can be observed on a monitor, printed or transmitted over long distances. These processes are also accompanied by other events, such as electromagnetic, acoustic or vibration emissions. Their formation is a natural phenomenon, accepted by a typical user of electronic devices. However, it is disturbing that these emissions can propagate into the surrounding space without major obstacles, and they can be used for non-invasive obtaining of information. A 3D printer is an example of a device that can be considered a source of the above-mentioned emissions. 3D printing, also referred to as Material Extrusion 3D Printing (ME3 DP) or Additive Manufacturing (AM), is the technology that enables creating 3D objects of various materials based on their computer model developed by using popular Computer Aided Design (CAD) type software. 3D printers are most commonly used to design the prototypes of various objects. An interesting overview of 3D printing techniques is presented in [1,2]. Fused Deposition Modelling (FDM) type machines are the most common 3D printers used in non-professional applications and small design companies. The FDM type 3D print technology, also referred to as Layer Plastic Deposition (LPD), is a solution that uses a continuous thermoplastic fiber, the so-called filament, to form the shape of an object. The hot filament in the printing zone is applied by using a movable, heated head that keeps the filament in a semi-liquid state. The printer head (printhead) is moved along the single print layer plane by the printer driver controlled by commands received from the computer-based analysis of the printed model object. The controller generates signals to control the operation of stepper motors moving the head in X and Y directions (horizontal plane). Movement in the Z direction (vertical plane) can be carried out in two ways: (1) head H moves up, while platform P remains stationary, (2) platform P moves down, at a constant head height (Figure 1). The speed of releasing plastic material from the printhead can be controlled, allowing to stop the printing process and restart it in another device zone to obtain the complex geometry of the final product. The FDM printers currently offer a high resolution and at the same time provide a low purchase price and reduced costs of operation. The experience of the authors of this article shows that each information processing device becomes a potential source of sensitive emissions. The type of signal that is most valuable in the process of non-invasive information acquisition depends on the type of device. In the case of graphic data processing, the most valuable emissions allowing for non-invasive acquisition of information about the processed data are electromagnetic emissions. They allow for a reliable reconstruction and acquisition of data about graphic symbols displayed on a computer monitor. Printing devices equipped with a laser system or a strip of LED diodes are an equally susceptible type of device for electromagnetic infiltration. In this case, the electrical signal as the revealing emission source, which controls the irradiation system of the photosensitive drum, has the characteristics of printed graphic data. Thus, the recorded electromagnetic emissions make it possible to obtain data on the content of printed documents. The above-mentioned devices for displaying the processed data are well known and described from the point of view of susceptibility to electromagnetic infiltration. A less recognized device in terms of the possibility of non-invasive acquisition of data about printed objects is a 3D printer.