Micro-Electric Discharge Machining ($\mu$-EDM) is one of the widely applied micromanufacturing processes. However, it has several limitations, such as a low cutting rate, difficult debris removal, and poor surface integrity, etc. Hybridization of the $\mu$-EDM is proposed as an alternative to overcome the process limitations. Conversely, it complicates the process nature and poses a challenge for modelling and predicting critical process responses. Therefore, in this work, two distinct, nonparametric, previously unreported, workpiece material independent models using a Generalized Regression Neural Network (GRNN) and Gaussian Process Regression (GPR) were developed and compared to assess their performance with limited training data. Various smoothing factors and kernels were tested for GRNN and GPR, respectively. The prediction of models was compared in terms of the mean absolute percentage error, root mean square error, and coefficient of determination. The results showed that GPR outperforms GRNN and accurately predicts the $\mu$-EDM process responses. The GRNN’s performance was better for less stochastic output with a discernible pattern than other outputs. The Automatic Relevance Determination (ARD) squared exponential kernel was found to be the best performing kernel among those chosen. GPR models can be used with reasonable accuracy to predetermine critical process outputs as they have R² values above 0.90 for both training and validation data for all outputs. This work paves the way for future industrial implementation of GPR to model and predict the outputs of complex hybrid machining processes.

This paper contains the results of the biomass cutting process in which wheat straw was used. Tests were made on the prototype test stand which made it possible to control the parameters of the cutting process and based on that define its energy consumption. During the research the following parameters were measured: rotational speed of electric motor, which drives the rotor with a set of cutting knives, electric current supply and torque on the shaft. Tests were made for the variable moisture content of the biomass and with knives with three different back-rake angles 5°, 15° and 30°. Using these measured parameters it was possible to calculate the power and the cutting force necessary to disintegrate biomass. The main goal was to find out if there is any influence of moisture content and the back-rake angle of the cutting knife on the dynamic parameters of the process - power and cutting force. The presented results can be very useful in a design process for a working assembly of biomass disintegrating machines which are directed to the energetic efficiency.

The work presents the construction of a device designed to perform the cross-cutting process of conveyor belts. The device is equipped, among others, with a pneumatic drive in the form of a double acting piston rod. This actuator ensures reciprocating movement of the knife. The paper also presents the results of the pressure changes in the working chambers of the actuator as a function of displacement, recorded during the working movement of the knife which it performs during the cutting process. The tests were carried out in order to assess the level of pressures in the cylinder chambers during the cutting of belts of various constructions. These values were converted into cutting force values. It is important from the point of evaluation of changes in the value of cutting force of belts characterized by a different internal structure (composite belts made of different materials) and total thickness.

The paper presents the characteristics of consolidation of natural fibrous materials for getting the renewable solid fuel. A special attention was focused on the perpetual screw technique. A detailed analysis of the consolidation process for this technique allowed to find its advantages and drawbacks. Economic reasons for this technique are also presented. Detailed characteristics of the process allowed to separate the stages when the designer can improve the construction and get the higher efficiency of the consolidation process of the material. Design algorithm for designers of such type of machines is presented.

Most of the industrial machines use round-shaped drive belts for power transfer. These drive belts are often a few millimeters in diameter, and made of thermoplastic elastomer, especially polyurethane. Their production process requires the bonding step, which is often performed by hot plate butt welding. The authors have undertaken an effort to design an automatic welding machine, which calls for an analysis of the hot plate welding process consisting in describing the dependency between the technological parameters (temperature, pressure force, time) and the quality of the joint. To analyze this process in a proper way, it is necessary to describe the physical phenomena in the material during temperature and force impacts. In this case the research of thermomechanical properties of the belts is needed. The paper shows results of some preliminary research of the thermomechanical properties of the polyurethane. This research allows to predict the material reaction to increased temperature and force during hot plate welding.