Abstract. The regular cleaning up of the materials deposed in sewer networks is realised with equipment that uses pressure water jets. The functioning of this equipment is dependent on certain process parameters that can vary, causing variations of the impact forces. The research method of this study is the experiment. The purpose of this study is to determine the equation of impact forces produced by water jets in two ways: once using the Taguchi design of experiments and secondly using the full factorial design of experiments. For the experimental determination of the impact forces a stand for generating water jets and a device for measuring the impact forces are used. Finally, an analysis of the advantages and disadvantages of the two methods used is presented.

The precision of the thread processed by tapping is closely related to the precision of the pre-drilling of the blank. Currently, the technologies for processing threads with the tap in the case of metals are well established. In this sense, there are tables and clear recommendations about the tool pairs—helical drill-tap, depending on the size of the thread, but in the case of plastics, no correlations or recommendations have been found. A well-known aspect concerns the fact that the hole made in plastics is obtained with a smaller diameter than the diameter of the drill bit used. To determine the differences between the drill bit and the diameter of the resulting hole, and its precision on different types of plastic materials, experimental research was started. At the same time, the tolerance of the resulting hole was checked and the influence of the cutting regime on the processing precision was studied. During the experiments, plastic materials often used in the aeronautical and car-building industries were used: POM-C, PA6, PEHD1000, Sika Block 700, Sika Block 960, and Sika Block 980. Following the experiments, differences in the diameter of the holes processed were found according to the plastic mass of even 0.3 mm, which is 4.4% of the diameter of the hole. Based on the experimental results and the design of the experiment, recommendations could be made about the diameter of the drill to use to obtain the desired diameter of the hole after processing.

Since 1950, the use of water jets has grown in the field of cleaning pipes and sewers. The regular cleaning of the materials deposed in sewer networks is realised especially with equipment that uses high pressure water jets. The functioning of this equipment is dependent on certain process parameters that can vary, causing variations of the impact forces. The impact force directly affects the cleaning of sewer systems. This article is a part of research activity what is centered on the study of the cleaning head - sewer system. The purpose of this research is to determine an equation of the impact forces of the water jet that depend on process parameters. The research method used is that of the full factorial plan. For the experimental determination of the impact forces a stand for generating water jets and a device for measuring the forces of impact are used. The equation of the impact forces measured is determined using the software Minitab 17.

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