The shaft technology is a very popular subject in the process of technological education. There is an independent class of shafts as a class of parts in the technological context. Parts of this class are very commonly used components. The rollers (shafts) are among the simplest machining objects. The framework technological processes of the parts of the roller class were presented in the article titled Rollers – frame technological processes. In another article / post, namely rolling of cylindrical surfaces – rollers, I presented issues related to machining (turning) of cylindrical external surfaces. Shaft technology is the subject of a series of this and the following several articles, in which an example of a multi-variant technological process of the roll described below will be presented (fig. 2).

Shaft technology is primarily a turning and grinding operation [1]. There are less frequent operations such as machining of splineways and splines, as well as making threads and cross holes. During the TOOLEX 2018 fair, I had the opportunity to see special tools for generation of shafts on a fragment of the surface cooperating with the seal (fig. 1).

Fig. 1. Special tools for generation shaft – EMAG – TOOLEX 2018.

The shaft performs rotary motion and the tool moves relative. The result is a surface that does not have a characteristic spiral trace of the tool (turning). Thanks to this, the sealing achieves much greater efficiency. Tools (knives) have been developed in response to the needs of the car industry.

Shaft desing

Figure 2 shows a drawing, a technical construction sketch of the shaft, whose multivariate technological process is the subject of this and the next few articles. The shaft should be made of structural (machinery) steel. Shaft technology is characterized by its specific simplicity and the possibility of varianting the technological process.

Fig. 2. Technical drawing of the selected shaft.

Workpiece

The choice of type of the blank depends on the material used. In the case of accepted structural (machinery) steel, it should be noted that it is necessary to precisely determine the species. This is due to the fact that within the categorization of structural steels the following types can be distinguished:

• general-purpose steel (constructions and machine parts);
• construction steel of higher quality (has a low level of pollution, dedicated to heat treatment);
• low-alloy structural steel (contains up to 0.22% of coal, used for the construction of bridges, railway cars, masts);
• case-hardening steel (after the thermo-chemical treatment is characterized by high surface hardness and ductility);
• nitriding steel (after thermo-chemical treatment is characterized by high resistance to abrasion);
• heat-treatable steel (parts of machines);
• spring steel (increased silicon content and according to the name is used for the production of springs, springs);
• free-cutting steel (addition of sulfur up to 0.35% and phosphorus up to 0.15%, bolts, washers, nuts, etc.);
• bearing steel (precise composition control required, manufactured under strict technological regime).

The steel designation consists of a letter and a three-digit number (minimum yield stress Re [MPa] or minimum tensile strength Rm [MPa] for steel on R rails and Y compression strings). The numerical part may contain letters. In the case of constructional steels, the letter S is used. The shaft shown in figure 1 is made of S235J2G3 steel, which, among others, is dedicated to:

• making welded structures in machine building and steel construction;
• a lever;
• pins;
• axles;
• shafts exposed to a small load.

Returning to the designation of the accepted constructional steel S235J2G3, this designation J2 means at what temperature (here -20 ° C) the sample percussive breaks down (breaking operation KV = 27 [J] – notch type V). G together with a digit is the state of the steel (1 – effervescing steel, 2 – solid steel, 3 – normalized steel, 4 – condition determined by the manufacturer). According to the Consortium of Steel S.A. round smooth round bars with a diameter of ø70 ± 1 are available – the weight of 1 mb is 30.2 kg. The standard bar length ranges from 3000 to 6200 with a tolerance of ± 100. Depending on the size of this type of production, the information allows to estimate the necessary weight of the bars, and thus the purchase costs of the material.

The process of material selection requires exactly the same attitude from the technologist as from the designer in the context of manufacturing technology. The steel market offers a specific range despite the seemingly wide range of products available. Especially in the initial design period, it is necessary to analyze the availability of materials at the design stage. This will enable faster implementation into production.

Technological process

Shaft technology would be presented in the best way and requires the basic technological process of the roller to be developed using conventional machine tools (educational advantages). Such an approach, as I have repeatedly mentioned, enables the presentation of fully technological dependencies. The basic technological process consists of 6 main technological operations, including the final technical inspection operation and the washing, maintenance and packing operation.

In the case of using CNC turning centers with the milling option, the number of technological operations will be reduced.

Sources

1. Feld M., Podstawy projektowania procesów technologicznych typowych części maszyn, WNT 2000
2. Puff T., technologia budowy maszyn, PWN 1985
3. Maciej Horczyczak Ph.D. – knowledge and consultations
4. POLMET, ZWCAD, AKROSTAL, PS LOGISTYKA reference books
5. Cognor S.A. HSJ branch in Stalowa Wola reference book