Workpiece – the object of work, which after the technological process has been completed, after all the provided treatments have been completed (change of shape, dimensions, surface and material properties) is the final product (part, machine or device). Workpieces are manufactured using various methods depending on the production volume.

The blank is identified with the workpiece before the start of the technological process. It is not possible to develop an exact technological process without a semi-finished project. The blank with its shape, dimensions, surface and material properties deviates from the final product. The blank design allows you to specify specific machining allowances. In the case of mass production forgings (fig.1) or castings are used, then it is important whether the blank will have pre-made holes, whether their machining will be in the full material.

The following types of blanks are distinguished:

• from metallurgical materials (eg rolled rods of circular, square, rectangular, hexagonal cross-section; sheets, pipes, various profiles – angle bars, channel sections, tees, drawn products),
• welded (piece production), soldered,
• forgings (mass production),
• castings (mass production),
• plastic (moldings, moldings),
• punching dies,
• produced by cold forming method (blanks, extrudates),
• produced by technologies of powder metallurgy (metal, metal-ceramic powders).

The constructor is responsible for the material selection, taking into account structural, technological and economic factors. When developing a construction, technological considerations should be taken into account, including the selection of a blank. The size of production is very important here. Other types of blanks are accepted for series production (castings, forgings – figure 1) and others for piece production (welded, glued blanks). Already at the stage of developing the blank, the technologist takes up the issues of the producibility.

Fig. 1. Blank forged and finished product.

Piece production

The blank in the didactic process is a challenge. The semi-finished product can be manufactured in any way. The condition is to meet economic conditions from the point of view of the entire production process. In the case of aluminum parts, special structural adhesives (eg from Loctite) may be used. In the case of steel components with significantly different dimensional dimensions, they can be welded (welded), eg a plate and a rod (with a large diameter). Thermal stress and potential grooves at the weld location is a problem.

The forging and final product shown in Figure 1 is a part of the sleeve class. In the case of piece production, this workpiece can be machined from a rod that is commercially available in 1 or 2 technological operations.

Analysis of the technological character of the structure in unit production can lead to a change of material from which part it should be made (instead of cast iron used in castings, constructional steel is selected). Such action requires consultation with the constructor (ordering person).

Such manufacturing techniques as laser or water cutting, and in recent years also additive techniques (3D printing) have significantly influenced the production of workpiece for piece production. On the one hand, the development of these manufacturing techniques expands the technological capabilities of creating semi-finished products while reducing costs. At the same time, the development of manufacturing techniques extends design capabilities.

Particularly interesting in the preparation of semi-finished products for unit production are incremental manufacturing techniques referred to as 3D printing. Such manufacturers of machine tools as Yamazaki MAZAK and DMG MORI have in their offer machine tools hybrid. These machines enable 3D metal printing, and then the ability to perform 5-axis machining of the workpiece thus produced.

References

1. Feld M., Podstawy projektowania procesów technologicznych typowych części maszyn, WNT 2000
2. Kapiński S., Skawiński P., Sobieszczański, Sobolewski J.Z., Projektowanie technologii maszyn, OWPW2002
3. Puff T., Technologia budowy maszyn, PWN 1985