# A Solution for Predicting the Timespan Needed for Grinding Roller Bearing Rings
## 2 Manufacturing Process for Bearing Rings  
### The Identification of the Flow Diagram for the Manufacturing of an Inner and Outer Bearing Ring  
Bearings are the most common machine parts [15] and have extensive applications in industrial fields, such as the railway, automotive, aeronautical, and machine tool manufacturing industries. In order to obtain a bearing which is suitable for the intended usage, the manufacturing process should be under control from both the process and product parameters. The designed process parameters are dedicated for each process step and the setting up of these parameters on machine tools involves some activities that are time consuming. The collection and usage of the values of the set-up parameters and the measured process and product parameters in a database, which could be used as a reference for future orders, quotations or in some improvement strategies, becomes necessary in the actual manufacturing environment and also in the transfer of knowledge between employees. To be able to follow products in the production field and to assure the traceability of products, process, measurements, and decisions to be taken in bearings manufacturing processes, one of the most important steps is to identify flow diagrams and then, based on these documents, compile the operation and verification plans for each process step and phase. Figure 1 presents the generic flow diagram for the manufacturing of inner and outer bearing rings, as well as the manufacturing processes used to produce bearing components. To manufacture a conforming bearing component, each step of the process must be defined, designed, implemented, and controlled during production. The main production steps, starting from raw material reception, are as follows: the forging of rings, this process is controlled by checking temperature and dimensions of the produced sample; the annealing process, which is controlled through the temperature, time, and microstructure of the sample; the shot blasting process, which is controlled through process time and surface quality by visual inspection; turning, controlled through process parameters, set-up parameters, dimensions, visual inspection, and surface quality; secondary heat treatment (quenching and tempering), controlled through temperature, time, microstructure and the hardness of the sample; the grinding process, characterized through process parameters, set-up parameters, and, for the obtained product, through geometrical and shape deviation control and surface aspect control; the demagnetization process, controlled through process time and remanent magnetism; and the washing process, controlled through the degree of cleanliness of the product. The final inspection, before the assembly of the bearings, involves complete measurements of the product parameters and a visual inspection. From the generic flowchart depicted in Figure 1, which applies to the manufacture of bearing rings, the grinding process was selected for this research. This process plays an important role in geometrical and shape deviations, surface quality, and, ultimately, bearing function. It is known that the geometrical and surface parameters requested for bearing components are strongly related to the bearing's main application. To produce components within the technical requirements, the grinding process should be controlled from both the process control and the product parameter control perspectives. Considering the relationship between process parameters and product parameters, this paper presents data collected from an industrial manufacturer in the bearing production industry. A set of parameters specific to the grinding process, such as the inner and outer diameter of the ring, its width and weight, the machined surface roughness, the grinding stone rotation speed, the cutting speed, the feed rate, and the cutting depth, were considered as input data for the proposed application of the HOM. The database was then used to apply the HOM to predict and optimize the process in terms of timespan.