Raw material supplier quality control
The raw material quality control performed by JB applies to both through-hardened and case-hardened steels and is based on multi-test inspections , according to our Material Guidelines. These multi-test inspections strictly follow the applicable international standards and include: raw material chemical composition analysis, macro- and micro-structure inspections, mechanical properties determination and the Raw Material Quality Control Final Report issue for lot traceability. This final report is released by the Metallographic Quality Control Laboratory and the Mechanical Testing Laboratory, which are parts of the JB Product Approval Control Department. Also, periodically, according to the JB internal protocols, all of the measuring instruments and devices are metrologically checked by our Metrological Laboratory.
Pre-process quality control
After the positive results of quality controls on raw materials, the pre-process control level comes into play. This level mainly involves the use of masterpieces for rings and rollers manufacturing. The masterpieces are extremely accurate bearing component prototypes that, having high quality machined surfaces and very tight ranges of dimensional and geometrical tolerances, are used to calibrate the measuring instruments involved in the production process.
In-process quality control
The in-process quality controls refer to the controls performed throughout the bearing manufacturing process, They ensure consistency in product quality during all stages of bearing production by adopting modern quality control techniques in forging, heat treatment, machining and assembly.
KEY PROCESS CONTROL
Forging quality control
More in depth, after the raw material approval by the Product Approval Control Department, the forging process begins, encompassing steel bar or ingot cutting, heating, upset forging or upset pressing and rolling. Every steel bar or ingot lot enters the forging area accompanied by the related Control Data Sheet emitted by our Raw Material Warehouse that specifies the type and quality of steel and the dimensions and weight of the material. In this way, our technicians, according to the Forging Operational Plan, can easily set the heating temperature, After forging, all the components are dimensionally checked and the relevant data are digitally recorded.
Heat treatment quality control
All JB bearing steels are in-house heat treated in order to obtain optimum mechanical properties. In addition to the conventional thermal cycles, JB can carry out two special heat treatments on its products: Bainite Treatment (HB) for decreasing ring crack incidence and JB Dimensional Stabilization Treatment (S) for ring dimensional stability up to an operating temperature of 350 °C. Finally, two thermo-chemical surface treatments are available: JB Anti-Wear Treatment (AWT), essential to reduce the metal-to-metal friction between contact surfaces, and JB Phosphate Treatment (PT), suitable for bearings operating in highly corrosive environments. Bearing components enter the heat treatment area accompanied by the related Control Data Sheet issued by the previous workshop, where the steel type and the dimensions of the parts are specified. Taking into consideration these parameters, furnace atmosphere, treatment time curve and quenching conditions are programmed according to the Heat Treatment Operational Plan.
After heat treatment, a series of parameters concerning form, hardness and microstructure are checked If test results are not in accordance with the specifications set by the applicableinternational standards and JB internal protocols, the cause of error is determined and all suspected components, if recoverable, are treated once again, after the corrective action is applied. All the parameters specific to every lot are recorded in a special digital database.
Machining quality control
The quality controls connected to the machining process starts with the set-up of every machine tool according to the JB production method. These settings are verified at regular breaks during production. At the end of every turning and grinding operation of rings and rollers, a check for compliance with the tight tolerances of masterpieces is performed.
A series of dimensions and geometrical and surface quality parameters are controlled by an integral calibrated system that ensures all measures are within the allowable tolerances and in accordance with JB internal manufacturing drawings. This system guarantees the quality of every lot before it is transferred to the next workshop.
Specific non-destructive controls like the Magnetic Particle Inspection, for detecting superficial micro-cracks, and the Ultrasonic Micro-Crack Detection, for under-surface micro-cracks location, are regularly performed on rings and rollers during the production process.
Post-process quality control
After accomplishing the in-process cycle, bearing samples are subjected to the post-process controls, which encompass both non-destructive tests (visual, dimensional, geometrical and surface quality control, and mechanical properties determination) and destructive tests (chemical composition, and macro- and micro-structure evaluation.
These multi-test inspections are regularly performed by the JB Advanced Measurements Laboratory and Metallographic Quality Control Laboratory by means of the latest measuring instruments in strictly controlled environments, according to the applicable international standards. In more detail, for dimensional, geometrical and surface quality controls.