Field of the invention

The invention falls in the field of surface treatment and deals with method of fast surface machining of rotary components, especially hard ceramic or metaloceramic coatings prepared by method such as thermal spraying on the rotary component with the length usually greater than 2 meters. This method enables such machining without necessity of continuous exchange of grinding discs and interruption of machining track while achieving surface hardness Ra≤ 0.2 μιη.

Background of the invention

Very hard ceramic, metaloceramic or metallic coatings are deposited on the surface of rotary component of various diameter and length in order to modify the surface and protect the component against adverse effect of electrochemical and/or chemicai corrosion, static or cyclic mechanical loading during operation, interaction with particles or suspensions etc. These coatings can be deposited on the surface by means of thermal spraying methods such as Water Stabilized Plasma (WPS), Atmospheric plasma spraying (APS), High Velocity Oxygen Fuel (HVOF) and High Velocity Air Fuel (HVAF) or by hard chromium plating as stated in patents CZ 305206, CN 104411083, CN 203144504, EP 2868388, JP 2012112012 and RU 2235795. Typical, but not limiting, examples of the rotary components are for example long piston rods with extreme length over 2 meters, which are used in hydraulic systems in power industry as overspeed devices or floodgate systems. As application outside of power industry, piston rods for cranes working on the offshore platforms or rotary component of large presses for fireclay production can be mentioned. Key parameters is case of such surface treated rotary components are mainly dimensional precision, minimal eccentricity , high hardness, wear resistance of the surface or the coating and high quality of the surface treatment along the whole component while meeting the condition of continuous machining track. The actual final surface machining of hard coatings is problematic, but not impossible when the rotary components are not too long. However, the problem with hard surface machining arises, when the rotary components are longer than 2 meters. Up to this length, surface of rotary components can be continuously machined requiring only change of grinding discs for different abrasive grain size before the following toolpaths. So the. limitation for the workpiece length is the standard length of the toolpath of rotary surface grinders used in industry as is evident from patents AU 2015101299, US 2015298279, US 6306018 a EP 2036669. So the continuous machining track with no need for grinding disc change is always guaranteed. However, this method of rotary components grinding leads to increase in financial expenses due to need of variety of grinding discs with different abrasive grain size and finishing diamond discs as follows from patents CZ 1998-1878, CZ 2000-3542, CZ 305187, CN 204248677, CN 204382113, CN 204339573, CN 204339540 a CN 104526584. There is also limited value of final surface roughness (Ra ~ 0,8 μιη), while this method is used. To decrease the final surface roughness, combination of time consuming sequential techniques can be used such as grinding by industrial rotary surface grinders, lapping and polishing using industrial belt grinders and diamond abrasive belts as described for example in patents EP 636671 , US 5622526, CN 103273434 or GB 1357292. After this lengthy process, such combination of techniques can theoretically lead to final surface with roughness of Ra ~ 0,2. Rotary components over 2 meters and especially over 6 meters undesirably bend in the centre between the supports due to a significant increase in the weight which leads to excessive eccentricity. Therefore the aforesaid method is not suitable for machining of long components including grinding, lapping and polishing, without use of fixed or follow support, also called stay, as stated in patents CZ 295493, TWM 495260 U, EP 2516109 or US 8474140. Nevertheless even this modification of surface machining method does not completely ensure constant machining track when using fixed stays. While the follow stays are used, surface damage occurs in the form of grooves at the contact point of rotary surface and the stay. In both cases, it is not possible to ensure requirement for continuous machining track and high surface quality of long rotary components with surface treatment.

The purpose of the invention is to present a completely unconventional device, simple in design and easy to operate, for fast surface machining of hard materials or surfaces treated rotary components. Presented method consists of sequential machining steps of grinding and polishing using discs that can be quickly changed right in the device. Unlike the above mentioned technologies, this method exploits high surface hardness of the workpiece. Machining method is completely independent on size, sag and eccentricity of the component and enables achieving of very low surface roughness (Ra ~ 0,1 ) very quickly, depending on the component size, while ensuring requirements for high precision of machining and continuous machining track. Present invention enables a substantial reduction of the buying or production costs of the device, whose operation is highly economically effective due to substantial reduction in hard-surface machining time and also reduction in consumption of gas, electricity and filler material, that are needed for surface coating deposition. Proposed method, which can be used for various types and sizes of rotary components, enables fast meeting of commonly or completely unrealistic requirements for surface quality and continuity of machining track.

Description of the invention

Aforesaid objective is achieved, to large extent, by present invention, the method of machining of rotary components, especially hard ceramic, metaloceramic or metallic coatings on the rotary component with the length greater than 2 meters. The merit of invention is the linear movement of the supporting construction along the axis of the clamped rotating component, which is being extensively cooled during the process. Supporting construction is equipped with at least one radially adjustable machining disc holder while discs are profitably diamond discs. in case of expediential design, the revolutions speed and thrust between the machining disc and workpiece are recorded, evaluated and set by control and monitoring unit, which also control parameters of linear movement of supporting construction. Based on the actual data, concerning diameter change and surface topography parameters, received from the measuring unit, the process parameters are continuously modified and updated, including relevant machining disc change.

Further, the invention includes also device for surface machining of rotary components, especially hard ceramic, metaloceramic or metallic coatings on the rotary component with the length greater than 2 meters. The invention is supporting construction modified for connecting with linear movement mechanism, which enables its movement along the axis of rotary component. The merit of invention is firstly connection of supporting construction to at least one radially adjustable rod with holder, which is adapted for mounting of quickly changeable machining discs, profitably diamond discs. Secondly, it is connection to the supply of coolant, regulator of pressure between machining disc and rotary workpiece, and measuring unit. The rod, the coolant supply connection and measuring unit are linked with control and monitoring unit, which is also connected to the linear movement mechanism that enables movement of the supporting construction.

In case of expediential design, supporting construction consists of two detachable semicircular-arched components with four rods arranged around circle and it is connected to the linear movement mechanism by two carriers. The coolant supply connection is equipped with stop valve and pump to ensure circulation and recycling of coolant. The measurement unit consists a diameter meter and/or by optical profilometer. Ideally, the outer parts of the rods are connected to the electromotors via transmission. The electromotors, finked with control and monitoring unit, are equipped by frequency convertors to enable regulation of revolutions speed of machining disc holders.

Comparing to up to now known methods, very low surface roughness parameters of machined surface or coating can be achieved by use of this invention when machining very long rotary components of various lengths. Also the requirement for high dimensional precision and minimal eccentricity along the whole workpiece is fulfilled. Moreover, the requirement for continuity of the machining track, low time demand on machining process and demand on high energetic and economic efficiency of the whole technological process, which is yet unresolved issue, is met.

Brief description of the drawings

Specific examples of the invention in a simplified form are shown in the attached drawings, where

Fig. 1 shows axonometric view of schema of the basic construction of the device with four machining discs, drawn without control and support components,

Fig. 2 shows schema of the device from Fig.1 including control and support components that ensure operational precision and high precision of machining,

Fig. 3 shows axonometric view of schema of the alternative construction of the device with one machining discs,

Fig. 4 shows surface topography before machining with the device, Fig. 5 shows surface topography after machining with the device,

Fig. 6 shows the evolution of the surface roughness parameter (Ra) during the sequential machining operations,

Fig. 7 shows the evolution of the machined surface diameter (D) during the sequential machining operations.

Drawings which illustrate the presented invention and the described specific examples does not limit in any way the scope of protection specified in the definition, but only explain the merit of invention.

Description of preferred embodiment

Referring to a Fig 1 , basic construction of the device is comprised of supporting construction I consisting of two semicircular-arched components detachably joint by tightening components 102. usually threaded joints. Supporting construction 1, namely components 101. is connected to four rods 2 arranged around circle, which are adjustable in radial direction with respect to workpiece 3 axis. Rods are equipped with holders 4 that are adjusted for mounting of quickly changeable machining discs 5, profitably diamond discs with different abrasive grain size. Adjacent surfaces between holders 4 and machining disc 5 are modified to enable quick change i.e. attachment and removal of machining discs 5, for example by use of Velcro. Contact area of the machining discs 5 i.e. grinding and polishing faces, which are not shown in detail, have radial and circumferential grooves that ensure continuous coolant supply and permanent removal of debris from the surface of machined rotary component 3. Supporting construction 1 is via two carriers 103 connected to the components (not in the figure), for example rods, bars, springs, pneumatic or hydraulic components, which are further connected to the linear movement mechanism, for example lathe carriage, chain gear, leadscrew, electric, pneumatic or hydraulic drive. Thus the movement of the supporting construction in the direction of the axis of rotary component 3 is ensured.

To ensure declared function, the device is equipped with the control and support components. These components are linked to monitoring unit 6, profitably computer, as illustrated in Fig. 2. The device is equipped with coolant supply connection 7 including stop valve 7J_ and pump 72 to ensure circulation and recycling of coolant, with measuring unit 8, which consists of a diameter meter and/or by optical profilometer, and with regulator of pressure 9 between machining disc 5 and rotary workpiece 3. The outer parts of the rods 2 are connected to the electromotors 10 via transmission H. The electromotors 10, are further equipped by frequency convertors to enable regulation of revolutions speed of machining disc holders 4.

When using basic construction of present device for surface machining of hard ceramic, metaloceramic or metallic coatings on the rotary component 3, preferentially lengthy components, the semicircular-arched components 101 of supporting construction 1 are connect to all the control and support components 7, 8, 9 that are linked to the control and monitoring device 6, and assembled around the clamped rotary component 3. For the positioning of the semicircular-arched components 101 around the workpiece, . height adjustable machining disc holders 4 are used with undefined thrust. Rotation of the rotary component 3 together with linear movement of the device along the component 3 and sequential change of the machining discs, leads to gradual reduction in component diameter and surface roughness as illustrated in Fig. 4 and Fig. 7. During the process, workpiece is intensively cooled down by the coolant, which flows through the stop valve 71. Control and monitoring unit 6 records and regulates revolutions speed of the machining disc 5 during the process and also during start period and run-down, and thrust of height adjustable machining disc holders 4. Individual components 71_, Z , 9 and 10, influencing machining process, are also switched on/off and regulated. At the same time, the data from the measuring unit 8 containing information about diameter change and change of topographic parameters of machined rotary component 3 surface are continuously collected by the control and monitoring unit 6. Based on these data, machining process parameters are modified and set. For example, based on the data obtained from continuous contactless measurement by means of diameter meter and optic profilometer, the control and monitoring unit 6 changes revolutions speed of rods 2 with machining discs holders 4 via frequency converter of electromotors 10, or changes or maintain constant thrust between machining discs 5 and machined rotary surface 3.

Described construction of the device with supporting construction 1 consisting of two semicircular-arched components 101 with four machining discs 5 holders 4 around the circumference is optimal, but not only possible construction of the invention. Based on the same principle, device illustrated in Fig. 3 can be used. It consists of L-shaped supporting construction 1 connected to only one rod 2 with machining discs 5 holder 4. Also device with more than four holders 4 for quickly changeable machining discs 5 can be used while the disc are static or rotating or combined (some of the disc are rotating and some of them are static). Arched design is not the only possible design of supporting construction 1, which can be circular, oval, square, rectangular or irregular or even combination of those. Also the shape of the machining, grinding and polishing, discs 5 and also the holders 4 can be not only circular but also oval. Example construction, mounting and shape of holders 4 and adjustable rods 2 illustrates mounting only by the standard screw thread, which can be replaced by different mechanism, for example by slide-in mechanism or by groove. industrial applicability

Present invention falls in the field of honing machines or devices for machining of outer surface of rotary components with high requirements for the surface properties, surface topography and final appearance. The components with the length greater than 2 meters are machined without continuous change of the machining discs and interruption of the machining track, for which the commonly used techniques are unusable or unsatisfactory. Industrial applicability of the invention is very wide with possible use in many industrial fields as the heavy engineering, civil engineering, chemical and petrochemical industry, textile industry, nuclear power engineering and power engineering.