WO2024189078A1 - Procédé de polissage de pièces par traitement avec un rayonnement énergétique - Google Patents

Procédé de polissage de pièces par traitement avec un rayonnement énergétique Download PDF

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Publication number
WO2024189078A1
WO2024189078A1 PCT/EP2024/056670 EP2024056670W WO2024189078A1 WO 2024189078 A1 WO2024189078 A1 WO 2024189078A1 EP 2024056670 W EP2024056670 W EP 2024056670W WO 2024189078 A1 WO2024189078 A1 WO 2024189078A1
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WIPO (PCT)
Prior art keywords
processing
energetic radiation
workpiece
machining
radiation
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PCT/EP2024/056670
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German (de)
English (en)
Inventor
Manuel Jung
Edgar Willenborg
Karsten Braun
Emra ULUZ
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Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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Publication of WO2024189078A1 publication Critical patent/WO2024189078A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
    • B23K26/3568—Modifying rugosity
    • B23K26/3576—Diminishing rugosity, e.g. grinding; Polishing; Smoothing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K15/00—Electron-beam welding or cutting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/03—Observing, e.g. monitoring, the workpiece
    • B23K26/034—Observing the temperature of the workpiece
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/073—Shaping the laser spot
    • B23K26/0738—Shaping the laser spot into a linear shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/60—Preliminary treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/30—Organic material
    • B23K2103/42—Plastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
    • B23K2103/54—Glass

Definitions

  • the application relates to a method for polishing workpieces, in particular made of glass or plastic, by processing with energetic radiation, in particular laser radiation, comprising the following method steps: providing a workpiece which has a first surface and a second surface lying opposite it, polishing the first surface by irradiation with energetic radiation with first processing parameters and polishing the second surface by irradiation with energetic radiation with second processing parameters.
  • Polishing surfaces with energetic radiation is based on the absorption of the energetic radiation in a thin surface layer of the workpiece, so that temperatures close to the surface are achieved just below the material-specific evaporation temperature of the respective material.
  • the viscosity of the material is reduced by heating, which results in the surface being smoothed by the surface tension. In principle, this results in a fundamentally different operating principle compared to conventional polishing processes. Instead of physically removing material through mechanical processing, the surface is smoothed by remelting it, i.e. by redistributing the material.
  • WO 2012 / 1 19 761 A1 describes a method for manufacturing optical elements by processing with energetic radiation.
  • blanks made of quartz glass are first treated with coarse removal and then polished with energetic radiation.
  • Surface parameters are then compared with a target value. If the surface parameters are outside a defined tolerance range, further steps of fine removal of Material using energetic radiation until the surface parameters are within the defined tolerance range.
  • the surface of the workpiece to be processed is scanned with a radiation source in parallel paths, for example in a meandering shape.
  • the object of the present invention is therefore to provide an efficient method for smoothing and polishing thin glasses and thermoplastics by processing with energetic radiation, which causes smaller deviations in the shape of the workpiece geometry when smoothing or polishing the workpieces with energetic radiation.
  • a method is to be specified with which very smooth and highly precise surfaces of optical elements or other thin workpieces made of glass or thermoplastics can be produced.
  • the object is achieved with the method according to patent claim 1.
  • Advantageous embodiments of the method are the subject of the subclaims or can be taken from the following description and the embodiments.
  • the object is achieved by a method for polishing workpieces, in particular made of glass or plastic, by processing with energetic radiation, in particular laser radiation.
  • a workpiece is provided which has a first surface and a second surface opposite it. The first surface is polished by irradiation with energetic radiation with first processing parameters and the second surface is polished by irradiation with energetic radiation with second processing parameters.
  • the method is characterized in that the first processing parameters for polishing the first surface and the second processing parameters for polishing the second surface are selected such that by irradiating the second surface with energetic radiation with second processing parameters, the second surface is subjected to a higher thermal stress than the first surface by irradiation with energetic radiation with the first processing parameters, in order to thereby reduce distortion of the workpiece.
  • the inventors of the present invention have found that by machining the second surface with second machining parameters that induce a higher thermal stress in the workpiece than is the case with machining the first surface with the first machining parameters, a smaller distortion of the workpiece can be achieved than in comparison to machining the workpiece on one side or in comparison to machining the first and second surfaces of the workpiece with identical machining parameters.
  • the thermal stress that arises in the workpiece when machining the second surface with the second machining parameters is increased compared to machining the first surface with the first machining parameters by selecting the appropriate parameters in order to reduce the distortion of the workpiece. To do this, either individual machining parameters or several machining parameters in combination can be adjusted, whereby the total thermal stress generated when machining the second surface must be higher than when machining the first surface.
  • thermal stress is mentioned in connection with the method according to the invention, what is meant is, strictly speaking, thermally induced mechanical stress.
  • this has the technical advantage that there is no need for complex mechanical regrinding after processing a workpiece with energetic radiation to compensate for distortion. This technical advantage is reflected in a reduction in processing time and processing costs. Furthermore, no foreign substances such as chemicals and polishing agents need to be applied to the surfaces of the workpiece, which can prevent contamination and the resulting loss of surface quality. In addition, occupational safety is increased because avoiding mechanical regrinding prevents the release of fine material dust, which the operator should avoid inhaling for health reasons.
  • laser polishing also enables the selective polishing of workpieces with different complex geometries.
  • the energetic radiation is directed, preferably vertically, onto one of the surfaces of the workpiece.
  • the energetic radiation is absorbed within a thin edge layer close to the surface, which heats up the material. In the case of quartz glass, for example, this is an edge layer area on the order of several micrometers.
  • the increase in temperature reduces the viscosity of the material and the material begins to flow. As a result, surface roughness is smoothed out by the surface tension without any material being removed.
  • WLI White light interferometry
  • AFM atomic force microscopy
  • laser scanning microscopy or profilometry are suitable for determining surface roughness.
  • WLI White light interferometry
  • laser interferometry laser scanning microscopy or profilometry are suitable for determining the shape deviations in the workpiece geometry.
  • the so-called peak-to-valley distance is measured in white light interferometry. This distance is the distance between the highest and lowest point on the surface being measured.
  • the peak-to-valley distance can be measured in accordance with the standards DIN EN ISO 101 10-5 and ISO 14999-4.
  • the method according to the invention has its advantageous effect particularly in the case of thin workpieces. Accordingly, the advantages of the method according to the invention are particularly evident in the case of workpieces that have a first and a second surface that are considerably larger in relation to the other outer surfaces of the workpiece. The distance between the first and the second surface corresponds to the thickness of the workpiece. This particularly applies to workpieces with a thickness in the range of 0.5 mm to 10 mm.
  • Workpieces made of materials such as glass, in particular quartz glass, borosilicate crown glass (e.g. N-BK7) and heavy flint glass (e.g.
  • thermoplastics such as polycarbonate (PC), polymethyl methacrylate (PMMA) and polyamides (PA) are suitable for the method according to the invention. It should be noted that the materials made of thermoplastics do not necessarily have to be transparent.
  • the workpieces include, for example, imaging optics, aspherical lenses or free-form lenses.
  • the first and second surfaces of the workpiece can be prefabricated by cutting, drawing, forming, grinding, injection molding, laser ablation or additive manufacturing processes.
  • the energetic radiation is preferably laser radiation that is absorbed close to the surface. It is particularly preferably infrared laser radiation from a CO 2 laser.
  • a laser can be operated in continuous, pulsed or modulated mode and a laser power of between 1 W and 4000 W, preferably between 100 W and 2000 W, can be used. If, for example, a laser is used in pulsed mode, the laser can be operated with a pulse duration of 1 ps to 1000 ps and a repetition rate of 1000 Hz to 150,000 Hz.
  • Infrared radiation, microwave radiation or electron radiation are also suitable as energetic radiation.
  • the surface section to be processed can be irradiated over its entire surface by expanding a laser beam with suitable optics, such as lens systems, or it can be scanned by at least one energetic beam.
  • the beam can be guided over the surface section to be processed using mirrors and/or machine axes.
  • Several beams of energetic radiation can also be used for simultaneous or consecutive processing of the surface, for example to achieve a more uniform temperature application to the workpiece or a higher surface rate. Either consecutive processing of the first and then second surface or simultaneous processing of the first and second surfaces.
  • the gases argon, helium, carbon dioxide and nitrogen are particularly suitable for this. This prevents contamination from burning into the surface of the workpiece during processing with energetic radiation and reduces the surface roughness.
  • the first and second processing parameters are selected from the group comprising process temperature, interaction time of the energetic radiation with the respective surface, scanning speed, beam diameter, track spacing and combinations thereof.
  • the process temperature is the maximum temperature of the workpiece within the interaction zone of the energetic radiation with the workpiece.
  • the interaction zone represents the area in which the energetic radiation interacts with one of the surfaces during irradiation.
  • Process temperatures range between 300 °C and 2500 °C for glass and between 100 °C and 500 °C for plastics.
  • the interaction time is the time in which the energetic radiation interacts with the material.
  • the interaction time is in the range between 0.5 s and 10 s for glasses and 1 s and 1000 s for plastics, with interaction times over 60 s being particularly relevant for extremely rough surfaces (surface roughness Ra > 3 pm), such as additively manufactured components.
  • the beam diameter of the energetic radiation can be in the range of 100 pm to 25 mm, preferably in the range of 1 mm to 10 mm.
  • the track spacing is the distance between the individual processing tracks on which a surface is treated with the energetic radiation being processed are offset from each other.
  • the track spacing is in the range of 1 pm to 2000 pm, preferably in the range of 5 pm to 200 pm.
  • the workpiece cools between the machining of the first and second surfaces during consecutive machining of the first and then the second surface.
  • the workpiece cools to a temperature below the material-specific glass transition temperature or melting temperature in the case of materials with a fixed melting temperature. It is preferred that the workpiece has the same initial temperature at the start of processing the second surface as at the start of processing the first side, thereby achieving a reproducible polishing result.
  • the processing of the second surface with energetic radiation with the second processing parameters produces a higher temperature gradient in the workpiece than the processing of the first surface with energetic radiation with the first processing parameters.
  • the second surface Due to the higher temperature gradient between the temperature on the second surface and the internal temperature of the workpiece, which is caused by processing the second surface with energetic radiation using the second processing parameters in the workpiece, the second surface is subjected to a higher thermal stress than the first surface. This results in the surprising technical effect that the distortion of the workpiece is reduced when processing the workpiece with energetic radiation according to the invention.
  • the process temperature when machining the second surface is higher than the process temperature when machining the first surface.
  • the process temperature is in the range from 100°C to 2500°C, preferably in the range between the material-specific glass transition temperature or melting temperature for materials with a fixed melting temperature and the material-specific evaporation temperature of the workpiece.
  • process temperature for processing the first and second surface depends heavily on the material.
  • a temperature in degrees Celsius that is 0.1% to 30% higher than that for processing the first surface should be selected for processing the second surface.
  • the workpiece is subjected to a higher thermal stress when the second surface is machined and a higher temperature gradient is generated in the workpiece, so that the technical advantage is achieved that the distortion of the workpiece when machining the workpiece with energetic radiation is lower than with conventional laser polishing processes.
  • the interaction time of the energetic radiation when processing the second surface is higher than the interaction time when processing the first surface.
  • interaction time for processing the first and second surface is highly dependent on the material.
  • an interaction time that is 1% to 500% longer than that for processing the first surface must be selected.
  • the energetic radiation interacts with the second surface for a longer period when irradiating the second surface than when irradiating the first surface.
  • the workpiece is subjected to a higher overall thermal stress when machining the second surface due to the longer interaction time.
  • the workpiece is preheated before irradiation with energetic radiation.
  • the preheating temperature is selected to be lower during consecutive processing of the first and then second surface before irradiating the second surface with second processing parameters than before irradiating the first surface with first processing parameters.
  • the preheating temperature is selected material-specifically in the range between 25°C and 1300°C. Preheating provides the technical advantage that the development of thermal stresses in the workpiece can be regulated when processing a surface with energetic radiation. Higher preheating temperatures lead to lower thermal stresses in the workpiece.
  • the preheating temperature when irradiating the second surface with second processing parameters is therefore selected to be lower than when irradiating the first surface with first processing parameters.
  • irradiating the second surface with the second processing parameters creates a higher temperature gradient in the workpiece and subjects the workpiece to a higher thermal stress, which reduces the distortion of the workpiece.
  • a temperature of the first and/or second surface is monitored and in particular controlled during processing, wherein in particular the process temperature of the first and/or second surface is measured.
  • the respective temperature can be measured at one or more fixed positions relative to the interaction zone or at one or more variable positions on the first and/or second surface. These measurements can be carried out using a point, line or area thermal camera or using a pyrometer.
  • the thermal radiation in the immediate interaction area of the energetic radiation on the surface of the workpiece can be measured and the temperature determined from this.
  • a pyrometer can be permanently connected to the energetic radiation source.
  • the temperature recorded in this way can be used, for example, to adjust the power of the radiation source.
  • the scanning speed can be adjusted instead of the power of the radiation source in order to achieve the desired process temperature.
  • the temperature can be controlled, for example, for heat-sensitive materials or for workpieces with localized Particularly sensitive surface areas or complex workpiece geometries where different heat conduction properties exist at different positions must be kept within a specific tolerance range between a maximum and a minimum temperature.
  • the first and second processing parameters are adjusted in such a way that a constant process temperature or a defined temperature profile is produced on the first and/or second surface.
  • a pyrometer can be used to determine the temperature and, via a suitable control technology, the temperature recorded in this way can be used, for example, to adjust the first and second processing parameters in such a way that a constant process temperature or a defined temperature profile is achieved.
  • the energetic radiation is directed at the respective surface for irradiation and is guided over the respective surface at a relative speed so that the energetic radiation is formed into a quasi-line, wherein the respective surface is polished in particular by repeatedly passing over the respective surface with energetic radiation formed into the quasi-line.
  • the energetic radiation is moved back and forth along a line, wherein the length of the line is at least as long as an extension of the surface to be polished.
  • the translatory oscillating movement component has a scanning speed in the range of 100 mm/s to 10000 mm/s, preferably in a range of 2000 mm/s to 10000 mm/s
  • the feed movement component has a feed speed in the range of 0.1 mm/s to 50 mm/s, preferably in a range of 1 mm/s to 10 mm/s.
  • a quasiline which is generated by the energetic radiation oscillating in a translatory manner at high speed on the workpiece and which is moved over the surface at the feed rate. If the surface is irradiated with energetic radiation in this way, this is also referred to as a quasiline processing strategy.
  • the quasi-line processing strategy is chosen, especially for polishing glasses, but also thermoplastics, using energetic radiation.
  • the surface of the workpiece is polished by passing over the respective surface once. It is also possible to polish the respective surface by passing over the corresponding surface several times with the energetic radiation.
  • the number of passes can be between 1 and 20. The number of passes depends, among other things, on the scanning speed used. Processing with a single pass is particularly preferred. At high scanning speeds, more passes tend to be required, with each individual pass partially reducing the surface roughness and healing or melting the microcracks in the area of the surface and in the area just below the surface close to the surface.
  • the respective energy input can be set lower when using several individual passes than when using a single pass, the overall energy input is more homogeneous.
  • passing over a workpiece surface several times has the technical advantage that a low surface roughness can be achieved in a more gentle manner than when using a single pass.
  • the process pause between the individual passes on a surface achieves the technical advantage that the workpiece can move during the pause can cool down and thus overheating of the surface due to preheating from previous passes can be avoided, thereby preventing unwanted material evaporation.
  • the number of passes is between 1 and 20, preferably between 1 and 5, wherein the number of passes when machining the second surface is higher, preferably 1 to 2 passes higher, than when machining the first surface.
  • the energetic radiation interacts with the second surface for a longer time overall when irradiating the second surface than when irradiating the first surface.
  • the workpiece is subjected to a higher overall thermal stress when machining the second surface due to the longer overall interaction time.
  • thermoplastics As a rule, a higher number of passes is selected for processing thermoplastics than for processing glass, and the other processing parameters are adjusted accordingly to suit the material. This enables the workpiece to be processed more gently and reduces distortion, which plastics are generally more susceptible to.
  • the first surface is machined with one pass and the second surface is machined with several passes, wherein when machining the second surface in the first pass the second machining parameters are identical to the first machining parameters for machining the first surface.
  • the workpiece can be examined and in particular the surface quality of the first or second or both surfaces can be determined. Furthermore, the distortion of the workpiece can be measured after one or a certain number of passes and the processing parameters can be adjusted based on these measurement results. For example, one or both surfaces can be optically measured and with a target surface contour and target surface roughness. If such measurements show deviations outside a specified tolerance range, a further pass is carried out. With a further pass, any remaining waviness or other deviations from the target surface contour or target surface roughness can be reduced. This allows the process to be flexibly adapted to the respective workpiece.
  • the process temperature corresponds to 10% to 90% of the process temperature during the first pass and/or the interaction time corresponds to 10% to 90% of the interaction time during the first pass.
  • the workpiece can be examined and in particular the surface quality of the first or second or both surfaces can be determined. Furthermore, the distortion of the workpiece can be measured after one or a certain number of passes and the processing parameters can be adjusted step by step with each subsequent pass based on these measurement results. In particular, the process temperature and/or the interaction time can be selected to be gradually lower with each subsequent pass of the second surface. This step-by-step processing process can be carried out until the measurement results are within a desired tolerance range.
  • the process can be flexibly adapted to the workpiece.
  • the energetic radiation for irradiation is directed onto the respective surface and guided over the respective surface at a relative speed such that the energetic radiation is formed into a quasi-tophat distribution.
  • the processing strategy in which the energetic radiation is formed into a quasi-tophat distribution is characterized by the fact that, unlike the quasi-line processing strategy, the feed movement component of the scanning speed is also very high, so that the entire surface of the workpiece to be processed is scanned with the energetic radiation in a very short time, typically in less than a second. After each scanning cycle, the surface area to be processed is immediately scanned again, so that scanning takes place several times per second.
  • the orientation of the scanning paths is preferably rotated by an angle, e.g. 90°.
  • the aim of this processing strategy is to achieve a temperature field that is as homogeneous as possible across the entire surface area to be processed.
  • the scanning speed can be varied within the surface area to be processed and/or during a scanning cycle. This makes it possible, for example, to compensate for the increased heat dissipation at the edge of the surface area to be processed.
  • the scanning process which consists of a large number of scanning cycles, is repeated for a fixed time corresponding to the interaction time.
  • thermoplastics which are processed at a lower process temperature than glass.
  • Fig. 1 is a schematic representation of the machining method according to a preferred embodiment of the invention.
  • Fig. 2 is a schematic representation of the processing of the workpiece by means of energetic radiation in quasi-line distribution.
  • Fig. 3 is a schematic representation of the processing of the workpiece by means of energetic radiation in quasi-tophat distribution.
  • Fig. 1 shows a workpiece 1 whose first surface 1 1 and second surface 12 are polished by means of energetic radiation 2.
  • the first surface 1 1 is polished by irradiation with energetic radiation 21 with first processing parameters.
  • the workpiece 1 ' which has already been polished on one side, is further processed in a subsequent step and the second surface 12 is polished with energetic radiation 22 with second processing parameters. If the surface parameters of interest lie outside a defined tolerance range after the first 1 1 and second surface 12 have been processed once, further steps of polishing using energetic radiation are carried out until the surface parameters of both surfaces (1 1, 12) lie within the desired tolerance range and the workpiece 1 ” has been polished to the desired extent.
  • Fig. 2 shows the movement of the energetic radiation 2 over the workpiece 1 in the quasi-line machining strategy.
  • the energetic radiation 21 with first machining parameters is directed onto the first surface 1 1.
  • Fig. 2 also shows how the energetic radiation 21 with first machining parameters is guided over a partial area 1 1 1 of the first surface.
  • the energetic radiation 21 with first machining parameters is moved back and forth along a line 21 a and, in addition, the entire line 21 a is guided over the partial area 1 1 1 of the first surface.
  • This movement is generated by the superposition of a translationally oscillating movement component v scan y and a feed movement component v scan x .
  • the second surface 12 can be polished with second machining parameters in the quasi-line machining strategy, even if this is not explicitly shown in Fig. 2.
  • Fig. 3 shows the movement of the energetic radiation 2 over the workpiece 1 in the quasi-tophat processing strategy.
  • the energetic radiation 21 with first processing parameters is directed onto the first surface 1 1 .
  • Fig. 3 also shows how the energetic radiation 21 with first processing parameters is guided over a partial area 1 1 1 of the first surface at the scanning speed v scan . After a scanning cycle, the partial area 1 1 1 of the first surface is immediately scanned again, with the alignment of the scanning paths being rotated by an angle.
  • the second surface 12 can be polished with second machining parameters in the quasi-tophat machining strategy, even if this is not explicitly shown in Fig. 3.
  • the method according to the invention can be used to polish a thin workpiece 1 made of N-BK7 glass using laser radiation.
  • a quasi-line scanning strategy is selected as the scanning strategy.
  • the workpiece 1 has a thickness of 5 mm.
  • a laser power of 700 W, a beam diameter of 20 mm and a feed rate of 8 mm/s are selected and the machining is carried out within one pass.
  • two passes are carried out.
  • a laser power of 700 W, a beam diameter of 20 mm and a A feed rate of 8 mm/s is selected.
  • an adjusted laser power of 350 W is selected, while the beam diameter and feed rate are maintained as in the first pass.
  • the distortion of the workpiece 1" is then determined using white light interferometry via the peak-to-valley distance.
  • a peak-to-valley distance of 9 pm is measured on the second surface 12, which corresponds to a geometric deviation from the planar target geometry, i.e. the distortion of the surface.
  • the machining parameters selected are those which are used in the application of the method according to the invention when machining the first surface 11 of the N-BK7 workpiece 1 to be compared.
  • first the first surface 1 1 and then the second surface 12 of the reference workpiece 1 are machined with a laser power of 700 W, a beam diameter of 20 mm and a feed rate of 8 mm/s using a quasi-line machining strategy.
  • the method according to the invention can be used for polishing a thin workpiece 1 made of the thermoplastic polymethyl methacrylate (PMMA) using laser radiation.
  • a quasi-line processing strategy with temperature control that keeps the process temperature constant is selected as the scanning strategy.
  • the workpiece 1 has a thickness of 3 mm.
  • a process temperature of 225°C and a feed rate of 2 mm/s are selected and the machining is carried out within one pass.
  • a process temperature of 225°C and a feed rate of 2 mm/s are selected for the first pass.
  • a process temperature of 180°C and a feed rate of 2 mm/s are selected.
  • the distortion of the workpiece 1" is then determined using white light interferometry via the peak-to-valley distance.
  • a peak-to-valley distance of 8.7 pm is measured on the first surface 11 and a peak-to-valley distance of 9.4 pm is measured on the second surface 12, which corresponds to a geometric deviation from the planar target geometry.
  • the machining parameters used in the inventive application of the method for machining the first surface 11 of the PMMA workpiece to be compared are selected. Specifically, first the first surface 11 and then the second surface 12 of the reference workpiece are machined with one pass, a process temperature of 225°C and a feed rate of 2 mm/s with a quasi-line scanning strategy and a temperature control that keeps the process temperature constant. This leads to a distortion measured by white light interferometry on the first surface 11 of 21.7 pm and on the second surface 12 of 23.8 pm.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Engineering (AREA)
  • Plasma & Fusion (AREA)
  • Laser Beam Processing (AREA)

Abstract

La présente invention concerne un procédé de polissage de pièces (1), en particulier en verre ou en plastique, par traitement de celles-ci avec un rayonnement énergétique (2), en particulier un rayonnement laser. Tout d'abord, on dispose une pièce (1) qui comprend une première surface (11) et une seconde surface (12) positionnée à l'opposé de celle-ci. Ensuite, la première surface (11) est polie en l'exposant à un rayonnement énergétique (21) ayant des premiers paramètres de traitement et la seconde surface (12) est polie en l'exposant à un rayonnement énergétique (22) ayant des seconds paramètres de traitement. Le procédé est caractérisé en ce que les premiers paramètres de traitement pour polir la première surface et les seconds paramètres de traitement pour polir la seconde surface sont sélectionnés de telle sorte que, en raison de l'exposition de la seconde surface (12) à un rayonnement énergétique (22) ayant des seconds paramètres de traitement, la seconde surface (12) est soumise à une contrainte thermique supérieure à celle de la première surface (11), en raison de son exposition à un rayonnement énergétique (21) ayant les premiers paramètres de traitement.
PCT/EP2024/056670 2023-03-15 2024-03-13 Procédé de polissage de pièces par traitement avec un rayonnement énergétique WO2024189078A1 (fr)

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DE102023106479.7A DE102023106479A1 (de) 2023-03-15 2023-03-15 Verfahren zum Polieren von Werkstücken durch Bearbeitung mit energetischer Strahlung
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US20210260842A1 (en) * 2016-12-13 2021-08-26 AIXLens GmbH Method for producing a transmissive optics

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