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DE-102025107900-B3 - Mobile processing chamber for laser polishing of glass workpieces, as well as the use of several mobile processing chambers

DE102025107900B3DE 102025107900 B3DE102025107900 B3DE 102025107900B3DE-102025107900-B3

Abstract

A mobile processing chamber for laser polishing of glass workpieces comprises a workpiece carrier, a shielding element for the laser radiation used in the polishing process, and a protective enclosure. The shielding element is designed and positioned to surround a receiving area for the workpiece to be polished on the workpiece carrier, thus shielding the workpiece carrier from direct exposure to the laser radiation during the polishing process. The protective enclosure, either alone or in conjunction with the workpiece carrier, forms a closed chamber around the surface of the workpiece to be polished and features a removable lid. The workpiece carrier, shielding element, and protective enclosure are made of materials that can withstand temperatures of at least 500 °C. The material of the workpiece carrier is also selected to have a low thermal conductivity, preferably less than 10 W/(m K). The mobile processing chamber enables the high-yield, industrial-scale laser polishing of glass workpieces.

Inventors

  • Manuel Jung
  • Edgar Willenborg

Assignees

  • Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung eingetragener Verein

Dates

Publication Date
20260513
Application Date
20250303

Claims (20)

  1. Mobile processing chamber (10) for the laser polishing of glass workpieces (5), comprising at least: - a workpiece carrier (4) that can hold a workpiece (5) to be polished in the processing chamber (10); - a shielding element (3) against laser radiation used for laser polishing, which surrounds a receiving area for the workpiece (5) to be polished on the workpiece carrier (4) in such a way that it largely shields the workpiece carrier (4) against direct incidence of the laser radiation during laser polishing of the workpiece (5) in the workpiece carrier (4); and - a protective enclosure (1, 2) which, alone or in combination with the workpiece carrier (4), forms a closed chamber around a surface to be polished of a workpiece (5) held by the workpiece carrier (4) and has a removable lid (1); - wherein the workpiece carrier (4), the shielding element (3), and the protective enclosure (1, 2) are made of materials that can withstand temperatures up to at least 500°C; and the material of the workpiece carrier (4) is selected such that it has a thermal conductivity of less than 20 W/(m K) at a temperature of 500 °C.
  2. Mobile processing chamber (10) according to Claim 1 , characterized in that the material of the workpiece carrier (4) is selected such that it has a thermal conductivity which is less than 10 W/(m K) at a temperature of 500 °C.
  3. Mobile processing chamber (10) according to Claim 1 , characterized in that the material of the workpiece carrier (4) is selected such that it has a thermal conductivity which is less than 1 W/(m K) at a temperature of 500 °C.
  4. Mobile processing chamber (10) according to one of the Claims 1 until 3 , characterized in that a support surface of the workpiece carrier (4) for a workpiece (5) to be polished is structured, such that a received workpiece (5) has a smaller contact area to the workpiece carrier (4) than without structuring of the support surface.
  5. Mobile processing chamber (10) according to one of the Claims 1 until 4 , characterized in that the workpiece carrier (4) has an opening or recess for receiving the workpiece (5) to be polished and is designed such that a received workpiece (5) only rests on the workpiece carrier (4) at the edge of the opening or recess.
  6. Mobile processing chamber (10) according to one of the Claims 1 until 5 , characterized in that the workpiece carrier (4), the shielding element (3) and the protective enclosure (1, 2) are made of materials that can withstand temperatures up to at least 800 °C.
  7. Mobile processing chamber (10) according to one of the Claims 1 until 5 , characterized in that the workpiece carrier (4), the shielding element (3) and the protective enclosure (1, 2) are made of materials that can withstand temperatures up to at least 1100 °C.
  8. Mobile processing chamber (10) according to one of the Claims 1 until 7 , characterized in that the removable cover (1) projects laterally beyond a side wall (2) of the protective enclosure (1, 2).
  9. Mobile processing chamber (10) one of the Claims 1 until 8 , characterized in that the workpiece carrier (4) forms a base of the mobile machining chamber (10).
  10. Mobile processing chamber (10) according to Claim 9 , characterized in that the shielding element (3) and the protective housing (1, 2) are designed to be removable from the workpiece carrier (4).
  11. Mobile processing chamber (10) according to Claim 10 , characterized in that the removable cover (1) of the protective enclosure (1, 2) is identical to the workpiece carrier (4).
  12. Mobile processing chamber (10) according to one of the Claims 1 until 11 , characterized in that the workpiece carrier (4) is made of a ceramic.
  13. Mobile processing chamber (10) according to one of the Claims 1 until 12 , characterized in that the shielding element (3) is in contact with the workpiece carrier (4) only at an outer edge.
  14. Mobile processing chamber (10) according to one of the Claims 1 until 13 , characterized in that the shielding element (3) is plate-shaped.
  15. Processing chamber (10) Mobile according to one of the Claims 1 until 14 , characterized in that the shielding element (3) has a reflective coating.
  16. Use of several of the mobile processing chambers (10) according to one of the Claims 1 until 15 in the laser polishing of glass workpieces, in which - each of the workpieces (5) to be polished is placed in the workpiece carrier (4) of one of the mobile processing chambers (10) and the processing chambers (10) are closed with the lid (1); - the processing chambers (10) are then preheated with the workpieces (5) contained therein in one or more ovens and fed to a laser polishing arrangement or directly to a laser polishing arrangement; and - the lid (1) of each processing chamber (10) is automatically lifted, the workpieces (5) are each polished in the processing chambers (10) with a laser (12) and the lid (1) is then automatically replaced.
  17. Use according Claim 16 , in which the processing chambers (10) are conveyed into an oven (13) after laser polishing, together with the workpieces (5) contained therein, and cooled there in a controlled manner.
  18. Use according Claim 17 , in which the processing chambers (10) are tempered together before cooling in the furnace (13).
  19. Use according to one of the Claims 16 until 18 , in which the shielding element (3) and the protective housing (1, 2) of the mobile processing chambers (10) are designed to be removable from the workpiece carrier (4) and the respective workpiece (5) is turned over in the laser polishing arrangement after laser polishing of a first side and then a second side of the workpiece (5) is polished with the laser (12), wherein to turn the workpiece (5) - the shielding element (3) and the protective housing (1, 2) are removed from the workpiece carrier (4), hereinafter referred to as the first workpiece carrier (4), - a second workpiece carrier (4) is placed on top of the workpiece (5) with its receiving area directed towards the workpiece (5), - the two workpiece carriers (4) with the workpiece (5) in between are turned over by 180°, - the first workpiece carrier (4) is removed from the workpiece (5), and - the shielding element (3) and the protective housing (1, 2) are placed on the second workpiece carrier (4) be set up.
  20. Use according Claim 19 , in which the second workpiece carrier (4) is either held separately or forms the removable cover (1) of the protective enclosure (1, 2).

Description

Technical application area The present invention relates to a mobile processing chamber for the laser polishing of workpieces made of glass, in particular optics, and to the use of several of these mobile processing chambers in laser polishing. The surface of glass workpieces, especially optical components and optics, often requires polishing during or after manufacturing to meet the desired surface quality requirements for a given application. Laser polishing offers significant advantages, achieving a very high surface quality and reducing polishing costs by up to 90% compared to mechanical polishing methods, particularly for small to medium production runs and non-spherical optics. During laser polishing, a CO₂ laser beam heats and softens the surface layer of the optic. In this softened state, the roughness peaks flow into the roughness valleys, and the surface is smoothed by surface tension. Laser polishing achieves process rates of more than 1 cm² /s, even on complex surfaces such as aspheres or freeform surfaces, and a micro-roughness comparable to conventional A/20 polishing. The high processing rates induce large temperature gradients, which cause thermally induced stresses and can lead to both lens deformation and – if the strength limit is exceeded – cracking. The latter is successfully prevented by preheating the optics before laser polishing. State of the art For the production of small to medium quantities of glass optics, mechanical grinding and polishing techniques are typically used. Polishing aspheres is a time-consuming and expensive process performed on CNC machining centers. Laser polishing offers significant advantages here, as the polishing time for an asphere is only a matter of seconds. In comparison, mechanical polishing can take anywhere from minutes to hours, depending on the size of the optics. Examples of laser polishing of optics can be found, for instance, in… EP 1516068 B1 or the EP 2683521 B1 . However, one problem with laser polishing of optics is the limited applicability of this technique in industrial settings. On a laboratory scale, due to the numerous manual steps and time-consuming processes on hot plates, only a very small number of optics can currently be polished to optical quality using a laser each day. Another problem with laser polishing is that temperature inhomogeneities occurring during preheating, sometimes amounting to just a few Kelvin, lead to shape defects and waviness in the laser-polished optics, thus limiting their usability. The DE 10 2022 109 123 A1 , the KR 10 1 425 410 B1 , the EP 4 338 959 A2 and the DE 295 18 138 U1 Each reveals mobile processing chambers for processing workpieces using laser radiation. From the US 2019 / 0 291 214 A1 A plasma processing chamber is known that has a removable lid and multiple shields. The object of the present invention is to provide means by which workpieces made of glass, in particular optical elements or optics, can be polished with high yield by means of laser polishing, even on an industrial scale. Description of the invention The problem is solved by providing a mobile processing chamber according to claim 1. Claim 16 relates to the use of several such processing chambers for laser polishing of glass workpieces. Advantageous embodiments of the mobile processing chamber are the subject of the dependent claims or can be found in the following description and the exemplary embodiments. The proposed mobile processing chamber comprises at least one workpiece carrier, a shielding element, and a protective enclosure. The workpiece carrier is designed to hold a workpiece to be polished within the processing chamber. The shielding element, which protects against laser radiation used for laser polishing, is arranged around the workpiece carrier's receiving area. This shielding element is designed to surround the receiving area on the workpiece carrier in such a way that it largely protects the workpiece carrier from direct laser radiation during the polishing process. This is important because, during laser polishing, the laser beam must extend slightly beyond the workpiece surface to be polished and would therefore strike the workpiece carrier without the shielding element. and would heat it up further. The shielding element is designed so that it does not break when irradiated with the laser radiation used for laser polishing and should ideally not release any particles (> 5 µm) under thermal stress. The protective enclosure is designed so that, alone or in conjunction with the workpiece carrier, it forms a closed chamber around the surface to be polished of a workpiece held by the workpiece carrier. The protective enclosure has at least one side wall and a removable lid. The workpiece carrier, the shielding element, and the protective enclosure are made of materials that can withstand temperatures up to at least 500 °C, preferably up to at least 800 °C, and particularly preferably up to at least 1100 °C. The mate