Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
  • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
  • C03B37/0253—Controlling or regulating
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/012—Manufacture of preforms for drawing fibres or filaments
  • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
  • C03B37/01225—Means for changing or stabilising the shape, e.g. diameter, of tubes or rods in general, e.g. collapsing
  • C03B37/0124—Means for reducing the diameter of rods or tubes by drawing, e.g. for preform draw-down
  • C03B37/01242—Controlling or regulating the down-draw process
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2205/00—Fibre drawing or extruding details
  • C03B2205/60—Optical fibre draw furnaces
  • C03B2205/62—Heating means for drawing
  • C03B2205/63—Ohmic resistance heaters, e.g. carbon or graphite resistance heaters
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2205/00—Fibre drawing or extruding details
  • C03B2205/60—Optical fibre draw furnaces
  • C03B2205/72—Controlling or measuring the draw furnace temperature

Definitions

• the present invention relates to a method for producing a cylindrical glass component by elongating an output cylinder using a process control comprising a plurality of control loops, including a temperature control loop, the output cylinder starting with one end and at a feed rate v f of a heating zone a Schuzonen- temperature Tofen supplied and partially softened in the heating zone, and withdrawn from the softened area to form a drawing bulb continuously and at a withdrawal speed v s a component strand in the direction of a drawing axis and from the component is cut to length.
• the temperature in the drawing bulb keep as constant as possible.
• a glass preform is fed from above to an annular electric heating element, softened therein, and the optical fiber is withdrawn from the softened area to form a drawing onion.
• the fiber passes through a diameter measuring device, by means of which the fiber diameter is measured continuously.
• the fiber pullout is equipped with a device for measuring the tension of the fiber.
• the measured values for the fiber diameter and the tensile stress are fed to a control unit.
• the tension serves as a measure of the temperature of the glass in the drawing bulb and is used to control the temperature of the heating element.
• the temperature of the heater reacts quickly to changes in the corresponding temperature controller.
• the temperature of the drawing bulb is measured by means of a pyrometer and, in a cascade control, this temperature is used as the main control variable and the temperature of the heating device as an auxiliary control variable.
• a controlled system with a low integration time for highly constant control of the temperature of the heater is obtained, and on the other hand a controlled system with a long integration time, which can serve to adjust the viscosity in the region of the drawing bulb.
• the known control process based on measurements of diameter and temperature in the area of the drawing bulb in conjunction with a model for the prediction of the final component diameter, leads in stationary phases of the elongation process to a dimensional accuracy of the removed component, which also meets high requirements.
• the drawing bulb In the area of the drawing bulb shows a strong spatial dependence of the surface temperature. In addition, the drawing bulb can shift within the heating zone. The local measurement of the surface temperature in the region of the drawing bulb results in only a single temperature value, which is of little significance in relation to the average viscosity of the glass in the area of the drawing bulb.
• the invention is therefore based on the object of further developing the process control of the known method in such a way that a component line having a high dimensional accuracy can be drawn even when temperature-influencing impurities occur during the elongation process.
• the purpose of the temperature control is to keep the viscosity of the glass in the deformation zone, which is referred to herein as "drawing onion”, as constant as possible during the elongation process.
• “Drawing onion” or “deformation region” is understood to mean the softened region the output cylinder undergoes a plastic deformation.
• the temperature control in the invention is based not on a single local measurement of the surface temperature of the glass in the region of the drawing bulb, but on a measurement of two temperatures at measuring points, which are spaced apart in the direction of the drawing axis.
• the upper measuring point - for the first temperature value - is above or within the upper drawing onion area; in a vertical drawing method from top to bottom, for example, at the upper edge of a heating element.
• the lower measuring point - for the second temperature value - lies within the lower drawing bulb area or below the drawing bulb, for example at the lower one Edge of the heating element.
• Measurement of temperatures is "continuous", ie continuous or discontinuous, with discontinuous measurement, the more accurate the process control, the shorter the time intervals between successive measurements are chosen simulated or three dimensional realistic temperature distribution of the outlet cylinder, at least for that region of 0 b s and the second temperature value T un t s is currently located between the measuring points of the first temperature value T as integral or average value of the temperature distribution determined in this way results in a modeled -.
• Deforming temperature Tmodeii which represents a measure of an average temperature or an average viscosity of the glass in the deformation region.
• the modeled deformation temperature T m0C ieii has a similar importance to the withdrawal stress in order to determine a mean viscosity in the drawing bulb in the case of the technique mentioned in the introduction.
• the modeled deformation temperature T m0C ieii is based on actual and actual temperature readings that allow for early consideration of changes as soon as they announce themselves as temperature changes of first or second temperature and in any case significantly before they become noticeable Change in the mean viscosity in the drawing onion.
• the algorithmic model can also contribute to this by including realistic simulations and predictive control responses, in particular for the frequently occurring parameter changes in the elongation process.
• the control variable used here is the heating zone temperature Tofen or a parameter that can be correlated therewith, such as the heating current for heating the heating zone.
• the algorithmic model simulates a temperature distribution at least between the measuring points of the first and second temperature is a Constant adjustment possible by comparing the actual temperature measured values with the modeled temperature values at the respective measuring point.
• the model is suitable for adaptation during the elongation process.
• the algorithmic model is calibrated during Elongierens, in the sense that it continually raging differences between the modeled at the measuring points of the first temperature value and second temperature value temperature values T 'un t s of the measured temperature values T s and T whether un t e n detected and the measured temperature values as new calibration values for determining the deformation temperature Tmodeii.
• the algorithmic model is constantly recalibrated by reality.
• the method according to the invention is designed for the early detection of disturbances in the course of the process, and to that extent allows for predictive control.
• the defect manifests itself, for example, as a discontinuity in the geometry or in a change in the chemical composition of the starting cylinder.
• the model qualitatively knows the probable effects of the defect on the temperature in the heating zone and especially in the drawing bulb. The exact effects are determined online during the elongation process and, in conjunction with the temperature controller, as a function of this output. Effects and the current impurity position generates a suitable control response to keep T M0 deii constant despite the impurity.
• an output cylinder which is welded frontally via a welded joint with an upper cylindrical glass component, wherein the algorithmic model, the axial position of the welded joint is communicated as an input, and that when Elongieren the output cylinder, the position the weld joint relative to the heating zone and their position-dependent effect on the temperature in the heating zone are taken into account.
• the upper glass component is connected to the output cylinder via an end face
• the upper glass component is, for example, another output cylinder to be elongated or a welded holder for the output cylinder.
• the weld is a recurring in each Elongierlui disturbance or discontinuity in the process, when this weld approaches the heating zone.
• the weld causes heat accumulation and has a significant effect on the temperature in the heating zone. In the model, it can be considered as a source of heat. It has been shown that the temperature in the deformation range increases and the viscosity decreases accordingly. This makes the glass less viscous and higher throughput.
• the algorithmic model recognizes the weld joint as an impurity on the one hand by means of a temperature increase of the upstream temperature measurement at the upper measurement point, and in the preferred method also on the basis of input data about the axial position of the weld. If the output cylinder and the axial position of the weld joint are measured before the beginning of the elution process, these input data can be entered in advance for the model. Alternatively or additionally, the algorithmic model can receive this input data "online" during the elongation process from a detection device for the welded connection, which is upstream of the upper temperature measurement point. Here, too, the model qualitatively knows the expected effects of the weld on the temperature in the heating zone and the theoretical effects on the deformation range. In order to keep T M0 deii at the setpoint, the exact effects during the elongation process are determined online and, in conjunction with the temperature controller, a suitable control response is generated as a function of these effects and the current position weld.
• the duration for the calculation of the deformation temperature T m0C ieii depends on the calculation effort for the determination of the modeled temperature distribution. This is the smaller, the smaller the scope of the data to be considered. Symmetry conditions permit the consideration of a one-dimensional temperature distribution along the drawing axis for cylindrical, and in particular rotationally symmetric, output bodies, and thus a considerable reduction in the amount of data and computation time for the modeling.
• the term "one-dimensional temperature distribution" thus characterizes only the height distribution dependent temperature distribution. It has also proved to be advantageous if the pull rate v s and the feed rate v f serve as input variables of the algorithmic model.
• the lower measuring point lies in the lower region of the drawing bulb or below.
• the glass shows a higher temperature at this point of measurement when pulling off the component strand more quickly than at a slower drawing off. This results in an apparent effect, which alone suggests a higher temperature in the region of the drawing bulb due to the increase in the drawing speed, although this temperature remains unchanged.
• the model captures the pull rate v s and the concomitant cooling of the drawn component strand to the lower measuring point and also the feed rate v f .
• the calculation of the deformation temperature T m0C i e ii is preferably based on solutions of differential equations according to the finite element method.
• the drawing onion is divided into a number of finite small elements that can be described with a finite number of parameters.
• Figure 1 shows a pulling device for carrying out the method according to the invention in a side view
• FIG. 1 shows the structure of a deadtime-free temperature control according to the invention.
• the drawing device of FIG. 1 comprises a resistance heating furnace, which essentially consists of a vertically oriented heating tube 1 made of graphite, which surrounds a heating space 3 which is circular in horizontal cross-section.
• a quartz glass hollow cylinder 4 In the upper open end of the heating tube 1 projects a quartz glass hollow cylinder 4, the longitudinal axis 5 is aligned coaxially to the central axis 2 of the heating tube 1.
• a pyrometer 6 is arranged, which detects the surface temperature T 0 b en of the hollow cylinder 1.
• a further pyrometer 7 is arranged, which detects the surface temperature T U nt e n of the elongated hollow cylinder 1.
• the temperature measured values of the pyrometers 6 and 7 and the temperature measured by the pyrometer 16 of the heating tube 1 Tof en are each fed to a computer 8.
• the upper end of the hollow cylinder 4 is connected via a welded joint 9 with a quartz glass holding tube 10, by means of which it is displaceable in the horizontal and vertical directions.
• the hollow cylinder 4 is softened in the heating chamber 3 and withdrawn from the softened region to form a drawing bulb 1 1 a quartz glass tube 12 vertically downwards.
• the quartz glass tube 12 is thereby guided through a sliding contact ring 13, which simultaneously serves as a guide rail for a wall thickness measuring device 14, which is rotatable about the outer circumference of the quartz glass tube 12.
• a wall thickness profile of the withdrawn quartz glass tube 12 can be recorded during the drawing process and this profile can be evaluated with the aid of the computer 8 with respect to diameter D and wall thickness W.
• the pipe speed v s is detected by means of a trigger 15 and adjusted via the computer 8.
• the problem to be solved by control technology is to estimate a reliable value of the deformation temperature T M0 deii by a model that is as realistic as possible.
• the solution according to the invention is to implement a spatially distributed, one-dimensional temperature model of the hollow cylinder from the height E1 of the upper temperature sensor to the height E2 of the lower temperature sensor and to run it online during the elongation process.
• the measured in E1 and E2 temperature values of the hollow cylinder 4 and the ab- drawn tubing 12 are fed as an input into the model as well as the usual model inputs such as oven temperature, feed rate, take-off speed and wall thickness of hollow cylinder 4 and withdrawn tube 12th
• the computer 8 is part of a central process control device, with several interleaved control loops, including a temperature control loop. Its structure and function will be explained in more detail below with reference to FIG.
• Essential components of the control circuit are a PI controller 21 for the control of the oven temperature Tof en .
• Diameter D and wall thickness W of the withdrawn pipe string 12 and for adjusting the manipulated variables take-off speed v s , feed rate v f of the cylinder 4 in the furnace 3 and the tube internal pressure P.
• a finite element model 24 (hereinafter also referred to as FEM Model for modeling a one-dimensional spatial temperature distribution in the deformation region between the planes E1 and E2, from which a radially integrated, average modeled temperature T m0C ieii this temperature distribution is determined.
• the deformation range essentially corresponds to the area of the drawing bulb 1 1.
• the drawing device as a whole is denoted by the reference numeral 23 in FIG.
• Input variables for the FEM model 24 are measured at the furnace 3 and the quartz glass cylinder 4 temperature values T whether s, T un t e n and T 0 f s, the actual measured values for pipe diameter D and pipe wall thickness W, the current speeds of feed v f and deduction v s .
• information about the original length of the hollow cylinder 4 is entered into the FEM model 24 25 beforehand, so that the model 24 always knows the current position of the weld 9 relative to the heating tube 1 on the basis of the integrated feed rate data.
• the FEM model 24 calculates the current actual value for the modeled temperature T m0 deii- This value serves as a controlled variable and becomes
• the central process controller (computer 8) are fed the following parameters: The detected by the velocity meter off speed, measured by the wall thickness meter 14 pipe diameter D and the pipe wall thickness W, as measured by the pyrometer 16 temperature T 0 f s of the heating tube 1 and the from a (also not shown) pressure measuring device determined pipe internal pressure P.
• the process control device 8 controls the compressed gas valve, the temperature controller 21 of the furnace and the controller 22 for withdrawal and feed.
• the furnace temperature controller 21 is given a setpoint value for the modeled temperature T m0C ieii calculated from the above-mentioned input data from the FEM model in the deformation area and this is taken into account when setting the furnace temperature Tofen.
• the quartz glass hollow cylinder 4 is fed to the furnace 3 at a constant feed rate v z , the temperature of the furnace 3 initially being set at approximately 2200 ° C.
• the modeled temperature determined by the FEM model 24 T m0 deii, which is set, for example, in advance and to a setpoint around 1800 ° C.
• the outer diameter D of the pipe string 12 and the modeled temperature T m0C ieii in the deformation range (1 1) are thus used.
• the oven temperature T 0 f en are used as manipulated variables for the outer diameter of the blowing pressure and for the modeled temperature T m0C ieii in the deformation range (1 1).
• the regulation on the guide value of the modeled temperature T m0C ieii in the deformation range (1 1) is explained below:
• the surface temperatures on the hollow cylinder 4 run around and on the drawn-off tube strand 12 are T un t s measured at the measuring points E1 and E2.
• the data are transmitted to the FEM model 24, which first calibrates the model from the deviations of the measured values ( ⁇ 00 ⁇ , T un t e n) from the model values (T ' 0 b en , T' un t e n). Subsequently, the deformation temperature T m0C ieii is calculated with the calibrated model and transferred to the controller 21. Regulator 21 adjusts the Tofen.o setpoint for the oven temperature according to the deviation from the setpoint Tmodeii.o.
• This control can be switched off in stationary operation, wherein the end of the stationary phase is characterized for example by falling below a minimum residual length of the hollow cylinder 4.
• the invention proves itself especially in the following unsteady phase, which results from the fact that the weld 9 approaching the furnace 3 from above acts as an additional radiation source which leads to an increase in temperature with the furnace chamber 3. Since the FEM model simulates a one-dimensional spatial temperature distribution over the current deformation range, which is "in line" with the advance of the hollow cylinder, the temperature change at the measuring point E1 is detected early and the temperature increase is counteracted, because the FEM model determines the position of the weld 9 also contains as input.
• the final phase of the elongation process is detected by a temperature increase in the measurement plane E1 and by prior input of the geometric data of the hollow cylinder 4 and can be compensated by reducing the furnace temperature.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
• Manufacture, Treatment Of Glass Fibers (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

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• 2011
  • 2011-10-25 DE DE102011116806.4A patent/DE102011116806B4/de active Active
• 2012
  • 2012-10-17 IN IN2983CHN2014 patent/IN2014CN02983A/en unknown
  • 2012-10-17 CN CN201280052658.6A patent/CN104053634B/zh active Active
  • 2012-10-17 WO PCT/EP2012/070538 patent/WO2013060606A1/de not_active Ceased
  • 2012-10-17 JP JP2014537559A patent/JP5959655B2/ja active Active
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