DD297594A5 - METHOD FOR DETECTING THE CONDITION OF GRINDING POINTERFLAKES - Google Patents

Abstract

The invention relates to a method using an opto-electronic sensor for detecting the state of Schleifkoerper-Wirkflaechen by in-process or post-process measurement. By a sensor correlated with the state of Schleifkoerper Wirkflaeche signal is generated, which is directly displayed or supplied to a computer for evaluation, thereby influencing the process flow during grinding (detection of life end of the abrasive body) and dressing (determining the minimum required Dressing amount) is given (objectification or optimization of the process design). {Prozznahes measuring; in-process measurement; post-process measurement; Oberflaechensensor; Schleifkoerper; Schleifkoerper-Wirkflaeche; Grind; Life end detection; Dressing abrasive bodies; Dressing amount; automated manufacturing}

Description

For this 1 page drawings

The invention relates to a method using an optoelectronic sensor for detecting the state of Abrasive surfaces by in-process or post-process measurement. It serves for continuous or intermittent Control of the state of abrasive abrasive surfaces preferably on grinding machines in the metalworking Industry and allows influencing the process sequence during grinding (detection of the end of life of the Abrasive body) and during dressing (determination of the minimum dressing amount). The state of the abrasive body surface (microgeometry or abrasive body topography and macrogeometry) is one

significant input in grinding and determines the productivity and the achievable workpiece accuracy significantly.

In particular, due to the mechanical and thermal stress, grinding wheels are subject to other tools Wear and tear, resulting in dimensional and shape changes (macrogeometry) and changes in the Examining the surface of the abrasive body (microgeometry) and finally leading to the end of life. The abrasive body topography is closely related to the grinding behavior of the grinding wheel (grinding forces, Workpiece roughness, grinding temperatures). Changes in the abrasive body topography may be due to eruption or dulling of abrasive grains as well Metal deposits in the pores or deposits on the abrasive grains result. The elimination of Verschloißerscheinungen done by dressing the abrasive body. For the practical application of Grinding process, it is desirable during grinding the real time of end of life and at

subsequent dressing the time to complete the dressing process (required total dressing amount).

In practice, the specification of a fixed service life over a certain number of workpieces, a specific one, is widespread Grinding time or a certain chip volume. This predetermined service life is based on experience under Consideration of safety factors and rarely corresponds to the true (sometimes fluctuating) values. The same applies to the

(Total) dressing amounts.

Deviations from the actual values of the service life and the required total dressing amount are technical For reasons and / or economic reasons (rejects, rework, increased loss of shoe body, depreciation of the Dressing tool, increased Zbitaufwendungen) not justifiable. To assess the condition of the abrasive body surface or to detect the life end of the abrasive body are

various solutions bekanm.

The literature has described a number of mechanical scanning or imaging methods using statistical techniques Characteristics of the abrasive body effective area (number of edges, effective roughness depth) can be determined. An application under Production conditions are unacceptably high due to the sensitivity of the equipment to environmental conditions Time expenses not possible or severely limited. Other solutions are based on the measurement of components of the stress force or related thereto Sizes or on the evaluation of vibrations. According to DE-OS 3529427 is from the signal of the machine-internal position measuring system (nominal feed path) and the Signal of the measuring control device (real feed path) an actual difference value formed (system deformation). The signal to Truing is given when the actual difference value is at least equal to a predetermined desired difference value. The patent DE-PS 1023362 is based on a solution that determines the degree of dulling of the grinding body by means of a Current measurement or on the basis of the dimensional change of the workpiece in a given period of time (corresponds to the real Feed rate). The wear of the abrasive body is i. a. also with a more or less pronounced development of the processing

associated vibrations.

In the invention description SU 1148771, the minimum value of the amplitude of vibrations in a certain Frequency range detected within the life of the grinding wheel. The increase in amplitude to 2.3 ... 2.5 times

of the minimum is regarded as the indicator of the end of service life.

The solution described in DD-PS 263489 is based on the detection of the vibration amplitudes in two frequency bands

(8 ... 300Hz, 300 ... 1200Hz).

If the amplitude of the signal in the upper frequency range has reached that in the lower frequency range, this is According to the patent, the end of life has been reached. The clogging of the pores of the abrasive body is not a wear in the usual sense, but even this phenomenon can under

certain conditions determine the end of life of the grinding wheel.

This is the description of the invention SU 1152771. With an inductive pickup is the addition of the Abrasive surface with metal particles detected. Also known are various optoelectronic methods, either generally for the evaluation of rough surfaces, or

but also specifically designed for abrasive active surfaces.

In some solution variants, the rough surface is irradiated with relatively extended light bundles. This procedure

It is based on the idea that a very rough surface influences the ratio of directly and diffusely reflected light differently than a less rough surface.

The reflected light components are either with one or two receivers in selected fixed reflection angles or

detected over the entire angle range.

In the latter case, this can be either single swivel receivers or a large number of receivers above the

are arranged distributed angular area of interest, for use.

A disadvantage is the high cost of evaluating the signals. If the optoelectronic sensor only one Receiving beam path possesses, consuming measures are required to the jang rays or to be examined Surface clean or störfroi to keep. In contrast, the application of two separate radiation receiver with separate signal processing results in contrast

a lower susceptibility to interference, but the effort is also higher and the sensitivity limited because differences in the two channels are often too low, and the receiver usually have a different behavior.

These disadvantages are with the similar circuit variants described in the patents DD 219854 and DD 252880

overcome. The optical path is part of a ring closure. The ring closure ensures a high

General sensitivity. However, the provided relatively large light spot is hardly suitable, partial changes

in their nature and location on the Schleifkörperwirkfläche clearly detect.

Methods are also known in which attempts are made with very fine bundles of rays to the area of interest

analyze.

A method described in the literature works according to the triangulation method (grinding wheel geometry and

Topography in Real Time / Gosebruch, H .; In: VDI journal, Dusseldorf 131 [1989] 1, p68-71).

In this case, a fine light beam is projected onto the abrasive-effective surface by a laser light source and the reflected light

imaged with an optic on a receiver line.

The distance from the measurement object determines the location on the receiver line on which the light spot is imaging, and can thus

be calculated.

What is remarkable about such a sensor principle is that both the macro and the micro geometry of the grinding wheel

could be analyzed.

The effort for the evaluation, however, is due to the large amounts of data and the required computing speed

too high.

The invention aims to develop a method and a measuring device arrangement, with which a direct, objective and

largely trouble-free assessment (in-process or process -intermitti6rend) of the state of the micro-geometry (dress state or wear state) of abrasive active surfaces can be realized so that an indirect (advice to the operator) or direct control of the process flow during dressing and / or grinding is possible ,

It contributes to the objectification and / or optimization of the process design during grinding after technical and

economic aspects.

The invention is based on the object for detecting the state of abrasive active surfaces a method

to develop a measuring device arrangement based on an optoelectronic sensor.

This measurement and erection arrangement should be based on development trends to high accuracy requirements, the broad Application of grinding processes in the future, even under conditions of flexible automated production,

be conceived.

To solve this problem, it makes sense to use a measuring method that both the evaluation of wear progress on Abrasive grinding during grinding (end of life detection) as well as the control of wear removal during dressing

klaubt. For detecting or evaluating the state of the grinding wheel Wiikfläche is in connection with

Wear phenomena related change in the optical properties, in particular the reflection properties,

used.

According to the invention, this object is achieved by using a known principle in that a radiation source is directed to the abrasive active surface and the intensities of the regularly reflected and a portion of the diffuse reflected radiation with two radiation receivers using the known measuring principle of the ring closure are detected (DD 252880).

By the ring closure while the radiation power of the light source is controlled so dall Reguläranteil remains constant under varying measurement conditions. As a result, the state of the abrasive body effective area is reflected by the amplitude of the scattering proportion.

Opposite the o.g. Solution is the measuring device in addition to the special further signal processing characterized in that the light spot has a significantly smaller extent than the abrasive width and that the sensor is moved axially relative to the grinding wheel.

Due to the smaller extent of the light spot can also be partial impermissible wear conditions of the abrasive active surface, as z. B. when longitudinal grinding or even during plunge grinding (workpiece or grinding width smaller than the abrasive width) occur by different load, safer recognize.

Since the signal at the output of the measuring device is dependent on the specification of the abrasive body used, according to the embodiment, a desired value or desired course of the signal corresponding to a specific state (dressing or wear state) of the abrasive-active surface must be specified by teach-in. The in-process or process intermittent during dressing or grinding detected sensor signal is, possibly after filtering (low-pass filter), compared by a comparator (computer) with the desired value or desired course. Depending on the result of the comparison, the end of service life is displayed during grinding or the dressing process is ended.

It is also conceivable to use a non-engaging width element of the abrasive body effective area to obtain a setpoint value of the sensor signal.

With the solution according to the invention, the state of the abrasive-active surface during dressing and grinding can be detected with relatively little effort, creating an essential prerequisite for objectification or optimization of processing on grinders geschaffer

 The invention will be explained in more detail with reference to FIGS. 1 and 2.

Appropriate locations for the optical scanning of the surface of the abrasive body on the abrasive body 1 are offset from the machine by 180 "to approximately 340 ° in the cutting direction to the processing zone (FIG. 1).

It is conceivable attachment of the sensor 3 on the tailstock or on the dressing device 5 on the longitudinal slide of the grinding machine (Fig. 1 a), whereby in the exclusive use for in-process monitoring of Schleifkörperzustdndes during the dressing process or for process intermittent monitoring during grinding a workpiece 2 additional means for axial relative movement or for radial positioning u. U. can be omitted.

In order to keep the beam path and measuring spot largely free of direct coolant influences in this mounting variant, would be in the process intermittent monitoring during grinding, z. B. during a workpiece change, the coolant supply through the coolant nozzle 4.1 (if not so provided) to interrupt. For in-process monitoring of the dressing process, an additional coolant nozzle 4.2 (below the sensor 3 and top of the dressing tool 6 according to FIG. 1 a) must be provided when attaching the sensor to the dressing device 5. The supply of the coolant through the usual coolant nozzle 4.1 is switched off during the dressing. If the sensor is realized with an independent positioning device, the arrangement according to FIG. 1 b in the angular range β within the protective hood 7 is practically possible.

For reasons of accessibility and less disturbing influences (coolant, grinding chips, sparks), the arrangement in point B is favorable.

For positioning the sensor 3 relative to the grinding wheel 1, stepping motor drives are particularly suitable (not shown in FIG. 1) due to the small masses to be moved and the low speeds to be realized. The radial positioning to maintain a constant base distance of the sensor from the abrasive-active surface of the grinding wheel 1 should be based on the measurement with a non-contact distance sensor, practically a pneumatic length measuring system (principle nozzle baffle plate) is a suitable solution (not in Fig. 1) shown). The basic distance sensor / abrasive active surface is maintained by keeping constant the pressure drop at the pneumatic length measuring system by adjustment with the stepper motor drive. It is also conceivable a purely pneumatic solution, wherein the sensor is supported on an air cushion against the abrasive body effective area. The beam path in the sensor system and the instantaneous measuring spot are to be blown free with compressed air to reduce interference. After a new grinding wheel has been mounted on the grinding spindle and the grinding wheel has been dressed with quasi-optimal conditions (quasi-optimal with regard to the manipulated variables and the total dresser depth of cut), this is optically scanned with the sensor and the signal course is stored.

The signal curve is provided with a wider tolerance band I (corresponding to a permissible wear state at the end of service life) and a narrow tolerance band II (corresponding to the permitted scattering range of the dressing state of the abrasive body) (FIG. 2).

In order to monitor the state of the grinding wheel active area during grinding, the current sensor signal obtained in-process or intermittently (for example during a work piece change) is compared with the tolerance band I. After exceeding this tolerance band the machine operator is displayed the end of life or triggered by a signal to the machine control of the dressing process.

The dressing process is continued until the sensor signal detected in-process or process-intervening (for example, between two dressing overruns) is again within the tolerance band II and the grinding body is thus again in a workable state.

Optionally, the desired course of the sensor signal and the tolerance bands I and II are to be readjusted for large changes in diameter during the useful life of the grinding wheel.

Claims (3)

1. A method for detecting the state of Schleifkörperwirkflächen, characterized in that the radiation source of an optoelectronic sensor is directed to the Schleifkörperwirkfläche and the reflected radiation is detected with their Reguläranteil and a selected Streuanteil on the principle of the split beam path and processed so that a Specific operating conditions corresponding learning waveform is provided with a tolerance band I, which corresponds to a permissible state of wear of the abrasive active surface (within the life of the grinding wheel), and whose exceeding is indicated during a continuous or intermittent measurement during the grinding process and to detect the end of life of the grinding wheel by the Machine Bedian serves. 2. The method according to claim 1, characterized in that the learned waveform is provided with a (narrower) tolerance band Il, in which the signal of the optoelectronic sensor according to the state of the abrasive body effective surface after a proper dressing and that after grinding and reached end of life of the Grinding the re-entry of continuously or intermittently measured during the dressing process signal of the optoelectronic sensor is displayed in this tolerance band Il for determining the minimum required dressing amount for the machine operator and thus can be used as a criterion for the completion of the dressing process. 3. A method for detecting the state of Schleifkörwirkwirkflächen according to claim 1 and 2, characterized in that the monitoring of the signal waveform (exit of the signal from the tolerance band I or entry of the signal in the tolerance band II) by a machine control associated device (computer) automatically executed and used to influence the processing on the grinding machine (Objectification of the process design according to technical and economic aspects).