Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
  • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
  • G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
  • G01B21/045—Correction of measurements

Definitions

• the present invention relates to a three-dimensional measuring method and a device for implementing this method.
• the design of a part comprises, firstly, a phase of producing a drawing having dimensions and tolerances.
• the definition pattern thus defines surfaces that delimit the volume of the part to be produced during an industrial molding, stamping, removal of material, etc. Each surface is defined by its shape and its position in a linked reference frame. piece.
• the role of the control is to evaluate the concordance between the drawing and the part actually made, that is to say a three-dimensional solid.
• the multicote control uses a facility dedicated to controlling a part.
• This installation is equipped with measurement means (inductive sensor, pneumatic, optical, capacitive) which each perform a measurement of a dimension relative to a standard.
• measurement means inductive sensor, pneumatic, optical, capacitive
• a multicast control installation uses a series of sensors that are specifically positioned according to the geometry of the part in question. These sensors measure a deviation from the nominal dimension, which is materialized by the surface of the standard. Usually, the sensors are calibrated at a predetermined periodicity.
• Multicote control is particularly suitable for controlling parts on the margins of a mass production line.
• the first drawbacks include the significant cost of study and implementation of an installation, as well as relatively long delivery times.
• a multicote control installation is specifically adapted to the geometry of a room.
• a modification of this part entails a redefinition of the multicote installation that is assigned to the control of the part in question.
• the other type of mechanical part control uses a three-dimensional measuring machine (CMM).
• CCM three-dimensional measuring machine
• These machines have a structure comprising three orthogonal guidance rules two by two. These guidance rules make it possible to reach, in a unique way, all the points of a parallelepipedal volume defined by the guiding rules. These machines are completed by a probe and a calculator.
• the probe performs a measurement of the coordinates of the surface of a workpiece to be measured by contact with the surface of the workpiece.
• the coordinates are recorded in the reference) of the machine.
• the measurement using a three-dimensional measuring machine has, as an advantage, the the fact that the same machine can measure parts of any geometry at the cost of a simple reprogramming between the measurement of two pieces.
• three-dimensional measuring machines are sensitive to the environment in which they work (temperature variation, vibration ).
• an object of the invention is to provide a three-dimensional measurement method that can be installed in an industrial environment, for example, on a production line, while ensuring the accuracy of the coordinates of the points before their digital processing and the speed of the controls .
• the subject of the invention is essentially a method for three-dimensional measurement of coordinates of significant points of a part, comprising the steps of:
• the basis of the invention is to measure coordinates with respect to a physical standard.
• the method according to the invention can therefore be implemented in an industrial environment since the measurements are are relative to a physical standard and still allow the collection of coordinates that can be digitally processed to determine part compliance.
• the corrected coordinates can then be processed by a mathematical method applied to the three-dimensional measurement.
• the corrected X PC Yp C Z PC coordinates are processed by the least squares method.
• the method comprises:
• the invention also relates to a device for implementing the method of three-dimensional measurement of coordinates of significant points of a part comprising:
• a calculation unit connected to the measuring equipment having storage means in which can be stored the coordinates X E Y E Z E
• the method uses measuring equipment operating by probing, optical, pneumatic or capacitive measurement.
• the measuring equipment is a three-dimensional measuring equipment capable of determining three coordinates of a point of the part in a frame of reference related to the part.
• the measuring equipment can then be a three-dimensional measuring machine.
• the measuring equipment comprises elements of unidirectional measurements and three-dimensional measurement elements.
• FIG. 1 represents a measurement of a standard on measuring equipment under industrial conditions
• FIG. 2 represents a measurement of a part resulting from an industrial process on a measuring equipment under industrial conditions
• Figure 3 shows a table of values of the coordinates of six points palpated on a plane.
• the function of the measurement operation of a mechanical part is the verification of its conformity with respect to a drawing having dimensions and tolerances .
• the first step of the method according to the invention consists in producing a standard part 2 representative of the part to be produced.
• This standard part 2 is generally made of steel and undergoes heat treatments to give it high dimensional stability.
• the piece deliberately has a simple L shape and on this piece, it will be admitted that what we want to measure, is the thickness of the vertical branch by referring to the piece as it is oriented on the drawing and the flatness of one of the upper faces of the piece.
• the standard piece 2 representative of the piece is measured in the laboratory. This measurement is done, in a conventional manner, using a three-dimensional measuring machine under controlled conditions, especially temperature. In the example, the thickness is measured at one point and the flatness at six points. For each of these points, ie seven in the example shown, there are therefore X E Y E Z E coordinates which are located in a reference linked to the part.
• the values of the six points palpated on the upper face of the standard part 2 are recorded in column III of the table of FIG. 3. The following step is done on a measuring equipment which has means for positioning the part.
• the measuring equipment consists, on the one hand, of a unidirectional sensor 5, oriented in a horizontal general direction and of a probe 6 oriented in a generally vertical direction and placed on the three-dimensional measuring machine 7. .
• the peculiarity of the unidirectional sensor is that it is placed in the part repository according to precise coordinates.
• the standard part 2 is placed on the plane 4 against the fingers 3 in the part frame.
• the unidirectional sensor 5 and the probe 6 of the three-dimensional measuring machine perform their measurement.
• the unidirectional sensor 5 thus measures the coordinate Y E giving the thickness of the standard part 2 measured by the machine in the part reference and, simultaneously, the probe 6 of the machine carries out the measurements along the three axes X, Y, Z of the six points chosen to define the flatness of the upper face of the piece.
• the coordinates X E. Y E. Z E are recorded in column IV of the table of figure 3. Knowing for the standard part 2 the X E Y E Z E coordinates measured in the laboratory and the X E coordinates. Y E. Z E , measured on the machine, one can easily determine for each point, the difference ⁇ between the coordinates X E Y E Z E and the coordinates X E. Y E. Z E. which corresponds to the measurement error due to the equipment under conditions (including temperature) of an industrial environment.
• the difference ⁇ is stored in a memory of a computing unit 9 which can be a microcomputer. Since the error related to the measuring equipment is known, the standard part 2 is removed from the measuring equipment. A part 10 resulting from a manufacturing process is then placed in the part repository defined in the equipment.
• the seven significant points are measured by the unidirectional sensor and the probe of the three-dimensional measuring machine.
• a series of X P Y P Z P coordinates is thus obtained, especially for the six points palpated on the upper face of the part to be measured, the coordinates of which are recorded in column V of the table of FIG. 3.
• the method according to the invention thus makes it possible to measure point coordinates relative to a standard part, which makes it suitable for an industrial environment.
• the invention is not limited to the embodiment described above by way of non-limiting example, but it encompasses all the embodiments.
• a downgraded three-dimensional measuring machine can be used in the context of the method according to the invention, since it is then not used to make a measurement obtained directly with respect to its measurement rules, but corrected relative to a representative standard of the piece.
• the measuring equipment can be manually, semi-automatically or automatically controlled with regard to the positioning of the part and the standard in the reference system defined in the measuring equipment, but also with regard to the mode of measurement. management of unidirectional sensors as well as the displacement of three-dimensional sensors.
• the acquisition of the coordinates of points by the measuring equipment can be done in static mode, ie point by point, or in dynamic mode, ie by scanning.
• a point that is also important to note is that, to facilitate the exploitation of the significant points and, in particular, to correct them as a function of the temperature, the coordinates of these points are expressed in a room reference in the example. described. Any other repository can be considered, such as the machine repository.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)

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• 2004
  • 2004-06-08 FR FR0406174A patent/FR2871228B1/fr not_active Expired - Lifetime
• 2005
  • 2005-06-07 WO PCT/FR2005/001394 patent/WO2006003300A1/fr active Application Filing
  • 2005-06-07 JP JP2007526493A patent/JP2008501969A/ja active Pending
  • 2005-06-07 EP EP05775333A patent/EP1759171A1/de not_active Ceased
  • 2005-06-07 US US11/628,923 patent/US20080052035A1/en not_active Abandoned

Non-Patent Citations (1)

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