GB2163697A - Apparatus and process for deburring unfired ceramic blanks - Google Patents

Abstract

The apparatus comprises electronic storage, computer and control means and accommodating means (30) to accommodate a ceramic blank to be deburred. The apparatus includes means for rigidly connecting an elongate non-rotary deburring tool (27) to a force sensor (24) and means either for displacing, or for tilting, the longitudinal axis of the tool (27) to a point on the blank (33) to be deburred. The displacing means enable the displacment along the straight lines not parallel to one another and which are not situated in the tangential plane but which are parallel to the tangential plane, or the tilting means are such that the said two straight lines constitute axes (20,22) for tilting movements. <IMAGE>

Description

SPECIFICATION Apparatus and process for deburring unfired ceramic blanks The invention is concerned with the removal of the burr occurring in the casting, pressing or turning of unfired ceramic blanks and is applicable with advantage in large scale production.

The invention described in West German Specification (DE-OS) 3150431 is based on a scanning station which is installed separately from the deburring and trimming tools and which consists of two positionally adjustable transmitters scanning the articles to be trimmed and which serves to obtain the geometrical data of the blank in question. The original data of a sample trimmed by hand are stored and are used, after they have been processed, for the control of the subsequent trimming machines. Geometrical differences between the blanks of a series, such as occur, for example, as a result of varying drying shrinkage, are not taken into account. There may therefore be differences in trimming quality between blanks in one and the same series.This prior apparatus suffers from the further drawback that if the data obtained from a hand-trimmed blank are to be used for a number of blanks and for a whole series of blanks the position to which the blank to be processed has rotated on the rotary table must first of all be known.

The purpose of the present invention is to develop an apparatus for the deburring of unfired ceramic blanks by which the burr occurring in the casting, pressing or turning of the blanks can be removed rapidly and with uniform quality regardless of the geometry of the blanks, their position on the accommodating platform, e.g. rotary table, and the geometrical differences occurring between the blanks of one and the same series, owing to varying drying shrinkage, for example, and also without the use of a separate scanning station for obtaining the geometrical data of the blanks.

In the invention described in the said West German Specification the geometrical data of the blanks are obtained by means of a separate scanning station consisting of two positionally adjustable transmitters which scan the articles to be trimmed. The data thus obtained are stored and are used, after being processed, for the control of the subsequent trimming stations. All the data for the control of the trimming stations for the trimming of a blank are stored in the storage, computing and control apparatus before the actual trimming process commences.Owing to the considerable time consumed by the scanning of a blank, the storage of the data obtained, the processing of the latter and the operation of making the data ready for the control of the trimming stations, the system in which each blank is scanned individually and the data obtained in each case are processed is rendered untenable by the time factor. For the efficient operation of the trimming machine described in the said West German Specification, therefore, the original data have to be taken from a sample trimmed by hand, these data being used, after processing, for the control of the trimming of a number of blanks or of a whole series thereof. Geometrical differences such as occur between the blanks of a series as a result of varying drying shrinkage, for example, are thus not taken into account.Differences of trimming quality may thus occur within one and the same series of blanks.

This apparatus suffers from the further drawback that if the data obtained from a handtrimmed blank are to be used for a number of blanks and for a whole series of blanks the position to which the blank to be processed has rotated on the rotary table must first of all be known.

The purpose of the present invention is to develop an apparatus with which unfired ceramic blanks can be deburred rapidly and with uniform quality without the use of a separate scanning station, regardless of their geometry and thus independently of the position to which they have been set on an accommodating platform, for instance rotated on a rotary table and also regardless of the geometrical deviations occurring within one and the same series of blanks as a result, for example, of varying drying shrinkage.

According to one aspect of the invention there is provided an apparatus for deburring unfired ceramic blanks comprising electronic storage, computer and control means and accommodating means to accommodate a ceramic blank to be deburred, the apparatus including means for rigidly connecting an elongate non-rotary deburring tool to a force sensor and means for displacing or tilting the longitudinal axis of the tool to a position normal to a plane tangential to a point on the blank to be deburred, the said displacing means constituting means for displacing the longitudinal axis along two straight lines not parallel to one another and which are not situated in the tangential plane but which are parallel to the tangential plane or the said tilting means constituting tilting means wherein the said two straight lines constitute axes for tilting movements.The force sensor may be a deformation body with semi-conductor strain gauges, piezo-torsional elements or a force receiver based on a distance measurement. Preferably the said two straight lines are perpendicular to each other. Usually the accommodating means comprises a rotary platform. In one desirable form of apparatus the deburring tool is linearly displaceable parallel to its longitudinal axis. Preferably sensor means are provided on a mounting means for the deforming tool and/or the tool itself.

According to another aspect of the invention there is provided a process for removal of the burr occurring in the casting, pressing or turning of unfired ceramic blanks by employing the defined apparatus. The process is also applicable to unfired ceramic blanks which are not rotationally symmetrical in which case the accommodating means excludes a rotary platform.

In an expedient embodiment of the invention the qualitative recognition of the point on the blank to be deburred is signalled by a sensor (such as an optical or pneumatic approximation sensor) guided by the tool mounting means, while in order to cause the longitudinal axis of the tool to assume the position normal to the plane tangential to the point on the blank to be deburred the motional coordinates are preselected in a stored form or the normal position is directly determined by a further sensor (such as an annular jet nozzle or optical distance sensor) guided by the tool mounting means.

As accommodating platform there may be provided a rotary table driven by an electric motor and serving to accommodate and rotate the ceramic blank to be deburred and a first transport unit displaceable vertically for the purpose of adaptation to blanks of various heights may advantageously be mounted on a horizontal basic body. The driving means may consist of an electric motor with a helical gearing. This first transport unit may bear a horizontally displaceable first frame driven by an electric motor via a helical gearing. The first frame may contain a U-shaped support which is tiltable, by an electric motor driving system, about a horizontal axis perpendicular to a spindle driving the first frame, and in which a second frame may be mounted in such a way as to be tiltable, by an electric motor drive system, about a horizontal axis parallel to the tilting axis of the U-shaped support.This second frame may contain a sensor support tiltable by an electric motor drive system about a tilting axis situated perpendicularly to the tilting axis of the second frame.

This sensor support may contain the force sensor to which is affixed the tool mounting means bearing the non-rotating tool (such as a hardened needle, scraper or knife).

For guiding the non-rotating deburring tool connected with the force sensor a freely programmble industrial robot with equivalent motional axes and equivalent positioning accuracy can be used in place of the aforementioned tool mounting means.

For deburring a rotationally symmetrical ceramic blank to be processed, the blank can be secured centrally in any desired rotational position on a rotary platform by means of a vacuum suction device. In a convenient embodiment a tool guide is provided which is then displaced or tilted in such a way that the spatial position of the longitudinal axis of the tool coincides with the position of the surface normal of the plane tangential to the point of the blank to be deburred. The notional coordinates for this purpose are taken from the store, or else the normal position is determined directly by a further sensor after the qualitative recognition of the point to be deburred has been signalled by a sensor. After the tool has assumed this initial position in respect of the workpiece the deburring process itself commences.For this purpose the non-rotating tool by means of displacements along the two non-parallel straight lines, which are preferably perpendicular to each other and which are not situated in the tangential plane and which are parallel to the tangential plane, or by tilting movements about these straight lines, which then constitute tilting lines, is caused to come in contact with the blank, this being communicated to the storage, computer and control unit by a corresponding indication of the force sensor. From the signal of the force sensor the magnitude and direction of the contact pressure of the tool against the blank are determined by the computer, the magnitude of the contact pressure being compared with a preselected stored value.The computer then emits signals to the driving element of the aforementioned tool guide mechanism, these signals causing the deburring tool to be constantly moved by a certain distance in a basic direction which is perpendicular to that taken by the contact pressure measured and to which is added a further component parallel to the direction of the contact pressure measured.

If the magnitude of the contact pressure measured is identical with the comparative value the component to be added is zero. If the magnitude of the contact pressure measured is lower than the comparative value a positive component is added to the basic direction, as a result of which the deburring tool is pressed with greater force against the contour to be deburred on the blank, whereas if the contrary is the case a negative component is added, which moves the deburring tool somewhat farther away from the contour to be deburred, thus reducing the contact pressure.

The operations of measuring the contact pressure, deriving from its magnitude and direction a decision for the further movement of the tool and effecting the said movement are repeated cyclically as many times as required to fulfil a preselected final criterion and thus deburr the blank completely.

In the case of blanks of complicated shape the preselected contact pressure in the form of the comparative value can be varied, with programme control, during the cyclic repetitions of the aforementioned operations, in accordance with the requirements for the faultless deburring of the blank, as can also the lengths of the steps in which the work piece is fed forward.If in the cyclic repetitions of the said processes the limits of the working space of the motional mechanism enabling the aforementioned movements to take place in two degrees of freedom are reached, then the present processing point of the blank is conveyed, taking all the degrees of freedom of the apparatus into account, to a central point of the operating space of the aforementioned movement mechanism, this process being equivalent to the assumption of a fresh initial position, and the deburring process is continued as described.The blank is thus deburred regardless of the geometry of the blanks and automatically taking into consideration any geometrical differences between the blanks in one of the same series, since the cyclic repetitions of the said processes cause the deburring tool to be moved along the contour to be deburred, the preselected contact pressure being maintained, the burr thus being removed. There is likewise a freedom of choice as regards the rotational position of the blank on the rotary table.

The aforementioned apparatus can also be used for blanks which are not rotationally symmetrical and thus without a rotary table.

Examples The invention will be explained in greater detail by reference to two examples and to the accompanying diagrammatic drawings in which: Figure 1 is an overall view of a deburring apparatus embodying the invention, shown in dimetric projection, and Figure 2 is a sectional diagram to an enlarged scale of a sensor carrier used in conjunction with the deburring apparatus shown in Figure 1.

Example 1 With this example of the deburring apparatus embodying the invention, deburring may be carried out, for example, on ceramic articles such as plates, dishes or vases, having perforations. As shown in Figure 1, a stationary horizontal basic body 1 bears a rotary plate 32 which is driven by an electric motor drive system 30 and which is provided with a vacuum suction device 31 and which serves to accommodate and rotate the ceramic article 33 to be deburred, such as a plate, dish or vase, of which outer contours and contours of perforations are to be deburred, and three parallel vertical guide tubes 2, 3 and 4 on which a first support 5 for adaptation to blanks of different heights is mounted in such a way as to be vertically displaceable by means of an electric motor 6, vertical rotary spindle 7 and a spindle nut 8.

To this first support 5 are affixed two parallel horizontal guide tubes 9 and 10, on which a first frame 11 is horizontally guided by means of an electric motor 12, a horizontal rotary spindle 13 and a spindle nut 14.

In the first frame 11 there is provided a second U-shaped support 17 which is tiltable by an electric motor drive system 15 about a horizontal axis 16 perpendicular to the axis of the horizontal rotary spindle 13 and in which a second frame 18 is mounted in such a way as to be tiltable by means of an electric motor drive system 19 about a horizontal axis 20 taking a parallel course to the tilting axis 16.

In this second frame 18 is a force sensor support 23 which is tiltable by means of an electric motor drive system about a tilting axis 22 perpendicular to the tilting axes 16 and 20. As may be seen from Figure 2, the force sensor support 23 contains a force sensor 24 which consists of a displacement body and semiconductor strain gauges and to which is affixed a tool mount 25 bearing a non-rotating tool 27, such as a hardened needle, which can undergo linear displacement parallel to its longitudinal axis by means of a miniature pneumatic cylinder 26. The tool mount 25 bears a sensor 28, constructed as a reflex light barrier, for the qualitative recognition of a required deburring point on the blank, and a pneumatic annular jet sensor 29 serving to determine that position of the longutdinal axis of the tool which is normal to the plane tangential to the said processing point of the blank.

Example 2 The deburring device described in Example 1 is modified by replacing the two tilting axes 20 and 22 shown in Figure 1 by a thrust axes, so that the deburring process may be effected by displacements.

Claims (8)

1. An apparatus for deburring unfired ceramic blanks comprising electronic storage, computer and control means and accommodating means to accommodate a ceramic blank to be deburred, the apparatus including means for rigidly connecting an elongate nonrotary deburring tool to a force sensor and means for displacing or tilting the longitudinal axis of the tool to a position normal to a plane tangential to a point on the blank to be deburred, the said displacing means constituting means for displacing the longitudinal axis along two straight lines not parallel to one another and which are not situated in the tangential plane but which are parallel to the tangential plane or the said tilting means constituting tilting means wherein the said two straight lines constitute axes for tilting movements.

2. An apparatus according to claim 1, wherein the said two straight lines are perpendicular to each other.

3. An apparatus according to claim 1 or claim 2, wherein the accommodating means comprises a rotary platform.

4. An apparatus according to any preceding claim, wherein the deburring tool is linearly displaceable parallel to its longitudinal axis.

5. An apparatus according to any preceding claim, wherein sensor means are provided on a mounting means for the deburring tool and/or on the tool itself.

6. An apparatus for deburring unfired ceramic blanks substantially as herein described and with reference to the accompanying drawings.

7. A process for removal of the burr occurring in the casting, pressing or turning of unfired ceramic blanks by employing the apparatus as claimed in any preceding claim.

8. A process for removal of the burr occurring in the casting, pressing or turning of unfired ceramic blanks which are not rotationally symmetrical by employing the apparatus as claimed in any one of claims 1,2,4,5,6 and wherein the accommodating means excludes a rotary platform.