SE544647C2

SE544647C2 - Positioning device for a positioning system

Info

Publication number: SE544647C2
Application number: SE2051226A
Authority: SE
Inventors: Erik Sundström
Original assignee: Zerofix Tooling Ab
Priority date: 2020-10-21
Filing date: 2020-10-21
Publication date: 2022-10-04
Also published as: SE2051226A1

Abstract

The invention relates to a positioning device for a positioning system for positioning a first object in relation to a second object in a XY-reference system. The positioning device comprises a spring arrangement (130) comprising at least one first spring portion (132) serially coupled to at least one second spring portion (134), and the first spring portion (132) is configured to deflect in a positive Z-direction (+Z) in operation and the second spring portion (134) is configured to deflect in a negative Z-direction (-Z) in operation to compensating for the deflection of the first spring portion (132) in the positive Z-direction. Thereby, improved accuracy in positioning the first object in relation to the second object is provided.

Description

POSITIONING DEVICE FOR A POSITIONING SYSTEM Technical Field The invention relates to a positioning device for a positioning system for positioning a firstobject in relation to a second object. Furthermore, the invention also relates to a positioningsystem comprising such a positioning device.

Background When placing two objects, e.g. a working table or a base plate on a milling machine table, it isimportant to be able to accurately position these tvvo objects in relation to each other in orderto be able to use e.g. a milling machine reference system for an object arranged on the workingtable. Before the 1960:s a majority of the machining and measuring within the engineeringindustry took place by making relative measurements using e.g. micrometer calipers, slidingcalipers and templates for dimensional accuracy. Drawings were produced manually to fitthese manufacturing methods. The precision depended more on the skill of the workers andoperators of the machines than the stability and the lack of freedom of play of the machines.When numerically controlled machines for the production appeared on the market, themanufacturing methods began to be more and more automated and today the production is toa large extent more or less automated using e.g. CNC-controlled multioperation machines.

During the above development of the production processes, the manufacturers of themachines have also minimized the previous problems of the machines being able to turn theinput instructions to corresponding output process steps without accuracy problems. This isalso the case regarding problems with temperature stability, freedom of play and elasticdeformation. The above enables for metalworking equipment to move to completely digitalizedproduction by absolute coordinated originating from a given zero offset point using digitalmeasurement and control systems and automated tool changing systems in the machines.

A reference system commonly used in e.g. machine shops is the Cartesian coordinate systemhaving XYZ-directions. When talking about accurate positioning in machine shops and e.g.turning, milling and drilling, tolerances of 0.01 mm - 1 um are considered “accurate”, whereastolerances smaller than 1 um are often difficult to use in production applications as suchtolerances often are difficult to measure in real production. Whereas it is relatively easy toachieve and maintain high tolerances in a laboratory environment, temperature changes andpollution as well as wear are issues that have to be handled in real production equipmentwhether it is manually operated or automated.

SummaryAn objective of embodiments of the invention is to provide a solution which mitigates or solvesthe drawbacks and problems of conventional solutions.

Another objective of embodiments of the invention is to provide a solution with improvedaccuracy in the XY-plane positioning of a first object in relation to a second object.

The above and further objectives are solved by the subject matter of the independent claims.Further advantageous embodiments of the invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives areachieved with a positioning device for a system for positioning a first object in relation to asecond object in a XY-reference system, the positioning device comprising: a first XY-reference means configured to be fixed to the first object, and a second XY-reference means configured to be fixed to the second object; wherein the first XY-reference means comprises a spring arrangement configured to abut againstthe second XY-reference means in operation for positioning the first object in relation to thesecond object in XY-directions, the spring arrangement comprising at least one first springportion serially coupled to at least one second spring portion, and the first spring portion is configured to deflect in a positive Z-direction in operation andthe second spring portion is configured to deflect in a negative Z-direction in operation tocompensating for the deflection of the first spring portion in the positive Z-direction.

The positioning device may also be denoted a zero-positioning device or a positioning device.The XY-reference system may also mean the XY-plane of a Cartesian coordinate system. Thedeflection of the first spring portion and the second spring portion may occur when a radialforce is acting on the spring arrangement due to a press fit mounting. The deflection may alsobe understood as a deformation. The first XY-reference means may be denoted first XY-positioning means and the second XY-reference means may be denoted second XY- positioning means.An advantage of the positioning device according to the first aspect is that the accuracy of thepositioning of the first object in relation to the second object in the XY-plane is improved compared to conventional solutions. ln an implementation form of a positioning device according to the first aspect, the first spring portion is configured to deflect in the positive Z-direction with a firstdeflection amount, and the second spring portion is configured to deflect in the negative Z-direction with asecond deflection amount, wherein the first deflection amount is substantially the same as the second deflection amOUFlt.

Hence, the deflection of the first spring portion and the second spring portion is balanced forcontrolled deflection of the spring arrangement. ln an implementation form of a positioning device according to the first aspect,the first XY-reference means has a in a Z-direction conical inner surface; andthe second XY-reference means has a in a Z-direction conical outer surface.

Hence, the conical inner surface of the first XY-reference means may abut/press against the conical outer surface of the second XY-reference means in operation. ln an implementation form of a positioning device according to the first aspect,the spring arrangement has an annular disc shape; andthe second XY-reference means comprises a taper. ln an implementation form of a positioning device according to the first aspect,the second XY-reference means is configured to be fixed to the second object via aspacer. ln an implementation form of a positioning device according to the first aspect, the springarrangement comprises a rim portion serially coupled to the first spring portion and being configured to pressagainst the taper of the second XY-reference means in operation. ln an implementation form of a positioning device according to the first aspect, the springarrangement comprises a press fit guiding means serially coupled to the second spring portion and configured topress against the first object in operation. ln an implementation form of a positioning device according to the first aspect, the rim portion is arranged at an inner circumference of the spring arrangement, and the press fit guiding means is arranged at an outer circumference of the spring arrangement. ln an implementation form of a positioning device according to the first aspect, the springarrangement comprises a spring coupling portion configured to serially couple the first springportion and the second spring portion. ln an implementation form of a positioning device according to the first aspect, the spring coupling portion comprises a groove. ln an implementation form of a positioning device according to the first aspect, the groove is apunched groove. ln an implementation form of a positioning device according to the first aspect, the groove iscircularly arranged with a constant radius around a center axis of the positioning device. ln an implementation form of a positioning device according to the first aspect, the springarrangement is formed from a single sheet metal piece with constant thickness. ln an implementation form of a positioning device according to the first aspect, the secondobject is configured to support the first object in the positive Z-direction in operation.

According to a second aspect of the invention, the above mentioned and other objectives areachieved with a system for positioning a first object in relation to a second object in a XY-reference system, the system comprising at least one positioning device according to any oneof the preceding claims.

Further applications and advantages of the embodiments of the invention will be apparent fromthe following detailed description.

Brief Description of the DrawingsThe appended drawings are intended to clarify and explain different embodiments of theinvention, in which: - Fig. 1 shows in a cross sectional view a positioning system according to an embodiment of the invention;- Fig. 2 shows in a cross sectional view a positioning device according to an embodiment of the invention; - Fig. 3a and 3b show a spring arrangement according to an embodiment of the inventionin a cross sectional view and in a view from above, respectively; - Fig. 4 shows in a cross sectional view a section of a spring arrangement according toan embodiment of the invention; and - Fig. 5 iliustrates exemplary measurements of an exemplary spring arrangement.

Detailed Description Fig. 1 shows in a cross sectional view a positioning system 200 according to an embodimentof the invention. The positioning system 200 may comprise any number of positioning devices100 and in the exemplary case of Fig. 1 two positioning devices 100 are shown in its mountedoperating position. Each positioning device 100 may act as a zero-reference in the system 200for high accuracy. Further, the system 200 also comprises a first object 302 and a secondobject 304 to be positioned in relation to each other in the XY-reference system or the XY-plane. The positive Z-direction +Z and the negative Z-direction -Z are also illustrated hence aCartesian coordinate system is illustrated. However, in embodiments of the invention whencylindrical symmetry is at hand cylindrical coordinates may also be used with an axis A and aradial extension R as also illustrated in the Figs.

Furthermore, the first object 302 may e.g. be a working table, a base plate, a fixture, a pallet,a tool, etc., and the second object 304 may e.g. be a machine table, a machine base, etc. butare not limited thereto. The first object 302 may comprise a downward directed cavity in whichcavity the first XY-reference means 102 may be fixed to as shown in Fig. 1 against the sidewalls of the cavity. Therefore, the first XY-reference means 102 may be arranged to be fixedagainst an inner wall of the cavity by a press-fit, e.g. if the first XY-reference means 102comprises a spring arrangement, and may be mounted non-removably therein, e.g. bypressing it therein using a mandrel. The second XY-reference means 104 may be configuredto be fixed to the second object 304 with or without a spacer 110. The second XY-referencemeans 104 may be made of hard metal in order to withstand wear. ln embodiments of the invention, the second object 304 is configured to support the first object302 in the positive Z-direction in operation as shown in Fig.Fig. 2 shows in a cross sectional view a positioning device 100 according to an embodimentof the invention. The positioning device 100 comprises a first XY-reference means 102configured to be fixed to the first object 302, and a second XY-reference means 104 configuredto be fixed to the second object 304. The first XY-reference means 102 comprises a springarrangement 130 configured to abut or press against the second XY-reference means 104 in operation for positioning the first object 302 in relation to the second object 304 in XY-directionsor in the XY-plane. Further, the spring arrangement 130 comprises at least one first springportion 132 which is serially coupled to at least one second spring portion 134. ln operation,the first spring portion 132 is configured to deflect or deform in a positive Z-direction +Z andthe second spring portion 134 is configured to deflect or deform in a negative Z-direction -Z soas to compensating for the deflection or the deformation of the first spring portion 132 in thepositive Z-direction. ln embodiments of the invention, the first spring portion 132 is configured to deflect in thepositive Z-direction +Z with a first amount, and the second spring portion 134 is configured todeflect in the negative Z-direction -Z with a second amount. The first amount is substantiallythe same as the second amount for balancing the deflection of the first spring portion 132 andthe second spring portion, respectively, for controlled total deflection of the spring arrangement130 of the positioning deviceWhen the first XY-reference means 102 is mounted, e.g. by press fit in which a high radialforce will act on the first XY-reference means 102, the first XY-reference means 102 maydeform in a non-controlled manner so that the positioning of the first object in relation to thesecond object is not accurate enough for precision applications. However, by having a springarrangement 130 according to embodiments of the invention the deformation or deflection ofthe spring arrangement 130 may be controlled. This means improved accuracy.

Furthermore, the positioning device 100 may comprise means for attaching/fastening thepositioning device 100 to the first object 302 and the second object 304, respectively. ln thedisclosed embodiment, the positioning device 100 comprises first attachment means 120 forattaching to the first object 302 and second attachment means 118 for attaching to the secondobject 306. The first attachment means 120 and the second attachment means 118 may e.g.be first h1 and second h2 through holes of different diameters arranged inside a body 106, thelatter having an axial extension and e.g. having cylindrical symmetry and further a section thatis encircled by a taper of the second XY-reference means 104. The body may be made of asuitable material such as a metal. The first h1 and second h2 through holes may compriseinner threads configured to receive outer threads of bolts (not shown) of the first 302 andsecond objects 304, respectively. Thereby, a secure attachment or fastening of the positioningdevice 100 to the first 302 and second objects 304, respectively, may be achieved. As alsoillustrated herein, the positioning device 100 may comprises a clearance 116 also in the formof a through hole h3 having a diameter larger than the diameter of the through holes of the first120 and second 118 attachment means. Thereby, the risk of the positioning device 100 being misaligned due to radial forces acting on the positioning device 100 so as to distort thepositioning accuracy in the XY-plane is reduced or minimized. This is especially the case whenthe positioning device 100 is to be mounted in the systemAs further disclosed in Fig. 2, the first XY-reference means 102 may have a in a Z-directionconical inner surface which in operation abuts or presses against a in a Z-direction conicalouter surface of the second XY-reference means 104. I\/|oreover, in embodiments of theinvention, the spring arrangement 130 has an annular disc shape and the second XY-referencemeans 104 comprises a taper. Therefore, in such cases, the disc may comprise the conicalinner surface whilst the taper comprises the conical outer surface abutting each other as shownin Fig. 2. lt may also be noted that the second XY-reference means 104 may be configured tobe fixed to the second object 304 via a spacer (also known as a spacing device or a distancepeace) 110 as shown in Fig. 1 and 2. The spacer 110 supports the first object in the Z-directionand depending on application the thickness and shape of the spacer 110 may vary.

Fig. 3a and 3b show a spring arrangement 130 according to an embodiment of the inventionin a cross sectional view and in a view from above, respectively. Furthermore, Fig. 4 shows ina cross sectional view a section of the spring arrangement 130. With reference to mentionedFig. 3a, 3b and 4 more details and aspects of the spring arrangement 130 will now bedescribed.

As disclosed, in embodiments of the invention, the spring arrangement 130 comprises a rimportion 136 which is serially coupled to the first spring portion 132. The rim portion 136 maybe of the type stiff rim and being configured to press against the taper of the second XY-reference means 104 in operation as shown in Fig. 2. Further, the spring arrangement 130may comprise a press fit guiding means 138 serially coupled to the second spring portion 134.The press fit guiding means 138 is configured to press or abut against the first object 302 inoperation as also shown in Fig. 2. The press fit guiding means 138 may in this respect comprisea beak portion 138' so as to lock and secure the spring arrangement 130 against the first object302 in operation after mounting. ln embodiments of the invention, the rim portion 136 isarranged at an inner circumference of the spring arrangement 130, whilst the press fit guidingmeans 138 is arranged at an outer circumference of the spring arrangementAs previously mentioned, the first spring portion 132 is serially coupled to the second springportion 134, or vice versa. This may be achieved by the use of a spring coupling portion 140that is configured to serially couple the first spring portion 132 and the second spring portion134 to each other. The spring coupling portion 140 may be considered as a spring hinge mechanically coupling independent springs but also demark different spring portions from eachother. lt is noted that the spring arrangement 130 herein may comprise any number of springcoupling portions coupling any number of first 132 and second 134 spring portions whichmeans that the invention is not limited to a single spring coupling portion coupling a single first spring portion and a single second spring portion. ln further embodiments of the invention, the spring coupling portion 140 comprises of a groovewhich may be circularly arranged with a constant radius around a center axis A of thepositioning device 100 as shown in 3a, 3b and 4. lt has been noted that a groove worksperfectly well in acting as a spring coupling portion 140 for many applications. However, thespring coupling portion 140 may be realized with other means having the same function aspreviously described.

When the spring coupling portion 140 comprises of a groove economic advantages isachievable when manufacturing the spring arrangement 130 herein. For example, the groovemay be a punched groove which is inexpensive to produce. ln embodiments of the invention,the spring arrangement 130 is formed from a single sheet metal piece with constant thickness,and the single sheet metal piece may be punched or stamped in a single manufacturing stepusing a dedicated tool so as to produce the spring arrangement 130. ln this way both highaccuracy in positioning and low cost at production of the positioning device 100 is possible.

For providing even deeper understanding of embodiments of the invention in respect of thespring arrangement 130, some numbers are given which are exemplary only and aredependent on the application of the positioning device 100 and positioning system 200. Withreference to Fig. 5, the spring arrangement 130 may have a symmetrical disc shape with asmaller outer diameter d2 of 36mm, a larger outer diameter d1 of 36.12mm, and an innerdiameter d3 at the stiffed rim of 17.50mm. The thickness of such a disc may e.g. be formedfrom a 0.9mm thick sheet metal with a punched groove acting as the spring coupling portion140. Generally, the different parts of the positioning device 100 may be made from any suitablematerial having the properties needed for its functioning such as different types of metal,plastics, etc.

Finally, it should be understood that the invention is not limited to the embodiments describedabove, but also relates to and incorporates all embodiments within the scope of the appendedindependent claims.

Claims

1. A positioning device (100) for a system (200) for positioning a first object (302) in relation toa second object (304) in a XY-reference system, the positioning device (100) comprising: a first XY-reference means (102) configured to be fixed to the first object (302), and a second XY-reference means (104) configured to be fixed to the second object (304);wherein the first XY-reference means (102) comprises a spring arrangement (130) configured toabut against the second XY-reference means (104) in operation for positioning the first object(302) in relation to the second object (304) in XY-directions, the spring arrangement (130)comprising at least one first spring portion (132) serially coupled to at least one second springportion (134), and the first spring portion (132) is configured to deflect in a positive Z-direction (+Z) inoperation and the second spring portion (134) is configured to deflect in a negative Z-direction(-Z) in operation to compensating for the deflection of the first spring portion (132) in thepositive Z-direction.

2. The positioning device (100) according to claim 1, wherein the first spring portion (132) is configured to deflect in the positive Z-direction (+Z) with afirst deflection amount, and the second spring portion (134) is configured to deflect in the negative Z-direction (-Z)with a second deflection amount, wherein the first deflection amount is substantially the same as the second deflection amOUFit.

3. The positioning device (100) according to any one of the preceding claims, whereinthe first XY-reference means (102) has a in a Z-direction conical inner surface; andthe second XY-reference means (104) has a in a Z-direction conical outer surface.

4. The positioning device (100) according to any one of the preceding claims, whereinthe spring arrangement (130) has an annular disc shape; andthe second XY-reference means (104) comprises a taper.

5. The positioning device (100) according to any one of the preceding claims, whereinthe second XY-reference means (104) is configured to be fixed to the second object(304) via a spacer (110).

6. The positioning device (100) according to claim 4 or 5, wherein the spring arrangement (130)comprises a rim portion (136) serially coupled to the first spring portion (132) and being configuredto press against the taper of the second XY-reference means (104) in operation.

7. The positioning device (100) according to claim 6, wherein the spring arrangement (130)comprises a press fit guiding means (138) serially coupled to the second spring portion (134) andconfigured to press against the first object (302) in operation.

8. The positioning device (100) according to claim 7, wherein the rim portion (136) is arranged at an inner circumference of the spring arrangement(130), and the press fit guiding means (138) is arranged at an outer circumference of the springarrangement (130).

9. The positioning device (100) according to any one of the preceding claims, wherein thespring arrangement (130) comprises a spring coupling portion (140) configured to seriallycouple the first spring portion (132) and the second spring portion (134) by acting as a springhinge mechanicaliy coupling the first spring portion (132) and the second spring portion (134).

10. The positioning device (100) according to claim 9, wherein the spring coupling portion (140) comprises a groove.

11. The positioning device (100) according to claim 10, wherein the groove is circularlyarranged with a constant radius around a center axis (A) of the positioning device (100).

12. The positioning device (100) according to any one of the preceding claims, wherein thespring arrangement (130) is formed from a single sheet metal piece with constant thickness.

13. The positioning device (100) according to any one of the preceding claims, wherein the second object (304) is configured to support the first object (302) in the positive Z-direction inoperation.

14. A system (200) for positioning a first object (302) in relation to a second object (304) in aXY-reference system, the system (200) comprising at least one positioning device (100)according to any one of the preceding claims.