NL2020079B1

NL2020079B1 - Welding Fixture

Info

Publication number: NL2020079B1
Application number: NL2020079A
Authority: NL
Inventors: De Wilde Ricardo; Johannes Cornelis Froon Everardus
Original assignee: Awl Techniek B V
Priority date: 2017-12-13
Filing date: 2017-12-13
Publication date: 2019-06-21

Abstract

A fixture system comprises a mounting frame of a predefined geometry with a mounting plate comprising a pattern of holes and/or screw openings therein for mounting a plurality of mounting parts thereon. The mounting parts have specified shapes and forms for mounting thereon a variety of end parts. The end parts can be connection parts or functional clamping elements for clamping a device element that is to be positioned in a relative position and orientation towards the mounting frame. At least some of said mounting parts are manufactured from freeform cut parts having a pattern of holes and/or screw openings, for mounting a plurality of mounting parts thereon.

Description

Title: Welding Fixture

Field of invention

The present disclosure relates to a workpiece fixture, and in particular to a welding fixture e.g. for use in robotic welding.

Description of the prior art

Fixtures are standard devices in the art of welding and assembly constructions, that are designed to temporarily maintain a work product in a well defined orientation relative to a base, in order to facilitate or assist assembly and welding processes. The fixtures are essentially made from construction parts that can be assembled e.g. via nuts and bolts and dowel pins for accurate positioning, e.g. on a mounting block, that can be a metal plate provided with well defined mounting positions, e.g. by workpiece stops (dowels) that are pressed into holes in support plates. The function of the workpiece stops is to correctly position workpieces on the workpiece support plates for a corresponding welding operation. Workpiece stops could also take the form of a raised edge or curb on the first support surfaces, rather than dowel pins. Steel dowel pins are machined to tight tolerances, as are the corresponding holes, which are typically reamed. A dowel pin may have a smaller diameter than its hole so that it freely slips in, or a larger diameter so that it must be pressed into its hole (an interference fit).

When designing mechanical components, mechanical engineers typically use dowel holes as reference points to control positioning variations and attain repeatable assembly quality. If no dowels are used for alignment (e.g., components are mated by bolts only), there can be significant variation, or "play", in component alignment.

Typical drilling and milling operations, as well as manufacturing practices for bolt threads, introduce mechanical play proportional to the size of the fasteners.

As is customary in this field, the components of welding fixtures are made of fixed building blocks, that are assembled for a specific purpose, and that support a work piece also by fixture pins, that fit in corresponding holes provided thereto in a work piece. The work piece is in this way integrally mounted to the fixture, in a well defined way. The building blocks are usually standard blocks, e.g. beam form blocks or plates, that can be assembled, together with adjusting shims to a well defined position and orientation in a coordinate frame. Basically, using these building blocks, supporting pins can be arranged in any suitable way on a mounting block for any 3D coordinate, together with an appropriate orientation.

Customary also in the field is the high level of specificity of the building blocks, that are used to assemble a fixture. The fixture is provided as a frame with a very high degree of accurate positioning pins, e.g. an accuracy of less than 1 or even less than 0.05 mm. This accuracy can be achieved by precise manufacturing techniques, that are able to produce these building blocks with tolerances e.g. less than 0.1 mm, and that are assembled with shims and dowel pins in ways essentially known in the art.

Some problems associated with these systems are related with the specificity needed in the design and production of the building blocks for these fixtures. US6439561 shows a modular positioning blade adapted for use in a modular system of fixtures, in that by stocking a variety of blades, each with a different set of through-bore locations, a different positioning fixture may be formed, as needed, without the need for custom manufacturing of blades. This positioning blade has through-bores positioned on the blade so as to define a predetermined location relative to the top and bottom edges, and together with a riser, allow for the precise positioning of a locating pin. US2004164474 similarly uses a modular midplate that may be selectively designed and formed, but is used in combination with a riser to provide for a plurality of selected holding positions. GB1217741 similarly uses modular platelets that are reusably used to provide a variety of construction jigs.

In the disclosed prior art the positioning blades require cutting and milling steps, and further utilizes risers for precise positioning, since the blade is a modular blade.

Therefore, it would be very useful to have a solution that could be assembled without undue effort or require specialized skills, and could form a suitable fixture that is easily moveable and demountable, and can be disassembled without problems, and can consist of building blocks that are easier and quicker produced in the required accuracy, at lower costs.

SUMMARY OF THE INVENTION

In one aspect, it is aimed to provide a fixture system for fixing a workpiece. The fixture system comprises a mounting frame of a predefined geometry with a mounting plate comprising a pattern of holes and/or screw openings therein for mounting a plurality of mounting parts thereon. The mounting parts have specified shapes and forms for mounting thereon a variety of end parts. The end parts can be connection parts or functional clamping elements for clamping a device element that is to be positioned in a relative position and orientation towards the mounting frame. At least some of said mounting parts are manufactured from freeform cut parts having a pattern of holes and/or screw openings, for mounting a plurality of mounting parts thereon.

In this way, the freeform cut parts can be designed with more freedom and flexibility than the prior art mounting parts, which are often manufactured through a complex milling process to provide a suitable accuracy with tolerances that are in right range of use.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further elucidated in the figures:

Figure la shows a prior art exemplary perspective view of a simple system embodiment;

Figure lb shows an exemplary embodiment according to the invention;

Figure 2a shows the exemplary embodiment in exploded view; Figure 2b shows a section bottom view of a part of the assembly of

Figure 2 a

Figure 3 shows a further exemplary embodiment;

Figure 4 (a, b) shows a further embodiment;

Figure 5 (a, b, c) shows a further aspect of the freeform cut parts.

DETAILED DESCRIPTION

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs as read in the context of the description and drawings. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. In some instances, detailed descriptions of well-known devices and methods may be omitted so as not to obscure the description of the present systems and methods. Terminology used for describing particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises" and/or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

While example embodiments are shown for systems and methods, also alternative ways may be envisaged by those skilled in the art having the benefit of the present disclosure for achieving a similar function and result. E.g. some components may be combined or split up into one or more alternative components. Finally, these embodiments are intended to be merely illustrative of the present system and should not be construed as limiting the appended claims to any particular embodiment or group of embodiments. Thus, while the present system has been described in particular detail with reference to specific exemplary embodiments thereof, it should also be appreciated that numerous modifications and alternative embodiments may be devised by those having ordinary skill in the art without departing from the scope of the present systems and methods as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner and are not intended to hmit the scope of the appended claims.

Turning to Figure 1 there is disclosed an exemplary perspective view of a simple system embodiment, in Figure 1A shown as a prior art solution 100 for a fixture pin 1 for fixating a product, and in Figure IB as a novel solution 10, including mounting parts 2, 3 manufactured from freeform cut parts having a pattern 4 of holes and/or screw openings, for mounting a plurality of mounting blocks 5 thereon. In contrast to a prior art solution shown in Figure 1A, freeform cut mounting parts 2, 3 replace custom milled part 55 (and/or standard mounting parts 5, 5’) cut in a milling process, with mounting holes and screw openings with standard dimensions. The cut part 2 is dimensioned for positioning pin 1 at the correct height and angle towards a build product. The freeform cut parts 2, 3 have a pattern 4 of holes and/or screw openings, for mounting a plurality of mounting parts thereon. The fixture system 10 further comprises a mounting frame 11 with a mounting plate 20.

Figure 2A in more detail shows in exploded view mounting parts manufactured from freeform cut parts 2, 3 having a pattern 4 of holes and/or screw openings, for mounting a plurality of mounting parts 5, 5a, 5b, 5c thereon. Mounting parts 5, 5a, 5b, 5c can be laterally positioned by shims (known in the art) denoted by numeral 6. A shim is a thin piece of material with a standard thickness e.g. of 1.0, 2.0,2.2,2.4,2.6,2.8,3.0 or 5.0 mm typically used between two parts so that the final production parts are created within the product drawing's specified tolerances. It is noted that the mounting blocks 5, 5a, 5b, 5c can have different shapes, but are selected from a limited set of standard stock parts, that can be suitably combined to any desired configuration. The mounting blocks 5, 5a, 5b, 5c have specified shapes and forms for mounting thereon a variety of end parts, such as fixture pin 1 to be positioned in a relative position and orientation towards the mounting frame 11.

Figure 2b shows a bottom section view of the cut parts 2, 3 assembled with a standard mounting block 5. Dowel pins 7 are often used as precise locating devices in machinery. When designing mechanical components, mechanical engineers typically use dowel holes as reference points to control positioning-variations and attain repeatable assembly quality. Bolts up to 10 mm in diameter typically have play on the order of 0.2 mm. When dowels are used in addition to bolts, however, the tighter dimensional tolerances of dowels and their mating holes—typically 0.01 mm—result in significantly less play, on the order of 0.02 mm. The freeform cut parts 2, 3 having a corresponding pattern of holes for receiving the dowels and the bolts, where the bolts may be designed to allow some lateral play in order to leave the positioning to the dowel pins as is commonly known.

Figure 3 provides another example, wherein mounting parts 30, 33 are manufactured from freeform cut parts having a pattern of holes and/or screw openings, for mounting a mounting block 5 thereon. In the exemplary embodiment, mounting part 30, 33 are positioner parts, to be mounted on a jig plate in ways similar as shown in the previous figures, e.g. with bolts.

The positioner parts function for rough positioning of the workpiece, so that it can be easily fitted on fixture pins. Preferably, parts 30, 33 are planar parts cut from sheet metal that is cut into a 2D preform. No further bending of the mounting parts is necessary, thereby retaining excellent positioning accuracy.

Figure 4 shows a further embodiment a cut part 40 has a distal geometry provided as a mounting element for mounting end parts, in this example a sensor 41 that is aimed for detecting a work product. Other end parts that may be mounted are connection parts, functional clamping or positioning elements 43. The sensor 41 may be a laser sensor, or other type of sensor, including contact/non-contact sensors, electromagnetic, magnetic, or optic sensors. Exotic shapes in sheet metal are allowed, depending on the tolerance, the plate metal may be bent out of plane. The sensor is mounted by a mounting arrangement depicted in Figure 4a in exploded view, and in Fig 4b in assembled view. In the embodiment, the cut part has a planar form for positioning the sensor at the correct height and angle towards the product. The cut part has a pattern of holes and/or screw openings, for mounting the cut part to a stock part, in this case mounting block 5, in a similar way as previously illustrated. In this embodiment, no dowel pins are used, and the mounting part is a freeform cut from a planar sheet metal.

The sensor 41 is received in mounting sleeve 43, shaped as a hollow cylinder that can be positioned and secured relative to a plate element 42, which is also a freeform cut mounting bracket having a screw opening, for receiving sleeve 43, to be fixed with corresponding nuts. In this way, plate element 42 forms a mounting face laterally extending from the cut part 40.

Figure 5 shows in more detail the distal geometry of cut part 40; and how the plate element 42 is affixed to the cut part 40. Figure 5a a shows a planar view of the cut part 40 with a side view of the plate element, extending laterally from said cut part 40; Figure 5b shows a perspective view with both plate element 42 and cut parts 40 visible; and Figure 5c shows a planar view of the plate element 42 with a side view of the cut part 40. Figure a, b, and c can be thought to provide a view on the same assembly by rotating it along an axis being the intersection between cut part and plate element. As can be seen in the corresponding figure, cut part 40 has a side with a recessed shape having a side face 401 flush or parallel to a side face of the cut part. The side face 401 is arranged to receive the plate element 42, so that the side face supports the plate element 42, in the direction of the bolt as well as against shifting perpendicular to the bolt axis direction and against rotating around the bolt axis. The recessed shape has lateral sides 402 extending laterally away from the side face 401 of the cut part 40. The recessed shape is arranged to receive a bolt 8, the lateral sides further shaped for form-fitting reception of a nut or bolt 80. Plate element 42 is clamped against the side face 401 of the cut part 40 by bolt 8. The bolt 8 is form-fittingly attached in the recessed shape 403 and extending through a hole 43 in the plate element 42.

Claims

Claims

1. A fixture system for fixing a workpiece, comprising; - a mounting frame of a predefined geometry having a mounting plate comprising a pattern of holes and/or screw openings therein, for mounting a plurality of mounting parts thereon, the mounting parts having specified shapes and forms for mounting thereon a variety of end parts, the end parts being one of connection parts or functional clamping elements for clamping a device element that is to be positioned in a relative position and orientation towards the mounting frame, wherein o at least some of said mounting parts are manufactured from freeform cut parts having a pattern of holes and/or screw openings, for mounting one or more mounting parts thereon; 2. , wherein said freeform cut part is a planar part manufactured of sheet metal that replaces a custom milled part cut in a milhng process.
3. The fixture system according to claim 2, wherein the freeform cut part has a geometry having holes provided therein to form connection with end parts being connection parts, functional clamping or positioning elements.
4. The fixture system according to claim 3, wherein the freeform cut part has a distal geometry provided for mounting the end parts.
5. The fixture system according to any of the preceding claims, wherein the end parts comprise a pattern of holes and/or screw openings for mounting a sensor or support pin thereon. The fixture system according to any of the preceding claims, further comprising a plate element; wherein the cut part has a side with a recessed shape having a side face flush or parallel to a side face of the cut part, said side face arranged to receive the plate element, so that the side face supports the plate element; and wherein the recessed shape has lateral sides extending laterally away from the side face of the cut part and arranged to receive a bolt, the lateral sides further shaped for form- fitting reception of a nut or bolt; so that the plate element can be clamped against the side face of the cut part by a bolt that is form-fittingly attached in the recessed shape and extending through a hole in the plate element, the plate element thereby forming a mounting face laterally extending from the cut part.