Title: Device for positioning a tool in relation to a workpiece
Abstract: The device for positioning a tool (1) in relation to a workpiece (6) controls drives (2, 3, 4) in relation to three spatial axes (x, y, z) through two cameras (10, 11), the first (1) of which takes an image essentially along a spatial axis (y), the other (11) being oriented essentially vertically with respect to a surface (8) of the workpiece.
Patent Number: 6,955,284 Issued on 10/18/2005 to Zakel, et al.
| Inventors:
|
Zakel; Elke (Falkenssee, DE);
Kasulke; Paul (Berlin, DE);
Uebel; Oliver (Berlin, DE);
Titerle; Lars (Berlin, DE)
|
| Assignee:
|
Pac Tec-Packaging Technologies GmbH (Nauen (bei Berlin), DE)
|
| Appl. No.:
|
398788 |
| Filed:
|
October 2, 2001 |
| PCT Filed:
|
October 2, 2001
|
| PCT NO:
|
PCT/EP01/11422
|
| 371 Date:
|
June 20, 2003
|
| 102(e) Date:
|
June 20, 2003
|
| PCT PUB.NO.:
|
WO02/28590 |
| PCT PUB. Date:
|
April 11, 2002 |
Foreign Application Priority Data
| Oct 06, 2000[DE] | 100 49 584 |
| Current U.S. Class: |
228/9; 219/121.65; 219/121.82; 228/49.1 |
| Intern'l Class: |
B23Q 015/00; B23Q 016/00; B23K 001/14; B23K 037/04 |
| Field of Search: |
228/102,103,105,245-255,8-10,32,41,45,491
219/121.6,121.63,121.65,121.78,121.82
356/401,403,407,614,615
|
References Cited [Referenced By]
U.S. Patent Documents
| 2696565 | Dec., 1954 | Shockley.
| |
| 4187051 | Feb., 1980 | Kirsch et al.
| |
| 4813588 | Mar., 1989 | Srivastava et al.
| |
| 5113565 | May., 1992 | Cipolla et al.
| |
| 5199628 | Apr., 1993 | Homma.
| |
| 5249035 | Sep., 1993 | Yamanaka.
| |
| 5501388 | Mar., 1996 | Takeuchi.
| |
| 5667130 | Sep., 1997 | Morita et al.
| |
| 5702049 | Dec., 1997 | Biggs et al.
| |
| 5897048 | Apr., 1999 | Cheng et al.
| |
| 5938952 | Aug., 1999 | Lin et al.
| |
| 6386433 | May., 2002 | Razon et al.
| |
| 6516990 | Feb., 2003 | Hess et al.
| |
| 6669076 | Dec., 2003 | Nogawa.
| |
| 6715660 | Apr., 2004 | Seki et al.
| |
| 6729528 | May., 2004 | Seki et al.
| |
| 6824037 | Nov., 2004 | Sakai et al.
| |
| Foreign Patent Documents |
| 0 859 681 | Aug., 1998 | EP.
| |
| 1 014 438 | Jun., 2000 | EP.
| |
Primary Examiner: Cooke; Colleen P.
Attorney, Agent or Firm: Dougherty, Clements & Hofer
Claims
1. Device for positioning a tool (
1) in relation to a workpiece (
6),
said device having:
three drives (
2,
3 and
4), which enable positioning of the
tool (
1) relative to the workpiece (
6) in at least two of three perpendicular
spatial axes x, y and z;
two cameras (
10,
11) positioned between the tool (
1) and
the workpiece (
6), the first camera (
10) essentially along a spatial
axis (y) being positioned for taking an image of a first workpiece edge, and the
second camera being positioned for taking an image with respect to spatial axis
(y), and the second camera (
11) being oriented perpendicularly with respect
to a second surface of the workpiece; and
a control unit operatively connected to said cameras and to said tool, whereby,
based on the two images from said cameras (
10,
11), said control
unit analyzes the position of the tool relative to the workpiece along the three
cartesian spatial axes (x, y and z-axes) resulting in the issuance of control commands
for the three drives (
2,
3,
4) along the perpendicular spacial
axes.
2. Device as described in claim 1, characterized in that the first camera (
10)
is oriented at an acute angle (alpha) in relation to the spatial axis (y).
3. Device as described in claim 1, characterized in that the first camera (
10)
is oriented vertically with respect to the spatial axis (y) and a mirror (
15)
is mounted at a tilt angle of 45 degrees in relation to the x-y plane for taking
an image of the workpiece (
6) essentially along the spatial axis (y) through
said mirror (
15).
4. Device as described in claim 3, characterized in that the mirror (
15)
is arranged to shift along the axis (z) in the first camera (
10).
5. Device as described in claim 1, characterized in that the tool is a capillary
(
1) adapted to feed pieces of material to the workpiece (
6).
6. Device as described in claim 5, further comprising means for liquifaction
of any meltable material fed to the workpiece.
7. Device as described in claim 6, characterized in that the liquefaction means
is a laser.
8. Device for positioning a tool (
1) in relation to a workpiece (
6),
said device having:
three drives (
2,
3 and
4), which enable positioning of the
tool (
1) relative to the workpiece (
6) in at least two of three perpendicular
spatial axes x, y and z;
two cameras (
10,
11) positioned between the tool (
1) and
the workpiece (
6), the first camera (
10) directly along spatial axis
(y) being positioned for taking an image of a first workpiece edge, and the second
camera being positioned for taking an image with respect to spatial axis (y), the
second camera (
11) being oriented perpendicularly with respect to a second
surface of the workpiece; and
a control unit operatively connected to said first and second cameras and to
said tool, for analyzing the position of the tool relative to the workpiece along
the three cartesian spatial axes (x, y and z-axes) and for issuing control commands
for the three drives (
2,
3,
4) to move the tool along the
perpendicular spacial axes to the proper position relative to the workpiece.
Description
The invention relates to a device for positioning a tool in relation to a workpiece.
U.S. Pat. No. 4,187,051 shows a device for positioning a tool in relation to
a workpiece with three drives for positioning the tool relative to the workpiece
along at least three spatial axes. The position of the workpiece is determined
with the aid of two cameras which are each oriented along a spatial axis, the two
spatial axes being perpendicular to each other. The cameras react to light/dark
contrasts and thus detect the position and orientation of the workpiece. One of
the cameras determines a coarse position image while the other detects a high-resolution
image for precision positioning. Drives move both cameras and the tool, a gripping
arm in this case. The position detection is effected in that the cameras are moved
until the image picked up corresponds with a stored image. The tool coupled with
drives is thus then correctly oriented relative to the workpiece.
U.S. Pat. No. 5,501,388 describes a bonding device which has a single camera
for detection of a workpiece. Used for bonding is a capillary which supplies pieces
of material to the workpiece.
EP 0 859 681 B1 shows a device for relative positioning of a capillary as a tool
and of a workpiece by means of drives which enable a relative motion along three
cartesian spatial axes.
It is customary with machine tools to control the drives for the individual spatial
axes through stepping motors, the increments of the stepping motors then being
counted which is a measure for the position. For precise machining, however, extremely
accurate clamping of the workpiece is also necessary then.
An important field of application for the invention is the application of pieces
of material to a workpiece.
For the purposes of the invention, pieces of material can be pieces of any material
in solid or liquid form. It can be a solderable material such as gold, copper,
tin, glass or a plastic which are, in particular, micro-size pieces of material
in the form of solder pellets, glass globules or plastic globules. It can also
be pieces of ceramic or components such as miniature circuits, surface mounted
devices or the like. Generally speaking, any material can be applied with the invention.
The application of pieces of material such as solder pellets in the form of so-called
bumpers also requires a maximum of precision in the positioning of the workpiece
such as a capillary which feeds the solder pellets. Accordingly, clamping of the
workpieces is quite costly because it directly determines the accuracy of the work.
A maximum of tool positioning accuracy is often also required in other operations
such as the assembly of components on printed boards, the removal of soldered joints
from boards, etc.
It is thus the object of the invention to improve the device so as to reduce
the
amount of work needed for clamping the workpieces while still maintaining the required
accuracy of positioning.
This object is achieved by the features indicated in patent claim
1.
Advantageous developments of the invention can be seen in the sub-claims.
The basic principle of the invention consists in the control of the relative
positioning through cameras. The accuracy of the workpiece clamping then has no
influence on the operating accuracy since the positioning of the tool is controlled
through cameras which orient themselves on the workpiece itself, particularly on
its edges.
The invention is explained in more detail below by means of example embodiments
in connection with the drawing in which:
FIG. 1 is a schematic diagram of the invented device in a first example embodiment;
FIG. 2 is a schematic diagram of a second example embodiment of the invention;
FIG. 3 is a schematic diagram of a third example embodiment of the invention;
FIG. 4 is a schematic image seen by the camera mounted in the y-direction according
to which the tool is positioned in the x- and z-directions;
FIG. 5 is an image of the second camera used to position the tool in the y-direction.
The same reference symbols in the individual figures designate the same or functionally
equivalent parts.
Although the example embodiments in FIG. 1 to
5 relate to the application
of solder pellets, it is expressly pointed out that any positioning of a tool relative
to a workpiece is possible with the invention and the application of pieces of
material such as defined at the outset can also be carried out as well as the removal
of pieces of material such as soldered joints from an object.
Reference is first made to FIG. 1. A capillary
1 through which a
solder pellet can be applied is displaced by means of three drives
2,
3
and
4 relative to a workpiece
6 along three cartesian spatial axes
x, y and z Naturally, this is a relative displacement, that is, the drives
2,
3 and
4 can also be associated with a cross table (not shown) on
which the workpiece
6 is clamped.
The solder is fed to the workpiece at the tip
5 of the capillary
1
and melted there in a conventional way by a laser impulse. Here, the workpiece
6 has two surfaces
7 and
8 which are vertical with respect
to each other, the workpiece being clamped so that the intersection line of the
two surfaces
7 and
8 are in precisely one axis, here the y-axis.
The surfaces
7 and
8 are thus each at an angle of 45 degrees to the
x-y plane.
The drives
2,
3 and
4 arc now to be controlled so that the
tip
5 of the capillary is positioned at preset points
9 of the workpiece
6 so that a solder pellet is applied there and a "bumper" is soldered on.
To control the drives, two cameras
10 and
11 are provided, the images
of which are analyzed by a control unit resulting in control commands for the drives
2,
3 and
4.
One camera, here camera
10, is oriented essentially on the y-axis. It
is thus used to detect the relative position between the tip
5 of the capillary
1 and the workpiece
6 with respect to the x-z plane. The processing
of the images of the camera is effected through edge recognition. The camera
10
thus essentially detects an image of the two edges
13 and
14 of surfaces
7 and
8 facing it as well as the tip
5 of the capillary
1.
The second camera
11 is positioned so that it is oriented vertically with
respect to a surface
8 of the workpiece. It is thus used to monitor the
relative position between the capillary and workpiece relative to the y-axis and
to control the drive
3 for this axis. The image analyzer can analyze the
edge
14 of the surface
8 here or also the contour of the place
9
where the solder is to be applied.
In the example embodiment shown in FIG. 2, the workpiece
6 in the y-direction
is so long that it would collide with the camera
10. The camera
10
is thus oriented at an angle alpha relative to the y-axis, the workpiece
6
being moved in the y-direction, not the capillary
1. The camera
10
detects the edges
13′ and
14′ of the surfaces
7
and
8 as well as the position of the tip
5 relative to the x-z plane.
The camera
11 is again oriented in the same way as in the example embodiment
of FIG. 1, that is, vertical to the surface
8 of the workpiece
6.
In the example embodiment of FIG. 3, a number of workpieces
6,
6′,
etc. are lined up one after the other along the y-axis, the workpieces being moved
at least along the y-axis here as well with the capillary
1 being stationary.
Since a camera positioned in the y-axis would collide with the workpieces here
as well, provision is made for running a mirror
15 between successive workpieces
6 and
6′, this mirror being tilted by 45 degrees relative
to the x-y plane. The camera is then oriented parallel with the z-axis and transfers
an image to the control
12 corresponding to the image taken directly in
the y-axis. The mirror
15 can be moved by an arm
16 and a drive
17
at least parallel to the z-axis so that individual workpieces can pass under it.
As soon as the next workpiece is lined up for processing, the mirror
15
will be run down again in the z-direction.
The camera
11 is again positioned vertical to the plane
8 of the
workpiece
6.
FIG. 4 schematically shows the image "seen" by the camera
10 with the
tool
1, the workpiece
6 in the form of two printed circuit boards
7 and
8 along with the edges
13 and
14 on which the
image analyzer and the control are oriented. So-called pads
16 and
17
having sharp edges on which the image analyzer can be oriented can also be mounted
on the workpiece. These pads are arranged in a predefined position with respect
to the soldered joint. The image represented in FIG. 4 can be used to position
the tool
1 in the z and x-direction.
FIG. 5 shows an image seen by the camera
11 which carries out the positioning
using the edges or the pads in the y-direction.
*
