EP4613450A1

EP4613450A1 - A cutting device able to detect abnormal cutting conditions

Info

Publication number: EP4613450A1
Application number: EP24305360.0A
Authority: EP
Inventors: Hangjune Choi
Original assignee: Automotive Cells Company SE
Current assignee: Automotive Cells Company SE
Priority date: 2024-03-08
Filing date: 2024-03-08
Publication date: 2025-09-10

Abstract

The cutting device (10) comprises a first cutting tool (14) having a first blade (18) and a second cutting tool (16) having a second blade (22), and a displacement mean (17) connected to the first cutting tool (14) for displacing the first cutting tool (14) relating to the second cutting tool (16), so that the first blade (18) is movable relating to the second blade (22) in order to cooperate each other to cut the electrode strip (12). The first cutting tool (14) comprises: a first part (14A) connected to the displacement mean (17), a second part (14B) holding the first blade (18), and at least one force sensor (26a, 26a', 26b, 26b') arranged between the first part (14A) and the second part (14B).

Description

The present invention relates to a cutting device for cutting a coated electrode strip. Cutting a coated electrode strip takes place in a manufacturing process of a battery.
A cutting device for cutting a coated electrode strip is already known from prior art. Such a cutting device usually comprises a stationary lower blade (also called "die") and a vertically moving upper blade (also called "punch"), the blades having cutting edges crossing each other with a specific shear angle. The lower and upper blades usually each have specific rake angle, independently from each other.
The electrode strip is usually provided in the cutting device in a longitudinal direction, and cut transversally, along a transverse direction perpendicular to the longitudinal direction, from a first lateral edge to a second opposite lateral edge.
It should be noticed that making a clean-cut edge at the coated electrode strip is quite challenging as it is quite thin. In disadvantageous cases, wrong cutting conditions may appear while cutting, for example due to degradation of the blades or a malfunction of the cutting device. This could lead to a poor quality cut edge.
However, in case the electrode does not have a clean-cut edge, it may cause a mild short-circuit between a cathode and an anode through a separator due to cutting burrs, which may lead to faster self-discharge of the battery cell, and which is a painful failure of the battery cell incurs high costs to correct.
The invention aims to solve this problem, by ensuring good cutting conditions without need of regular preventive maintenance.
To this end, the invention relates to a cutting device for cutting an electrode strip, comprising a first cutting tool having a first blade and a second cutting tool having a second blade, and a displacement mean connected to the first cutting tool for displacing the first cutting tool relating to the second cutting tool, so that the first blade is movable relating to the second blade in order to cooperate each other to cut the electrode strip, characterized in that the first cutting tool comprises:

a first part connected to the displacement mean,
a second part holding the first blade, and
at least one force sensor arranged between the first part and the second part.

The force sensors allow detecting abnormal cutting conditions. In case of such an abnormal cutting condition is detected, an operator is alerted that the edge of the electrode may have poor quality, and the operator can proceed to a maintenance to repair the source of abnormal cutting condition.
A cutting device according to the invention may comprise any of the following features, taken alone or in any possible combination.

The first and second blades extend in a transverse direction between a first end and a second end, the first cutting tool comprising at least one first force sensor near the first end, and at least one second force sensor near the second end.
The first cutting tool comprises two first force sensors near the first end, which are an upstream first sensor and a downstream first sensor, and two second force sensors near the second end, which are an upstream second sensor and a downstream second sensor.
The cutting device comprises a calculator configured to calculate: a first sum of a force measured by the upstream first force sensor and a force measured by the upstream second force sensor and a second sum of a force measured by the downstream first force sensor and a force measured by the downstream second force sensor.
The cutting device comprises a comparator intended to compare the first sum and the second sum.

The invention also relates to a method of detecting an anomaly in a cutting device as previously defined, wherein each force sensor measure force during cutting, and wherein each measured force is monitored to detect an anomaly.
Preferentially, an anomaly is detected when the first sum differs from the second sum by more than a predefined threshold.
Several aspects and advantages of the invention will be enlightened in the following disclosure, only given as a non-limitative example and made in reference of attached figures, in which:

Figure 1 is a perspective view of a cutting device according to an example of embodiment of the invention.
Figure 2 is a tridimensional graph showing an example of measured forces in a normal cutting condition
Figure 3 is a graph showing the measured forces of Figure 2 in normal cutting condition, with sums of forces shown;
Figure 4 and 5 are graphs showing examples of measured forces in abnormal cutting conditions.

Figure 1 shows a cutting device 10 according to an example of embodiment of the invention. The cutting device 10 is intended to cut a coated electrode strip 12 in view of a manufacturing process of a battery.
The cutting device 10 comprise a first cutting tool 14 and a second cutting tool 16.
The second cutting tool 16 is fixed, forming a die, and the first cutting tool 14 forms a punch at least partially movable in a vertical direction Z towards the second cutting tool 16. To this end, the first cutting tool 14 comprises a classical displacement mean 17 for displacing the first cutting tool 14 in the vertical direction Z.
The first cutting tool 14 comprises a first blade 18 having a first cutting edge 20. In the disclosed embodiment, the first cutting edge 20 forms a straight line.
The second cutting tool 16 comprises a second blade 22 having a second cutting edge 24. In the disclosed embodiment, the second cutting edge 24 forms a straight line.
The first cutting edge 20 and the second cutting edge 24 are intended to cooperate on at least one movable cutting point, that is the point where the coated electrode strip 12 is cut. The cutting point is an abstract point, that moves transversally along the coated electrode strip 12 in a transversal direction Y perpendicular to the vertical direction Z, while the first blade 18 moves towards the second blade 22 in the vertical direction Z.
The cutting point is formed because the first cutting edge 20 is tilted by respect to the second cutting edge 24. We define a cutting angle that is the angle between the first cutting edge 20 and the second cutting edge 24 at the cutting point 26.
The first 18 and second 22 blades extend in the transversal direction Y between a first end and a second end. While cutting, the cutting point moves from the first end towards the second end.
The first cutting tool 14 comprises a first part 14A connected to the displacement mean 17, and a second part 14B holding the first blade 18.
At least one force sensor is arranged between the first part 14A and the second part 14B.
More particularly, at least one first force sensor is arranged near the first end, and at least one second force sensor is arranged near the second end.
Preferentially, two first force sensors 26a, 26a' are arranged near the first end, and two second force sensors 26b, 26b' are arranged near the second end.
The two first force sensors are arranged as an upstream first sensor 26a and a downstream first sensor 26a', in a longitudinal direction X, perpendicular to the transversal direction Y and the vertical direction Z, the longitudinal direction X being the direction of advancement of the electrode strip 12 into the cutting device 10.
The two second force sensors are arranged as an upstream second sensor 26b and a downstream second sensor 26a', in the longitudinal direction X.
Preferentially, the two first sensors 26a, 26a' and the two second sensors 26b, 26b' are arranged each on a respective corner of a rectangular shape. In other words:

the upstream first sensor 26a is aligned with the upstream second sensor 26b in the transversal direction Y,
the downstream first sensor 26a' is aligned with the downstream second sensor 26b' in the transversal direction Y,
the upstream first sensor 26a is aligned with the downstream first sensor 26a' in the longitudinal direction X, and
the upstream second sensor 26b is aligned with the downstream second sensor 26b' in the longitudinal direction X.

The cutting device 10 comprises a monitoring device 28, connected to the sensors. The monitoring device 28 comprises a calculator 30 configured to calculate:

a first sum of a force measured by one of the first force sensors 26a, 26a' and a force measured by one of the second force sensors 26b, 26b', and
a second sum of a force measured by the other of the first force sensors 26a, 26a' and a force measured by the other of the second force sensors 26b, 26b',

In the disclosed example, the first sum is the sum of the force measured by the upstream first sensor 26a with the force measured by the upstream second sensor 26b, and the second sum is the sum of the force measured by the downstream first sensor 26a' with the force measured by the downstream second sensor 26b'.
Figure 2 shows:

a first curve C1 which represents the force measured by the upstream first sensor 26a as a function of the transversal position of the cutting point,
a second curve C2 which represents the force measured by the upstream second sensor 26b as a function of the transversal position of the cutting point.

The first end of the blades is on the right, and the second end on the left.
The cutting starts at the first end, i.e. on the side of the first sensors 26a, 26a', at a cutting starting point CSP. At this cutting starting point CSP, the blades encounters with the electrode strip, thus the first curve C1 shows a peak of Force. Then, the Force measured by the upstream first sensor 26a decreases when the cutting point moves towards the second end. This Force is zero when the cutting ends, at a cutting ending point CEP.
Besides, when the blades encounters with the electrode strip at the cutting starting point CSP, the second curve C2 shows a peak of Force, and after the peak the force measured by the upstream second sensor 26b increases when the cutting point moves towards the second end. This force is zero when the cutting ends, at the cutting ending point CEP.
Figure 2 also shows:

a third curve C1' which represents the force measured by the downstream first sensor 26a' as a function of the transversal position of the cutting point,
a fourth curve C2' which represents the force measured by the downstream second sensor 26b' as a function of the transversal position of the cutting point.

In a normal cutting condition, the third curve C1' is similar to the first curve C1, and the fourth curve C2' is similar to the second curve C2.
Figure 3 shows the same measured forces as in Figure 2, and also:

a fifth curve C3 which represents the sum of the first curve C1 and the second curve C2, thus the "first sum", as a function of the transversal position of the cutting point, and
a sixth curve C3' which represents the sum of the third curve C1' and the fourth curve C2', thus the "second sum", as a function of the transversal position of the cutting point.

Except on the peaks when the blades encounters with the electrode strip, the first sum shown by the fifth curve C3 is substantially constant, with a difference usually under 5%. Thus, the fifth curve C3 has a substantially flat top shape, except in the area of the cutting starting point. In the same manner, the second sum shown by the sixth curve C3' is substantially constant, with a difference usually under 5%. Thus, the sixth curve C3' has a substantially flat top shape, except in the area of the cutting starting point.
Usually, in normal cutting conditions, the force measured by the upstream first sensor 26a is substantially equal to the force measured by the downstream first sensor 26a', and the force measured by the upstream second sensor 26b is substantially equal to the force measured by the downstream second sensor 26b'.
The monitoring device 28 comprises a comparator 32 configured to compare the first sum with the second sum. Indeed, comparing the sums gives a more reliable result than just comparing the forces, but just comparing the force may be considered in an alternative embodiment.
In the example embodiment, it is considered that there is an abnormal cutting condition when the first sum and second sum are different, for example with a difference higher than 5%.
Figures 4 and 5 show an example of abnormal cutting condition.
Figure 4 shows:

the first curve C1 which represents the force measured by the upstream first sensor 26a as a function of the transversal position of the cutting point,
the second curve C2 which represents the force measured by the upstream second sensor 26b as a function of the transversal position of the cutting point,
the fifth curve C3 which represents the sum of the first curve C1 and the second curve C2, thus the "first sum", as a function of the transversal position of the cutting point.
a third curve C1' which represents the force measured by the downstream first sensor 26a' as a function of the transversal position of the cutting point,
a fourth curve C2' which represents the force measured by the downstream second sensor 26b' as a function of the transversal position of the cutting point,
the sixth curve C3' which represents the sum of the forth curve C1' and the fifth curve C2', thus the "second sum", as a function of the transversal position of the cutting point.

The fifth and sixth curves of Figure 4 each shows an impulsive peak shape at a particular position. The peaks of the two curves have a substantially similar shape, at a substantially same position.
Such an abnormal condition occurs when at least one of the cutting edges is damaged or lose its sharpness at the position of the peak.
It should be noticed that, since the first sum and the second sum are, in normal conditions, substantially constant except in the initial peak, the anomaly is, in this case, detected when the first and/or second sum varies more than a fixed threshold (for example more than 5%).
Figure 5 shows the same curves as Figure 4, with a loss of force in an abnormal area L for the fifth curve C3 and a gain of force in an abnormal area L' for the sixth curve L'.
Thus, in the abnormal areas L and L', the first sum and the second sum are not equal, so the comparison device 32 detects an abnormal cutting condition.
Such a defect may be due to the cutting progressing with stretched (uncut or not completed cut) burr, which is the most critical defect of electrode cutting quality, between the two cutting edges 20, 24. The stretched burr would get squeezed between the two cutting edges 20, 24, generating horizontal force to push the moving blade 18 towards the longitudinal direction X. This horizontal force would be converted into a mechanical moment to rotate the moving blade 18 about the transversal axis. This moment will increase the compressive forces sensed by the downstream sensors 26a', 26b', and simultaneously decreases the compressive forces sensed by the upstream sensors 26a, 26b.
This defect would cause a difference between the first sum and the second sum, as shown on figure 5.
It should be noticed that, in alternative embodiments, it may be considered to detect anomalies with other comparisons.
For example, an anomaly can be detected when the force measured by one of the first sensors 26a, 26a', or by the two first sensors 26a, 26a', increases at a point during the cutting, out of the initial peak.
In the same manner, an anomaly can be detected when the force measured by one of the second sensors 26b, 26b', or by the two second sensors 26b, 26b', decreases at a point during the cutting, out of the initial peak.
In another example, an anomaly can be detected when the forces measured by the two first sensors differ by more than a predefined threshold (for example more than 5%), and/or when the forces measured by the two second sensors differ by more than a predefined threshold (for example more than 5%).
An embodiment with only one sensor may be considered, with the measured force compared with a predefined profile, and an anomaly detected when the measured force differs from the predefined profile, more than a predefined threshold.
Any other anomaly detection using force sensor can also be considered.

Claims

A cutting device (10) for cutting an electrode strip (12), comprising a first cutting tool (14) having a first blade (18) and a second cutting tool (16) having a second blade (22), and a displacement mean (17) connected to the first cutting tool (14) for displacing the first cutting tool (14) relating to the second cutting tool (16), so that the first blade (18) is movable relating to the second blade (22) in order to cooperate each other to cut the electrode strip (12), characterized in that the first cutting tool (14) comprises:
- a first part (14A) connected to the displacement mean (17),

- a second part (14B) holding the first blade (18), and

- at least one force sensor (26a, 26a', 26b, 26b') arranged between the first part (14A) and the second part (14B).
The cutting device (10) according to claim 1 wherein, the first (18) and second (22) blades extend in a transverse direction (Y) between a first end and a second end, the first cutting tool (14) comprising at least one first force sensor (26a, 26a') near the first end, and at least one second force sensor (26b, 26b') near the second end.
The cutting device (10) according to claim 2, wherein the first cutting tool (14) comprises two first force sensors near the first end, which are an upstream first sensor (26a) and a downstream first sensor (26a'), and two second force sensors near the second end, which are an upstream second sensor (26b) and a downstream second sensor (26b').
The cutting device (10) according to claim 3, comprising a calculator (32) configured to calculate:
- a first sum of a force measured by the upstream first force sensor (26a) and a force measured by the upstream second force sensor (26b), and

- a second sum of a force measured by the downstream first force sensor (26a') and a force measured by the downstream second force sensor (26b').
The cutting device (10) according to claim 4, comprising a comparator (32) intended to compare the first sum and the second sum.
Method of detecting an anomaly in a cutting device (10) according to any of preceding claims, wherein each force sensor measure force during cutting, and wherein each measured force is monitored to detect an anomaly.
The detection method of claim 6, using the cutting device (10) of claim 5, wherein an anomaly is detected when the first sum differs from the second sum by more than a predefined threshold.