Method for laser cutting acceptable parts from a sheet-metal panel

Abstract

The invention relates to a method for laser cutting acceptable parts (20) from a sheet-metal panel (21), in which critical acceptable parts (20), which after cutting owing to their size and / or shape and / or position relative to the position of support elements of a workpiece support for the sheet-metal panel (21) can fall down between the support elements or tilt over said support elements or which can sag downwards over the underside of the sheet-metal panel by more than a predefinable value, are defined and remain connected to the sheet-metal panel (21) by means of at least one connection point (N1), wherein the need for possibly further connection points (N2) is determined by calculating the torque acting on the first connection point (N1).

Description

[0001] Process for laser cutting good parts from a sheet metal panel

[0002] Background of the invention

[0003] When laser cutting two-dimensional parts from a sheet metal panel in a laser processing system, the sheet metal panel rests on support elements of the system's workpiece support. Small, good parts being cut can fall out of the sheet metal panel between the support elements after cutting or tip over a support element, thus creating an obstacle for the system's laser processing head.

[0004] For the cutting of good parts that can tip over a support element after cutting, it was proposed in DE 10 2014 200 208 B3 that those sections of the contour lines of these good parts, the cutting of which can trigger tipping, should only be cut at the very end of the processing of the sheet metal panel in order to avoid collisions between tipping parts and the laser processing head.

[0005] It is also known to leave very small parts, in particular, connected to the sheet metal via a connection point until removal. However, such connection points can hinder the removal of the parts and should therefore only be provided in the required number. Another problem can be caused by parts that sag downwards over the underside of the sheet metal after cutting. The cut sheet metal is automatically removed from the workpiece support by a removal rake. Parts that sag downwards can hinder this removal.

[0006] Object of the invention

[0007] The invention is based on the object of creating a possibility with which even critical parts can be safely cut out of a sheet metal panel and then removed in a short time.

[0008] Description of the invention

[0009] This object is achieved according to the invention by a method for laser cutting good parts from a sheet metal panel, which is characterized by the steps:

[0010] - Determination of the cutting lines for the good parts under the aspect of optimal sheet utilization,

[0011] - Determination of critical good parts which, after cutting, due to their size and / or shape and / or position relative to the position of support elements of a workpiece support for the sheet metal panel, may fall downwards between the support elements or tip over these support elements or which may sag downwards over the underside of the sheet metal panel by more than a predefined value;

[0012] - Determine a connection point at which the critical part remains connected to the sheet metal after cutting;

[0013] - Calculate the moment acting on the connection point for each critical part; - If a permissible maximum moment on a connection point is exceeded, specify at least one additional connection point for the critical part in question,

[0014] - Cutting the good parts while leaving out the joints.

[0015] The subclaims relate to preferred embodiments.

[0016] With the method according to the invention, all potentially critical parts are automatically identified by evaluating the size and shape of the parts as well as their position in relation to the support elements of the workpiece support for the sheet metal panel. For each of the identified critical parts, a connection point is defined at which the part remains connected to the sheet metal panel after cutting. Since the size and thus the weight as well as the position of the critical parts with respect to the support elements can vary greatly, the moment acting on the respective connection point is calculated. If the moment exceeds a predefined maximum value, at least one additional connection point is defined for the part in question to ensure that the first connection point does not deform or break.After cutting all the good parts, leaving out the joints, all the good parts are securely held in the cut sheet metal so that it can be removed from the system and cleared away without any problems.

[0017] Preferably, the or one of the connection points can be placed at the starting point of the cutting line for cutting the contour of the critical part. The contour damage to the part caused by the connection point thus coincides with the cutting start point, where a minor contour damage also occurs. The damage to the contour line can thus be reduced to a point on the circumference of the part. Furthermore, this point can be positioned by programming the cutting line of the part so that it causes little disruption to the finished part or can be easily reworked. The additional connection points can be formed at an angular distance from the first connection point on the circumference of the critical part. Advantageously, the angular distance from a straight line from the center of gravity of the critical part to the first connection point is measured with the center of gravity as the pivot point.The point on the contour line of the good part that lies at the specified angular distance from the first connection point is defined as the further connection point.

[0018] The angular spacing between the connection points can preferably be selected between ±90° and 180°. Tests have shown that an angular spacing between ±130° and ±140° results in the statistically smallest number of required additional connection points, so this angular range appears to be the most advantageous.

[0019] The shape of the contour line can be used as a further criterion for the placement of additional connection points—or even the initial connection point. For example, the connection points can be formed in concave peripheral areas. In these areas, no post-processing of the finished part is usually required. Concave contour areas also do not form stop edges for possible subsequent bending of the finished part. Thus, contour violations caused by connection points in concave areas of the contour line are generally not a problem.

[0020] The permissible maximum moment for the connection points is preferably determined taking into account the size, weight, and position of the critical workpieces relative to the support elements of the workpiece support. The influence of the force of a cutting gas on the workpiece can also be taken into account. Naturally, the sheet thickness also plays a role in the moment acting on the connection point. Therefore, the permissible maximum moment for the connection points can be determined empirically depending on the thickness of the sheet. Different maximum values ​​for the permissible moment thus result for each sheet thickness. The connection points can be designed as micro- or nano-connections. Micro-connections extend linearly across the entire sheet thickness. Nano-connections, on the other hand, extend only across a portion of the sheet thickness and thus withstand lower moments than micro-connections.However, this also makes them more prone to breakage during removal. The joint type is therefore selected depending on the sheet thickness and the size of the good parts.

[0021] To optimize the production process for good parts, in addition to ensuring optimal utilization of the sheet metal by appropriately positioning the good parts on the sheet, the cutting of the good parts can also be optimized to ensure the shortest possible runtime for a laser processing head. This optimization can also include the formation of the joints for critical good parts.

[0022] For efficient production of the good parts, it is also advantageous if the good parts are released from the sheet metal by vibration. This allows for simultaneous removal of all good parts from the sheet metal and therefore requires very little time.

[0023] It goes without saying that the method according to the invention can also be applied to sheet-shaped workpieces other than metal sheets. The method offers similar advantages for cutting finished parts from sheets of plastic, glass, or ceramic.

[0024] Further features and advantages of the invention will become apparent from the description, the claims, and the drawings. According to the invention, the above-mentioned and further-described features can be used individually or in combination in any convenient way. The embodiments shown and described are not to be understood as an exhaustive list, but rather as examples for describing the invention. Detailed Description of the Invention and Drawings

[0025] Fig. 1 shows a first good part with a connection point to a sheet metal panel on its contour line;

[0026] Fig. 2 shows a second good part with two connection points on its

[0027] contour line;

[0028] Fig. 3 shows a third good part with two connection points on its

[0029] contour line;

[0030] Fig. 4 shows a fourth good part with two connecting parts on its contour line.

[0031] Fig. 1 shows a square blank 10 that was cut out of a sheet metal panel 11 by a cutting or contour line 12 that was generated by a laser processing head (not shown here) of a laser processing system. For this purpose, the laser beam was pierced into the sheet metal panel 11 at a point 13 and then moved to a cutting point 14, from which the contour line 12 was cut by the laser beam until the laser beam returns to point 14. When the laser beam reaches the cutting and end point 14, the blank 10 would normally be cut free from the sheet metal panel. In the example shown, however, a connection point - preferably a nano connection point - NI is formed at the cutting and end point 14, i.e. the material of the sheet metal panel 11 was not completely severed there, so that the blank 10 remains connected to the panel 11 at this point NI after cutting.

[0032] The good part 10 can therefore not fall downwards out of the sheet metal 11 or tip over support elements for the sheet metal 11 (not shown here). The release of the good part 10 only occurs after the finished cut sheet metal 11 has been removed in a clearing station of the laser processing system.

[0033] Fig. 2 shows a second blank 20 which, after cutting along a contour line 22, remains connected to a sheet metal panel 21 via two connection points NI and N2. After determining the position of the first connection point NI, the moment acting on the connection point NI was calculated, taking into account the size and thickness of the blank 20 and its position relative to support elements of a workpiece support of the laser processing system. In the example shown, the determined moment was greater than a permissible maximum value, so that an additional connection point N2 was necessary to prevent deformation or breakage of the first connection point NI. The position of the second connection point N2 could be placed on the opposite corner of the blank 20. However, the algorithm shown here for positioning additional connection points follows a more general approach that is better suited for blanks 20 of any shape.For this purpose, a connecting line 23 is drawn between the first connection point N1 of the finished part 20 and its center of gravity S2. Starting from this line, a straight line 24 is drawn through the center of gravity S2 at an angular distance a of a = 135° to the straight line 21. The position of the second connection point N2 is defined by the intersection point of the straight line 24 with the contour line 22 of the finished part 20.

[0034] The finished part 30 shown in Fig. 3 also has a contour line 32 at which two connection points NI and N2 with the surrounding sheet metal panel 31 are provided. After determining the first connection point NI and calculating the moment acting on this connection point, it was also determined here that the permissible maximum moment on this connection point NI is exceeded and thus a further connection point N2 is necessary. To determine the position of this second connection point N2, the algorithm explained in Fig. 2 was first applied, i.e. a connecting line 33 was drawn from the first connection point NI to the center of gravity S3 of the finished part 30 and a straight line 34 was drawn from this connecting line 33 through the center of gravity S3 at an angular distance of a = +135°. However, this straight line 34 does not have an intersection point with the contour line 32 of the finished part 30.For this reason, another straight line 35 was drawn through the center of gravity S3, starting from the connecting line 33 and at an angular distance of a = -135°. The intersection of this straight line 35 with the contour line 32 determines the position of the second connection point N2. Fig. 4 illustrates a different algorithm for defining connection points NI, N2 on the contour line 42 of a critical good part 40. The first connection point NI is placed in a concave area of ​​the contour line 42. However, the position of the second connection point N2, which is also necessary here due to the exceeding of a maximum moment on the first connection point NI, is not determined using the algorithms from Fig. 2 or 3, but rather from the perspective of also positioning the second connection point N2 in a concave area of ​​the contour line 42.In concave areas of the contour line 42, the damage to the contour of the good part 40 caused by the connection points NI, N2 is the least disturbing.

Claims

Patent claims 1. A method for laser cutting good parts (10, 20, 30, 40) from a sheet metal panel (11, 21, 31, 41), characterized by the steps: - Determining the cutting lines (12, 22, 32, 42) for the good parts (10, 20, 30, 40) with a view to optimising the use of the sheet, - Determining critical good parts (10, 20, 30, 40) which, after cutting, due to their size and / or shape and / or position relative to the position of support elements of a workpiece support for the metal sheet (11, 21, 31, 41), can fall downwards between the support elements or tip over these support elements or which can sag downwards over the underside of the metal sheet by more than a predeterminable value; - determining a connection point (NI) at which the critical good part (10, 20, 30, 40) remains connected to the sheet metal panel (11, 21, 31, 41) after cutting; - Calculate the moment acting on the joint (NI) for each critical part (10, 20, 30, 40); - if a permissible maximum moment on a connection point (NI) is exceeded, specify at least one additional connection point (N2) for the critical part concerned (10, 20, 30, 40), - Cutting the good parts (10, 20, 30, 40) while leaving out the connection points (NI, N2).

2. Method according to claim 1, characterized in that the or one of the connecting points is placed at the cutting point (14) of the cutting line (12, 22, 32, 42) for cutting the contour of the critical good part (10, 20, 30, 40).

3. Method according to claim 1 or 2, characterized in that additional connection points (N2) are arranged at an angular distance (a) to the first Connection point (NI) is formed on the circumference of the critical good parts (10, 20, 30, 40).

4. Method according to claim 3, characterized in that the angular distance (a) from a straight line (23, 33) from the center of gravity (S2, S3) of the critical good part (20, 30) to the first connection point (NI) and the center of gravity (S2, S3) as the pivot point is measured.

5. Method according to claim 3 or 4, characterized in that the angular distance (a) is selected between ±90° and 180°.

6. Method according to claim 5, characterized in that the angular distance (a) is selected between ±130° and ±140°.

7. Method according to one of the preceding claims, characterized in that additional connection points (N2) are formed in concavely shaped peripheral regions of the good parts (40).

8. Method according to one of the preceding claims, characterized in that the permissible maximum moment for the connection points (NI, N2) is determined taking into account the size, the weight and the position of the critical parts (10, 20, 30, 40) with respect to the support elements of the workpiece support.

9. Method according to one of the preceding claims, characterized in that the permissible maximum moment for the connection points (NI, N2) is determined empirically as a function of the thickness of the sheet metal panel (11, 21, 31, 41).

10. Method according to one of the preceding claims, characterized in that the connection points (NI, N2) are formed as micro- or nanoconnections.

11. Method according to one of the preceding claims, characterized in that the cutting of the workpieces (10, 20, 30, 40) is optimized with regard to the shortest possible running times for a laser processing head.

12. Method according to one of the preceding claims, characterized in that the good parts (10, 20, 30, 40) are released from the sheet metal panel (11, 21, 31, 41) by vibration.

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