DE102007008653A1 - Workpiece i.e. sheet-metal board, cutting method, involves subjecting deformation zone of local pre-heating unit limited on section or contour line with optical or electromagnetic radiation, before deformation of workpiece - Google Patents

Abstract

The method involves subjecting a deformation zone of a local pre-heating unit limited on a section or contour line with optical or electromagnetic radiation, before the deformation of a workpiece i.e. sheet-metal board (2), where the duration of the radiation is 0.5-10 seconds. The surface temperature of the workpiece is maintained between 100-600 degree Celsius. A radiation source is arranged beside the material-deformation tool, and irradiance emission is directed to an area of the workpiece, which is positioned in a feeding direction. An independent claim is also included for a device for performing a method for cutting a workpiece.

Description

The The invention relates to a forming process, in particular a shear cutting process by means of a punching, nibbling, embossing tooling, wherein a forming tool, preferably a punch or punch on a workpiece, in particular a metal sheet placed and the workpiece in the area a forming zone, preferably along a cutting or contour line formed by single or multi-pronged cutting or punching cuts or embossing becomes. The invention also relates to a device for carrying out the Forming process.

Forming as shear cutting by means of a punching, nibbling, embossing machine tool are known. The achievable degrees of deformation are determined by certain Material properties such. B. yield point Rp 0.2 and elongation at break A80 limited.

It It is also known that the elongation at break A80 is temperature dependent. The smaller the elongation at break, the more brittle the material is. at increasing temperatures increases the elongation at break, with each Material an independent Elongation at break is to be expected.

This Effect can be used to make materials at room temperature can not be reshaped due to lack of elongation at break, so far to heat that up afterwards can be plastically and permanently deformed permanently. there However, no structural transformation or a change of state take place in the material. Similar conditions apply at the yield point Rp 0.2.

In practice have been the reshaped materials, for example Steel sheets for the automotive industry in ovens heated to a suitable temperature and then preferably fed to heated forming tools. This process is very time consuming, in addition to the heating time for the whole Materials also transport times must be added. In addition, can the required forming temperature can not be set exactly because there are certain cooling effects between the heating up and the forming to adjust. In addition, the energy used to heat the entire workpiece and often even the tool very large. Especially when heating the Tool leads the used heat too unwanted Changes in length, making compliance with tolerances and manufacturing more complicated Designs is often difficult. Also, let some materials of the tools the warming on the needed Temperature level not too.

since A few years ago there is a trend towards a more flexible production process in time- and volume-optimized lot sizes. It is sought, economically to work in smaller batches, allowing the energy input in the manner described above and the associated expense for the entire workpiece board is out of date.

task The present invention overcomes the disadvantages of known preheating To avoid the deformation and a flexible production with different Lot sizes at optimal preheating temperatures to enable. Optimal preheating is given when the for needed the subsequent forming Temperature is adjusted so that the processing power in the to disposal standing forming device is manageable and a cut edge length adjustable is that enables an economical production.

to solution This object is achieved according to the invention a forming process in particular a shear cutting method by means of a punching, nibbling, embossing machine tool proposed, which is characterized in that before forming the Forming a locally limited preheating, in particular one on the cut or Contour line or limited to the deformation surface preheating subjected to optical or electromagnetic radiation, wherein the duration of irradiation in the range of 0.5-10 seconds and the surface temperature of the workpiece between 100 and 600 ° C preferably below 400 ° C and more preferably below 250 ° C.

Surprisingly has been shown to be particularly in the case of irradiation in the form a laser irradiation the temperature of the forming zone during the preheating can be kept relatively low and yet an essential Improvement in the elongation at break occurs, so that the forming step can be performed with very little effort.

hereby The tools are spared and the cutting or punching movements executed very precisely, so that - despite the larger cut edge length one very high dimensional accuracy of the products can be achieved.

One more surprising The advantage is that the previously on relatively high preheating temperatures heated workpieces often dimensional inaccuracies by a temperature-dependent change in length showed that was no longer detected. Thus, that leads new processes for energy, time and quality-optimized production, where also the one for this used devices a relatively low investment needs exhibit.

in the The following is the invention with reference to several embodiments explained in more detail.

It demonstrate:

1 Overview drawing of a machine tool with inventive laser head preheating

2 Various punching patterns according to the prior art and produced by the method according to the invention

3 Embossing pattern, produced with an inventively designed laser head preheating

4 illustrates the forming process according to the invention with preheating the forming zone

The perspective view of an inventively designed machine tool according to 1 shows a processing table ( 1 ) on which a workpiece, for example a metal sheet ( 2 ) is positioned. About the processing table ( 1 ) on a rack ( 3 ) fixed punching head ( 4 ) via the arrow ( 5 ) indicated feed direction of the workpiece.

Also on the stand ( 3 ) is a robot arm ( 6 ) attached to the end of a laser head ( 7 ) is pivotally mounted. For a flexible production, it makes sense that the pivoting range of the laser head extends over the entire width of the processing table. In the case of a three-axis pivoting robot arm, the laser head can be aligned with any locally restricted cutting or contour line so that preheating can be carried out selectively.

At the in 1 shown robot arm is laterally in the feed direction in front of the laser head ( 7 ) a device for coating or roughening ( 8th ) the surface of the metal sheet ( 2 ). This makes it possible to produce surfaces which are designed to be particularly favorable for the coupling of the laser beams.

Specifically, the processing looks like this:
On a machine tool, a workpiece is placed and equipped for machining the right tool. With a laser, the point is heated prior to processing, to change the properties of the laser from the cutting mode in the heating mode, if necessary, the beam path of the laser is changed accordingly.

For heating, the laser is directed to the working surface, wherein by controlling the robot arm different surface or punctiform or linear irradiation of the workpiece are possible:
In a planar irradiation, which is greater than the laser beam diameter, the laser can produce by reciprocating motion a surface pattern having a correspondingly elevated temperature by the irradiation energy. Of course, conversely, it is also possible to move the metal sheets below a stationary laser. In any case, the surface to be heated must be covered by the laser beams accordingly. This can also be achieved by means of a dynamically moving optics or a correspondingly moving beam projector.

at a punctiform or linear heating are the movements of the laser point or linear, with in all cases the power of the laser with regard to energy input and irradiation time adapted to the required forming temperatures.

Subsequently, will when the laser is switched off, the heated area is moved under the machining head, so that the forming done by punching or nipple tools can. For example, after heating for 1-4 seconds with constant laser power, the metal sheet under the machining head be driven. The residence time during the procedure is more usual Way 0.5-4 Seconds to equalize the temperature profile over a heat conduction on the surface of the workpiece to reach.

In the 2 illustrated punching patterns are to show how the forming process according to the invention leads in practice to savings or significant quality advantages in the products produced.

To 2a : Hole surfaces, such. B. on housings, are usually made with punches ( 2a /above). The use of multiple punching dies ( 2a / below) makes economic sense. For high strength materials, however, the cut length can prevent the insert. A preheating is imperative here for a successful implementation of the method.

To 2 B : Special hole shapes like a keyhole are usually made with special stamps ( 2 B /above). Since with high strength materials, the cut edge length would lead to a large processing force, one uses several smaller punches one after the other. Without the preheating according to the invention, therefore, such a mold must be produced from a plurality of standard punches ( 2c / middle / bottom), which are used one after the other.

For special hole shapes whose complex contour shapes are specified by the component function ( 3 ), a special tool must be used, since it is not possible to assemble the mold from several standard tools. Here, the preheating invention has decisive advantages, especially because a production with high-strength materials is made possible in the first place.

2c shows an example of a punch-embossing method. So far, it has been possible to achieve an embossing depth H1 with a specific material. After preheating according to the invention could be achieved at significantly higher degree of forming an embossing depth H2.

all Examples are common that the material properties in one Machine tool only in the processing area of the workpiece board through targeted local warming for one certain machining process can be set. In the example was a combined punch-nibble preblaser machine tool used, the laser head for heating the working surface adjustable is. Subsequently, the processing surface of the punching nibbling embossing head supplied and the transformation of the permissible Deformation performed.

A contactless Surface temperature measurement is advantageous, but not a prerequisite to the process of the invention to control. A coating with a particular laser wavelength absorbing Surface profile is useful, so that the heating time can be shortened. The surface profile can be considered surface roughness or as a reflectance value, laser-wave absorbing as well Coatings possible are.

• 1. Rüsten einer Stanz-Nibbel-Prägelaserwerkzeugmaschine mit Werkstück, Werkzeugen und CNC-Fertigungsprogramm
• 2. Starten des Fertigungsprogramms
• 3. Positionieren des Laserkopfs über der zu erwärmenden Bearbeitungsstelle a) Optional: Temperaturmessung der Bearbeitungsfläche
• 4. Erwärmen der Bearbeitungsstelle innerhalb einer bestimmten Aufheizdauer mit mindestens einem der folgenden Verfahren: a) Bewegen des Laserkopfes über die zu erwärmende Fläche b) Kontrolliertes Einstellen und Verändern der Laserleistung währen des Aufheizens c) Aufweiten des Laserstrahls mit mindestens einem der folgenden Verfahren i. Vergrößern des Abstandes Laserkopf ↔ Werkstück (Ausnutzen des divergenten Strahlenverlaufs) ii. Entfernen der strahlenfokussierenden Elemente im Strahlengang des Lasers (wie parabolische Spiegel oder Sammellinsen) iii. Verwenden eines den Strahlengang aufweitenden Mittels (wie Streulinse oder Spiegel)
• 5. Verfahren des Werkstücks mit der Bearbeitungsstelle unter dem Stanz-Nibbelkopf
• 6. Optional: Verweilen, um eine Vergleichmäßigung des Temperaturprofils an der Bearbeitungsstelle zu erreichen, durch Wärmeleitung in dem Werkstück
• 7. Optional: Messen der Temperatur an der Bearbeitungsstelle um das weitere Vorgehen zu entscheiden a) Temperatur kleiner Bearbeitungstemperaturfenster Rückschritt zu 4, mit Änderung der Aufheizdauer und oder einem der anderen Parameter von 4 i. Optional: Information an SPS-Benutzer, um diese zu Parameterveränderungen zu veranlassen b) Temperatur größer als Bearbeitungstemperaturfenster: Verweilen, bis Temperatur im Bearbeitungstemperaturfenster i. Optional: Information an SPS-Benutzer, um diese zu Paramterveränderungen zu veranlassen c) Temperatur innerhalb Bearbeitungstemperaturfenster
• 8. Herstellen der Umformung, mit dem dafür zuvor gerüstetem Werkzeug an der Bearbeitungsstelle
• 9. Durchführen des nächsten Bearbeitungsschrittes des Fertigungsprogramms, dabei ggf. Wiederholen der Schritte 3–8

The program flow in a numerically controlled manufacturing process is explained below:

• 1. Prepare a stamping nibbling preblaser machine tool with workpiece, tools and CNC manufacturing program
• 2. Start the production program
• 3. Positioning the laser head above the workstation to be heated a) Optional: Temperature measurement of the processing surface
• 4. Heating the processing station within a certain heating time by means of at least one of the following methods: a) moving the laser head over the surface to be heated b) controlling and adjusting the laser power during heating c) expanding the laser beam by at least one of the following methods i. Enlarging the distance Laser head ↔ workpiece (exploiting the divergent beam path) ii. Removing the radiation-focusing elements in the beam path of the laser (such as parabolic mirrors or converging lenses) iii. Using a beam-expanding agent (such as diffusing lens or mirror)
• 5. Procedure of the workpiece with the processing point under the punching Nibbelkopf
• 6. Optional: Linger to achieve a homogenization of the temperature profile at the processing point, by heat conduction in the workpiece
• 7. Optional: Measuring the temperature at the processing point to decide how to proceed a) Temperature lower processing temperature window Back to 4, with change of the heating time and or one of the other parameters of 4 i. Optional: Information to PLC users to cause them to change parameters b) Temperature greater than processing temperature window: Linger until temperature in processing temperature window i. Optional: Information to PLC users to cause parameter changes c) Temperature within processing temperature window
• 8. Make the forming, with the previously prepared tool at the processing site
• 9. Carry out the next processing step of the production program, possibly repeating steps 3-8

10. End of the production program

The heating time depends on of the type (material pretreatment) and the geometry (thickness) of the Workpiece the laser (power, wavelength, beam diameter during heating) and the surface condition of the workpiece (Absorption of the respective laser wavelength, reflection or coating).

In the following, some parameters are given for a forming process carried out according to the invention:
With a stainless steel sheet 1.4404, thickness 0.3 mm, a 3.2 KW CO2 laser at a distance of 1 m with a heating time of 4 s achieves a temperature increase of approx. 230 K for a working range of D = 40 mm , During heating, the laser describes a circular path on the processing area. The punch-nipple embossing treatment was carried out in a period of 1 second to 4 seconds after the end of heating.

The inventive device for Implementation of the forming process comprises a forming tool with a radiation source whose beam exit opening is directed onto a region of the workpiece which, viewed in the feed direction, is positioned laterally in front of the forming zone. In addition, a device for coating or roughening the material surface may be arranged laterally in front of the irradiated surface, for example an atomization or evaporation device or else a mechanical roughening.

Especially It is advantageous if the radiation source is a focusing device has, which is pivotable or rotatable within the forming zone, so that the beam path aligned exactly on the surface to be heated can be. The beam-focusing elements are parabolic mirrors or collecting lenses proven, as scattering elements can Scattering lenses or mirrors are arranged. Advantageously is the radiation source with an intensity control for short-term increase equipped the temperature profile. This allows even within the Umformbereiches a graduated temperature profile, the exact Unform conditions is adjusted.

In the 3 the contour shown represents the embossing of a surface pattern with an embossing tool, which is not or only partially produced due to its leg length and sharp-edged transitions, especially in high-strength materials. In the method according to the invention, however, due to the special preheating, the predetermined contour can be maintained precisely and even with relatively low embossing forces and, associated therewith, little tool wear, good production results can be achieved.

To clarify the measure according to the invention is a temperature profile below the punched-out area after 3 shown. The temperature profile was measured along the dashed line and plotted on the S-axis. It can be seen that the maximum temperature is reached at the contour lines within a narrow range of less than 1 mm. This means that only within the forming zone a short-term heating of the sheet material is made. Any influences on the dimensional accuracy can therefore be avoided.

Another application of the method according to the invention is based on the 4 be clarified. In 4a a pattern plate produced by embossing is shown which has a radially symmetrical shape. One recognizes a cup-shaped characteristic, which was manufactured with a sharp-edged tool. This is problematic in high-strength sheets, because this considerable compressive forces are required and also the dimensional stability is at risk in a preheating of the entire body.

According to the invention, only the forming area II has been determined according to FIG 4b heated. This is from the areas I, II, III shown in dashed lines in FIG 4b combined with 4c recognizable. It is a plan view of the in cross section 4a cup-shaped depression.

The temperature profile with temperature peaks in area II is in 4c specified. It can be seen that the temperature profile along the Kreishalbierenden immediately before processing has a maximum at 230 ° C within the forming region II. Length changes, for example, by the drawing-drawing process in the well cavity have been avoided by the small area heating. The areas I and III were not heated.

The previously described warm-up uses the absorbed part of the irradiation energy. The remaining one Part is reflected or penetrates transparent materials through them. As a result, a control of the preheating is possible by the Reflection values on the surface a part to be formed, for example by Application of reflective coatings.

to controlled leadership the radiation energy can Continue to use radiation traps to absorb the unabsorbed Energy controlled to capture and dissipate. This serves first Line the protection of the environment from too much heat input.

Claims (20)

Forming method, in particular shearing method using a punch nibbling embossing machine tool, wherein a forming tool, preferably a punching, embossing or cutting punch on a workpiece, in particular a metal sheet, placed and the workpiece in the region of a forming zone, preferably along a cutting or contour line, by one - or mehrhubige embossing, is formed by cutting or punching cuts, characterized in that before forming the forming zone of a locally limited to the cutting or contour line preheating is subjected by optical or electromagnetic radiation, wherein the duration of the irradiation in the range of 0.5-10 seconds and the surface temperature of the workpiece is maintained between 100 ° C and 600 ° C. A method according to claim 1, characterized in that in addition to the forming a Radiation source is arranged, the beam exit is directed to a region of the workpiece, which is seen in the feed direction positioned in time before the forming zone. Method according to claim 1 or 2, characterized that preferably in the region of the forming tool before the time irradiated area a coating or roughening of the material surface made becomes. Method according to claim 1, characterized that the irradiation takes place in the form of a laser irradiation, the aligned with the forming zone. Method according to one of the preceding claims characterized characterized in that to improve the coupling before the surface of the workpiece irradiation is coated, roughened or dyed. Method according to one of the preceding claims, characterized characterized in that in a separating, embossing or punching step more Tools are used simultaneously. Method according to one of the preceding claims, characterized characterized in that special tools by combining different Tool shapes with overlapping Cutting or punching pattern are formed. Method according to one of the preceding claims, characterized characterized in that the material is metallic or thermoplastic Materials are used. Method according to one of the preceding claims, characterized characterized in that the material is a radiopaque material is used, with reflected radiation over a preferably cooled radiation trap is absorbed. Device for carrying out a forming process according to one of the preceding claims, characterized that a radiation source is arranged next to the forming tool, whose Beam exit opening on an area of the workpiece is directed, seen in the feed direction laterally in front of the Forming zone is positioned. Device according to the preceding claim, characterized characterized in that in the region of the forming tool preferably temporally before the irradiated area arranged a device for coating or roughening the workpiece surface is. Device according to the preceding claim, characterized characterized in that the means for coating or roughening the workpiece surface a sputtering or evaporation device. Device according to the preceding claim, characterized characterized in that the means for coating or roughening and / or the radiation source with a mechanical control for Adjusting the size and the Direction of the beam exit opening Is provided. Device according to one of the preceding claims, characterized characterized in that the device is a radiation trap, preferably with cooling device, for the from the radiopaque material reflected radiation. Device according to one of the preceding claims, characterized characterized in that the radiation source is designed as a laser, whose radiation focuses on the area within the forming zone is. Device according to one of the preceding claims, characterized characterized in that the radiation source with a to the forming zone pivoting or rotatable laser head is equipped, wherein the beam path of the laser is adjustable. Device according to one of the preceding claims, characterized characterized in that beam-focusing in the beam path of the laser or scattering elements are arranged einschwenkbar. Device according to one of the preceding claims, characterized characterized in that in the beam path of the laser parabolic mirror or Collection lenses are arranged. Device according to one of the preceding claims, characterized characterized in that in the beam path of the laser scattering lenses or Mirrors are arranged. Device according to one of the preceding claims, characterized characterized in that the radiation source with an intensity control for a short-term increase equipped with a temperature gradient.