DE3621030C2 - Method and device for welding and / or separation welding using laser beams - Google Patents

Abstract

The present invention relates to a process and a device for the non-contact welding and/or severing and welding of plastic films or plastic film webs by means of a laser beam with a wavelength in the transmission range of the plastic of higher than 50%, preferably 400-2000 nm. The distance of the plastic films or plastic film webs to be welded, which lie one on top of the other, in front of the laser emitter is larger than the distance of the laser emitter from the point of maximum intensity of the focused laser beam, so that the focused laser beam passes through the plastic films or plastic film webs outside or below this point and the plastic films or plastic film webs are welded and/or severed and welded in the passage point or passage region. The plastic films or plastic film webs to be welded are, before welding or severing and welding, in each case electrostatically charged separately and then laid flat one on the other or pressed one against the other by means of linear gas jets. The laser emitter used within the device is a solid-state laser.

Description

The present invention relates to a method and an apparatus for welding and / or separation welding of Plastic films or plastic film sheets, with tels laser beams with a wavelength of 400 to 2000 nm, at which the welding and / or separation welding contactlessly by means of Laser beams take place, the distance between those to be welded superimposed plastic films or plastic film webs from the laser emitter is greater than the distance of the laser emitter from the point of maximum intensity of the focused laser beam, so that the focused laser beam through the plastic films or Plastic sheeting outside or below this point passes through and the plastic films or plastic film webs in Passage point or areas welded and / or separating welds, the plastic film or art to be welded Determine fabric webs before welding or separation welding Pretreatment or preparatory measures are subjected.

It is already known to sharply bundle plastic films Separate laser beams. Furthermore, it is known plastic films by means of such laser beams by radiation absorption, preferably at the absorption maximum, to be welded together.

Furthermore, there is a method for the separation welding of plastic films described with laser beams in DE 28 41 062 C3. Here will only for tailoring or separating a sharply bundled, so point-focused laser beam and for welding or ver a second laser melts the resulting cut edges larger diameter beam used.  

There are at least two different laser beams or one Distribution of the laser beam as well as a complex optics and a Adjustment required.

In addition, the production of a weld seam as a connection cannot use two foils using this procedure.

EP-A-0159169 describes the welding of different ones Plastic items using laser beams with a Wavelength of approx. 1.06 µm is known. According to this procedure for example different plastic sheets used and in Brought into contact with each other. The laser beams cross the Plate with the "second type made of synthetic material" (see drawing plate 2) and concentrate or collect on the Contact surface of the plate made of other synthetic material (Plate 1). Accordingly, the contact surfaces of the melt first first plate and then the contact surfaces of the second plate.

The laser emitter according to EP-A-0159169 is guided onto the superimposed plates until the laser beam device rests on the plates in the working position ( FIG. 3) and a compressive force is exerted on the plates (see description EP 0159169, page 6, last paragraph sentence). This method has disadvantages with thin and soft plastic films. This creates, for example, indentations or damage when guiding the laser beam device on the film web under pressure.

From DE-OS-14 79 686 it is known plastics u. a. Films by means of electromagnetic rays of the same wavelength, e.g. B. laser beam len to be welded together, chemical agents (e.g. Chromic acid, chlorine, termanganate or ammonia) to form polar chemical groups act on the surface of the plastic, to get polar groups there. According to the films DE-OS-14 79 686 even gas inclusions remain.  

DE-OS-22 61 388 describes a method for welding an end piece of plastic on a stepless, tubular body known from plastic, the end piece being laser beams is welded. It is therefore a different area of application the welding of hollow plastic bodies.

According to DE-OS-22 61 388, a relative rotary movement must be carried out at the same time be performed between the laser beam and the hollow body. Such a rotary movement is at all in the film welding not possible. There are also laser beams with a wave length of z. B. 10 microns used.

DE-OS-16 29 219 relates to a radiation welding device for Joining plastic films together during a continuous relative movement between the welding device and the art fabric films, with a laser with continuous radiation as the radiation element Emission on the wavelength of at least one absorption maximum the plastic film is used. The laser beam hits it the kind of a welding wedge between the first one at its impact point merged plastic sheet, which immediately thereafter between two press rollers run in. The point of impact of the laser beam therefore lies in the contact area of the plastic film webs and has its maximum there.

The aim and object of the present invention was therefore, the pre to avoid mentioned disadvantages and plan plastic bodies from minde at least two foils or foil webs by welding and / or Separation welding without damaging the film and without complex optical measures and without dividing the laser beam len. The aim and task is still to ensure that the weld seams are undamaged and / or parting welds of art lying flat on top of each other to achieve sheeting or plastic sheeting.

According to the invention, it was found that these objectives and tasks  a method for welding and / or separation welding of art fabric or plastic sheeting, using laser beams with a wavelength of 400 to 2000 nm, at which the Welding and / or separation welding without contact using a laser blasting takes place, the distance between the welded one another the underlying plastic films or plastic film webs from the Laser emitter is greater than the distance of the laser emitter from Point of maximum intensity of the focused laser beam, see above that the focused laser beam through the plastic films or art webs of fabric outside or below this point occurs and the plastic sheeting or plastic sheeting in through welded point and areas or / and welded separately, the plastic films or plastic films being welded together before welding or separation welding, separate elec be charged statically and then placed flat on top of each other and / or across the entire film width or film web width one or more linear or predominantly linear Gas jet (s) against each other before welding or separation welding be pressed.

The method according to the invention makes it possible to use plastic films and / or plastic sheeting to ver without corrugation welding and / or a separation welding without several laser beams, in particular different laser beams Wavelength and / or direction or a division of the laser beam, e.g. B. by prisms. Through the electrostatic The flat plastic films adhere to the charge even during the welding and / or the separation welding closely together, so that Ver corrugations, unwanted welding errors and the like avoided become.

The locally different energy required for welding or separation welding is done by changing the focus according to the invention so that the distance of the art to be welded fabric films or plastic film webs outside the point of maximum intensity of the focused laser beam remains,  so that the distance of the laser emitter from the plastic films or Plastic sheeting is larger than the distance between the laser emitters from the point of maximum intensity of the focused laser beam.

So z. B. in the context of the inventive method at Separation welding or when thicker material occurs the distance of the laser emitter from the plastic film or art cloth film slightly (mostly slightly) reduced, with observance the aforementioned minimum distance. Decreases when welding the film thickness to be welded together, so the distance of the laser emitter from the plastic film or plastic film web somewhat enlarged. According to a preferred embodiment the distance measurement optically through the visible adjustment beam Helium-argon laser with a wavelength of 633 nm and / or the Distance control optically, electronically and / or mechanically, wherein the distance regulation immediately by changing the distance the maximum energy of the laser beam and the plastic film or Plastic film web and / or immediately, e.g. B. via a mirror system and the like, and / or mechanically.

According to a further preferred embodiment of the method the plastic films or plastic film sheets over the entire film wide or foil web width through one or more linear Gas jet (s) against before welding and / or separation welding pressed each other. Due to the linear arrangement of the openings, Mouths or nozzles of the gas jets are almost linear pressing the plastic films or plastic film webs welding or separating welding and displacement may be possible closed air, preferably to an accurate and / or curly to obtain free welding and / or separating seams.

According to another embodiment of the method is below the plastic films or plastic film webs to be welded a metallic base is arranged. As metallic documents  can plan sheet metal, aluminum parts, preferably with a Surface shape and other metals or metal body with a plan Surface can be used.

For certain purposes, e.g. B. for "tacking" by means of a weld or to produce interrupted welds or separating welds interrupted welds according to the inventive method or interrupted separating welds with pulsed laser beams made with a length of 400 to 2000 nm.

In the method according to the invention while observing the previously described The laser hits the distance and the aforementioned wavelength beam with an ellipsoidal intensity distribution on art fabric or plastic sheeting. But the distance is of the laser emitter from the plastic films or plastic film webs smaller than the distance of the laser emitter from the maximum point Intensity of the focused laser emitter, so occurs evenly ge or approximately uniform intensity distribution on and die Wavelengths of the laser beams must be in the absorption maximum of the plastic can be placed to a certain ver to be able to achieve welding. The laser beam hits accordingly of the method according to the invention on the art to be welded fabric surface circular or similar or elliptical or including a circular or elliptical surface, where always the distance of the welded one on top of the other plan plastic films or plastic film sheets from the laser beam ler is greater than the distance of the laser emitter from the point of maximum intensity of the focused laser beam ("focus").

According to a preferred embodiment, the plastic films or plastic film webs by means of one or more transport devices directions in the welding plane continuously or discontinuously moved forward, preferably guided over rollers and then or simultaneously using the method according to the invention welds and / or separately welded.  

The laser beam is controlled according to a preferred route Embodiment by a mirror system, preferably by control te rotating mirrors.

To carry out the welding and / or separation welding according to a preferred embodiment, the laser beam or the Laser emitter moved from or around a point and / or the laser beam device itself and / or a mirror system for the path Control of the laser beam moves, the movement being mechanical or electronically controlled and, if necessary, for correction against is controlled. The movement is forced according to one embodiment controlled. Successful using the method according to the invention it also, hard-to-weld plastic films and / or art fabric films made of different plastic material with each other to weld, so z. B. polyolefin films or polyolefin films different composition. According to a preferred embodiment Example of the invention are opaque or colored on the one hand Plastic films, plastic film sheets or plastic film cutting te, on the other hand, transparent plastic films, sheets or sheets cuts used. Known per se as plastic films lien, preferably polyolefin films and / or polypropylene and / or polyethylene-based films used.

According to one embodiment, the material dispenser for roll goods is a film unwinding device used with the possibility of several preferably up to 3 roller conveyors one above the other and / or several Feed the webs next to each other without tension to the main machine ben, and / or a sheet feeder, which has the task, z. B. Sheet goods printed by screen and / or offset printing, preferably wise passer to insert exactly into the machine.

The invention further relates to a device for welding and / or separation welding of flat plastic bodies, preferably Plastic films or plastic film webs using laser emitters and a transport and / or support device for plastic films  or plastic sheeting, which the plastic to be welded lien or plastic sheeting to and / or through the weld lead, the support device and / or transport device is interrupted or uninterrupted in the area of the weld, the laser emitter having laser beams in a wavelength range from 400 to 2000 nm and the distance of the transport and / or Support device at the welding point of the laser emitter larger is the distance of the laser emitter from the point of maximum intensity intensity of the focused laser beam (larger than the "focal length"). The laser emitter is preferably from a point or moved by a point. In another embodiment, this is Laser beam device itself and / or a mirror system movably arranged net, the movement being controlled mechanically or electronically and if necessary can be counteracted for correction.

According to a preferred embodiment of the device is the laser a solid jet, preferably a solid jet with quality control.

According to the method according to the invention, a distance of to weld plastic foils or art lying on top of each other Sheets of fabric adhered to by the laser emitter, which is larger than the distance of the laser emitter from the point of maximum inten intensity of the focused laser beam. The laser beam hits it circular on the plastic film surface to be welded or like a circle, preferably elliptical or closes one circular or circle-like surface, preferably an elliptical Area.

The mean diameter of the adjustment beam is at the focal point of the main beam 0.7 to 1.0 mm. As the distance increases the diameter of the adjustment beam also increases, so that the distance according to the invention with an average diameter of the adjustment beam of 1.2 to 6 mm, preferably 1.5 to 5 mm.  

This diameter and this mean distance of the circular or circle-like, preferably elliptical tread the plastic surface is among the specified according to the invention Process conditions the same or nearly the same as the use th laser beam appearance diameter.

Examples example 1

A gray polypropylene film, 0.2 mm, is placed on a flat plate thick, and a transparent polypropylene film, 0.08 mm thick, placed. A continuous YAG laser is used for welding a wavelength of 1004 nm and a maximum output power of 100 watts used.

The laser beam is with a specific power (N / V) of 15 W × min / cm "below" the point max. Energy over the slides led, d. H. the distance between the layers to be welded Plastic films are larger than the distance between the laser emitter and Point of maximum intensity of the focused laser beam. Here the point corresponds to max. Energy one diameter of the adjustment beam of 0.7 mm. With the same specific performance by changing the focus the following welding properties achieved:

Local differences in the tests de the seam strength were due to poor Contact of the non-flat foils on the Causes welds.

Example 2

For close contact - without air gaps  - Both films are not absolutely flat reach, the foils were accordingly play 1 immediately before the laser beam a known electrostatic charger charged and additionally with an air knife - Gap 1.0 mm, width 60 cm, air pressure 50 mbar, Distance 1.0 cm, blowing angle 60 ° - on top of each other pressed.

With an adjustment beam diameter of 1.5-5 mm weld seams were created over the whole Length of uniform strength.

Example 3

To perform a cut weld, d. H. Cut the film while ver the adjacent areas were welded Films according to Example 1 with a spec fish energy of 17 W × min. irradiated.

The defocused laser beam led to one Diameter of the adjustment beam of 1.5-5 mm for a simultaneous severing and ver welding the adjacent areas with high Strength (material tear).

Example 4

Two transparent films made of polyvinylidene fluo rid (PVDF) 20 µm thick on a matt aluminum minium plate laid and with the laser according to Bei game 1 with a power of 8 W × min / cm welded. During the separation test, the Films next to the seam with longitudinal stretching.

Claims (6)

1. Process for welding plastic films or plastic Lines using laser beams with a wavelength of 400 up to 2000 nm, in which the welding and / or separation welding non-contact by means of laser beams, the distance the plastic foils to be welded or Plastic sheeting from the laser emitter is larger than that Distance of the laser emitter from the point of maximum intensity of the focused laser beam so that the focused laser beam through the plastic films or plastic film webs outside or passes below this point and the plastic lien or plastic sheeting in the passage point or area Chen welded and / or welded separately, the ver welding plastic sheeting or plastic sheeting in front of the Welding or separation welding each separately electrostatically charged and then laid flat on top of each other and / or across the entire film width or film web width by one or several linear or predominantly linear Gas jet (s) against each other before welding or separation welding who are pressed. 2. The method according to claim 1, characterized in that the local different energy required for welding or cutting welding is done by changing the focus so that the distance of the plastic films or art to be welded webs of fabric outside the point of maximum intensity of the focused laser beam remains so that the distance of the laser emitter from the plastic films or plastic films orbits is greater than the distance of the laser emitter from the point the maximum intensity of the focused laser beam.   3. Process according to claims 1 and 2, characterized in that the laser beam has an ellipsoidal intensity distribution the plastic films or plastic film webs hits that thereby below the plastic films or plastic film webs a metallic base is arranged and the plastic films or plastic sheeting by means of rollers in the welding plane be carried out continuously or discontinuously. 4. The method according to one or more of claims 1 to 3, characterized characterized in that path control of the laser beam by a Mirror system is done. 5. The method according to one or more of claims 1 to 4, characterized characterized in that the laser beam or the laser emitter of or moved around a point or the laser beam device itself and / or a mirror system for the path control of the laser beam be moved, the movement being mechanical or electronic is controlled and, if necessary, counteracted for correction. 6. Device for welding and / or separation welding of art Fabric films or plastic film webs using laser beams in a wavelength range from 400 to 2000 nm, consisting of a laser emitter and a transport and / or support device for the plastic sheeting or plastic sheeting that the welding plastic sheeting or plastic sheeting and / or lead through the weld, the support device device and / or transport device in the area of the weld is interrupted or uninterrupted, characterized in that that the distance of the transport and / or support device on the Weld point from the laser emitter is greater than the distance of the laser emitter from the point of maximum intensity of focus based laser beam that the laser emitter is a solid emitter is that rolling for continuous or discontinuous Guide the plastic films or plastic film sheets arranged are and the laser emitter controlled by a mirror system is.