DE3621030A1 - Process and device for welding and/or severing and welding by means of 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 a device for welding and / or Separation welding of flat plastic bodies, preferably plastic films or plastic lienbahnen, by means of laser beams, the Touch welding and / or separating welding only with a laser beam a wavelength in the transmission range of the Plastic of more than 50% in one be agreed to keep the distance to be ver welding superimposed plastic foils or plastic sheeting from the laser spotlight.

It is already known to go through plastic films to separate sharply focused laser beams. Wei terhin it is known to use plastic films such laser beams through radiation absorption, preferably in the absorption maximum, with each other to weld.

Furthermore, a method for the separation welding of Plastic films with laser beams in DE-PS 28 41 062. This is just a sharp bundle for cutting or separating ter, i.e. point-focused laser beam and for welding or fusing them together resulting cut edges a second  Larger diameter laser beam used. There are at least two different lasers for this radiate or a division of the laser beam as well as a complicated look and a justie required.

In addition, the manufacture of a Weld seam as a connection point between two fo not possible using this procedure.

The aim and object of the present invention was it is therefore to avoid the aforementioned disadvantages the and plan plastic body from at least two foils or foil webs by welding ß and / or separation welding with only one La serstrahl without complex optical measures and to manufacture without dividing the laser beam.

The aim and task is still to be curly free welds and / or parting welds of flat plastic films or to achieve plastic sheeting.

According to the invention it was found that this Goals and tasks a procedure for welding Eating and / or welding of flat art fabric bodies, preferably plastic films or Plastic sheeting, using laser beams is justified, the welding and / or Non-contact separation welding using a La with a wavelength in the pass range of the plastic of greater than 50%, preferably 400-2000 nm, takes place Distance of the welded  superimposed plastic films or art fabric sheets from the laser emitter larger is the distance of the laser emitter from the point the maximum intensity of the focused laser beam, so that the focused laser beam through the plastic films or plastic films orbits outside or below this point passes through and the plastic films or Plastic sheeting at the point of passage or - area welded and / or welded separately.

By the used within the procedure Wavelength in combination with that during the Practice the distance to be observed the laser emitter from the plastic films or Plastic sheeting, which according to the Invention the procedure must be greater than the Ab the laser emitter stood at the point of maximum Intensity, flat plastic bodies succeed, preferably plastic films and / or art fabric sheeting with each other without curling weld and / or a separation weld without multiple laser beams, especially different laser beams Wavelength and / or direction or a division the laser beam, e.g. through prisms, he becomes necessary.

According to a preferred embodiment of the Ver are the art to be welded fabric films or plastic film webs before Welding or separation welding each ge separates electrostatically charged and then laid on top of each other. Through the  electrostatic charges adhere to the tarpaulins Plastic films even during welding and / or the separation welding close together, so that curls, unwanted welding defects and Like. Avoided.

According to a further preferred embodiment The procedure is regulated locally different energy required for Welding or separation welding through a change change of focus or distance so that the distance of the art to be welded fabric films or plastic film sheets still outside the point of maximum intensity of the focused laser beam remains so that the distance of the laser emitter from art fabric or plastic sheeting is larger than the distance of the laser emitter from the point of maximum intensity of the focused laser radiant.

For example, within the scope of the invention Separation welding process or Occurrence of greater material thickness the distance of the laser emitter from the plastic film or Plastic sheet a little (mostly minor) reduced, in compliance with the aforementioned Minimum distance. Decreases when ver weld the fo to be welded together line thickness, so is the distance of the laser beam lers of plastic film or plastic olienbahn slightly enlarged. After one preferred The th embodiment carries out the distance measurement optically through the visible adjustment beam of a Helium argon laser with a wavelength of 633 nm and / or the distance control optically, electronically and / or mechanically, the  Distance regulation immediately under change the distance of the maximum energy of the laser blasting and the plastic film or plastic railway and / or indirect, e.g. about a Mirror system and the like. And / or mechanically follows.

According to a further preferred embodiment of the process, the plastic films or Plastic film webs over the whole film pulp te or film web width by one or more linear gas jet (s) in front of the ver welding and / or separation welding against each other pressed. Due to the linear arrangement of the Openings, mouths or nozzles of the gas jets there is an almost linear pressing of the Plastic films or plastic film sheets welding or separation welding and a Displacement of any trapped air, preferably wise for an accurate and / or curl-free Obtain welding and / or separating seam.

According to another embodiment of the process rens is below the art to be welded fabric or plastic sheeting a me arranged metallic pad. As a metallic Documents can be sheet metal, aluminum parts, preferably with a flat surface shape and other metals or metal bodies with one flat surface can be used.

For certain purposes, e.g. to "pin" with welding seam or for manufacturing welding or separating welding seams  interrupted according to the inventive method welding seams or interrupted separation welding seams with pulsed laser beams a length of 400 to 2000 nm.

In the method according to the invention under one keeping the above distance and the the aforementioned wavelength hits the laser beam with an ellipsoidal intensity distribution the plastic films or plastic film sheets on. In contrast, is the distance of the laser emitter from the plastic film or plastic film rail NEN smaller than the distance of the laser emitter from the point of maximum intensity of focus based laser beam, so occurs evenly ge or approximately uniform intensity ver division and the wavelengths of the laser beam len must be in the absorption maximum of art fabric to be placed at all to be able to achieve certain welding. Here hits the laser beam according to the invention process on the art to be welded circular or similar to the surface of the fabric or elliptical on or a circular or including elliptical surface, whereby in mer the distance of the welded to each other plan plastic films or art fabric sheets from the laser emitter larger is the distance of the laser emitter from the point the maximum intensity of the focused laser beam ("focus").

According to a preferred embodiment the plastic films or plastic film sheets  by means of one or more transport devices continuous or dis continuously advanced, preferably over Rolled out and then or simultaneously under Use of the method according to the invention welds and / or separately welded.

The path control of the laser beam follows a preferred embodiment by a Mirror system, preferably by controlled rotating mirror.

To carry out the welding and / or Separation welding is preferred after the laser beam or the laser spotlight from a point or around a point moves and / or the laser beam device itself and / or a mirror system for path control of the laser beam moves, the movement mechanically or electronically controlled as well if necessary, countermeasures for correction. The Be movement is compulsory according to one embodiment controls. Using the invention The procedure is also difficult to weld plastic foils and / or plastic foils made of different plastic material to be welded to others, e.g. Polyolefin films or polyolefin films of different composites setting. According to a preferred embodiment examples of the invention are opaque on the one hand or colored plastic films, plastic films sheets or plastic film blanks, others on the one hand transparent plastic films, sheets or -cuts used. As slides are on  known plastic films, preferably poly olefin films and / or polypropylene and / or po foils containing ethylene are used.

As a material dispenser for roll goods is after one embodiment, a film unrolling device used with the possibility of several preferably up to 3 roller tracks one above the other and / or several webs next to each other inputted to the main machine, and / or a sheet feeder that has the job possibly e.g. in the screen and / or offset printing process ren printed sheet goods, preferably register, exactly into the machine.

The invention further relates to a Vorrich device for welding and / or separation welding of flat plastic bodies, preferably Plastic films or plastic film sheets with tels laser beams, consisting of a laser spotlights and a transport and / or support direction for plastic films or art Sheets of fabric covering the parts to be welded Plastic films or plastic film webs too and / or lead through the weld, where the support device and / or transport device interrupted in the area of the weld or is continuous with the laser emitter Laser beams in a wavelength range from 400-2000 nm and the distance of the trans port and / or support device on the sweat place of the laser emitter is larger than that Distance of the laser emitter from the point of the maxima len intensity of the focused laser beam  (larger than the "focal length"). The laser emitter is preferably from a point or moved by a point. After another out the laser beam device itself is in the form of management and / or a mirror system arranged movably, the movement being mechanical or electronic is controlled, and if necessary to correct against can be controlled.

According to a preferred embodiment of the front direction, the laser emitter is a solid heater, preferably a solid heater with Quality control.

According to the method of the invention a distance between each other to be welded lying plastic films or plastic films tracks adhered to by the laser emitter, the is greater than the distance between the laser emitters from the point of maximum intensity of the fo kissed laser beam. The La spray onto the plastic to be welded film surface circular or similar, preferably elliptical or includes one circular or circular area, preferred assign an elliptical surface.

The average diameter of the adjustment beam is 0.7- at the focal point of the main beam 1.0 mm. Enlarged as the distance increases the diameter of the adjustment beam, so that the distance according to the invention at one average diameter of the adjustment beam from 1.2-6 mm, preferably 1.5-5 mm.  

This diameter and this mean distance the circular or circle-like, preferred wise elliptical tread on the Plastic surface is among the specified process conditions according to the invention the same or almost the same with the laser used beam appearance diameter.  

Examples: example 1

A gray poypro will be placed on a flat plate pylene film, 0.2 mm thick, and one over it transparent polypropylene film, 0.08 mm thick, placed. For welding is a continuous cher Y A G laser with a wavelength of 1004 nm and a maximum output power of 100 Watts used.

The laser beam is used with a specific Power (N / V) of 15 W × min. / Cm "below" of the point max. Energy over the foils leads, i.e. the distance of the welded plastic films lying on top of each other is larger than the distance of the laser emitter from the point of maximum intensity of the focused laser radiant. The point corresponds to max. Ener gie a diameter of the adjustment beam of 0.7 mm. With the same specific performance were changed by changing the focus achieved the following welding properties:  

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

Example 2

In order to achieve close contact - without air gaps - between the not absolutely flat foils, the foils were charged in accordance with example 1 immediately before the laser beam by a known electrostatic charging device and additionally with an air knife - gap 1.0 mm, width 60 cm, air pressure 50 m.bar, distance 1.0 cm, blowing angle 60 ° - pressed together.

With an adjustment beam diameter of 1.5-5 mm created welds with over the whole Length of uniform strength.

Example 3

To carry out a separation welding, i.e. Cut the film while ver the welding of the adjacent areas 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 (12)

1. A method for welding and / or separation welding of planar plastic bodies, preferably as plastic films or Kunststoffolienbah NEN, by means of laser beams, characterized in that the welding and / or separation welding contact-free by means of a laser beam with a wavelength in the permeability range of the plastic greater than 50%, preferably 400-2000 nm, the distance between the plastic foils or plastic foils that are to be welded is greater than the distance of the laser emitter from the laser emitter from the point of the maximum intensity of the focused laser beam so that the focused laser beam passes through the plastic films or plastic film webs pass outside or below this point and the plastic films or plastic film webs are welded and / or separately welded in the passage point or area. 2. The method according to claim 1, characterized in net that the plastic films to be welded or plastic sheeting before welding or separation welding each separately electrostatic table loaded and then stacked flat be placed. 3. The method according to claims 1 and 2, characterized ge indicates that the local  energy required for welding or cutting weld by changing the focus tion takes place so that the distance to ver welding plastic foils or plastic railways outside the point of maximum Intensity of the focused laser beam ver remains so that the distance of the laser emitter from the plastic film or plastic film rail NEN is greater than the distance of the laser beam lers from the point of maximum intensity of the fo kissed laser beam. 4. The method according to one or more of the claims 1 to 3, characterized in that the art fabric films or plastic film webs over the entire film width or film web width one or more linear or over mainly linear gas jet (s) in front of the Welding or separating welding against each other be pressed. 5. The method according to one or more of the claims 1 to 4, characterized in that below of plastic films or plastic film webs a metallic base is arranged. 6. The method according to one or more of the claims 1 to 5, characterized in that Unterbro welding seams or interrupted separation welding seams with pulsed laser beams a wavelength of 400 to 2000 nm be put. 7. The method according to one or more of the claims  1 to 6, characterized in that the laser beam with an ellipsoidal intensity distribution on the plastic film or plastic olienbahnen meets. 8. The method according to one or more of the claims 1 to 7, characterized in that the art fabric films or plastic film webs by means of Transport devices in the welding plane con forward continuously or discontinuously be moved, preferably performed on rollers will. 9. The method according to one or more of the claims 1 to 8, characterized in that the way control of the laser beam by a mirror system stem takes place. 10. The method according to one or more of the claims 1 to 9, characterized in that the laser beam or the laser emitter from or around you Point moves, or the laser beam device itself and / or a mirror system for path control of the laser beam are moved, the Bewe mechanically or electronically controlled as well as, if necessary, for correction is controlled. 11. Device for welding and / or separation welding of flat plastic bodies, preferred wise plastic films or plastic film sheets using laser beams consisting of a La and a transport and / or support device for plastic films or  Plastic sheeting to weld the the plastic films or plastic film webs lead to and / or through the weld, where in the support device and / or transport direction in the area of the welding point chen or uninterrupted, thereby records that the laser emitter laser beams in a wavelength range of 400-2000 nm issues and the distance of transportation and / or Support device at the weld from that Laser beam is larger than the distance of the La from the point of maximum intensity of the focused laser beam. 12. The apparatus according to claim 10, characterized records that the laser emitter is a solid heater, preferably a solid heater with Quality control is.