Laser beam welding method and molded components fabricated thereby

Abstract

The invention relates to a method for laser welding two plastic components A, B brought into contact at least in the joining area, wherein component B facing away from the laser radiation consists of a plastic matrix with a white pigmentation of 1.5 5-20 wt.-%, and component A facing the laser radiation, through which the laser beam passes in the welding process, exhibits a plastic matrix. For a given laser wavelength the travel distance of the laser beam through the component A measures at most 10 mm, and given a white pigmentation of the component A in wt.-%, the product of the travel distance of the laser 10 beam through the component A in mm and white pigmentation in wt.-% is less than 1.25, and the travel distance of the laser beam through the component A measures at most 1 mm.

Claims

1. A method for laser welding two plastic components, a first component and a second component, brought into contact at least in a joining area, wherein the first component facing away from a laser radiation consists of a plastic matrix based on a thermoplastic polyamide with a white pigmentation of at least 0.5 percent by weight, and at most 20 percent by weight, and wherein the second component facing the laser radiation, through which a laser beam of the laser radiation passes in the welding process, exhibits a plastic matrix based on a thermoplastic polyamide with a white pigmentation, wherein a laser wavelength of said laser beam ranging from 1200 to 2200 nm is used for welding, wherein, given a white pigmentation of the second component facing the laser radiation expressed in percent by weight, the product of the travel distance of said laser beam through said second component facing the laser radiation in mm and white pigmentation in percent by weight is less than 1.25, and that the travel distance of said laser beam through the second component facing the laser radiation measures at most 1 mm, and wherein both the second component facing the laser radiation and the first component facing away from the laser radiation are essentially free of laser absorbing additives in the NIR range and wherein the joining site is not pretreated with an additive that absorbs in the NIR range, and no additional component that contains an additive that absorbs in the NIR range is incorporated between the component facing the laser radiation and the first component facing away from the laser radiation, and wherein the method for laser welding leads to a welded bond without surface damage of the second component facing the laser radiation, through which a laser beam of the laser radiation passes in the welding process, and wherein the first component facing away from a laser radiation consists of a plastic matrix based on a thermoplastic polyamide selected from the group consisting of MACM9-12, PACM9-18 and PA12 with a white pigmentation of at least 0.5 percent by weight, and at most 20 percent by weight, and wherein the second component facing the laser radiation, through which a laser beam of the laser radiation passes in the welding process, exhibits a plastic matrix based on a thermoplastic polyamide selected from the group consisting of MACM9-12, PACM9-18 and PA12 with a white pigmentation of at least 0.5 percent by weight, and at most 5 percent by weight.

2. The method according to claim 1, wherein the product of travel distance in mm and white pigmentation of said second component in percent by weight is less than 1.

3. The method according to claim 1, wherein the laser beam is focused on the joining zone while implementing the method, and/or that a laser power of 2-40 W is used at a feed rate ranging from 100 to 7000 mm/min, wherein the energy input per unit length ranges from 0.0005 J/mm to 0.05 J/mm.

4. The method according to claim 1, wherein the components are pressed against each other during the process at a contact pressure ranging from 1 to 10 bar.

5. The method according to claim 1, wherein the first component facing away from the laser radiation exhibits a white pigmentation of at least 1 percent by weight, and at most 15 percent by weight.

6. The method according to claim 1, wherein, when processed into a molded component with a smooth surface, the second component facing the laser radiation exhibits a color effect in the CIE LAB system, at which L*>80, and/or the value of a* or respectively independent value of b* is <10, and/or that, when processed into a molded component with a smooth surface, the first component facing away exhibits a color effect in the LAB system, at which L*>90.

7. The method according to claim 1, wherein the white pigmentation of the first component and/or of the second component is adjusted based on at least one white pigment that does not absorb in NIR.

8. The method according to claim 1, wherein the used laser operates in a wavelength area of 1400 to 2000 nm.

9. The method according to claim 1, wherein the second component through which the laser beam passes in the welding process, and/or the first component facing away, exhibit a transparent plastic matrix, wherein the matrix in the unpigmented state exhibits a light transmission of at least 80%, if the polymer forming the plastic matrix is present in the form of a platelet having a thickness of 2 mm.

10. The method according to claim 1, wherein the second component facing the laser radiation exhibits a white pigmentation, and the product of travel distance in mm and white pigmentation in percent by weight is ranging from 0.2 to 0.8.

11. The method according to claim 1, wherein both the second component facing the laser radiation and the first component facing away from the laser radiation contain less than 0.0001 percent by weight of laser absorbing additives in the NIR range.

12. The method according to claim 1, wherein both the second component facing the laser radiation and the first component facing away from the laser radiation are completely free of laser absorbing additives in the NIR range.

13. The method according to claim 1, wherein the laser beam is focused on the joining zone while implementing the method, and/or that a laser power of 5-40 W, is used at a feed rate ranging from 100 to 7000 mm/min, wherein the energy input per unit length ranges from 0.0009 to 0.01 J/mm.

14. The method according to claim 1, wherein the components are pressed against each other during the process at a contact pressure ranging from 2 to 5 bar.

15. The method according to claim 1, wherein the first component facing away from the laser radiation exhibits a white pigmentation of at least 5 percent by weight, and at most 15 percent by weight.

16. The method according to claim 1, wherein, when processed into a molded component with a smooth surface, the second component facing the laser radiation exhibits a color effect in the CIE LAB system, at which L*>95, and/or the value of a* or respectively independent value of b* is <3, and/or that, when processed into a molded component with a smooth surface, the first component facing away exhibits a color effect in the LAB system, at which L*>96.

17. The method according to claim 1, wherein the white pigmentation of the first and second component is adjusted based on at least one white pigment that does not absorb in NIR, selected from the following group: aluminum oxide (Al2O3); barium sulfate (BaSO4); lead carbonate (PbCO3); calcium carbonate (CaCO3); magnesium carbonate (MgCO3); titanium dioxide (TiO2); titanates, such as barium titanate (BaTiO3), zinc oxide (ZnO); zinc sulfide (ZnS); mica; chalk; lithopone; silicon dioxide; aluminum silicate sodium silicate; talc; metal-doted or coated variants of the mentioned materials or combinations that contain at least one of the mentioned materials.

18. The method according to claim 1, wherein the white pigmentation of the first and second component is adjusted based on at least one white pigment that does not absorb in NIR, selected to be titanium dioxide, in its rutile form, used essentially exclusively for the white pigmentation.

19. The method according to claim 1, wherein the resulting welded seam exhibits a welding strength of at least 20 N/mm.sup.2.

20. The method according to claim 1, wherein the second component through which the laser beam passes in the welding process, and/or the first component facing away, exhibit a transparent plastic matrix, wherein the matrix in the unpigmented state exhibits a light transmission of at least 90%, if the polyamide polymer forming the plastic matrix, is present in the form of a platelet having a thickness of 2 mm.

21. The method according to claim 1 wherein the laser power is ranging from 2 to 40 W.

22. The method according to claim 1, wherein the laser power is ranging from 5 to 40 W.

23. The method according to claim 1, wherein the energy input per unit length ranges from 0.0005 J/mm to 0.05 J/mm.

24. A method for laser welding two plastic components, a first component and a second component, brought into contact at least in a joining area, wherein the first component facing away from a laser radiation consists of a plastic matrix based on a thermoplastic polyamide selected from the group consisting of MACM9-12, PACM9-18 and PA12 with a white pigmentation of at least 0.5 percent by weight, and at most 20 percent by weight, and wherein the second component facing the laser radiation, through which a laser beam of the laser radiation passes in the welding process, exhibits a plastic matrix based on a thermoplastic polyamide selected from the group consisting of MACM9-12, PACM9-18 and PA12 with a white pigmentation of at least 0.5 percent by weight, and at most 5 percent by weight, wherein a laser wavelength of said laser beam ranging from 1440 to 1500 nm or 1910 to 1970 nm is used for welding, wherein, given a white pigmentation of the second component facing the laser radiation expressed in percent by weight, the product of the travel distance of said laser beam through said second component facing the laser radiation in mm and white pigmentation in percent by weight is less than 1.25, and that the travel distance of said laser beam through the second component facing the laser radiation measures at most 1 mm, and wherein both the second component facing the laser radiation and the first component facing away from the laser radiation are essentially free of laser absorbing additives in the NIR range and wherein the joining site is not pretreated with an additive that absorbs in the NIR range, and no additional component that contains an additive that absorbs in the NIR range is incorporated between the component facing the laser radiation and the first component facing away from the laser radiation.

25. The method according to claim 24, wherein the resulting welded seam exhibits a welding strength of at least 5 N/mm.sup.2.

26. A method for laser welding two plastic components, a first component and a second component, brought into contact at least in a joining area, wherein the first component facing away from a laser radiation consists of a plastic matrix based on a thermoplastic polyamide with a white pigmentation of at least 0.5 percent by weight, and at most 20 percent by weight, and wherein the second component facing the laser radiation, through which a laser beam of the laser radiation passes in the welding process, exhibits a plastic matrix based on a thermoplastic polyamide with a white pigmentation, wherein a laser wavelength of said laser beam ranging from 1200 to 2200 nm is used for welding, wherein, given a white pigmentation of the second component facing the laser radiation expressed in percent by weight, the product of the travel distance of said laser beam through said second component facing the laser radiation in mm and white pigmentation in percent by weight is less than 1.25, and that the travel distance of said laser beam through the second component facing the laser radiation measures at most 1 mm, and wherein both the second component facing the laser radiation and the first component facing away from the laser radiation are essentially free of laser absorbing additives in the NIR range and wherein the joining site is not pretreated with an additive that absorbs in the NIR range, and no additional component that contains an additive that absorbs in the NIR range is incorporated between the component facing the laser radiation and the first component facing away from the laser radiation, and wherein the method for laser welding leads to a welded bond without surface damage of the second component facing the laser radiation, through which a laser beam of the laser radiation passes in the welding process, and wherein the resulting welded seam exhibits a welding strength of at least 5 N/mm.sup.2, wherein the first component facing away from a laser radiation consists of a plastic matrix based on a thermoplastic polyamide selected from the group consisting of MACM9-12, PACM9-18 and PA12 with a white pigmentation of at least 0.5 percent by weight, and at most 20 percent by weight, and wherein the second component facing the laser radiation, through which a laser beam of the laser radiation passes in the welding process, exhibits a plastic matrix based on a thermoplastic polyamide selected from the group consisting of MACM9-12, PACM9-18 and PA12 with a white pigmentation of at least 0.5 percent by weight, and at most 5 percent by weight.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments of the invention will be described in the following based on the drawings, which serve only an explanatory purpose, and are not to be construed as limiting. The drawings show:

(2) FIG. 1 a diagrammatic, perspective view of the laser welding process; and

(3) FIG. 2 sectional views perpendicular to the welded seam for different component shapes: a) planar contact region; b) rib contact via component A; c) rib contact for both components.

DESCRIPTION OF PREFERRED EMBODIMENTS

(4) Specific welding tests performed in the following experimental section will be used to document how the welding method can be implemented, and which mechanical properties can be guaranteed by the welded seam.

(5) A method of the kind diagrammatically shown in a perspective view on FIG. 1 basically involves providing a component B that to some extent lies below and faces away from the laser beam, and bringing it into planar contact with another component A. A laser 3 emits a laser beam 2 focused on the contact plane of the two components, and travels along the desired welded seam 1 in a feed direction 4.

(6) The contact areas between the components can also vary in design, as respectively depicted on FIG. 2 in sectional views perpendicular to the welded seam 1. FIG. 2a here shows the situation where the two components are in planar contact, as also depicted on FIG. 1. As evident from FIG. 2b, for example, component A can consist of ribs that establish contact with a surface of component B. A welded seam 1 can here also be correspondingly formed, provided that the wavelength of the laser through the material of the component A lies within the boundaries specified above. FIG. 2c presents a situation in which both components exhibit ribs, which run correspondingly; in this case, it is also possible, given a contact that is likewise to some extent linear, to form the welded seam 1 along this line. These figures present a respective linear welded seam, and the case can here involve a straight line or in principle any shape desired. This shape can be realized by guiding either the laser or the laser beam along this shape, or by keeping the beam stationary and moving the components accordingly. Also possible are spot welds, wherein these can also be realized by a correspondingly pulsed laser, for example.

Experimental Section

(7) M12: Grilamid TR 90 is an amorphous, transparent polyamide of type MACM12, with a light transmission of 93 and a haze of <1, available from EMS-CHEMIE AG P12: P12 is a partially crystalline polyamide of type PA12, available from EMS-CHEMIE AG LV3H: Grilamid LV-3H is a glass fiber-reinforced, partially crystalline polyamide of type PAl2, available from EMS-CHEMIE AG CX: Trogamid CX7323 is an amorphous polyamide of type PACM12 with a light transmission of 93 and a haze of <1%, available from Evonik Degussa PMMA: Plexiglas Resist zk40 is a polymethylmethacrylate (PMMA) with a light transmission of 90, available from Evonik Rhm GmbH PC: Makrolon 2858 is a polycarbonate (PC) with a light transmission of 89, available from Bayer AG Ti-Pure R103 is a white pigment made of TiO.sub.2 in its rutile form available from DUPONT, and has a median particle size of 23 micrometers (median particle size) Kronos 2220 is a white pigment made of TiO.sub.2 in its rutile form available from Kronos, and its surface is stabilized with aluminum and silicon compounds, as well as a silicone bond Sachtolith HDS is a white pigment made of zinc sulfide, available from Sachtleben Chemie GmbH.

(8) The 0.5, 0.75 and 1 mm thick 45 cm plates used for the welding tests were injected out of these materials with a tempered tool on a fully electric injection molding machine from Arburg (device designation: ARBURG Allrounder 320 A 500-170). The following injection molding parameters were used.

(9) a) For M12:

(10) Tool 80 C., melt temperature 280 C.

(11) b) For PC:

(12) Tool 80 C., melt temperature 300 C.

(13) c) For PMMA:

(14) Tool 40 C., melt temperature 260 C.

(15) d) For CX:

(16) Tool 80 C., melt temperature 280 C.

(17) e) For P12:

(18) Tool 60 C., melt temperature 250 C.

(19) f) For LV3H:

(20) Tool 60 C., melt temperature 260 C.

(21) Components (A) and (B) were cut to a length of 50 mm and a width of approx. 12 mm for the welding tests. Components (A) and (B) were dry welded.

(22) The following diode lasers from DILAS Diodenlaser GmbH were used for the welding tests:

(23) a) Wavelength: 1940 nm, COMPACT Diode Laser System 18/600 (16 W, 600 m)

(24) b) Wavelength: 1470 nm, MINI Diode Laser System 40/400 (40 W, 400 m)

(25) c) Wavelength: 980 nm, COMPACT Diode Laser System 500/400 (500 W, 400 m)

(26) Execution of Welding Tests:

(27) The components (A) and (B) stored over a desiccant were placed one onto the other so as to overlap on a plate. A pneumatic plunger was actuated to press this plate against a PMMA plate fixed in place above it, which caused the contact pressure to build up. The laser beam was guided via a recess in the PMMA plate directly onto component A, and through the latter to the welded seam. The beam path or laser feed was manually adjusted at all wavelengths in such a way as to run through the entire width of component A. The energy input per unit length for the radiation is regulated via the feed, and was selected accordingly for the components to be welded. Depending on the chemical composition, thickness and pigment, the energy input per unit length should be specifically adjusted to avoid burning on the surface. A welding test was rated in Tables 2 and 3 if either no bond was achieved between component A and B, or if component A exhibited burnt regions, holes or blisters. A welding test was rated (+) if a visual evaluation revealed no burnt regions or other damage to the surface.

(28) The CIE L*a*b* values were determined on a spectrophotometer from Datacolor (device designation: Datacolor 650) under the following measuring principles in front of a contrast sheet that was painted white; mode of measurement: reflection; measuring geometry: D/8; type of light: D 65 10; brightness: included; calibration: UV calibrated; measuring orifice: SAV. The obtained L*a*b* values are presented on Tables 1 to 3. The bond strength (welding strength) of the welded seam was determined according to ISO 527 with a traction speed of 5 mm/min at a temperature of 23 C. The overlapping welded objects consisting of components (A) and (B) were clamped into the traction engine in a dry state, and a force was applied parallel to the plate plane. The individual thickness of the components may be gleaned from Tables 1 to 3.

(29) TABLE-US-00001 TABLE 1 Welding Tests with Molded Components made out of MACM12 and Ti-Pure R103 as the White Pigment VB1 VB2 B1 B2 B3 B4 B5 B6 VB3 VB4 B7 Material M12 M12 M12 M12 M12 M12 M12 M12 M12 M12 M12 Component A TiO.sub.2 0 0 0 0 0 0 0 0 0 2.6 1.3 [%] Component B TiO.sub.2 0 .sup.0.sup.a 1.3 1.3 5.2 5.2 5.2 5.2 5.2 5.2 5.2 [%] Thickness 1 1 1 1 0.5 0.5 1 1 1 0.5 0.5 component A [mm] Thickness 1 1 1 1 0.75 0.75 1 1 1 0.75 0.75 component B [mm] Laser wavelength 1940 1940 1470 1940 1470 1940 1940 1470 98 1940 1940 [nm] Energy input per 0.001 0.001 0.005 0.002 0.005 0.001 0.002 0.005 0.001 0.0009 0.001 unit length [J/mm] Contact pressure 4 4 4 4 4 4 4 4 4 4 4 [bar] Welding quality + + + + + + + + + Welding strength n.d. n.d. 30.95 28.97 15.87 11.46 n.d. n.d. 11.90 [N/mm.sup.2] L* value component n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 95 95 A a* value component n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 0.32 0.64 A b* value component n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 0.18 0.58 A L* value component n.d. n.d. 96 96 96 96 96 96 96 96 96 B a* value component n.d. n.d. 0.52 0.52 0.35 0.35 0.14 0.14 0.14 0.35 0.35 B b* value component n.d. n.d. 0.90 0.90 0.00 0.00 0.33 0.33 0.33 0.00 0.00 B .sup.a50% glass fiber reinforced. n.d. = not determined.

(30) TABLE-US-00002 TABLE 2 Welding Tests with Molded Components made out of MACM12 and other white pigments B8 B9 Material M12 M12 Component A white pigment [%] 1.3 1.3 Component B white pigment [%] 5.2 5.2 White pigment component A Kronos 2220 Sachtolith HD-S White pigment component B Ti-Pure R103 Ti-Pure R103 Thickness component A [mm] 0.5 0.5 Thickness component B [mm] 0.75 0.75 Laser wavelength [nm] 1940 1940 Energy input per unit length 0.0012 0.0013 [J/mm] Contact pressure [bar] 4 4 Welding quality + + Welding strength [N/mm.sup.2] 15.43 9.26 L* value component A 95 96 a* value component A 0.07 0.02 b* value component A 0.41 0.77 L* value component B 96 96 a* value component B 0.35 0.35 b* value component B 0.00 0.00

(31) TABLE-US-00003 TABLE 3 Welding Tests with Materials other than MACM12 and Ti-Pure R103 as the White Pigment B10 B11 B12 B13 B14 B15 B16 B17 Material PC PC PMMA P12.sup.b P12.sup.b P12.sup.b LV-3H.sup.a CX Component A TiO.sub.2 [%] 0 0.5 0 0 0 0 0 0 Component B TiO.sub.2 [%] 1.3 1.3 1.3 0 0 0 0 5.2 Thickness component A [mm] 1 1 1 0.5 0.75 0.75 0.75 1 Thickness component B [mm] 1 1 1 0.75 0.75 0.75 0.75 1 Laser wavelength [nm] 1470 1940 1470 1470 1470 1940 1940 1940 Energy input per unit length [J/mm] 0.001 0.005 0.008 0.006 0.008 0.018 0.002 0.002 Contact pressure [bar] 4 4 4 4 4 4 4 4 Welding quality + + + + + + + + Welding strength [N/mm.sup.2] 34.52 34.52 17.46 11.90 19.40 14.11 22.93 33.73 L* value component A n.d. 92 n.d. n.d. n.d. n.d. n.d. n.d. a* value component A n.d. 1.03 n.d. n.d. n.d. n.d. n.d. n.d. b* value component A n.d. 1.02 n.d. n.d. n.d. n.d. n.d. n.d. L* value component B 94 94 95 n.d. n.d. n.d. n.d. 96 a* value component B 0.79 0.79 0.81 n.d. n.d. n.d. n.d. 0.52 b* value component B 0.63 0.63 2.16 n.d. n.d. n.d. n.d. 0.90 .sup.a50% glass fiber reinforced. .sup.bPartially crystalline. n.d. = not determined.

(32) TABLE-US-00004 REFERENCE LIST 1 Welded seam 2 Laser beam 3 Laser 4 Laser advancer A Facing component B Component facing away