DE4116204A1 - Replacing worn needles on an anker support - by exposing area of support to defocussed, elongated laser beam until soldering desoldering temp. is reached - Google Patents

Abstract

Relacing a worn needle (1) on an amber support (2) of a pressure needle composite part consists of exposing the area (3) to a defocused laser beam which is inclined to the surface of the amber support instead of being perpendicular. The laser beam forms an elliptical shape over the area (3) until the soldering/desoldering temp. is reached. At this point the needle is removed and replaced by a new one. ADVANTAGE - Protects the part from laser burning.

Description

The invention relates to a thermoformed three-component Composite of the components hard material needle, needle-absorbing Anchor bridge and brazing alloy, the process being of a special kind of the heat input when soldering in and when unsoldering and is particularly suitable for a small joint cross-section, such as it for example, is applied when attaching a print needle its magnetic armature end-end within a needle print head.

Heat-bonded multi-component composite parts and processes for their manufacture position are well known (DE 28 16 455 B41J 3/10; DD 2 27 391 B41J 3/10; DE 30 05 662 H01H 11/04; / 1 / DE 38 10 370 B23K 26/00) as well as the special needle welding (/ 2 / EP 2 36 798 B41J 3/12), which however does not indicate the purposeful work order of assembly and assembly Welding process revealed. It is also known (/ 3 / EP 1 88 672 B41J 7/84, page 2 lines 9 to 22 and page 3, lines 1 to 21) that both the blunt soldering and the soldering of a Pushpin into an anchor pier breakthrough takes some effort on assistive devices and work care require what is confirmed by an experience report (/ 4 / F. Weickert and P. Bartsch: Laser contacting in microelectronics, fine devices tetechnik 32 (1983) Issue 10, page 468, left column last Paragraph of text up to middle column).

These special due diligence requirements result from the Properties of heat input from laser energy in small Joining cross-sections, especially protection against material burning conditions and their damage consequences are imperative. To contain this Damage effects are known:

• - The laser beam is in a preheating and / or post-heating defocused partial beam and into a power-enhanced melting focused beam split (/ 5 / DD 2 48 304 B23K 26/00),  
• - The power-increased laser beam oscillates and falls below an angle on the workpiece (/ 6 / DE 35 39 933 B23K 26/00) and is therefore well suited for difficult to access Solder joints (/ 6 / column 2, line 18) and as combustion protection (/ 6 / column 3, lines 31 to 47), but under Ver using the sharply focused beam (/ 6 / column 2, lines 16 to 19),
• - a variable focal spot, whose energy density by an electro-optical focusing element depending on the voltage controls, heats up a color paste (/ 7 / DE 38 21 267 B41J 3/20);
• - For the invention remote energy-rich Laser tools, the energy intensity before, on and after the entry point by mechanical means (e.g. by a rotating slit with slanted slats len) varies (/ 8 / DE 32 26 811 B23K 26/06),
• - very much during the process of attaching thermal needles in the dressing closely adjacent needle carrier (/ 2 /; / 3 /: page 5, lines 11 to 15 and page 7, lines 7 to 10 as a subassembly a compact 2 × 12-needle head with a star-shaped anchor arm Group) cannot be prevented with certainty that the neighboring "cold" needle carriers on one of the soldering / Desoldering temperature almost reached will.

Neither in isolation nor in combination can the aforementioned Means and method steps solve the problem of the invention.

The technical object of the invention is the effort reduction in the soldering and desoldering of pressure needles on Anchor bar connected with an easily manageable burning Protection of the workpieces to be heated.

The solution to the technical problem is through the fiction characterized and consists in the fact that the one Anchor web receiving the printing needle in a laser tool's own Positioning device aligned on the axis of the laser beam tet is that the laser energy entry surface at the anchor web end  both by the oblique encounter as well as by the defocusing Ren of the laser beam is realized in that the double cone-shaped beam region close to the focus of the laser beam energetic conditions by a fictitious incline th conic cut on the workpiece "pressure needle composite part" be projected.

The combustion achieved with little effort is advantageous protection and energetic control of the heat input point even under complicated joining conditions, such as. B. very close Workpiece distances. Another beneficial result is that the optical axis of the laser beam used does not match the Reflecting axis of the work inclined in the beam piece coincides, so that process-disturbing energy reflex lungs from the workpiece to the beam source with certainty excluded are.

Using the example of a Hartme soldered to the end of the anchor bar tall printing needle is the joining method / repair according to the invention ture process for this three-substance composite explained in more detail.

The drawing shows:

FIG. 1a is a limited to 2 anchor webs Darstellungsaus the star-shaped magnet armature subassembly section of known type,

Fig. 1b the laser thermal energy entry point in the working position (ie the laser beam is perpendicular to the plane of the drawing).

Process step sequence

• - In the vicinity of the focus, the workpiece (three-material composite anchor web end 2 a; pressure needle 1 ; hard solder) is inserted into one of the cones of the laser beam and exposed to the beam energy at an angle to the beam axis (ie in the position of a fictitious oblique cone section),
• - After heating the entry point 3 to the required soldering / desoldering temperature, the heat energy supply is interrupted in the usual manner.

Process sequence "needle soldering"

Anchor 2 together with anchor web 2 a are brought into the oblique position without the beam focus according to FIG. 1 and fed by means of a positioning device of known type to the laser beam axis. As soon as the defocused area of the double cone-shaped emerging laser beam has heated the entry point 3 sufficiently, the solder goes with the anchor web end 2 a and with the pressure needle 1 the intended soldered connection. This process sequence occurs both when the needle is first inserted and when it is re-soldered after the repair-related needle exchange.

Process sequence "Needle desoldering" for the purpose of repair

The soldered-in damaged and now replaceable pressure needle 1 is biased in the above-mentioned device with little deflection. In the aforementioned manner, the laser beam melts the solder seam between the anchor web end 2 a and pressure needle 1 and the pretensioned pressure needle is released from the joint, can be removed and replaced by another. The areal extension of the laser beam at its entry point 3 has an approximately elliptical shape; its duration of action and intensity are adjustable and this is part of another invention not explained here.

Claims (1)

Process for the production and repair of pressure needle composite parts by laser beam soldering / desoldering, characterized in that the laser energy entry surface (entry point 3 ) of the anchor web end ( 2 a) by an obliquely directed and defocused laser beam on the solder Temperature or to the desoldering temperature.