JP2000037767A - Marking method for synthetic resin pipe during extrusion molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for applying marking to a synthetic resin pipe during extrusion molding in which marking by laser is enabled so as to remove fear for lowering of water quality of transferred fluid and lowering of watertightness in the joining area of the synthetic resin pipe. SOLUTION: In the method in which resin is extruded from an extruder into a tubular shape and the resin tubular body is cooled and then marking is given to the resin tubular body while it is being taken out, laser emitted from a gas laser oscillator 41 is modulated by a modulator 42 in accordance with a marking signal, and the modulated laser is deflected by a rotary polygon mirror 46 and then scanned on the traveling resin tubular body P in the direction nearly orthogonal to the traveling direction. Marks corresponding to the marking signals are applied on the traveling resin tubular body P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laser marking a synthetic resin tube during extrusion molding.

[0002]

2. Description of the Related Art In order to manufacture a synthetic resin tube by extrusion molding, a resin is extruded into a tube from an extruder, the resin tube is cooled through a cooling tank, taken up by a take-up machine, and further printed. The mark is printed through a tool and then cut to a fixed size by a cutter. A main use of the synthetic resin pipe manufactured in this way is a fluid transfer pipe, which is used by being joined with a predetermined joining structure.

[0003]

When the above-mentioned fluid transfer pipe is used for transferring pure water or ultrapure water as water for electronics industry, water for pharmaceuticals / cosmetics, or water for hospitals, it is necessary to use a synthetic resin pipe joining method. In some cases, for example, in the rubber packing joining method, the surface of the synthetic resin pipe in the joint comes into contact with the transfer fluid, and the organic substance or heavy metal of the marking ink dissolves in the transfer fluid and the transfer fluid (pure water or pure water). The TOC (total organic carbon content) of ultrapure water is increased, and the specific resistance value is reduced.

[0004] Instead of the above-described marking with ink, it is conceivable to apply marking by engraving with a heating printing roll. In this case, when the marking location comes to the mounting location of the packing. It is difficult to guarantee watertightness, and there is a problem. An object of the present invention is to provide a marking method during extrusion molding of a synthetic resin pipe so as to eliminate the fear of a decrease in water quality and water tightness of a transfer fluid at a joint portion of the synthetic resin pipe. -To provide a method that enables the king.

[0005]

According to the method of the present invention for marking a synthetic resin tube during extrusion molding, a resin is extruded into a tubular shape from an extruder, and the resin tubular body is cooled and taken off while being taken off. In the above method, a laser from a gas laser oscillator is modulated in accordance with a marking signal, and the modulated laser is deflected by a rotating polygon mirror and travels on the traveling resin tubular body. And a mark corresponding to the marking signal is applied to the traveling resin tubular body by scanning in a direction substantially orthogonal to the direction of rotation. The rotational speed of the rotary polygon mirror is set to the extrusion speed. It is desirable to add means for proportioning.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an extrusion molding line for a synthetic resin tube used in the present invention.
Denotes a cooling water tank, 3 denotes a take-off device, 4 denotes a laser marking device, and 5 denotes a fixed-size cutter.

FIG. 2 shows an example of a laser marking device. In FIG. 2, reference numeral 41 denotes a gas laser oscillator, for example, a carbon dioxide laser oscillator is used. An optical modulator 42 modulates a laser corresponding to a mark signal. Reference numeral 43 denotes a semiconductor that oscillates a positioning laser, for example, a red laser semiconductor. 44 is a lens system, 45 is a mirror, 46 is a rotating polygon mirror having the same angle,
Is scanned from Zagaten a ₁ to the point b ₁ - The rotating polygon mirror -46 is when it is rotated an angle θ les.

[0008] That is, in (a) of FIG. 3, Le - The is imaged in to the point a ₁ incident on the corner m ₁ of the rotating polygon mirror -46, the imaging point in accordance with rotation of the rotary polygon mirror -46 is b is moved toward the _1, Les progressed rotation of the rotary polygon mirror -46 - the rotation polygon mirror - imaged in the point b ₁ when incident on immediately before the next corner m _2. This scanning width w is a rotating multi-surface mirror-4.
6 is determined by the angle θ of one surface and the focal length.

In FIG. 2, P indicates a synthetic resin tube being extruded, and its traveling speed is v. The scanning line of the laser is substantially perpendicular to the synthetic resin tube P. Assuming that the rotation speed of the rotating polygon mirror 46 is n times / unit time, the time Δt required for the rotating polygon mirror 46 to rotate at the angle θ is given by Δt = θ / (360n). It is scanned in a time Δt to a point b ₁ from the point a _1.

Further, the rotary polygonal mirror - After to The incident, further rotation polygon mirror - - rotates angle θ Les the next corner m ₂ by the rotation of the record - is The in FIG. 3 (b) It is scanned toward the point a ₂ to point b _2. This point a ₂ and distance [Delta] L between the point a ₁ is given by ΔL = v · Δt (v is extrusion speed or product travel speed), this interval is set from the resolution or the like as described later.

The angles of the respective surfaces of the rotating multi-surface mirror 46 are all equal. As shown in FIG. 3B, laser scanning is repeated with the above-described scanning width w and scanning interval .DELTA.L. To go. In FIG. 2, the lens system 44 is set to an optical system capable of making the scanning speed of the laser uniform (to correct the temporal scanning distortion) and focusing on the surface of the resin tubular body P. is there.

In order to perform the marking on the resin tubular body during the extrusion molding according to the present invention, first, as shown in FIG. 2, the semiconductor laser 43 is operated to form an image of the semiconductor laser at a predetermined position. The marking start position is determined. At this position, the gas laser oscillator 41 is operated to turn on and off the gas laser in response to the marking signal input to the optical modulator 42, and to irradiate the outer surface of the resin tubular body P by the above-mentioned scanning. Go. Accordingly, the gas laser is irradiated onto the outer surface of the running resin tubular body P in a pattern corresponding to the marking signal.

From the above equation, the scanning interval ΔL in this case is ΔL = v · θ / (360n). When ΔL is too small, the resolution of the mark decreases, and when it is too large, the mark becomes low. It is appropriate to set ΔL in the range of 20 to 200 μm according to the rotation speed n (for example, θ ° = 45 °, ΔL = 50 to 200 μm).
100 μm, v = maximum 4000 mm / min, n = 1
0000-5000 revolutions / minute).

In the marking method according to the present invention,
It is necessary for the uniformity of the mark to keep the scanning interval ΔL constant irrespective of the extrusion speed v (running speed of the resin tubular body; usually a fluctuation of about ± 3%), and as shown in FIG. A pulse generating a pulse in proportion to the traveling speed of the resin tubular body P;
It is effective to provide a tally encoder 6 and to proportionally control the rotation speed of the rotary polygon mirror 46 with this pulse number.

When the scanning width w of the laser is set to be large, the defocus caused by the curved surface of the surface to be scanned becomes remarkable, and the marking becomes unclear. Therefore, the width of the marking area is reduced to 50 mm or less. Is preferred. In the above,
The location where the laser marking device is disposed is preferably between the take-off machine and the cooling water tank as shown in FIG. It is.

According to the marking method of the present invention, the surface of the resin tubular body is marked yellow by irradiation with the gas laser, and the yellowing is caused by the shallow light carbonization of the resin body. It is sufficiently stable and practically does not dissolve in water (note that a semiconductor laser has low strength and cannot be marked). Therefore, even if the manufactured synthetic resin pipes are joined and the marking part in the joint part comes into contact with the transfer pure water or the ultrapure water, the TOC of the pure water or the ultrapure water increases and the resistivity decreases. Can be prevented well.

This can be confirmed from the comparison between the following examples and comparative examples.

[0018]

EXAMPLES EXAMPLES diameter vinyl chloride resin pipe extruded product speed 3m / min diameter of 16 mm, CO ₂ Les immediately after the take-up machine - The 12W (wavelength 10.6 [mu] m), the scanning width 50
mm, scanning interval 50 μm, octahedral rotation mirror rotation speed 3
Marking was performed at 400 revolutions / minute.

When the marked portion of the vinyl chloride resin tube thus obtained was immersed in ultrapure water to measure the TOC and the specific resistance value, the TOC and the specific resistance value caused by the marking were changed. Virtually not observed. [Comparative Example] A vinyl chloride resin tube was manufactured in the same manner as in the example, except that the marking was applied with a printing roll using ink.
When the changes in the OC and the specific resistance were measured, a marked decrease in the water quality of the ultrapure water caused by the marking was observed.

[0020]

According to the present invention, it is possible to apply marking to a synthetic resin tube during extrusion molding by a laser.
Even if pure water or ultrapure water comes into contact with the marking portion on the outer surface of the tube at the joint portion of the synthetic resin tube, a clean pipe that can stably maintain the water quality of the transferred fluid can be satisfactorily manufactured.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of a production line for synthetic resin tubes used in the present invention.

FIG. 2 is a drawing showing an example of a laser marking device used in the present invention.

FIG. 3 is a view showing an operation state of a laser marking device used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 extruder 2 cooling water tank 3 take-off machine 4 laser marking device 41 gas laser oscillator 42 optical modulator 44 lens system 45 mirror 46 multi-plane rotating mirror 6 rotary encoder

Claims (2)

[Claims] 1. A method of extruding a resin from an extruder into a tube and performing marking while cooling and taking up the resin tube, wherein a laser from a gas laser oscillator corresponds to a marking signal. And modulate this modulation laser with a rotating polygon mirror.
Extrusion molding wherein scanning is performed on the running resin tubular body in a direction substantially perpendicular to the running direction after the deflection, and the running resin tubular body is marked according to a marking signal. Marking method for the synthetic resin tube inside. 2. A method for marking a synthetic resin tube during extrusion molding according to claim 1, further comprising means for making the rotational speed of the rotary multi-surface mirror proportional to the extrusion speed.