JPH08142160A - Measurement of abrasion degree of inner surface of barrel of extruder - Google Patents

Abstract

PURPOSE: To obtain an accurate measuring result simply while enabling the timely maintenance and control of a barrel in the measurement of the abrasion degree of the inner surface of the barrel of an extruder. CONSTITUTION: Measuring parts 9, 10 capable of bringing the probes 11 of ultrasonic thickness meters into contact with the outer surface of the barrel B of an extruder are formed to the outer surface of the barrel B of an extruder and measuring points 12, 13 are set to the measuring parts 9, 10 and the wall thicknesses 15 of the barrel at the measuring points 12, 13 are measured by the ultrasonic thickness meters to calculate the deviation between the measured value at the time of non-abration and the measured value at an arbitrary point of time after the start of the operation of the extruder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the degree of wear when the inner surface of an extruder barrel is worn by friction with a screw or the like.

[0002]

2. Description of the Related Art An extruder melts and kneads a molding material such as a synthetic resin and extrudes it under a high pressure by rotating a screw arranged with a slight clearance in the barrel. , It is easy to wear due to friction with the screw, and if this clearance increases due to this wear, back flow of the molten resin occurs, causing extrusion fluctuation, thermal decomposition due to material stagnation, etc. There was a problem of inviting.

Therefore, it is necessary to frequently measure the degree of wear of the inner surface of the extruder barrel.
Conventionally, the extruder was stopped, the barrel and the screw were separated, the resin and other deposits on the inner surface of the barrel were removed, and then the diameter of the through hole of the barrel was manually The measurement method was adopted.

[0004]

However, in the case of a twin-screw extruder, for example, the barrel of the extruder has a length of about 2 m, and the internal through hole is a round hole with a diameter of about 100 mm as shown in FIG. As shown in the figure, the two are partly overlapped with each other, and the measurement work becomes more troublesome as it goes to the central part in the longitudinal direction.
Even if there is a point that cannot be measured or if it can be measured,
It was not possible to measure accurately because the measured value may vary from person to person.

Further, even if the measurement is carried out periodically, there is a problem that the machine cannot be carried out unless the machine is stopped and disassembled and cleaned as described above. As a result, there has been a problem that the product defect rate increases due to missed times such as barrel renewal. Furthermore, the number of man-hours required for measurement, including the man-hours required for disassembly and cleaning, required about 2 hours for about 7 hours. As a result, there has been a problem that the machine operating rate is lowered and the production cost is increased in this respect as well.

The present invention solves the above-mentioned drawbacks of the prior art,
Provide a method for measuring the degree of abrasion of the inner surface of an extruder barrel that can obtain accurate measurement results by a simple method, yet enable timely maintenance and management of the barrel, reduce production costs, and improve product quality. The purpose is to

[0007]

The method of measuring the degree of wear of the inner surface of an extruder barrel according to the present invention is described in the following: "A measuring portion capable of contacting a probe of an ultrasonic thickness gauge is formed on the outer surface of the extruder barrel, and this measurement is performed. By setting a measurement point on the section, the thickness of the barrel at the measurement point at the time of non-wear of the barrel and at any time after the start of operation is measured with an ultrasonic thickness gauge, and the measured value at the time of non-wear and after the start of operation Is to obtain the deviation from that of
This achieves the above object.

As a result of various studies, the inventor of the present invention has to take a measure similar to so-called nondestructive inspection as a possible method for measuring the wear degree of the inner surface of the extruder barrel even while the extruder is in operation. Focusing on what is possible, X-ray,
Laser beam, ultrasonic wave, etc., and CT using these
(Computed tomography) and other technical means were tried. As a result, they have found that the use of ultrasonic waves is optimal as a method that is safe and economical in a manufacturing site, is easy to operate, and provides accurate measurement results.

By the way, even if the inner surface of the barrel is worn,
Normally, the inner surface of the twin-screw extruder rarely wears uniformly, and as shown in FIG. 3, the barrel B of the twin-screw extruder has two round holes a1 and a2 as described above, and a part of the round holes a1 and a2 overlap. A hole is formed. When the biaxial screws (not shown) each rotate outward, the pressures of the molten material at the portions where the flight parts mesh with each other cause the axial centers b1 and b2 of both screws to be directed obliquely outward at an elevation angle θ of about 30 °. Is slightly eccentric, and the top surface of the flight part is barrel B
Since the inner surfaces c1 and c2 are strongly pressed against each other, partial wear occurs.

Therefore, in order to measure the degree of wear of the barrel inner surfaces c1 and c2, it is not necessary to measure the entire inner surface of the barrel. In the example shown in FIG. 3, the inner surfaces c1 and c2 and the inclined surface having an elevation angle of 30 ° are used. It suffices to focus on the left and right sides of the intersections p1 and p2 with F1 and F2 as the center,
Conventionally, it has been measured and evaluated by this intensive measurement method.

In the method using the ultrasonic thickness gauge of the present invention,
As the measurement point, this method may be followed, and in consideration of such a fact, the measurement section in the present invention is, from the outer surface of the barrel, a plurality of places where the wear-prone portion of the barrel can be measured, It is selected and set up in one place.

[0012] By the way, as a means of using an ultrasonic thickness gauge, the present inventor initially, as shown in FIG. 3, in the case of the barrel inner surface c1, determines the shortest distance from the point to be measured to reach the screw axis b1. A thin female screw hole d1 having a connecting line as an axis is provided, and a pin e1 having a male screw having the same diameter as the tip portion of the probe f1 is screwed into the hole, and the probe f1 is attached to its head.
The method of contacting and measuring was attempted.

This method is convenient because the measuring points can be fixed and the measured values are fairly accurate, but the resin bites between the female screw hole d1 and the pin e1 during operation of the machine. In addition, it was found that they stayed and thermally decomposed, and it was found that this method could not be measured during the operation of the machine. Therefore, the measuring method of the present invention was devised, in which a measuring portion was formed on the outer surface of the barrel B and the probe was directly brought into contact with the measuring portion to perform measurement.

The ultrasonic thickness meter used in the present invention can achieve its purpose sufficiently by using a commercially available one. An ultrasonic thickness gauge usually has at least a probe incorporating a transmitter and a receiver, and a display, and the display converts the data from the receiver to immediately display the measurement result. be able to. Moreover, it is possible to measure only the wall thickness of the barrel regardless of the presence or absence of foreign matter on the inner surface of the barrel.
The depth can be measured regardless of the length of the barrel, and there is no individual difference in the measured value.

Therefore, if the thickness of the barrel when it is not worn, that is, when the barrel is new, is measured in advance, the deviation from the measured value at any time after the start of operation is determined, and the difference at that time is calculated. The degree of wear can be measured. Further, the size of the ultrasonic thickness gauge is excellent in handleability because the length of the probe is about 10 mm and the display unit is also the size of the palm. The measurement accuracy is usually about ± 0.03 mm for a thickness of 50.00 mm. Further, the number of man-hours required for measurement is 1 to 2 minutes for each measurement point, and even if there are many measurement points, one measurer is sufficient.

In the measuring unit according to the present invention, the center of the probe can be properly brought into contact with the measurement point, and the pulse transmitted and received from the probe accurately measures the wall thickness of the barrel which needs to be measured. It must be formed so that it can be formed. Therefore, the position of the measuring portion is first set on the actual outer surface of the barrel or on the drawing, and then the outer surface of the barrel is machined.

Since the wall thickness of the barrel is the shortest distance from the position to be measured to the inner surface of the barrel, for example, when the shape of the tip surface of the probe is flat, the outer peripheral surface of a normal extruder barrel is a curved surface. Therefore, if the probe is applied as it is, the contact angle of the tip surface changes each time, and the reflection point of the pulse cannot be specified.

Therefore, the probe has an area slightly larger than the tip surface of the probe, includes a measurement point therein, and intersects perpendicularly to a straight line which is the shortest distance from the measurement point to the inner surface of the barrel. The small plane is formed by cutting. This small plane is the measuring unit in the present invention. In this case, the measurement point is formed so as to be located substantially at the center of the measurement section.
In addition, it is preferable to mark a measuring point on this measuring portion.

In the ultrasonic thickness gauge, there is a slight difference in pulse speed due to the temperature difference between summer and winter, and the environmental temperature is 40 ° C. in summer and 5 ° C. in winter.
It will be ℃. Therefore, it is preferable that the adjustment value for each environmental temperature of the ultrasonic thickness gauge to be used is measured in advance, the environmental temperature is measured before the measurement, and the zero point is corrected at that temperature. The coefficient of thermal expansion of the barrel due to the temperature difference between summer and winter is about 1/100 mm, which is a measurement error range and can be ignored.

[0020]

According to the method of measuring the degree of wear of the inner surface of the extruder barrel of the present invention, the outer surface of the extruder barrel is provided with a measuring portion to which the probe of the ultrasonic thickness gauge can be brought into contact, and the measuring point is set to this measuring portion. Therefore, the probe can be properly brought into contact with the set measurement point. Moreover, since the measuring method using the ultrasonic thickness gauge is adopted in this manner, the measuring operation is simple and accurate.

Further, it goes without saying that the measurement can be performed while the extruder is in the assembled state, and the measurement can be performed while the extruder is in operation, so that the time of barrel renewal can be accurately grasped, and the number of times of measurement can be increased appropriately. However, since the number of man-hours required for measurement does not increase significantly, it is possible to grasp the precise wear condition with time.

[0022]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a view for explaining an example of a method for measuring the degree of wear of the inner surface of an extruder barrel according to the present invention.
Is a cross-sectional view showing a state in which a measuring portion is provided on the outer surface of the extruder barrel, and FIG. 8B is a partially cutaway front view showing only one half of the barrel as viewed from the direction of arrow B in FIG. Is.

In FIG. 1, B is a barrel in which round holes 1 and 2 and through-holes partially overlapped with each other are formed. 3 and 4 are the cores of the screws (not shown) and also the cores of the round holes 1 and 2, and are new ones manufactured for a twin-screw extruder having screws that rotate in mutually different directions. is there. The barrel B has a length of 2 m and is made of steel, and a nitride layer (not shown) having a thickness of 0.3 mm is formed on the inner surfaces 5 and 6 of the barrel B by a nitriding method in order to increase hardness. 7, 8 are screw shaft cores 3,
It is an inclined surface having an elevation angle of 30 ° from a plane passing through 4.

Reference numerals 9 and 10 denote flat measuring portions formed by cutting the outer surface of the barrel B, and are of a small circular probe 11 (one probe is omitted for convenience of description). It has a circular contact surface having an outer diameter larger by 0.1 mm than the outer diameter of the tip surface, and the centers thereof are the measurement points 12 and 13. The reason why the measuring units 9 and 10 are window-shaped when viewed from the front [see (b) in the figure] is that the lower half of the circular contact surface is directly cut down to facilitate cleaning. The actual measuring part is up to a circular part (a part shown by a dotted line in FIG. 6B) when it is hypothesized that the lower half is not cut.

Four measuring units 9 and 10 are provided at equal intervals on the left and right in the longitudinal direction of the outer surface of the barrel. The small planes of the measuring parts 9 and 10 are formed so that the lines connecting the shortest distances from the measuring points 12 and 13 to the inner surfaces 5 and 6 of the barrel (on the inclined surfaces 7 and 8) are orthogonal to each other. .

First, using the above-mentioned apparatus, a total of eight measurement points 12, 13 were measured by an ultrasonic thickness gauge before operation.
The wall thicknesses 14 and 15 of the barrels in Table 2 were measured, the values on the display (not shown) were recorded, and the continuous operation of the extruder was started. Although it may have stopped due to changes in product specifications, etc., the thickness of the barrels at the measuring points 12 and 13 was measured every 5,000 hours, with the total operating time of 5,000 hours as a turning point. Was measured, and the deviation from the thickness of the barrel before the above operation, that is, when the barrel was not worn was defined as the degree of wear. The measurement man-hours at one knot were 15 minutes / one on average.

The results are shown in FIG. In FIG. 2, the vertical axis represents the degree of wear of the barrel and the horizontal axis represents the operating time, and a graph showing the increasing tendency of the degree of wear with the elapse of the operating time is shown. A curve C1 from the 0th point to the time of reworking of the barrel and C2 after that point show the case of this embodiment, and curves C1 and C3 show the case of the conventional example. In addition, at the time of measurement, the measurement units 9 and 10
In the state where the probe 11 is applied to the upper semi-circular recess in the inside, the probe 11 is slid very slightly to obtain some measured values, and the thinnest dimension among them is the measured value. did.

Generally, the thickness of the nitride layer is 0.3 m as described above.
m, and when this layer is worn away and disappears, the curve C in FIG.
As shown in No. 3, it is known from the past results that the degree of wear sharply rises. Then, referring to the measured value at 15,000 hours and further measuring at 17,000 hours, it was confirmed that the measured value at each measurement point reached approximately 0.25 mm. Therefore, the same barrel was subjected to the nitriding treatment again, and then the operation was restarted. A curve C2 shows a tendency of increasing the degree of wear thereafter.

As a result, as a measure for knowing the life of the barrel, the degree of wear, which is a control limit value of the degree of wear of the barrel, is 0.6.
Originally, the operating time until reaching mm was 27,000 to 28,000 hours, but it was possible to operate up to 42,000 hours by performing the nitriding treatment again. Thus, in the case of the present embodiment, the operating time ΔT that could be extended by the improvement was recorded as 15,000 to 16,000 hours, and the extension of the barrel life could be achieved.

[0031]

EFFECT OF THE INVENTION The method for measuring the degree of wear of the inner surface of the extruder barrel of the present invention employs an ultrasonic thickness gauge to obtain accurate measurement results by a simple method, and to improve workability and speed of measurement.
Safety is improved. Further, since it is possible to predict the time for reworking or renewing the barrel, timely maintenance and management of the barrel can be performed, which does not lead to an increase in the defective rate of the product or a decrease in the operating rate of the extruder. It is possible to reduce production costs and improve product quality.

[Brief description of drawings]

FIG. 1 is a view for explaining an example of a method for measuring the degree of wear of the inner surface of an extruder barrel of the present invention, in which FIG. 1 (a) is a cross section showing a state in which a measuring portion is provided on the outer surface of the extruder barrel. It is a figure and the same figure (b) is a partially notched front view which shows only one half part of the barrel seen from the direction of the arrow (b) above.

FIG. 2 is a graph showing the degree of wear of a barrel based on the measurement result of the same method as that of the conventional example.

FIG. 3 is a cross-sectional view for explaining a conventional method of measuring the degree of wear of the inner surface of an extruder barrel.

[Explanation of symbols]

 B Barrel 3,4 Screw shaft axis 5,6 Barrel inner surface 7,8 Inclined surface with an elevation angle of 30 ° 9,10 Measuring part 11 Transducer 12,13 Measuring point 14,15 Barrel wall thickness

Claims (1)

[Claims] 1. An external surface of an extruder barrel is provided with a measuring portion to which a probe of an ultrasonic thickness gauge can be brought into contact, and a measuring point is set at this measuring portion, which is optional when the barrel is not worn and after starting operation. At the point of time, the thickness of the barrel at the measurement point is measured with an ultrasonic thickness gauge, and the deviation between the measured value during non-wear and that after the start of operation is determined, and the degree of wear of the inner surface of the extruder barrel is measured. Method.