JPS628228B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating coating method for welding rods, and in particular, to a method for coating welding rods with a coating material, and in particular, to reduce variations in coating diameter that occur during the process of manufacturing coated welding rods by continuously applying coating coatings to welding rod core wires. This relates to a method devised so that it can be automatically controlled using a simple mechanism.

The method shown in FIG. 1, for example, is currently the most widely used method for manufacturing coated welding rods by applying a coating material to the outer periphery of a welding rod core wire. That is, a coating material feeding cylinder 2 is connected to the die block 1, and a nipple 3 for guiding the core wire is arranged therein.
A coating cake 4 that has been pressure-formed (usually formed into a cylindrical shape) to a shape and size equivalent to the inner diameter of the nipple 3 is continuously press-fitted by a piston 6 connected to a hydraulic cylinder 5, etc. The welding rod core wire 7 is discharged at a high speed, and in the process of passing through the die 8, the core wire 7
A coated welding rod 9 is manufactured by coating the outer circumference of the rod with a coating material 4. At this time, the coating diameter is determined by the inner diameter of the die 8. In such a coating method, for example, a plurality of devices for forming the coating cake 4 are installed in parallel,
By inserting the coating cake into the cylinder 2 one after another, coated welding rods 9 can be manufactured continuously. In such a coating method, by keeping the feeding pressure by the piston 6 and the feeding speed of the core wire 7 constant, it is considered that the coating diameter can be kept substantially constant. However, the present inventors have confirmed empirically that defective coatings occur periodically during the coating process, and most of these defective products have coating diameters that are too large and fall outside the specifications. When we observed the occurrence of defective products in more detail, we found that the frequency of defective product occurrence changed in accordance with the size of the coating cake 4, and that the boundary between the continuously fed coating cakes 4 It was confirmed that this occurs when reaching point 8. That is, FIG. 2 is a graph showing the relationship between coating time and coating diameter corresponding to FIG. be. However, the coating diameter increases rapidly before and after the boundary A between the coating cake 4a remaining in the die block 1 and the newly supplied coating cake 4b reaches the die 8, and the coating diameter increases beyond the specified coating diameter tolerance. If the product falls outside range B (Fig. 2), it will appear as a defective paint product.
There are various possible causes for this phenomenon, but
The biggest reason is thought to be that air tends to get mixed into the boundary A, and after passing through the die 8, the air is released from the pressure and expands rapidly, causing the coating layer to expand. Therefore, painting workers strictly inspect the coating diameter using a micrometer or the like, especially for the area to be painted, and remove non-standard defective products from the line. However, when a large number of products are manufactured in a short period of time, such as in the manufacture of the above-mentioned coated welding rods, the sorting work is extremely complicated and requires a great deal of labor.
Furthermore, the decrease in production efficiency and productivity due to the decrease in yield cannot be ignored.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to prevent the occurrence of defective coatings as much as possible by simple operations in the manufacturing process of coated welding rods as shown in Figure 1. The objective is to develop a method that can improve yield while reducing the labor burden on painting workers.

The structure of the coating method of the present invention that achieves the above purpose is, for example, when coating the welding rod core wire with the coating material formed into a cake shape as shown in Fig. 1, the inside of the cylinder is The time when the boundary surface of the coating cake that is successively inserted into the die reaches the die is determined by the forming conditions of the coating cake (shape, size, density, etc. of the coating cake) and the operating conditions of the coating machine (the pressing force of the piston, the The amount of coating material applied to the core wire is automatically controlled when the boundary surface reaches the die, so that the coating diameter of the welding rod is uniform. The purpose is to control the

In the present invention, the cycle at which the boundary portion A comes to the die 8 portion, that is, the coating diameter varies (C in Fig. 2).
Area) This method utilizes the fact that the period T is determined depending on the size of the coating cake 4, and detects the timing when the refilling position (boundary part A) is in the 8th part of the die by using a timer or other means. . This detection is performed by determining the fluctuation period T determined by the size of the coating cake 4 in advance by experiment or calculation.
It is desirable to detect it automatically using a timer or the like. That is, as mentioned above, the occurrence period T of the coating diameter variation region C is determined by the size of the coating cake 4, and as long as coating material cakes 4 of the same size are used, the occurrence period T of the variation region C will be Always constant.
Therefore, if the period T of occurrence of the fluctuation region C is measured in advance when using the coating material cake 4 of a constant size, abnormalities in the coating diameter can be detected accurately without having to measure the coating diameter of the coated welding rod 9. can be grasped.
Therefore, in the present invention, if the amount of coating material 4 applied to the welding rod core wire 7 is controlled at intervals set by a timer or the like, abnormal increases in the coating diameter can be prevented as much as possible, and the coating diameter can be reduced. It can always be maintained within the specified tolerance range B. From the same point of view, when using a relatively long and large coating cake to complete one coating job with one extrusion, the previous cylinder 2
It is also possible to control the amount of application by predicting when the remaining cake 4a and the added cake 4b will reach the die at the boundary. Various specific means can be considered for controlling the amount of coating material 4 applied, but as confirmed by the inventors through experiments,
A method of controlling the feed pressure of a piston 6 that presses and feeds a coating cake 4 and controlling the amount of coating material discharged from a die 8, or a welding rod core wire 7 fed through a nipple 3. The simplest and most efficient method was to increase the feeding speed and relatively reduce the amount of coating material applied, or to combine the above methods. In other words, if the above-mentioned method is adopted, the operating pressure (hydraulic pressure, etc.) of the piston 5 and/or the feeding speed of the core wire feeding roller can be set to be changed in conjunction with the cycle time setting by a timer or the like. The device and mechanism are simple, and the amount of coating material to be applied can be controlled accurately.

As is clear from the example in Fig. 2, in the coating diameter variation region C, the coating diameter increases gradually at first, and the boundary A reaches the boundary when it is discharged from the die 8 (the part where the amount of entrained air is the largest). The coating diameter gradually decreases and returns to the steady coating diameter. Therefore, from the standpoint of maintaining the coating diameter as uniform as possible, the coating amount should be gradually reduced in the first half of the process of controlling the piston operating pressure and/or the core wire feeding speed, and the coating amount should be reduced in the second half. It is most advantageous to make the change gradually so that it increases gradually. However, as long as the coating diameter is at least within the allowable range of the standard (area B), there is no problem in practical use. Of course, it is also effective to maintain the coating diameter within the tolerance range B as shown by the chain line in the figure.

As is clear from the above description, the coating cake 4 used in the present invention should have a constant size and density as much as possible, thereby keeping the period T of occurrence of the coating diameter variation region C always constant. Therefore, time setting and coating amount control using a timer are extremely simplified. However, in cases where two or more types of coating cakes molded by two or more types of coating cake forming devices installed in parallel are fed alternately, the size and density of each coating cake may be different. It will be done.
In such a case, the period of occurrence of the fluctuation region will naturally change alternately depending on the coating material cake that is alternately fed, so by setting the timer at two points according to each period, the fluctuation region can be accurately predicted. In addition, the coating amount is controlled accordingly.

The present invention is roughly constructed as described above, and as shown below, it is possible to enjoy various benefits that cannot be obtained with conventional examples.

Since there are almost no defective products due to coating diameter abnormalities and the yield is extremely high, production losses are drastically reduced. In particular, the present invention employs a method of predicting and controlling the period in advance according to the period of abnormality occurrence, rather than detecting the abnormality of the coating diameter by post-inspection, so that almost no defective products are produced.

There is no need to directly measure the coating diameter abnormality, and it can be automatically controlled using a timer and a coating amount control mechanism, reducing the labor burden on painting workers. Moreover, productivity can be greatly improved.

The device used in the present invention performs its functions only by a timer for setting the abnormal area occurrence period determined by the size and density of the coating cake and a coating amount control device linked to the timer. Therefore, the device and operation are simple. By the way, as an automatic control mechanism to keep the coating diameter constant, an automatic control device with an automatic coating diameter measurement device, a comparison device with the standard coating diameter, a calculation device, a coating amount control device, etc. attached to the rear of the die can be considered. However, the apparatus and mechanism become extremely complicated, and the entire coating apparatus inevitably becomes complicated and expensive. Moreover, in this type of automatic control device, the control mechanism is constantly operating even in a steady state where coating diameter abnormalities hardly occur, which is wasteful, and in any case, the mechanism is designed to detect abnormalities after the fact.
It is not possible to eliminate all defective products. However, in the present invention, the device and mechanism are simple and can be manufactured at extremely low cost, there is no waste because it operates only in the area where an abnormality occurs, and the method detects and controls abnormal areas in advance, so there are no defective products. can do.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view illustrating a coating method using a coating cake, and FIG. 2 is a graph showing the relationship between coating time and coating diameter. 1...Dive block, 2...Cylinder, 3...
Nipple, 4... Coating material cake, 5... Hydraulic cylinder, 6... Piston, 7... Welding rod guide wire, 8
...Dice, 9...Coated welding rod.

Claims (1)

[Scope of Claims] 1. A plurality of coating material cakes, which have been previously formed to have an outer diameter approximately equal to the inner diameter of the cylinder, are successively packed into the cylinder in the axial direction of the cylinder, and the coating material is fed out from a nipple. In the method of extruding the welding rod core wire through a die and coating the welding rod core wire with a coating material, it is the interface between the rearmost end of the previously inserted coating cake and the leading edge of the next inserted coating cake. The time required for the coating agent refilling position to reach the vicinity of the die is predicted based on the forming conditions of the coating cake and the operating conditions of the coating machine, and when the predicted time is reached, the coating agent is applied to the core wire. A method for coating a welding rod with a coating agent, which is characterized by controlling the amount of coating agent and controlling the coating diameter of the welding rod to be uniform. 2. The method according to claim 1, wherein the amount of coating agent applied to the welding rod core wire is controlled by changing the discharge pressure of the coating agent cake. 3. The method according to claim 1, wherein the amount of coating agent applied to the welding rod core wire is controlled by changing the feeding speed of the core wire fed out from the nipple.