aluminum foil strip


How to deburr the edge of transformer winding aluminum foil?

Source:Original Editing:frank Time:2022-08-02 18:20
Transformer winding aluminum foil is a kind of aluminum strip produced with the application of dry-type transformer. The transformer winding with aluminum strip instead of aluminum wire has the characteristics of small volume, small loss, high short-circuit strength, good heat dissipation performance, easy welding and winding efficiency, convenient daily maintenance and so on. It is a new technology and product emerging in the 1970s abroad, and has been widely used in power transmission and distribution projects. In today's industrialized countries, almost all the low-voltage coils of distribution transformers use aluminum foil winding.
Transformer winding aluminum foil requires large volume, high precision, good surface quality, and no stain, oxidation, oil film or defect on the surface; The copper strip should be packed with lining paper, which is several millimeters wider than aluminum to protect the edge; There is no tower in coiling.

Transformer aluminum foil has strict requirements on the edge burr and edge shape of the strip. The theoretical cross section of the strip shall be rectangular. However, the actual shape of the strip after longitudinal cutting is not an ideal rectangle, but a more complex shape. There is a depression area near the edge of the upper surface of the strip because the cutting pressure exceeds the yield strength of the strip; The upper part of the cutting surface is a smooth shear zone; In the lower part of the cutting surface, there is a rough tearing area formed by the cutting pressure exceeding the tensile strength of the remaining material, and under the edge of the strip is the burr generated in the tearing process of the strip. In view of the fact that the transformer aluminum strip is used to wind the transformer, it is necessary to prevent burrs from piercing the insulation layer and avoiding the discharge of the tip of the burrs. Therefore, the production of transformer aluminum strip must be subject to edge treatment, removing the cutting burrs and trimming to a certain shape.
At present, the edge shapes of transformer aluminum strip in market demand mainly include the following:
1) Deburring
For copper strips with a thickness less than 0.3, it is usually required to remove only the burrs formed in the shearing process. Do not puncture the insulation layer, and avoid the discharge of the burr tip.
2) Chamfer
Some transformer manufacturers in the Americas require an inclined angle of about 12 degrees with the surface of the aluminum strip to be repaired at the edge of the strip.
3) Rounding
Most customers require that the edges of the transformer aluminum strip be trimmed into relatively rounded corners
4) Full circle
With the increasingly extensive application of transformer aluminum strip, the increasing number of transformer aluminum strip manufacturers, the increasingly perfect aluminum strip trimming technology, and the increasingly strict requirements for the trimming of transformer aluminum strip edges. In recent years, many customers require the deburring the edge of transformer winding foil into full round edges.

How to deburr the edge of transformer winding aluminum foil
The easiest thing to think of is edging. Edging is to press the burr part of the strip edge into the strip body with a vertical roll of a certain shape. Edging not only has low operation cost, but also does not remove materials, which can improve the yield compared with cutting removal method. However, in application, it is found that although the burr of the strip is pressed into the body after edging, the burr pressed may separate and stretch out during the winding process of the transformer, resulting in discharge and insulation damage of the transformer. Due to the possible disastrous consequences, the edge trimming of transformer aluminum strip cannot be carried out by vertical roll edging.
Another economical trimming method is grinding, which uses grinding wheel or abrasive belt to polish the edges of the strip and remove the burrs. At present, there are still some manufacturers that let employees carry out simple manual grinding of transformer aluminum strip. However, the aluminum strip of transformer is soft and easy to adhere, and the sharp blockage and passivation of the grinding wheel often occur. Therefore, the grinding wheel grinding is not suitable for the edge trimming of the aluminum strip of transformer, especially for the mechanized operation on the production line.
Mechanical cutting is a more suitable method for trimming the edges of transformer aluminum strip, which is also adopted by the majority of transformer aluminum strip manufacturers. With the increase of customers' requirements for full round edges, modern transformer aluminum strip trimming unit should be able to trim the full round edges. Of course, all equipment that can trim the full round edges can also fully realize the above trimming of edge shapes such as deburring, beveling and fillet. Envelope method and forming tool method can be used for mechanical cutting of full round edges. The forming tool method is to use one or several cutters with a certain shape notch to put on the edge of the running strip and cut the edge of the strip into the corresponding shape.
The envelope method uses straight cutting tools. The cutting edges of several straight cutting tools are arranged on the edge of the strip according to a certain angle. The strip moves forward, and each knife removes the material of the corresponding part of the strip edge in turn to form a full round edge shape. A large amount of cutting heat will be generated in the cutting process of the strip, and some of the heat will be taken away by the scrap, but some of the heat will still accumulate on the tool and strip, causing the temperature to rise. If it is not controlled, it will sometimes cause the change of the strip structure. Therefore, the cutting part should be equipped with a cooling and lubrication device to cool and lubricate the tool and strip. The choice of coolant should not pollute the strip as much as possible. It should also be noted that in the process of trimming the edges of the strip, all measures should be taken to maintain the stability of the strip, and the stable operation of the strip is the premise to ensure the trimming quality. Therefore, the corresponding strip guide rollers should be configured at the cutting position of each group of tools, including not only surface guide, but also side guide and vertical guide.