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#076 Method of Using Standard Components (25) Stripper Guide - 4: Shapes and Features of Stripper Guide Bushes

Category : Die Design
April22, 2011

Stripper guide bushes can be divided into two types based on their external appearance. These are the type with a head (with a flange) and the straight type. Further, the changes in the sliding part are also included in the classification into types. In addition, as the method of assembly, there is the press fit insertion method and the adhesive fixing method. The adhesive fixing type can be further divided into the Loctite adhesive and the Devcon adhesive types. Devcon adhesive fixing has become considerably rare, and Loctite adhesive fixing has become the mainstream method. There are some difficulties with the press fit insertion method. When the degree of tightening in press fit insertion becomes large, distortion appears in the internal diameter of the bush after press fit insertion and can cause fusing, etc. On the other hand, the degree of tightening is made extremely small (light mating), and accuracy is increased by assembling with a force equivalent to that of pressing with the fingers. In this case, the machining of the hole becomes difficult.

The shapes and assembling methods of bushes are shown in Fig. 1 and Fig. 2.

Fig. 1

Fig. 2

In the press fit insertion type of the straight type, the guide diameter becomes distorted if the press fit insertion is made strongly, and the bush can easily get detached if the press fit insertion is made lightly, and hence their use is less frequent. In the adhesive fixing method, there are bushes in which a groove is formed on the outer periphery of the bush, thereby making it easier for the adhesive material to enter.

Fig. 3 shows the changes in the sliding part.

Fig. 3

The basic type is a plain guide with the raw surface of the bare material (bearing steel is used very frequently) is used as it is as the sliding surface. As a countermeasure for fusing, there are some types in which the sliding surface has been coated with a copper alloy.

The above is used with oil lubrication. When oil is not acceptable, a solid lubricant (molybdenum sulfide) is embedded in the sliding surface and the bush is used without any oil lubrication. This type wears out rather quickly compared to the oil lubricated type. The movement of the plain guide is rather sluggish (heavy), and since fusing can occur in such types of guides, there are types in which balls are placed between the post and the bush with the balls in rotating contact with the post and the bush. Although the movement becomes smooth and light, this becomes weak against eccentric loads. The container that supports the balls is called a retainer, and the retainer moved by about a half of the stroke (the part indicated by A in Fig. 3).

As has been described above, the combination conditions of bushes are many and although a bush is a part with a simple shape, one may find it difficult to make the selection.

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