Classification and definition of the hottest clamp

2022-08-13
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Classification and definition of clamping features

I. Introduction

clamping features are the features of workpiece shape elements (shape elements) used for positioning or clamping on the workpiece. On the one hand, the shape element characteristics of the workpiece are diverse, so it is necessary to clarify the shape element characteristics of the workpiece required for clamping design in fixture design. The tensile testing machine involved in this paper is a type of experimental equipment used to test the reliability of various conductors and connectors used in the project in power transmission and transformation construction. On the other hand, the clamping characteristics are the analysis object and design object for decision-making in clamping planning and structural design. In short, the classification and definition of clamping features is the basis of fixture design, and it is also one of the basic factors that determine the richness of fixture design methods and methods

clamping feature is the feature of workpiece solid morpheme with clamping meaning, which has general feature attributes such as shape, size parameters, position, direction and accuracy, as well as clamping attributes different from general morpheme feature attributes such as accessibility and accuracy grade

up to now, there is little systematic classification and definition of clamping features and related research, but this is an urgent need for the development and development of Computer-Aided Fixture design system

II. Classification and definition of clamping features

clamping features are represented by positioning features and clamping features. The purpose of its definition is to clarify the surface type of workpiece used for clamping, provide the feature range of operation object for clamping planning, and serve as the feature basis of fixture structure design

in fixture design, the main analysis and processing object is the feature surface on the workpiece feature model. Obviously, the main form of clamping feature is clamping feature surface. Although the geometry of the workpiece may be very complex, in the practical application of the fixture, the workpiece surface used for clamping in most cases is no more than three types: plane, outer cylindrical surface and inner cylindrical surface (i.e. hole). This is mainly because these three types of surfaces have good contact and fit performance, and are easy to process and measure. In this system, the clamping features mainly use these three surface types

for the needs of fixture design, the clamping feature is further divided into clamping feature surface and clamping feature point. The clamping feature point is attached to the clamping feature surface, which is used to clarify the specific orientation of the fixture functional elements when they contact or cooperate on the clamping feature surface

the clamping feature has typical directionality and contains the significance of clamping. Therefore, it is generally classified and defined as follows in terms of surface type, direction and clamping mode

1 clamping characteristics of plane type

in the workpiece solid model, the direction characteristics of the plane are represented by its normal vector v. the clamping characteristics of the plane type are defined as follows. The illustration of its legend is shown in Figure 1, where va=-z, vb=z, vc^z, vd^z, ve^z, and the workpiece coordinate system is represented by x-y-z

Fig. 1 plane type clamping feature

bottom positioning surface: v=-z plane surface of the workpiece for positioning, such as bottom plane a in Fig. 1

side positioning surface: the plane surface of the workpiece used for positioning v^z, such as surfaces C, D and E in Figure 1

side clamping surface: the plane surface of the workpiece used for clamping v^z, such as surfaces C, D and E in Figure 1

top clamping surface: the plane surface of the workpiece used for clamping with v=z, such as top plane B in Figure 1

the position where the clamping feature surface of plane type contacts the clamping of fixture functional elements can be described clearly by only one clamping feature point on the surface. For the convenience of narration, this clamping contact mode is referred to as one point clamping for short

2 clamping characteristics of cylindrical surface type

the contact area between cylindrical surface and fixture functional elements is a section of its surface busbar, so its direction characteristics generally have two: cylindrical axis direction VA, radial normal direction VR of busbar

in the clamping use, the cylindrical surface has two typical contact modes with the fixture functional elements. One is to contact the positioning or clamping elements on a surface bus, which belongs to the case of one point clamping; The other is that at the same time with the clamping element, two non repeated moisture absorption and drying will produce enough shortcomings to offset the advantage of weak fiber matrix bonding to contact with the bus (such as using V-shaped blocks), which is called two-point clamping. For the case of one point clamping, the clamping feature point is taken on the generatrix of the cylindrical surface, which is an actual shape point; In the case of two-point clamping, the clamping feature point is taken as the intersection of the axial symmetry plane of the V-shaped block and the axis line of the cylinder, which is a virtual shape point, as shown in point P5 in Figure 2C and point P2 in Figure 3C. In this way, the contact mode with the fixture functional elements can be clearly reflected through the position state of the clamping feature points

Figure 2 clamping characteristics of horizontal cylindrical surface type

Figure 3 clamping characteristics of vertical cylindrical surface type

according to the axis direction VA, the cylindrical surface is divided into two clamping available states: when va^z, it is called horizontal cylindrical surface (as shown in Figure 2a); When VA ‖ Z, it is called the vertical cylindrical surface (as shown in Figure 3a)

when the horizontal cylindrical surface is clamped at one point, only four surface busbars can be used as clamping features, which are defined as follows:

· top clamping: horizontal cylindrical surface busbars for clamping with vr=z, as shown in P1 in Figure 2B

· side positioning: the horizontal outer cylindrical surface busbar for positioning of vr^z, as shown in P2 and P4 points in Figure 2B

· side clamping: horizontal outer cylindrical surface busbar for clamping of vr^z, as shown in P2 and P4 points in Figure 2B

· bottom positioning: horizontal outer cylindrical surface busbar for positioning with vr=z, as shown in point P3 in Figure 2B

when the horizontal cylindrical surface is used for two-point clamping, it is defined as the positioning of the horizontal cylindrical surface, and the available area is its lower half surface, that is, vr=-z, as shown in point P5 in Figure 2C

when the vertical outer cylindrical surface is clamped at one point, the circumferential surface generatrix can be used as clamping features, which are defined as: positioning on the side of the vertical outer cylindrical surface and clamping on the side of the vertical outer cylindrical surface, as shown in point P1 in Figure 3B

the case that the vertical cylindrical surface is used for two-point clamping is defined as the positioning of the vertical cylindrical surface or the clamping of the vertical cylindrical surface, and the surfaces of all parts may be used for this clamping feature, as shown in point P2 in Figure 3C

the cylindrical surface is used for clamping. The feature can be the whole cylindrical surface, or a section or part of the cylindrical surface

3. The clamping feature of the inner cylindrical surface type

the inner cylindrical surface, that is, the hole, is mainly used for positioning. Its feature direction is generally represented by the direction of its axis, VA, which points opposite to the contact feature direction of the corresponding fixture functional elements. The clamping features of this type are divided into the following two categories:

· vertical positioning hole: the inner cylindrical surface used for positioning of VA ‖ Z, as shown in Figure 4a

· horizontal positioning hole: the inner cylindrical surface for positioning of va^z, as shown in Figure 4B

Figure 4 clamping characteristics of inner cylindrical surface type

4 Other non basic clamping features

edge positioning: edge positioning is actually a combined clamping form in which the side positioning surface and the bottom positioning surface are used together for specific positioning elements (such as angular support). This clamping form takes the intersection of its two positioning surfaces as the representation of clamping features, so it is called edge positioning, as shown in Figure 5

Figure 5 edge positioning

edge positioning is not considered by clamping planning like the basic clamping features introduced above, but as the result of selecting fixture meta transformation experience pieces according to the actual situation in the structural design. However, in the state of human interaction design, the user can directly define the clamping feature on the workpiece feature module as a whole

special positioning surface and special clamping surface are clamping features in the user-defined category, which are mainly used to define other special morphemes or combinations of several morphemes on the workpiece entity to hook with specific fixture components. Thus, it provides an interface for the special fixture equipment, and also ensures that the fixture elements, component types and clamping methods have the ability to expand according to the user's mode. Special clamping has obvious specificity, which will not be discussed in this paper

III. summary

the classification and definition of clamping features is the basic work of fixture design. Once the universal workpiece geometric surface is defined as clamping features, it has a clear clamping meaning. In this paper, various workpiece clamping features are systematically classified and defined, and the surface types of workpiece used for clamping are defined as the feature basis of fixture structure design. (end)

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