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1、Mechanical Manufacturing TechnologyComposition of the clamping device and determination of the clamping force of the workpieceClamping device：After the workpiece is positioned on the positioning element,a certain device must be used to clamp the workpiece,so that it will not vibrate or displacement
2、in the processing process due to the cutting force,inertia or centrifugal force,etc.,so as to ensure processing quality and production safety.The fixtures used in machining must generally have clamping devices.When drilling small holes in large workpieces,the clamping device may not be designed sepa
3、rately.u 1、Composition and basic requirements of the clamping deviceComposition of the clamping device:p force source device p Intermediate transmission mechanism p clamping element Fig.1 Diagram of the composition of the clamping device1cylinder；2linkage；3pressure platep The clamping must not destr
4、oy the correct position in the workpiece holder.p The clamping force should be appropriate.p The clamping mechanism should be easy to operate,quick and labor-saving.p The structure should be compact and simple,with good structural craftsmanship,using standard parts as much as possible.u 1、Compositio
5、n and basic requirements of the clamping deviceBasic requirements of the clamping device:u 2、Determination of the clamping force(1)Determination of the direction of the clamping force The determination of clamping force is to determine the size,direction and action point of clamping force.1）The clam
6、ping force should be directed towards the main limit plane.A single clamping force shall be applied to the workpiece,or several clamping forces in the same direction at the same time,the direction of the clamping force shall be directed,as far as possible,towards the main limit surface.As shown in F
7、ig.2,the workpiece is bored with a perpendicularity requirement to the A-face,so when machining,the A-face is the main limiting surface and the direction of the clamping force Fj should be directed towards the A-face.If the clamping force is changed to face B,the clamping will disrupt the positionin
8、g of the workpiece and affect the required perpendicularity of the hole to the left end face due to the error of the clamping angle between the left end face and the ground.Fig.2 Diagram of the direction of the clamping force 2)The direction of action of the clamping force should correspond as much
9、as possible to the direction of action of the cutting force,gravity,etc.of the workpiece so as to reduce the clamping force.As shown in Fig.3.Of the three directional relationships of clamping force,cutting force and gravity,Figure a)requires the smallest clamping force and Figure c)requires the lar
10、gest clamping force.Fig.3Fig.4 Direction of clamping force in relation to workpiece rigidity 3)The direction of the clamping force should be such that the workpiece is deformed as little as possible.As shown in Fig.4,the direction of the clamping force should correspond to the direction of maximum w
11、orkpiece stiffness to reduce workpiece deformation.This should be particularly noted when clamping thin-walled workpieces.(a)unreasonable(b)reasonable(2)Determination of the point of action of the clamping force 1）The point of action of the clamping force should fall within the bearing range of the
12、positioning element.As shown in Fig.5,the point of action of the clamping force Fj falls outside the support range of the positioning element and will disrupt the positioning of the workpiece during clamping.Fig.5 Inaccurate location of the clamping forces point of action 2)The point of action of th
13、e clamping force should fall in the direction and part of the workpiece where the rigidity is good,a principle that is particularly important for workpieces with poor rigidity.As shown in Fig.6(a),the axial rigidity of the thin-walled sleeve is better than the radial rigidity,radial clamping with th
14、e jaw,the workpiece deformation is large,if the clamping force is applied along the axial,the deformation will be much smaller.The clamping force should not act on the top surface of the thin-walled box,as shown in Fig.b,but on the rigid convex edge of the box.If the box does not have a convex edge,
15、change the single point clamping to a three point clamping as shown in Fig.c to reduce clamping distortion of the workpiece.Fig.6 Relationship between clamping force point and clamping deformationFig.7 The point of action of the clamping force should be close to the machined surface 3)The point of a
16、ction of the clamping force should be as close as possible to the machined surface for a firm and reliable clamping.As shown in Fig.7.(3)Principles for determining the size of the clamping force The size of the clamping force can be calculated according to the cutting force,the size,direction and mutual position of the gravity of the workpiece.For safety reasons,the calculated clamping force should be multiplied by the safety factor K,so the actual clamping force is generally 2 to 3 times greater than the theoretical calculated value.Thanks for watching