Automotive Fixture Accuracy And Positioning Principle

- May 28, 2018-

The first point of the positioning pin position accuracy is ± 0.25mm, processing accuracy is -0.05mm;

The second point is that the measuring point tolerance of the fixture reference plane to all fixtures is ±0.25mm.

The third point The tolerance between the positioning hole and the positioning hole on the horizontal plane is ±0.05mm and the roughness is 1.6um.

The fourth point of all positioning holes and reference plane tolerance is ± 0.05mm, roughness is 1.6um.

Fifth point The accuracy between the reference planes is ±0.1mm, and the accuracy between measurement planes is ±0.2mm.

The sixth point of reversal mechanism repeatability accuracy is ± 0.2 (Φ200);

The seventh point uses the three-dimensional detection fixture manufacturing accuracy, and fills the detection record into the equipment detection record.

Firstly, first select the same positioning point as the design reference. The positioning holes used for the positioning pins must have corresponding accuracy requirements, and must be both the stamping reference and the reference for inspection and inspection to ensure the design basis of the welding assembly. The unity of the product's design benchmarks reduces design errors and facilitates the analysis of error causes.

Second, fixtures with logical relationships between the upper and lower processes must be unified in the upper and lower processes during the design and must be unified with the positioning criteria of the mold and the gage.

Third, as far as possible to avoid the enhanced pit or complex changes in the area of the surface, in order to avoid instability of the welding products from the stability of the stamping itself.

Fourth, in order to ensure the use of safety, when the fixture is in the clamped state, it should be able to self-locking; clamp open should limit, the opening angle should not be too large, generally less than 135o, with the exception of special circumstances.

Fifth, when the clamping surface of the chuck has a slope, a limiting block must be installed at the chuck arm.

Sixth, when the chuck is positioned and welded, under the condition of the positioning pin and the inclined pressure surface, it is necessary to consider the installation of the process positioning block at the chuck arm. After the positioning is accurate, the welding will not be guaranteed. Precise positioning (in the case of flat clamping, no positioning block is allowed).

Seventh, the manual chuck clamping force is generally ≥50Kg.f (referring to the center of the application point).

Eighth, the length of the manual operation handle should be suitable, and the position of the handle when the clamp is opened should be above the horizontal plane.

The ninth, the fixture operation has a sequence of priority should be marked on the handle.

Tenth, all the support positioning points, in the case of effective compression, must ensure that the workpiece positioning is full and reliable, the workpiece does not deform, does not move.

Its eleventh, clamping should not damage the surface quality of the workpiece. When clamping thin-walled stampings, measures should be taken to limit the clamping force, increase the contact area of the chuck, and increase the copper-aluminum gasket.

Twelfth, when the collet has a positioning pin or there is no supporting point at the collet pressing position, the limited position block must be installed at the collet arm.

The thirteenth, in the welding area far from the positioning clamp point, should increase the auxiliary support clamping point, in order to reduce the unqualified finished product caused by welding deformation.

In the fourteenth, the supporting clamping point near the welding point must have sufficient welding passages for the welding tongs or the welding torch in the design. For arc welding equipment, corresponding anti-splash devices must be designed to protect the support clamping profile and extend the service life of the welding fixture.

The fifteenth, the force point of the fixture should be at the support of the workpiece, the positioning point is located close to the support, to prevent the support reaction force and clamping force, supporting reaction force and the force formed by gravity, leading to deformation of the workpiece.

Sixteenth, when the inclined surface is pressed tightly, it is necessary to install a clearance adjustment piece in two component directions; when the plane is pressed, a clearance adjustment piece must be installed below the vertical surface.

Seventeenth, the diameter of the positioning pin penetrates the upper surface of the workpiece by 3 to 5 mm. For positioning two reference pins of a workpiece, one pin is used in principle and one is a diamond pin.

18. The positioning block on the outer surface of the positioning component is made of nylon or polyurethane material to prevent damage to the surface of the workpiece.


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