Market positioning principle

What are the functions and principles of market positioning?

Correct selection of positioning datum is the key to formulate machining process regulations and design fixtures. undoubted

Bit datum is divided into fine datum and coarse datum. In the initial operation, only the blank list that has not been added can be selected.

This surface is used as a positioning datum and is called a coarse datum. Positioning reference scale of machined surface.

This is a good benchmark. In the process of designing process planning, we should first select fine datum, and then select coarse datum according to the working drawing of the parts.

Benchmark. The whole process should be considered in a unified way, and the first process should create conditions for the subsequent processes.

Five principles should be mastered in selecting fine datum: (1) the datum coincidence principle takes the design datum as the positioning datum to avoid datum dislocation error. When machining parts by adjustment method, if datum dislocation occurs, datum dislocation error will occur. The so-called adjustment method is to adjust the relative position between the tool and the machine tool in advance and add a number of parts.

A machining method that maintains this relative position during work. Corresponding to this is the trial cutting method, that is, trial cutting, measurement, adjustment, re-cutting, and cycling until the parts meet the size requirements. attempt

Cutting method is suitable for processing parts one by one in small batch production. So please think about it and try to cut it.

If the benchmarks do not coincide, will it cause benchmark dislocation error? Why? (2) Unified Datum Principle Select a unified positioning datum to process each machining surface on the workpiece. To avoid data conversion.

These errors will help to ensure the position accuracy of each surface, simplify the technological process and reduce the design and manufacture of fixtures.

The production lead time is short. The typical principles of datum unification are shaft parts, disc parts and box parts. Accurate datum of shaft

It is the central hole at both ends of the shaft, and the gear is a typical disc-shaped part, which is often finished with a central hole and an end face.

Benchmark, and boxes often take a plane and two positioning process holes on the plane as the precise benchmark. (3) Principle of Self-reliance When some finishing surfaces require a small and uniform machining allowance, the machining surface itself can be selected.

So as to locate the datum and improve the precision and surface quality of the machined surface itself. (4) The principle of cross-reference can improve the mutual position accuracy between important surfaces, or make the machining allowance small and uniform. (5) The principle of ensuring accurate workpiece positioning, safe and reliable clamping, convenient operation and labor saving.

The choice of rough datum is to ensure the uniform allowance of an important machined surface, and this surface is chosen as the rough datum. In order to ensure the mutual position and size requirements between the machined surface and the non-machined surface on the workpiece

Choose the raw surface as a rough benchmark. Only one coarse datum is allowed in the same direction. Ensure accurate positioning, reliable clamping, simple fixture and convenient operation. Among the four principles, the rough benchmark is

The principle of "only one use in the same direction" must be achieved. but

The remaining principles are implemented conditionally.