Fixture design of tooling and accessories


Fixture design of tooling and accessories

The basic goal of using the equipment is to increase the production rate of the product parts, achieve better economic benefits, and ensure the safety and stability of the product parts and meet the technical requirements. Therefore, the design of equipment accessories is not only a technical problem, but also an economic problem. In the design of accessories, it is necessary to carry out necessary technical and economic analysis to make the designed accessories obtain better economic benefits.

Know the technical requirements of product parts

After taking over the design mission of the letter of acceptance, necessary raw materials shall be prepared to design the accessories, including the design drawings and drawings of film and technology requirements, process specification, processing equipment associated with the process and other information. After understanding the product parts, dimensional accuracy yamen, mode and other technical requirements, and looking for the key points of the parts and the basic structure of the important dimensions (the size must be guaranteed), the design of the parts is basically confirmed.

Some important parts design plans should be discussed and completely revised before affirmation. At the beginning and the end of this method, it is a better design and processing plan to ensure that the equipment design can meet the requirements of the production plan.

Position reference in positive attachment

With respect to each group of equipment, the size of key parts and important parts must be used as positioning pieces (design positions) in accessories, and the design (precision design) positioning of dreams must be confirmed to confirm the reference key positioning (first reference point). )And auxiliary positioning reference point (second reference point).

In principle, the first reference point must be the same as the design. If it can not be guaranteed, it is advisable to convert the design basis to process basis through calculation, but the design basis requirements must be guaranteed.

There must be two conditions for selecting a location reference:

The process reference should be selected as the positioning reference to complete the reference matching and reduce the positioning deviation;

Therefore, the average positioning datum should be selected not only to ensure the quality of components and improve the processing efficiency, but also to simplify the structure of accessories (usually using reference holes and positioning shafts).

For example, when designing fixture, the designer must first look at the design of positioning reference drawing from the beginning to the end of positioning reference, and then see that the processing of positioning reference is confirmed (still confirm the process specification). If the positioning reference point is general. If they are not all, the basic design becomes the reference point of the whole calculation process, but the requirements of the design reference point must be guaranteed.

When the designed components are positioned, the basic technical requirements are: good precision, good wear resistance, sufficient strength and rigidity, good processing strength, simple disassembly and other characteristics. For example, the selection of the positioning part of the welding device used for assembling components must be in the positioning mode of the positioning pin according to the requirements; there must be a certain space between the positioning pin and the reference hole of the workpiece, and the size depends on the accuracy of the hole of the workpiece, and it cannot be artificial. The locating pin is fastened by yamen service pin, while the locating pin of 45 × steel and alloy steel Cr12 must have sufficient strength and rigidity through quenching, tempering and heat treatment cooling to improve wear resistance and prolong service life

Structure design of equipment and design of 2-3 parts

Once these parts are placed in the equipment, they are usually fastened so that the parts remain in the process of being processed without being damaged. In the process of machining, workpiece will occur, displacement deformation and vibration, which will affect the machining quality of workpiece.

Therefore, the fastening of parts is also a very important problem to ensure the machining accuracy. In order to achieve good machining efficiency, it is necessary to control the displacement and vibration of parts in machining time within the boundary of machining accuracy. As a result, the handling of the fastening problem of accessories is sometimes more troublesome than the positioning design, and the problem should not be ignored.

Design and affirmation of clamping organization

After the selected connection point is confirmed, the clamping force is designed, the clamping organization is determined and the force exerted by the specific organization is maintained. In general, the clamp system is composed of, power supply and transmission mechanism.

The clamping structure refers to a perfect structure that can implement the clamping of the parts selected at the maintenance point to confirm the performance of the clamping force, and the key point includes that the force applied is a plate, pressure and structure related to the component.

The use mechanism of clamping force can select floating structure and self-locking link,,, with the following four modes:

The fastening structure of bolt and nut: simple structure, simple manufacturing, clamping line width, good self-locking performance, has been used in ordinary;

Application organization of skew force: applicable to large clamping force and small stroke, mainly based on pneumatic and hydraulic power;

Eccentric force application organization: simple structure, fast behavior, but small pressure, mainly used for small parts of accessories;

Push button organization: simple structure, large force ratio, used in pneumatic fixture, reduce the strength of cylinder or air chamber, and get ordinary use.

Careful economy and joint cooperation of parts

The key goal of using accessories is to ensure the quality of works. In detail, when using accessories, ensure the accuracy of dimension (form) and position accuracy of components. Machining deviation of parts completely reflects the deviation of process system, and accessory deviation is the key deviation component of machining deviation. Equipment error is divided into two parts: static error and dynamic error, in which static error represents an important proportion.

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