The design fixtures is generally in the development of the machining process of parts in accordance with the specific requirements of a process. Formulation of the process, should give full consideration to the realization of the possibility of fixtures, and the design of jigs and fixtures, if necessary, can also be proposed to modify the process.
Tooling fixture design quality should be stable to ensure that the quality of workpiece processing, high productivity, low cost, convenient chip removal, safe operation, labor-saving and manufacturing, maintenance and so on for its measurement index.
First, the basic principles of fixture design
1, to meet the use of the process of workpiece positioning stability and reliability
2, there are enough bearing or clamping strength to ensure that the workpiece in the fixture for the machining process
3, to meet the clamping process is simple and fast operation
4、Fragile parts must be able to quickly replace the structure, the conditions are sufficient when the best not to use other tools to carry out
5, to meet the fixture in the process of adjustment or replacement of the reliability of repeated positioning
6, as far as possible to avoid the structure of complex, expensive cost
7, as far as possible to use standard parts as components
8, the formation of the company's internal product systemization and standardization
Second, the basic knowledge of tooling fixture design
An excellent machine tool fixture must meet the following basic requirements:
1, to ensure the machining accuracy of the workpiece to ensure the key to machining accuracy, first of all, correctly selected positioning reference, positioning methods and positioning elements, if necessary, positioning error analysis, but also pay attention to the structure of other parts in the fixture on the impact of machining accuracy, to ensure that the fixture to meet the requirements of the workpiece machining accuracy.
2, improve production efficiency of the complexity of special fixtures should be adapted to the capacity of the situation, should try to use a variety of fast and efficient clamping mechanism to ensure easy operation, shorten the auxiliary time, improve productivity.
3, good process performance special fixture structure should strive to be simple, reasonable, easy to manufacture, assembly, adjustment, inspection, maintenance and so on.
4, the use of good performance jigs and fixtures should have sufficient strength and rigidity, the operation should be simple, labor-saving, safe and reliable. In the objective conditions allow and affordable premise, should be used as far as possible pneumatic, hydraulic and other mechanized clamping devices to reduce the operator's labor intensity. Tooling fixture should also be convenient chip removal. If necessary, chip removal structure can be set up to prevent chips from destroying the positioning of the workpiece and damage to the tool, to prevent the accumulation of chips to bring a lot of heat and cause deformation of the process system.
5, economic good special fixture should be used as far as possible standard components and standard structure, and strive to simple structure, easy to manufacture, in order to reduce the manufacturing cost of fixtures. Therefore, the design should be based on the order and production capacity of the fixture program to carry out the necessary technical and economic analysis, in order to improve the fixture in the production of economic efficiency.
Third, the standardization of tooling fixture design overview
1, the basic methods and steps of tooling fixture design
Preparation before the design of tooling fixture design of the original data include the following:
a) design notification form, finished parts drawings, blank drawings and process routes and other technical information, to understand the processing requirements of each process, positioning and clamping program, the processing of the previous process, the blank situation, the processing of machine tools, cutting tools, inspection gauges, machining allowances and cutting amounts, etc.
b) understand the production batch and the need for fixtures and fittings
c) to understand the main technical parameters of the machine tool used, performance, specifications, accuracy and connection with the fixture part of the structure of the contact size;
d) fixture of the standard material inventory situation
2, jig and fixture design considerations
Fixture design is generally a single structure, giving the impression that the structure is not very complex, especially now that the popularity of hydraulic fixtures, so that the original mechanical structure is greatly simplified, but if the design process is not to consider in detail will inevitably lead to unnecessary trouble:
a) the blank allowance for machined parts
Caused by the blank size is too large, resulting in interference. So before the design must be prepared blank drawings. Leave enough space
b) Smoothness of chip removal of the fixture
Design due to the limited machining space of the machine tool, the fixture is often designed to be more compact space, which is often ignored in the machining process generated by the chip in the fixture dead center of the deposit.
Including the chip liquid outflow is not smooth, bring a lot of trouble to the future processing. So in the beginning of the actual process should be considered in the process of the problem, after all, the fixture is to improve efficiency, ease of operation for this!
c) Overall openness of the fixture
Neglecting the openness of the fixture will make it difficult and time-consuming for the operator to mount the fixture, which is a big taboo in design.
d) Basic theoretical principles of fixture design
Each set of fixtures have to go through countless times of clamping, loosening action, so may be at the beginning of the user's requirements can be achieved, but the fixture should have its accuracy to maintain, so do not design something contrary to the principle of things.
Even if the fluke can be at the moment, there will be no long continuity. A good design should be able to withstand the time of the hammer!
e) Replaceability of positioning elements
Positioning elements are subject to heavy wear and tear, so quick and easy replacement should be considered. It is better not to design larger parts.
The accumulation of experience in fixture design is very important, sometimes the design is one thing, in practical application is another, so good design is a continuous accumulation and summarization of the process.
Commonly used jigs and fixtures are mainly divided into the following categories according to their functionality:
01 clamping mold
02 drilling, milling fixture
03 CNC, instrumentation chuck
04 test gas, water test fixture
05 cutting edge, punching tooling
06Welding tooling
07Assembly fixtures
08Pad printing, laser engraving tooling
01 Clamp Mold Definition:
With the product shape positioning clamping tool
Design points:
1, this type of clamping mold is mainly used in the vise, its length can be intercepted according to need
2、The clamping mold can be designed with other auxiliary positioning devices, generally using welding to connect the clamping mold;
3, the above figure is a sketch, mold cavity structure size determined by the specific circumstances
4, in the appropriate position on the moving mold tightly fitted with a diameter of 12 positioning pins, fixed mold corresponding position of the positioning holes sliding with the positioning pins
5、Assembly cavities should be designed with an offset of 0.1mm on the basis of the profile of the non-shrinking blank file.
02 Drilling and milling tooling
Design points:
1, if necessary, in the fixed core and its fixed plate design some auxiliary positioning devices;
2, the above figure is the structure of the sketch, the actual situation needs to be based on the product structure to do the corresponding design;
3, cylinder according to the size of the product and the processing of the force situation, commonly used SDA50X50;
03 CNC, instrumentation collet, A CNC collet, internal beam collet
Design points:
1, the above chart does not identify the size of the actual product based on the structure of the size of the inner hole
2, and product positioning contact with the outer circle of the inner hole in the production need to leave a margin of 0.5mm on one side, and finally mounted on the CNC machine in the precision turning to size, to prevent deformation and eccentricity caused by the quenching process.
3, the assembly part of the recommended material to use spring steel, tie rod part of 45 #
4、Tie rod part of the thread M20 for the common thread, according to the actual situation can be adjusted to the thread instrumentation within the beam collet
Design points:
1, the above picture is a reference illustration, assembly size and structure according to the actual product dimensions of the structure depends on
2、Materials use 45#, quenching treatment.
Instrument outer beam collet
Design points:
1, the above figure is a reference illustration, the actual size according to the product's inner hole size structure;
2, and the product positioning contact with the inner hole of the outer circle in the production of the need to leave a margin of 0.5mm on one side, and finally mounted to the instrumentation lathe in the fine-turning to the size, to prevent deformation and eccentricity caused by the quenching process;
3、Materials use 45#, quenching treatment.
04Test gas tooling
Design points:
1, the above figure is the reference diagram of the test gas tooling, the specific structure needs to be based on the actual structure of the product to design, the idea is to use the simplest way possible to seal the product, so that the need to test the sealing part of the gas filled to confirm its sealing properties
2, the size of the cylinder can be adjusted according to the actual size of the product, but also need to consider whether the cylinder stroke to meet the convenience of picking up and placing the product.
3, the sealing surface in contact with the product is generally used Yuli rubber, NBR rubber ring and other materials with good compression, and note that if there is contact with the product appearance of the positioning block as far as possible to use the white plastic block and in the process of using the cover with a cotton cloth to prevent bruising the appearance of the product
4, the design should consider the direction of the product positioning, to prevent the leakage of gas held inside the product cavity and the occurrence of false detection.
05 Punching Tooling
Design points: The above figure shows the common structure of punching tooling. The role of the base plate is to facilitate the fixation of the worktable in the punching machine; the role of the positioning block is to fix the product, the specific structure is designed according to the actual situation of the product, the center point around the safe and convenient access to the product; the role of the baffle plate to facilitate the product to be detached from the punching knife; the pillar plays a role in fixing the baffle plate. The assembly position and size of the above parts can be designed according to the actual situation of the product.
06 Welding tooling
Welding tooling is mainly used to fix the position of each component in the welding assembly and control the relative size of each component in the welding assembly, and its structure is mainly a positioning block, which needs to be designed according to the actual structure of the product. It is worth noting that the situation in the product placed on the welding fixtures should not be used between the fixtures to produce a sealed space, to prevent the welding and heating process leads to sealing the space pressure is too large to affect the size of the parts after welding.
07 assembly tooling assembly tooling is mainly used in the assembly of components in the assembly process to assist in the positioning of the device. The design idea is based on the structure of the component assembly can be convenient to pick up and place the product, in the assembly process can not damage the product's appearance surface, in the use of the process can be covered with cotton cloth to protect the product. In the selection of materials to try to use white glue and other non-metallic materials.
08 Pad printing, laser engraving tooling
Design points:
According to the actual situation of the product engraving requirements to design the positioning structure of the tooling, need to pay attention to the convenience of the product pick and place, and the protection of the product's appearance, positioning blocks and auxiliary positioning devices in contact with the product as far as possible to use non-metallic materials such as white glue.