machine design

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Machine design, according to the use requirements, conceives, analyzes and calculates the working principle, structure, motion mode, force and energy transmission mode, material, shape and size of each part, lubrication method, etc. of the machine, and converts them into specific descriptions as the basis for manufacturing working process 。

Mechanical design is an important part of mechanical engineering, the first step of mechanical production, and the decision Mechanical properties The most important factor of. The goal of mechanical design is: Theoretical knowledge And calculation means, etc.) optimal design 。 Optimization design needs to comprehensively consider many requirements, generally including the best working performance and the lowest Manufacturing cost , minimum size and weight, the most reliable in use, the least consumption and the least environmental pollution. These requirements are often contradictory, and their relative importance varies with the type and use of machinery. The task of the designer is to weigh the weight according to the specific situation, make overall plans, and make the designed machinery have the optimal synthesis Technical and economic effects 。 In the past, the optimization of design mainly depended on the knowledge, experience and foresight of designers. With mechanical engineering Basic theory and value engineering Development of new disciplines, such as system analysis, and technologies for manufacturing and use economic data Accumulation of data, promotion and application of computers, and gradual abandonment of optimization subjective judgment And rely on Scientific computing 。

The design of industrial machinery, especially the mechanical design of the whole and the whole system, must be attached to the relevant Industrial technology It is difficult to form an independent discipline. Therefore, agricultural machinery design, mining machinery design, pump design Compressor design 、 Steam turbine Design, internal combustion engine design, machine tool design and other professional mechanical design disciplines.

Chinese name: machine design
Foreign name: machine design
Category: Design

Classification: New design, inheritance design and variant design
Instance: Textile machinery design automobile Design
Discipline code: forty-six thousand and twenty^[1-2]

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Design classification

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Mechanical design can be divided into new design, inheritance design and variant design.

1. New design

Apply mature science and technology or new technology that has been proved feasible by experiments to design new machines that have not been used in the past.

2. Inherit Design

Design and update the existing machinery according to the use experience and technical development to improve its performance, reduce its manufacturing cost or reduce its operating expenses.

3、 Variant design

In order to adapt to the new needs, the existing mechanical working parts are modified or added or deleted, and the variant products different from the standard ones are developed.

Main processes

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1. Design tasks are formulated according to user orders, market needs and new scientific research achievements.

2. Preliminary design. It includes determining the working principle and basic structural form of machinery, carrying out motion design Structural design The preliminary general drawing and preliminary review shall be prepared.

3. Technical design. It includes modifying the design (according to the preliminary review comments), drawing all parts and new general drawings and the second review.

4. Working drawing design. Including the final modification (according to the opinions of the second instance), drawing all working drawings (such as Parts drawing , component assembly drawing, general assembly drawing, etc.), develop all technical documents (such as parts list Wearing parts List, instructions for use, etc.).

5. Design finalization. Machinery used for batch or mass production. Some design tasks are relatively simple (such as Simple machine The preliminary design procedure can be omitted for the mechanical design.

design phase

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The quality of a machine basically depends on the design quality. The effect of the manufacturing process on the quality of the machine is essentially to achieve the quality specified in the design. Therefore, the machine's design phase It is the key to determine whether the machine is good or not.

The design process discussed only refers to the technical design process in a narrow sense. It is a creative working process At the same time, it is also a job to make use of the existing successful experience as much as possible. Only by combining inheritance with innovation can we design high-quality machines. As a complete machine, it is a complex system. To improve the design quality, a scientific Design procedure 。 Although it is impossible to list a unique program that is effective in any case, according to people's long-term experience in machine design, the design program of a machine can basically be shown in Table 2-1.

Each stage is briefly described below.

（1） Plan

In the planning stage, the demand of the designed machine should be fully Research And analysis. Through analysis, further clarify the functions that the machine should have, and put forward the environmental, economic, processing, time limit and other aspects of the determination for future decisions constraint condition 。 On this basis, clearly write out the overall requirements and details of the design task, and finally form the design task book as a summary of this stage. Design specification In general, it should include: machine functions, Economy And the estimation of environmental protection, the rough estimation of manufacturing requirements, the basic use requirements, and the expected deadline to complete the design tasks. At this time, these requirements and conditions can only be given a reasonable range, not an accurate number. For example, it can be determined by means of requirements that must be met, minimum requirements, and requirements that are expected to be met.

(II) conceptual design

According to different working principles, specific schemes of various actuators can be formulated. For example, for thread cutting only, the workpiece can be used as Rotary motion The tool Rectilinear motion To cut thread (such as cutting thread on an ordinary lathe), or to cut thread (such as using threading die Machining thread). That is to say, even for the same working principle, there may be several different structural schemes.

Prime mover Of course, there are many options for some schemes. Due to the power supply universality and Electric drive With the development of technology, it can be said that most fixed machinery Preference The motor serves as the prime mover. The thermal prime mover is mainly used for transport construction machinery Or agricultural machinery. Even if the motor is used as the prime mover, there are also choices of AC and DC, high speed and low speed.

The transmission part of the program is more complex and diverse. The same transmission task can be completed by multiple mechanisms and combinations of different mechanisms. Therefore, if IV is used to represent the number of possible schemes for the prime mover, and N2 and N3 respectively represent the number of possible schemes for the transmission part and the execution part, then the number of possible schemes IV for the overall machine is Ni × N2 × N3.

The above is only about the three main parts that make up the machine. Sometimes configuration must also be considered Auxiliary system This is not discussed in this book.

Among so many schemes, only a few are technically feasible. These feasible schemes should be carried out from the technical, economic and environmental aspects Comprehensive evaluation 。 There are many evaluation methods, and economic evaluation is taken as an example to illustrate. When evaluating according to the economy, the economy of design and manufacturing as well as the economy of use shall be taken into account. If the structural scheme of the machine is complex, its design Manufacturing cost It will be relatively larger, but its functions will be more complete, productivity It is also high, so the use economy is also good. Conversely, machines with simple structure and insufficient functions are designed and Manufacturing expenses Few, but Usage expenses But it will increase. When evaluating the design and manufacturing economy of the structural scheme, it can also be expressed by the cost of unit efficiency. E.g. Units output power Cost, cost of single product, etc.

When evaluating the machine, it is also necessary to analyze the reliability of the machine and take the reliability as an evaluation index. From the perspective of reliability, it is often unwise to blindly pursue complex structures. Generally speaking, the more complex the system System reliability The lower. In order to improve the reliability of complex systems, parallel standby systems must be added, which will inevitably increase the cost of machines.

Environmental protection is also an important aspect that must be carefully considered in the design. Causing adverse effects on the environment Technical proposal , must analyze in detail and propose technically mature solutions.

adopt Programme evaluation , and finally make a decision to determine a basis for the next step technical design Of schematic diagram or Schematic diagram of mechanism movement 。

stay Scheme design stage We should correctly handle the relationship between reference and innovation. The successful precedents of similar machines should be used for reference. The original weak links and nonconformities Task requirements The part of should be improved or fundamentally changed. We should not only actively innovate, oppose conservatism and copying the original design, but also oppose the two wrong tendencies of blindly seeking novelty and abandoning reasonable original experience.

（3） Technical design

The goal of the technical design phase is to produce General assembly Sketch and assembly sketch of components. Determine the shape and Basic dimensions , including the connection between components, the outline and basic dimensions of parts and components. The final drawing of the part Working drawing , Components Assembly drawing And general assembly drawing.

In order to determine the basic dimensions of main parts, the following work must be done:

one
Mechanical kinematics Design. According to the determined structure scheme, determine the parameters of the driving part (power, speed, linear speed, etc.). Then do kinematic calculation to determine Moving component Motion parameters of (speed, speed, acceleration, etc.).
two
Dynamic calculation of the machine. Combined with the structure and motion parameters of each part, calculate the size and characteristics of the load on each main part. The load calculated at this time is only the nominal (or nominal) load acting on the part because the part has not been designed yet load 。
three
The working ability design of parts. Given the size and characteristics of the nominal load on the main parts, the preliminary design of parts and components can be made. The working capacity criteria on which the design is based must be reasonably formulated with reference to the general failure conditions, working characteristics and environmental conditions of parts and components rigidity , vibration stability, life and other criteria. The basic dimensions of parts can be determined by calculation or analogy.
four
Design of assembly sketch and general assembly sketch. According to the determined basic dimensions of main parts and components, the assembly sketch and general assembly sketch of components are designed. The outline and dimensions of all parts shall be structurally designed on the sketch. In this step, it is necessary to coordinate the structure and size of each part well, comprehensively consider the structural technology of the designed parts and components, and make all parts have the most reasonable configuration.
five
Check the main parts. For some parts, it is difficult to calculate their working capacity in detail due to the undetermined specific structure in Step 3 above, so they can only do preliminary calculation and design. After the assembly sketch and general assembly sketch are drawn, the structure and size of all parts are known, and the relationship between adjacent parts is also known. Only at this time can the load acting on the part be determined more accurately, and the detailed factors affecting the working capacity of the part can be determined. Only under this condition, it is possible and necessary to accurately check and calculate some important parts or parts with complex shapes and forces. According to the results of the check, the structure and size of the parts are modified repeatedly until they are satisfactory.

In each step of technical design, the optimization design technology developed in the past thirty or forty years has increasingly shown its ability to make the selection of structural parameters reach the best. Some new numerical calculation methods, such as the finite element method, can make the problems that are difficult to calculate quantitatively obtain excellent approximate quantitative calculation results. For a few very important, complex and expensive parts, if necessary model test Design according to preliminary design The model shall be manufactured according to the drawings of. Through the test, the weak parts or redundant section dimensions on the structure shall be found out, and the original design shall be modified by strengthening or reducing them accordingly, so as to reach the perfect degree finally. Mechanics reliability theory In the technical design stage, it can evaluate whether the structure and parameters of the designed parts and components meet the reliability requirements according to the reliability point of view, and put forward suggestions for improving the design, so as to further improve the design quality of the machine. These new design methods and concepts should be applied and popularized in the design, so that they can be developed accordingly.

After the sketch design is completed, the working drawing of the part can be designed according to the basic dimensions of the part determined by the sketch. At this time, there are still a lot of structural details of parts to be considered and determined. When designing the working drawing, the processing and assembly process of parts, the inspection requirements and implementation methods of parts during and after processing shall be fully considered. If some detailed arrangements have an impact on the working capacity of parts that is worth considering, it is also necessary to go back to recheck the working capacity. Finally, the working drawings of all parts except standard parts are drawn.

According to the final design Part working drawing The structure and dimensions on the, redraw the component assembly drawing and general assembly drawing. Through this work, you can check out the size and structure errors that may be hidden in the part working drawing. This work is popularly called assembly on paper.

(IV) Technical documents organization

There are many types of technical documents, such as design calculation instructions an instruction manual , standard parts list, etc.

The design calculation specification shall include Scheme selection And all the conclusive contents of the technical design.

When preparing the machine operation manual for users, the user shall be introduced to the range of performance parameters, operation methods Daily maintenance And simple maintenance methods, spare parts catalogue, etc.

Other technical documents, such as inspection certificate Purchased parts The detailed list, acceptance conditions, etc. shall be prepared separately as required.

（5） Application of Computer in Mechanical Design

along with computer technology With the development of computer, computer has been widely used in mechanical design, and many efficient design and analysis software have appeared. These software can be used to compare multiple schemes at the design stage, and can be used to compare different schemes, including large and complex schemes structural strength , stiffness and dynamic characteristics. At the same time, you can also build virtual prototype The virtual prototype simulation is used to verify the design, so that the feasibility of the design can be fully evaluated at the design stage. It can be said that the popularization of computer technology in mechanical design has changed and is changing the process of mechanical design, and its advantages in improving design quality and efficiency are difficult to predict.

The design procedure of the machine is briefly introduced above. Broadly speaking, in the manufacturing process of the machine, it is possible to modify the design due to process reasons at any time. In case of modification, certain approval procedures shall be followed. After the machine leaves the factory, it should be carried out in a planned way Follow up investigation ； In addition, users will also feed back problems to the manufacturing or design departments during use. Based on this information, the design department, after analysis, may also modify the original design, or even remodel it. Although these works are also part of the design program in a broad sense, they belong to another level of problems, and their specific contents will not be discussed in this book. But as a designer, there should be strong Social responsibility We should extend our work vision to the whole process of manufacturing, use and even scrap utilization, and constantly improve the design, so that the quality of the machine can continue to improve and better meet the needs of production and life.

Stage description

（1） Planning stage

After putting forward the new machine to be designed according to the needs of production or life, the planning stage is only a preparatory stage. At this time, there is only a vague concept of the machine to be designed.

（2） Scheme design stage

This stage plays a key role in the success or failure of the design. In this stage, it also fully demonstrates the characteristics of multiple solutions (schemes) in the design work.

Mechanical functional analysis It is to comprehensively analyze the requirements that must be met, the minimum requirements and the requirements that are expected to be met in the machine functions proposed in the design specification, that is, whether these functions can be realized, whether there are contradictions between multiple functions, and whether they can be replaced. Finally, the function parameters are determined as the basis for further design. In this step, we should properly deal with the contradictions that may arise between needs and possibilities, between ideals and reality, and between development goals and current goals.

After the functional parameters are determined, possible solutions can be proposed, that is, possible solutions can be proposed. When seeking solutions, they can be discussed separately according to the driving part, transmission part and executive part., The more common way is to start from the executive part.

When discussing the execution part of the machine, the first question is about the selection of the working principle. For example, design and manufacturing screw The working principle of the machine can not only use the turning tool on the cylindrical blank turning The thread can also be rolled on a cylindrical blank with a thread rolling die. This puts forward two different working principles. The working principle is different, of course, the machine designed will be fundamentally different. In particular, it should be emphasized that research and development New working principle. This is the design technological development The important way.

step

Before the design starts, the design task should be formulated. When the design task is relatively complex, generally Three stage design , i.e. preliminary design, technical design and Working drawing design ； When the task is simple, such as Simple machine New design, inherited design of general machinery or Variant design , the design will reach the depth of technical design at the beginning, and the working drawing design will be done after review, modification and approval, thus becoming Two-stage design 。 In the preliminary design stage of the three-stage design, the main steps of the design are to determine the working principle and Basic structure Type, motion design, design of main parts and components, preliminary drawing General drawing , preliminary Design review 。 In the technical design stage, the main steps are: modify the design according to the review comments, design all parts and components, draw a new general drawing, and review the technical design. At the working drawing design stage, modify the design according to the review comments, draw all working drawings and prepare all technical documents. For products produced in batches or in large quantities, finalization design shall also be carried out.

In each step of design, it is possible to find that some decisions in the previous step are unreasonable, which requires you to go back to the previous step, modify the unreasonable decisions, and redo the subsequent design work.

1. Make design tasks It's designed Preliminary work 。 The design task is based on user orders, market needs and new Scientific research achievements 。 The design department applies various technologies and market intelligence to draw up possible plans, compare their advantages and disadvantages, discuss with the business department and users, and formulate reasonable design tasks and objectives. This is particularly important for new designs. The failure of mission objectives will cause serious economic losses, and even comprehensive failure.

2. Determine the working principle and basic structural type If the design task is not clearly specified, the first step of the design is to determine the overall scheme, that is, determine the working principle to be applied and the corresponding structural type. For example, design high power marine diesel , first make sure to use Two-stroke , double acting Crosshead , Low speed Diesel engine , or use Four stroke , single acting, medium speed diesel engine. Another example is that designed for coarse rock crushing Crusher First of all, make sure to use Kink Jaw or gyratory crusher Or single rotor or double rotor impact crusher with impact as the main function.

3. After the overall scheme of sports design is determined, it is necessary to apply Mechanism And select the appropriate mechanism to obtain the required motion scheme. The above mentioned Jaw crusher Depend on it to move Jaw plate The rock entering the crushing chamber is crushed by squeezing, bending and splitting due to the swing of Bracket Simple swing of mechanism, or complex swing of single toggle mechanism. In a new design, it may be necessary to synthesize a new mechanism to obtain the required motion scheme, which is often a difficult task. Therefore, designers generally try to use the motion scheme provided by existing and mature mechanisms.

4、 Structural design After drawing the preliminary general plan and motion design, the designer starts to carry out structural design, calculate the force, strength, shape, size and weight of the main parts of the machine, and draw sketches of the main parts and components. If it is found that the original structure is not feasible, it must be adjusted or Modify Structure 。 At the same time, it should also consider whether there are parts that may cause overheating, excessive wear or vibration.

In this step, the designer will find contradictions in the shape, size, proportion and other aspects of each part by sketching. In order to strengthen or improve one aspect, the other aspect may be weakened or worsened. At this time, we must balance and coordinate to achieve the best comprehensive effect. After the sketch has been repeatedly modified and considered to be initially satisfactory, the preliminary general drawing and cost estimation can be made. The preliminary general drawing shall be drawn strictly to scale, and sufficient views and section drawings shall be selected.

5、 Preliminary review After the preliminary general drawing is drawn, it is necessary to invite experienced designers, manufacturers and users of this kind of machinery, as well as users or commission Designer A representative of. If the review results show that the design is not applicable (such as too large weight and volume, too high cost, doubt on the reliability of the structure, etc.), the motion design must be carried out again, or even change to other working principles and basic structural types. In most cases, some improvement measures are taken for the design.

6. The technical design shall modify the design according to the preliminary review comments, and draw all parts and Component drawing 。 Precise Stress analysis , press Analysis results Correct the shape, size and other details of parts, and specify the material and heat treatment. Identify parts Machining accuracy And assembly conditions of components and final assembly. Complete lubrication design, electrical design (drive and control). Redrawing the general drawing, and sometimes making models for some important and batch production machines. Submit the completed technical design to the second review.

7. After the working drawing is drawn and the final modification is made according to the opinions of the second review, the formal part drawing, component assembly drawing and general assembly drawing can be drawn, and the technical documents such as parts list, vulnerable parts list and use guide can be prepared. The design director shall pay attention to coordinating the dimensions between parts, checking the tolerance and fit between coupling parts, and rechecking the strength and stiffness of some parts. Parts drawing It is very important to check the drawings after completion. The carefully calibrated drawings can ensure the smooth assembly after processing. Most reliable Proofreading method A general assembly drawing is redrawn according to the drawn part drawing, and all contradictions will be shown. There are also two tasks to be carried out while drawing the part drawing: one is Workmanship Audit to make parts easy to process and reduce manufacturing costs; The second is the standard review, which makes the parts Structural elements Dimension, tolerance fit, heat treatment technical conditions And standards and Common parts And comply with the provisions of the standard.

8. Trial production and type approval design for single piece or small serial production After the above steps Design drawings It can be put into formal production. For batch or mass production machinery, prototype shall be trial produced before formal production, functional test and identification shall be carried out, and then batch production shall be carried out Production process Conduct batch trial production. Problems in batch trial production may also require corresponding modifications to the design before it becomes a finalized design for formal production.

constraint condition

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Mechanical parts The design of constraint condition Design criteria are the constraints that design should meet.

Technical performance criteria

Technical performance includes Product Functions , manufacturing and operating conditions, both static and Dynamic performance 。 For example, the power, efficiency, service life, strength, stiffness, friction resistance, wear resistance, vibration stability, thermal characteristics, etc. that the product can transmit. Technical performance criteria mean that relevant technical performance must meet the specified requirements. For example, vibration will produce additional dynamic load and Variable stress , especially when its frequency is close to mechanical system Or part natural frequency Will occur resonance Phenomenon, at this time amplitude It will increase sharply and may lead to rapid damage of parts and even the whole system. Vibration Stability criterion It is to limit the relevant vibration parameters of mechanical system or parts, such as natural frequency, amplitude, noise, etc., within the specified allowable range. Also like when the machine is working fever May cause Thermal stress 、 Thermal strain , or even thermal damage. The thermal characteristic criterion is to limit various relevant thermal parameters (such as thermal stress, thermal strain, temperature rise, etc.) within the specified range.

Standardization criteria

And machinery product design The main standards are:

Concept standardization: terms, symbols Unit of measurement Etc. shall meet the standards;

Standardization of physical form: structural form, size, performance, etc. of parts, raw materials, equipment and energy shall be selected according to uniform regulations.

Method standardization: operation method measuring method , test methods, etc. shall be implemented according to corresponding regulations.

The standardization criterion is that all behaviors in the whole process of design should meet the above standardization requirements. The published standards related to the design of mechanical parts can be divided into national standard 、 Industry standards and Enterprise standard Three levels. From the perspective of mandatory use, it can be divided into mandatory use and recommended use.

Reliability criterion

Reliability: the probability that the product or part can complete the specified function within the expected service life under the specified service conditions. Reliability criteria means that the designed products, components or parts shall meet the specified reliability requirements.

Safety criteria

The safety of the machine includes:

Safety of parts: refers to the safety of parts Specified time The internal parts shall be free from fracture, excessive deformation, excessive wear and loss of stability.

Safety of the whole machine: refers to the machine Guaranteed on lay down a condition It shall be able to meet the requirements of general function without failure.

Work safety: refers to the protection of operators to ensure personal safety and physical and mental health.

Environmental safety: it means no pollution and harm to the environment and people around the machine.

Design Methodology

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Design Methodology The purpose of Design thinking Rise to a rational process, so that the design can follow a certain logic, so that more designers can make good designs. It generally includes the following contents:

1. Divide the stages of design very carefully, so that each stage becomes a thinking activity with rules to follow and reasons to follow.

2. Store successful or good designs and establish designs database For reference or adoption in future design.

3. Introduced in design work value engineering To balance the function and cost of the contradiction in the design, so as to obtain a good use effect.

4. Used in the design tribology Vibration fracture mechanics 、 Finite element method 、 reliability design 、 optimal design , system engineering, ergonomics, etc Emerging disciplines To improve the scientificity of design and reduce blindness.

5. Design Scope of work It extends forward to market forecast and backward to after-sales service.

6. Application Computer Aided Design To reduce design Labor volume , improve Design speed and design quality 。

expectation

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In the future, the science of mechanical design will permeate into semiconductor manufacturing, bioengineering Nanotechnology And robot industries social development While making contributions, we should constantly improve ourselves to further innovate the theory.

(1) Further realize systematicness. That is, starting from the system point of view, mechanical products are regarded as a system or a whole, relying on computer technology to realize the coordination of human, machine and environment. To be specific, it is necessary to System decomposition For several Subsystem , adopt various modern design theories and methods, pursue system optimization as Goal coordination Design and matching of each subsystem.

(2) Deepen intelligent design. With the progress and development of science and technology, more and more intelligent factors should be considered in design. A large number of design contents can describe various working conditions and behaviors of mechanical products by establishing models, and the solution of models can predict the performance and design of products rationality and Optimality 。 For example, various vehicles performance evaluation 's intelligence decision-making system ， Gearbox Design expert system and fault diagnosis system have been applied in the development and design of new cars.

(3) Pay more attention to green ideas. Green design Technology is the key to the product life cycle Medium, according to environmental protection and resources Utilization Highest energy consumption Minimum requirements for design technology. Designers are required to consider the environmental attributes and basic attributes of products from the whole cycle, and always base on human physical and mental health, environmental protection, etc. during design. At the same time, the designed products are required to be recyclable and have minimal damage to the environment.

Modern design method

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Professional and modern

By mechanical design and computer professionals Co development It can reflect and describe the mechanism of various damage, failure and destruction of mechanical products under actual working conditions, and can be quantitatively analyzed and calculated Mechanical parts And mechanical dynamic behavior, and form a fixed design program, which is professional Modern Design Methods, such as vibration analysis and design, tribological design, thermodynamics Heat transfer design, strength and stiffness design, Temperature field Analysis, etc. These softwares are based on the traditional design methods and use computers technological development Out. For example: use Pro/M software analysis Mechanistic Dynamic characteristics Stress analysis with ANSYS software is a good example in this respect, which lays a foundation for accurately judging the reliability of the device and selecting design parameters.

Universal Modern

To meet the mechanical requirements Product performance In mechanical design, computer technology is widely used for aided design and system analysis, which is a common modern design method. Common methods include optimization Finite element , reliability, simulation expert system 、 CAD Etc. These methods are not only for mechanical products, but also for their own scientific theory And methods.

1 Optimization design

Mechanical optimization design is the optimization technology in machinery Design field Its basic idea is to establish a reflection based on the theory, method and standard specifications of mechanical design engineering design Problems and those meeting the requirements of mathematical planning mathematical model And then use mathematical planning methods and Computer calculation Technology automatically finds out design problems Optimal scheme 。 It is a combination of mechanical design theory, optimization mathematics and electronics computer A modern design method combined with each other.

2 Simulation and Virtual design

computer Simulation technology It uses computer as a tool to "establish actual or associative system model ”It is a comprehensive technology to conduct dynamic operation experiments on the model under different conditions. and Virtual technology The essence of the product design Phase, real-time parallel simulation product development The whole process and its impact on product design, predict product performance Product manufacturing cost , product Manufacturability , product Maintainability And disassembly, so as to improve the first time success rate of product design. This method not only shortens the product development cycle, but also shortens the distance between product development and users.

3 Finite element design

This method is to use mathematical approximation to physical system (geometry and load cases). By using simple and interacting elements, namely elements, a finite number of Unknown quantity To approach the infinite unknown Real system 。 It can not only be used for complex non linear problems in engineering Unsteady state The solution of the problem can also be used for the static and dynamic analysis of complex structures in engineering design, and can accurately calculate the Stress distribution And deformation, becoming a powerful analysis tool for strength and stiffness calculation of complex parts.

4 Fuzzy design

It will fuzzy mathematics A design method of applying knowledge to mechanical design. There are a lot of fuzzy information 。 For example, in the design of mechanical parts, the safety factor of parts is often taken from a conservative point of view. It is uneconomical to take a larger value, but there is a large fuzzy interval within its allowable range. Development of mechanical products at various stages Regular meetings When encountering various fuzzy problems, although the characteristics, properties and requirements for strategies of these problems are different, the fuzzy analysis methods adopted are similar. Its biggest feature is that the influence of various factors on the design results can be comprehensively and quantitatively analyzed, and the comprehensive number can be obtained Quantitative indicators , as the basis for selecting decisions.