Manufacturability of design: requirements for the technological design of parts, indicators and analysis

Manufacturability of the design is a comprehensive concept that includes an assessment of the complexity of manufacturing a product, material utilization, cost, and other parameters. Monitoring project documentation for the optimality of these parameters is one of the elements of the technical preparation of production. Each manufacturing technology has its own evaluation criteria, which are regulated by state standards for the manufacture of this type of product and other regulatory and technical documentation.

General concept

Under the manufacturability of the product design is understood a set of its properties, which contribute to the achievement of minimum labor costs, materials, tools and other indicators in the production, repair and operation. The main definitions relating to this concept are established in GOST 14.205-83. Manufacturability is worked out at the earliest stages of the product life cycle - at the stage of receiving a technical proposal, creating a preliminary design and developing design documentation.

In practical terms, manufacturability is provided by determining the most rational design of parts and assemblies, assortment and grades of materials used, controlled sizes and their maximum deviations, surface roughness, requirements for thermal and other types of processing. At the same time, all these criteria should contribute to the production of products with high consumer properties and operational characteristics.

When assessing the manufacturability of a design in production, qualitative and quantitative parameters are used: ease of manufacture, compliance with technical capabilities (existing technologies and equipment, staff qualifications), low cost of the product. Manufacturability is a relative indicator and also depends on the type of production (single, serial or mass).

Goals

The main tasks for ensuring the manufacturability of the product design are:

• increasing serial production through the unification of parts and assemblies, standardization, reduction of the range of materials and components used;
• the use of high-performance technologies, their typing (selection of elements that contain constructive solutions inherent in all the details of this class);
• increasing the level of mechanization and automation, the introduction of technological devices to reduce the complexity of the work;
• the use of design solutions that provide convenient access to parts, interchangeability and assembly without fitting during installation.

When developing design documentation, the manufacturability of the design of parts and assemblies should be evaluated by the technological service of the enterprise. The following criteria are taken into account:

• methods for manufacturing blanks;
• methods of control and testing;
• processing and assembly methods;
• features of material support of production.

Classification of evaluation criteria

Quantitative indicators of technological design are divided into the following groups:

• in the field of use of the product - production, repair, operational;
• by the number of taken into account features - private and complex;
• by assessed value - basic and additional;
• in the form of expression - relative and absolute;
• in the field of analysis - technical and technical and economic (performance indicators, durability and others).

The analysis of manufacturability is included in the product quality assessment system, which integrates several groups of indicators. In the practice of machine-building enterprises, the criteria most often determined are those indicated in the diagram below.

Relative quantitative characteristics

The most convenient are the relative indicators of the manufacturability of the product design, which have the form K = k ₁ / k ₂ . Among the most significant structural and technological characteristics are the following:

1. Constructive complexity, which is defined as the ratio of the number of elements in the developed product to the number of components in the mastered analogue.
2. The novelty of the design is the ratio of the number of new elements in the product to their total number.
3. The coefficient of ease of removal - the ratio of the complexity of dismantling work on the analogue and the developed object.
4. The coefficient of accessibility of service is the ratio of the complexity of directly repair work to its amount with auxiliary labor intensity.
5. The coefficient of application of standard technical processes is the ratio of the complexity of performing typical operations to the total complexity.
6. The coefficient of automation and mechanization (determined similarly to the previous one).
7. The suitability ratio is the ratio of the complexity of the main control operations to their total with auxiliary time.
8. The coefficient of unification and standardization is the ratio of the number of unified or standardized elements in a product to their total number.
9. The comparative complexity of manufacturing (for the base and development product).
10. The utilization of the material is the ratio of the mass of the part to the mass of the workpiece with allowances and other characteristics.

These indicators are used both for the analysis of the manufacturability of the design of parts, and with reference to assembly units.

Quantitative estimates in absolute terms

Among the absolute indicators of manufacturability, the following are distinguished:

• the complexity of technical preparation of production, manufacture and installation;
• material consumption;
• energy intensity;
• the cost of manufacturing (the sum of the cost of materials, wages and shop expenses).

Qualitative indicators of technological design

Qualitative assessment is carried out by visual inspection of design and technological parameters. It is carried out before quantitative analysis. In this case, the following conditions are determined:

• simplicity of geometry of parts and assemblies;
• methods of connecting the elements, the possibility of disassembling and reassembling them (the least technological in this regard are riveted seams and other non-separable assemblies);
• unification of parts, the use of one standard size of components;
• nomenclature of materials used and the possibility of its reduction, technological properties of raw materials;
• types of blanks and the rationality of their choice for one degree or another serial production.

Assessment methodology

Testing the design for manufacturability is performed in the following order:

• analysis of the source data, the study of drawings, sketches, technical specifications and other documentation related to the design, manufacture, operation or repair of the product;
• preliminary quality assessment;
• definition of a list of manufacturability indicators;
• calculation of quantitative parameters;
• analysis of the information received;
• development of recommendations or a plan of design and technological measures to improve manufacturability.

The nomenclature of the evaluated indicators should be minimal to reduce the complexity of production preparation, but sufficient to evaluate and improve the product.

Typical tasks

Typical decisions taken in assessing the manufacturability of structures include:

• exclusion from the composition of any parts or assemblies;
• replacing a monolithic part with an assembly (or vice versa) in order to simplify the geometry and manufacturing technology;
• typing of elements, development of group drawings;
• replacement of original parts with standardized ones, the geometry and production regulations of which are specified in state standards;
• reduced requirements for accuracy and surface roughness, which allows to reduce and simplify processing;
• replacement of the workpiece proposed by the designer with a more rational one;
• selection of material from the existing assortment;
• the use of joint cutting of several types of parts to reduce material consumption;
• checking the presence of surfaces that provide the output of the cutting tool during processing, and others.

The influence of the type of production

Manufacturability is not an absolute indicator. For example, stamped blanks are more technologically advanced in mass production (reduce the overall complexity), and with a single manufacture of the product - on the contrary, since this is due to the high cost of blacksmith tooling and equipment.

In a single production, technological methods may turn out to be the preparation of workpieces that involve more labor and material consumption (for example, gas cutting from sheet metal), but with less equipment and equipment. The final cost of products will be lower. The given example clearly shows that when evaluating manufacturability, it is necessary to take into account the type and conditions of production.

Operational manufacturability

When analyzing the manufacturability of the design, which is the object of operation, the following criteria are evaluated:

• ease of management and control of product performance;
• accessibility to various nodes and elements;
• the complexity of preventive and repair work, dismantling (easily removable);
• safety measures;
• suitability for transportation;
• interchangeability of parts and assemblies.

All these parameters affect the cost of operating the facility and its consumer properties.

Manufacturability of cast and forged workpieces

When evaluating the manufacturability of castings, the conformity of the drawing of the casting with the following basic requirements is checked:

• lack of sharp corners, high ledges and thin ribs;
• minimum number of internal cavities;
• the closest possible proximity to the contour of the part (to reduce material consumption and the volume of machining);
• the absence of sharp transitions from thin to thick sections;
• the presence of technological elements that ensure complete filling of injection molds and the absence of residual stresses;
• minimum number of detachable surfaces and rods;
• the presence of slopes that facilitate the extraction of the casting from the molds;
• simple geometry of the part, allowing the use of simple and inexpensive equipment and others.

The manufacturability of the stamping design must satisfy such requirements as:

• rational values ​​of tolerances and allowances, ensuring the necessary accuracy of the part after machining;
• the correct dimensioning provided by the tool (the radius of the concave surface when bending the sheet, the diameter of the glass obtained by the hood, and others);
• smoothness of mating surfaces;
• compliance with the minimum values ​​of the diameters of punched holes and the distances between them, bending radii (these parameters are limited by the ductility of the material);
• providing the necessary technological allowances for the capture of the workpiece during its formation (stipulated by the technical parameters of the equipment) and others.

If it is not possible to comply with these conditions, it is recommended to use a welded structure of several parts.

Assembly units

General requirements for manufacturability of assembly units are:

• minimization of the number of elements;
• the possibility of dividing the product into subassemblies, the manufacture of which can be distributed at work sites, as well as unified;
• providing convenient access for assembly and mounting tools, the possibility of mechanization of work (the use of wrenches, screwdrivers and other tools);
• observing a symmetrical assembly pattern to reduce warpage of parts;
• the ability to install clamps and other auxiliary devices;
• the use of parts to prevent self-loosening of fasteners.

As quantitative characteristics, labor intensity and production cost, the degree of unification, standardization and mechanization are most often calculated.

Welded joints

The manufacturability of welded structures is determined by such parameters as:

• compliance with the requirements for the minimum thickness of parts, at which there will be no warping due to residual stresses;
• good weldability of the material;
• the possibility of automation and mechanization;
• ease of access to the weld (horizontal layout is more technological);
• the possibility of using universal assembly equipment for fixing the connected parts;
• minimum number of welds, replacement (if possible) for parts obtained by sheet flexible or from long products;
• the possibility of heat treatment, a symmetrical arrangement of welded elements to minimize residual stresses;
• type of weld (fillet welds provide higher productivity and quality of welding) and other criteria.