Li Yisheng Tianjin Vocational and Technical College of Light Industry

This paper introduces the method of three-dimensional modeling and assembly design of mold using UG, and emphatically analyzes the role of sketch in parametric modeling and the use of UG WAVE technology in assembly process.

Keywords: UG sketch assembly UG wave from top to bottom from top to bottom

In recent years, with the attention of advanced industrial countries to the mold industry and the rapid development of mold manufacturing/design and application software, the speed of change is getting faster and faster, which requires the strong support of professional software, and digital design/processing/analysis and management technology in digital manufacturing is added to a series of CAD/CAE/CAM software.

Unigraphics (hereinafter referred to as UG) is the most advanced 3D parametric software integrating CAD/CAE/CAM in the world. Provide solutions for the whole process of manufacturing product development, including conceptual design/engineering design/performance analysis and manufacturing. Since 1990 entered the China market, it has developed rapidly. At present, it is widely used in aviation/aerospace/automobile/shipbuilding/general machinery and electronics industry, in which UG/Mold Wizard is an independent application module in UG series software and also a special application module for injection mold design.

1 product modeling

The modeling function of UG is very powerful, and the main modeling methods are: UG/ solid modeling UG/ feature modeling UG/ free modeling UG/ user-defined features, etc. Compared with other CAD software UG, feature modeling is a bright spot. For less complicated models, feature modeling is fully competent and can achieve high modeling efficiency. However, simple feature modeling is more troublesome for models with complex shapes/positions that need parameterization. At this time, sketch is the most commonly used simple and efficient method to solve this problem.

Sketch in UG refers to two-dimensional graphics associated with solid model. It can accurately express the designer's design intention by imposing dimensional and geometric constraints on the approximate curve outline, and then create the model by solid modeling methods such as stretching, rotating and scanning. In addition, designers can easily change the shape of the solid model by changing the shape and parameters of the sketch when modifying the model.

Generally speaking, sketches are mostly used in the following situations: (1) When the model needs parametric driving; (2) When the feature to be established is not a standard molding feature; (3) control lines as free-form features; (4) as a basic feature of stretching, rotating and scanning; (5) When it is necessary to establish a series of molding features and it is difficult to edit.

The modeling idea of establishing parametric model: no matter how complex the parts are, they are all composed of some characteristics. When modeling parts, we should first fully understand the design intent and determine the modeling order, then design the overall structure of the parts according to the needs, and then carry out detailed design.

In the following, an example of flange part modeling in UG NX environment (Figure 1) is used to illustrate the design method of creating model by using sketch function (Figure 1).

(1) Determine the structure of the part: the part consists of three parts: the revolving body/five evenly distributed holes/one through hole.

(2) Create three fixed datum planes and three fixed datum axes! XZ plane, YZ plane, ZY plane and x axis, y axis and z axis;

(3) Create a sketch, select the XZ plane as the sketch plane, draw the shape of the rotating section with the curve command in the sketch, and ignore the chamfers and fillets that do not affect the drawing annotation; Add geometric constraints and dimensional constraints to constrain the sketch and complete it (Figure 2). Change the constraints in the sketch, and the shape of the model will change accordingly. This fully embodies two outstanding advantages of the model created by sketch function: easy to edit and modify; Easy to realize parameterized and serialized design; (Figure 2)

(4) Generating a rotating body Select the sketch as the scanned cross-section line string, and take the X axis as the rotation axis, and establish the characteristics of the rotating body by using the modeling method of the sketched rotating body to generate the rotating body.

(5) Create five holes distributed along the circumference respectively: firstly, create a hole by using the forming characteristics of UG, and then evenly distribute five identical holes into a circular array.

(6) Create a central through hole: use the input parameters of the through hole in the molding feature to select the datum plane of the through hole operation.

2 Assembly application based on UG

UG NX assembly module provides bottom-up modeling and top-down modeling, which ensures the complete two-way correlation between assembly model and part design. Bottom-up design refers to the process of obtaining assembly based on the generation of a single part and given the matching constraint relationship between matching parts; Top-down design refers to the assembly design process of creating related parts in the assembly environment and generating sub-assemblies and parts from the top assembly level. In practical application, these two design methods can be used alternately according to specific conditions. In the design of tooling, the top-down design should be adopted for the establishment of non-standard parts that have a direct relationship with the product parts or influence each other in size, shape and position, while the standard parts can be added to the assembly through the bottom-up design method. UG's assembly module also has a simple animation to make the disassembly sequence of assembly. Take a set of molds as an example: we can simulate the assembly sequence of molds in the actual assembly workshop.

2. 1 unit assembly design method

In the process of assembly, two assembly design methods can be adopted: bottom-up and top-down.

2. 1. 1 Application of bottom-up design method

The bottom-up design and assembly method is similar to the assembly in the assembly workshop. Each manufacturing workshop assembles the manufactured products to the assembly workshop, and the assembly workshop completes the product assembly according to the product structure. The bottom-up design method is to add parts to working parts to become assemblies. This part can be an existing part or a member of a part family. Series product parts, standard parts and purchased parts stored in the logarithmic library can also be added to the assembly by bottom-up design method.

For example, when assembling a die assembly unit, first create a new unit assembly file as the parent, and then add it according to the sequence structure of fixed die, insert, movable template pad, pad and other elements, so as to complete the assembly, as shown in Figure 3.

(Figure 3)

2. 1.2 application of top-down design method

UG's assembly modeling technology fully supports the top-down design method, that is, the overall design first and then the detailed design, and the local design decision is subordinate to the overall design decision. It uses context control technology to support the design of parts in assembly environment. The combination of UG/WAVE technology and the expression technology between components can better reflect the designer's design ideas. The following describes the use of UG/WAVE technology in the assembly process.

UG's WAVE technology is a parametric design technology based on assembly modeling, which can be used to establish the association between different parts parameters, that is, the so-called "association between parts" relationship, and realize the association replication of geometric objects between parts. Using the powerful technology of UG NX WAVE, we can quickly develop new products from the same product structure. WAVE technology automatically transmits design changes by updating related components and tools, which reduces the cost of design changes, greatly improves the repetition rate of design, and can also realize rapid iterative testing and feasibility study.

2.2 Assembly modeling design method

According to the characteristics of die structure, top-down and bottom-up assembly methods are adopted. Firstly, a new parent body is constructed, and then sub-assemblies are added in turn. Finally, the whole assembly is completed by symmetrical method according to different assembly constraints. In assembly, the constraints should be correct, no conflicts are allowed, and the correct spatial freedom should be maintained. The assembly constraints must be effective to avoid unloading.

3 Conclusion

Using UG NX software in product design and development can design product model conveniently and quickly, and analyze the model to check whether the product meets the design requirements, reduce the work intensity of designers, constantly update products and promote the rapid development of mechanical field.