1. Concept elements of Dermatoglyphics
Dermatoglyphics refers to the natural lines born in the biological skin, usually refers to the natural lines on the skin surface of human or other animals such as cattle, deer, crocodile, etc.; it can also refer to the lines on the surface of plants such as tree skin, section, leaf, etc.; with the expansion of modern design concepts, it develops to the lines on the surface of other natural or artificial objects, such as stone lines, fabric lines, electric spark lines And so on.
"Dermatoglyphics" in this paper refers to the decorative patterns on the surface of plastic products. Due to different materials and different surface arrangement, organization and structure, plastic products have rough, smooth, soft and hard feeling, which shows different skin lines.
1.1 according to the style, the leather pattern includes the following three aspects:
Characteristic
The shape of fingerprint path unit can be described by geometric form or pictographic form. Common shapes such as line, block, line block combination and litchi shape are shown in Figure 1. The shape, direction, arrangement and combination direction of the grain units and the density of the unit combination have an important influence on the macro style of the leather grain.
directional
Some dermatoglyphic features have obvious directionality, as shown in Figure 2, we can see the obvious vein trend of this dermatoglyphic pattern. Some of the regular unit features have no orientation, as shown in Figure 3. The leather grain of automobile leather is not directional.
Hierarchy
The patterns on leather are basically three-dimensional leather patterns. The three-dimensional leather patterns are hierarchical. On the micro level, the leather patterns are composed of 2-5 layers with different depth values in the depth direction. On the macro level, the grain surface on the leather surface is full and round, the layers are rich and undulating, the characteristics are transitional and natural, and the visual impact is relatively soft. The layers can be viewed with the help of a magnifier of 50 times. The figure below shows a typical multi-layer skin pattern.
1.2 the dermatoglyphics can be divided into the following three types according to the size:
Coarse Dermatoglyphics
It is the evolution of the existing leather texture simulation in the real world. The texture is close to the real texture, more delicate, and has a sense of hierarchy. It can improve the level of the vehicle interior, and the general texture depth is between 80-150um. Rough leather grain is generally used as the main leather grain of automobile interior, which has a strong sense of overall coordination and needs to be considered in the integrated design of automobile interior.
Fine Dermatoglyphics
It is a kind of fine grain, similar to the state of sand and stone surface, with many processing technologies, mainly including spark grain, sand spray grain, etc. the fine grain is generally a single-layer sub grain, and the texture depth is between 0-80um. Fine grain can be decorated separately or matched with many other grains.
Geometric Dermatoglyphics
It presents geometric regular texture, mainly embodies the concepts of science and technology, power, trend, etc. on the automobile, the general texture depth is between 80-150um. Geometric pattern has strong directionality and regularity, large-scale use will greatly improve its processing difficulty and high price.
Coarse Dermatoglyphics
Fine Dermatoglyphics
Geometric Dermatoglyphics
2. Realization of Dermatoglyphics
The principle of common skin pattern / pear ground pattern biting flower:
Flower biting principle of three-dimensional texture:
3. Key points to avoid in plastic part design
The rationality of the structure design of plastic partsis closely related to the quality, clarity and forming difficulty of the leather grain. Based on the design experience of the industry, for two typical interior injection molding materials PP and ABS, the requirements for the draft angle of plastic parts are different for the depth of leather grain:
The drawing angle and the processing depth of the leather pattern directly affect the demoulding performance of the parts.
Generally, the draft angle of plastic parts needs to be defined above 0.5 °, but for decorative parts with skin texture, the conventional experience is that the draft angle is 1 ° for the skin texture of 13 μ m depth. For example, when 110 μ m skin texture corrosion is selected for the door guard body, the draft angle of preliminary design needs to be about 8 °.
However, the theoretical value must be combined with the actual situation. If some surfaces cannot make a large slope, the skin texture of this area can be treated with light treatment accordingly. According to the different forming conditions, materials, wall thickness and vertical height of the parts, the ratio of the skin depth and draft angle will be different. If the draft angle is small and the skin pattern is too deep, it may cause the parts to be stuck or whitened during demoulding.
Depth range of common patterns:
① The depth of fine striae is 0-80 μ M;
② The depth of spark pattern is 20-40 μ m, which is more delicate and soft than that of fine pattern with the same depth;
③ The depth of the drawing line is 20-80 μ M;
④ Coarse and geometric lines, with a depth of 100-150 μ M.
In general, the relationship between draft angle and processing depth of dermatoglyph is shown in the following table:
4. Basic principles of the definition of dermatoglyphic area
The dermatoglyphics of the parts are officially announced by the design department of the main engine plant, which are generally distributed in the visible area, including the high visible area and the low visible area, except for the painted parts and the chrome plated parts.
The effect of the same skin texture applied to different shapes of objects is different, while the requirements of different surfaces and overlapping parts of parts are different, so we expect to consider the layout and definition of skin texture in different areas of the interior in the stage of automobile modeling design.
The basic principles for the definition of leather area in interior design are as follows:
1) The instrument panel, door guard board, A-pillar guard board, etc. belong to the high visible area, and the surface area of plastic parts is large. These main visual parts need better skin texture. The three-dimensional dermatoglyph is rich in layers, soft in luster and good in decoration effect. Therefore, the three-dimensional multi-level dermatoglyph is usually selected in this part of the area.
2) On the surface of some smaller plastic parts, such as buttons, knobs, small electrical function operation panels, etc., due to the small area, it is not suitable for relatively large style
