The surface effect of injection molded automotive parts is like skin texture, which is called leather grain. This article mainly introduces the design requirements of leather grain direction, leather grain area and draft angle on the surface of interior and exterior injection molding parts.
When the interior is defined as leather grain, the modeling department is generally required to refer to the definition of interior leather grain in this article to maintain the consistency of the texture inside the car.
The color and texture design of car interior plays an important role in the entire interior design. The effect of the texture of the interior parts directly determines the final sensory effect of the entire interior.
When designing the leather texture of car interiors, we must not only consider the positioning of the car model, the preferences of the user group, and the matching of the leather texture with the overall interior, but also the draft angle and surface quality stability during the processing process.
Common types of skin texture injection molded automotive parts
Leather grain processing is a process of transferring a specific pattern to the surface of a mold. Nowadays, the types of leather grains for automotive interiors basically include leather grain, geometric technology grain, brushed grain, and sand grain, as shown in figure below.
Leather Texture
Sand Texture
Brushed Metal
Geometric
The leather texture is a traditional natural imitation leather effect, composed of cross-grain lines of different depths and rich layers. Most of them are mainly two or more layers of patterns, in which sand grain and spray grain process are added many times to finally form a three-dimensional leather grain.
The geometric technology texture is composed of geometric figures of the same depth, mainly highlighting the three-dimensional sense and regularity, but it has higher requirements for texture splicing technology.
Due to the structural regularity of geometric leather grain, the surface mirror reflection is very easy to produce scratches, and the scratch resistance is relatively poor; different from the diffuse reflection effect of ordinary leather grain, the mirror reflection of geometric leather grain is prone to local gloss non-uniformity, which amplifies the appearance defects of parts;
With the current leather grain technology, geometric leather grain is difficult to maintain, and the entire surface must be remade when damaged, and it cannot be repaired, and the stretching and seam lines are obvious. Due to the above defects, the shape of the parts should be fully analyzed when applying. Sand grain is sprayed on the mold surface by using a sandblasting machine and a ratio of sand particles.
The brushed texture is mainly used for car CDs, decorative panels, etc., and can be designed with different effects such as straight wire, broken wire, depth, and brightness. The process is mainly composite printing, and the wire is ultra-fine.
The rationality of the overall design of plastic parts is closely related to the quality of the grain, surface quality and molding difficulty. After simulating the design experience of the industry, for two typical car interior injection molding materials PP and ABS, the grain depth has different requirements for the draft angle of plastic parts:
The draft angle of parts and the depth of grain processing directly affect the demolding characteristics of parts.
The draft angle of general plastic parts needs to be defined above 0.5°, but for decorative parts with grain, the basic experience is that the grain with a depth of 13μm requires a draft angle of 1°. For example, when the door rain shield itself is etched with 110μm grain, the draft angle of the early design needs to be about 8°. However, the standard deviation must be combined with the actual situation. If some surfaces cannot make a large inclination, the grain in this area can be relatively shallow.
According to the different factors such as forming standards, materials, part thickness and standing height of parts, the proportion of grain depth and draft angle will be different. If the draft angle is small and the grain is too deep, it is likely to cause safety hazards such as jamming or white fogging when the parts are ejected from the mold.
Common grain depth range:
- Fine grain, grain depth is 0-80μm;
- Fire grain, grain depth is 20-40μm, which is more delicate and gentle than fine grain of the same depth;
- Metal brushed grain, grain depth is 20-80μm;
- Coarse grain and geometric grain, grain depth is 100-150μm.
Basic principles for defining leather grain areas
The leather grain of parts is announced by the technical department of automobile manufacturers and is generally distributed in visible areas, including high-visibility areas and low-visibility areas, except for painted parts and stainless steel parts.
The same leather grain has different effects when applied to objects of different shapes, and the requirements for leather grain vary for different slopes and steel lap joints of parts. Therefore, we hope to consider the layout and definition of leather grain in different areas of the interior of the car in the stage of automobile product design.
The basic principles for defining leather grain areas in car interior design are as follows:
1) The dashboard, door rain shield, A-pillar rain shield, etc. belong to the high-visibility area
The surface area of plastic parts is large, and these visual key positions require leather grains with good effects. Three-dimensional leather grains have rich levels, mild gloss, and good decorative effects. Therefore, these areas generally choose three-dimensional multi-layer leather grains.
2) On the surface of some small plastic parts
such as buttons, knobs, small appliance function operation panels, etc., due to the small area, it is not suitable for relatively large three-dimensional patterns and general patterns, but it is more suitable for small and delicate patterns. Generally, frosted patterns are used, which makes the whole part and the pattern look exquisite and harmonious.
3) On some uncommon surfaces
such as the inner side of the storage box, the inner side of the glasses box, the inner side of the armrest box, and the inner side of some opening and closing functions, general patterns can be made to save costs.
In addition, when etching the grain of individual parts and the grain of parts with mutual coordination, it is necessary to pay attention to its aesthetics and maintain the continuity of the grain. The main aspects are summarized as follows:
1) Grain etching area of individual parts
Generally, etching is done to the visible surface of the part as a whole, such as the door rain shield assembly in Figure 16. The grain etching of each individual part is based on the visible surface of the door rain shield assembly.
2) R angle of individual parts
That is, the area where two adjacent surfaces of the parts are connected and curved, the grain needs to ensure that the visible surface is within the range of about 2 to 4 mm from the R angle, and ensure that the area visible within the human visual range has been etched. As shown in Figure 5, when the right rear cover of the dashboard is matched with the surrounding parts, the exposed part is the R angle surface.
If the grain does not ensure the R angle, the surface will feel that the grain is interrupted, affecting the appearance.
3) The same part has two kinds of grains in the working intersection area:
For example, the door rain shield itself, two kinds of grains are defined in different areas on the same part. The grain etching of the working intersection area of the two must ensure the gentle connection of the two grains. Generally, the R angle needs to be treated accordingly, such as being slightly shallower than the R angle or starting to fade in the area 2-3 mm away from the joint.
Where can I find automobile precision injection mold manufacturers in China? Yuanfang Mold Manufacturing Factory has advanced equipment, superb technology, and honest management. The company is committed to high-quality automobile molds and excellent quality. Our 선루프 커버용 자동차 사출 성형 has win customer trust.
Korean 
English 
German 
Spanish 
French 
Italian 
Portuguese 
Japanese 
Polish 
Arabic 
Russian 
Chinese