R-angle, as the name suggests, refers to the circular arc angle. The R angle is ubiquitous in the structure of parts and can be divided into inner arc angle or outer arc angle. On the drawing, use R+numbers to represent, such as R5 representing a circular arc angle with a radius of 5. As shown in the figure below: the left side is the inner arc angle annotation, and the right side is the outer arc angle annotation.

Is the small R-angle optional? In fact, in practice, many "accidents" often occur due to neglecting the R-angle. So let's summarize the functions of the R angle:

1. Machining parts reduce stress concentration and avoid failures such as fracture. In the design of machined parts, the R angle at the root of each step of the step shaft can effectively reduce stress concentration, improve the strength and service life of the part. For example:

① The R angle of the cantilever shaft replaces chamfers or tool grooves to improve the strength of the shaft.

Example 1: Replacing the tool slot with an R-angle (large R-angle does not affect assembly)

Example 2: R angle replaces chamfer (large R angle affects assembly)

    ② The root of the bolt head is rounded to improve the strength of the bolt. According to GB-T 5782-2000 "Hexagonal Head Bolt", taking M5 bolt as an example, the minimum value of r angle in the figure is specified as 0.2mm.

If it is in a tight connection, the R angle here is the maximum stress concentration point except for the first thread. If it is designed to be 0.2mm according to the standard, there is a significant risk of strength. Usually, the R angle here should be as large as possible to improve the strength of the bolt.

③ Machining the R-angle at the end of the shaft can remove burrs, make the edges of the parts smoother, and improve machining accuracy and assembly quality. For example, all screw heads have rounded corners, making it convenient for sleeve installation; Machining parts with rounded shoulder corners, etc. The following picture shows the hammer striking the rod:

2. Plastic parts improve injection flowability and rib strength. Increasing the R angle in plastic molds can improve the fluidity of injection molding materials, reduce the generation of bubbles, facilitate mold demolding, enhance the appearance quality of products, and also increase the strength of internal reinforcement plates. For example:

① The rounded corners at the root of the screw column and reinforcement plate improve strength. Especially when using materials with lower strength, such as PP, more attention should be paid. Normally, the rounded corner R ≤ 0.3t (where t is the wall thickness) indicates significant stress concentration; The inner fillet R is ≥ 0.8t, and there is basically no stress concentration.       

② Increase the R-angle at the root of the fan blade to enhance its strength. As shown in the following figure:

      Stamping parts require R-angle transition to improve the processability and mold life of stamping. The following is the corner grinding stamping cover, with rounded corners at all bends:

4. Adding an R angle to product design can enhance product aesthetics, human-machine comfort, and safety. For example:

① The touchable parts of the product's appearance are generally treated with R-angles, which are both aesthetically pleasing and enhance the user's tactile experience; The handle design of some products features a large R-angle treatment to enhance the user's tactile experience.       

② Product safety specification requirements. In some designs that require compliance with safety regulations, such as through holes, cable trays, etc., the design of the R-angle can avoid sharp angles and prevent safety accidents such as scraping hands.       

Through the above introduction, the role of the R angle is significant. When designing the R-angle, the following points should also be noted:

① When designing wall thickness products, maintain consistent R-angle to ensure uniform wall thickness and improve overall structural stability;       

② The size of the R-angle may be larger in some scenarios, but at the same time, assembly space needs to be considered to avoid line contact at the R-angle instead of surface contact;       

③ The roughness at the R angle needs to be controlled in some scenarios, such as the outer arc angle, and some are assembly guidance for sealing rubber parts. Poor roughness can damage the sealing parts;       

④ In the structure of plastic parts, in addition to the necessary R-angles (such as the root of the screw column, the root of the reinforcing rib, and the cable slot), excessive R-angles will increase the complexity and cost of mold processing;       

In short, the role of the "small" R-angle cannot be ignored. By designing and applying the R angle reasonably, the performance, appearance, and safety of the product can be significantly improved, while also helping to improve production efficiency and reduce costs.

Article source: Internet

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