The design of the cam mechanism should not only ensure that the follower can achieve the predetermined movement pattern, but also ensure that the mechanism has good force transmission, has a compact structure, and meets the strength and installation requirements.
1. Material selection
Material requirements: high hardness of the working surface; wear resistance; sufficient surface contact resistance;
The material of the cam is selected primarily based on its moving speed and the size of the load.
The load is not significant. At low speed, HT250, HT300, QT800-2, QT900-2, etc. can be used as cam material. The contour surface should be heat treated to improve its wear resistance.
Medium speed and medium load cams are generally made of 45, 40Cr, 20Cr, 20CrMn and other materials, and are surface quenched to achieve a hardness of 55~60HRC.
High speed and heavy duty cams can be made of 40Cr, surface hardened to 56~60HRC, or 38CrMoA1, nitrided to 60~67HRC.
Commonly used roller materials: 20Cr or bearings
Cam surface treatment: black electroplating (note the plating thickness)
2. Cam mechanism pressure angle
The pressure angle of the cam mechanism refers to the angle between the tangent line and the normal line of the contact point during contact between the cam and the follower. When the cam is in contact with the follower, the pressure angle at different positions also changes due to the different shapes of curved surface of the cam and its radii of curvature. In order to ensure the smooth movement of the cam mechanism, it is generally required that the pressure angle of the cam contact point always be less than a certain limit value, generally less than 20°. If the pressure angle is too large, it will cause problems such as contact stress concentration and increased wear, thereby affecting the service life and working effect of the cam mechanism.
3. Selection of roller radius
The choice of the radius of the rollers in the cam mechanism depends on the shape of the cam curve and the size of the rollers. According to general design experience, the radius of the roller should generally be between 0.8 and 1.2 times the arc radius of the cam section. When the roller radius is correctly selected, the cam can produce even contact points across the roller, thereby reducing the concentration of contact stress and reducing noise and wear. If you choose too large or too small a roller radius, it will result in increased friction, increased wear or poor contact. Therefore, in the actual design, it is necessary to comprehensively consider various factors such as cam curve shape, roller material and size, etc., and carry out the calculations and calculations. necessary inspections.
4. Selection of cam base circle radius
Cam base circle refers to the imaginary circle of the cam profile, which is usually used as a reference point when designing cams. The following factors should be considered when selecting the cam base circle radius:
Cam shape and size: The radius of the cam base circle should be selected appropriately to meet manufacturing requirements, actual usage needs and quality assurance.
Stress situation: The base circle of the cam will also be subject to some load when it contacts the roller, so the size of the base circle radius must also consider the effects of contact stress and wear.
Travel Speed: As the cam travel speed increases, the radius of the base circle must increase accordingly, otherwise it may be too concentrated to cause high stress and increased temperature.
Manufacturing constraints: Depending on the limits of production cost and technical level, the cam base circle radius should be fully optimized and selected considering the feasibility and reliability of the manufacturing process.
Daguang focuses on providing solutions such as precision CNC machining services (3-axis, 4-axis, 5-axis machining), CNC milling, 3D printing and rapid prototyping services.
