Ⅰtype of parallel combination: The principle of parallel mechanism combination is the basic institutions of two or more parallel arrangement, the basic mechanism has its own input, an output component. This is equivalent to the synthesis of movement, its main function is to t the output component form of supplement, strengthen and improve, etc. The diagram of pass the following of motion is shown in Fig 1. 

 Fig. 1  Transmission diagram of parallel combination mechanism for I type 

   Ⅱtype of parallel combination: It has the common basic structure of each input and output components for the Ⅱ type, it can separate one movement into two movements, then make the two movements into one to out of movement. Its main functions are similar with the parallel combination of type , to change the Ⅰoutput state and trajectory of motion. Also can improve stress state agencies, improve their own balancing. The diagram of pass the following of motion is shown in Fig 2.

   Fig.2  Transmission diagram of parallel combination mechanism for Ⅱ type 

   Ⅲ type of parallel combination: Mechanisms have the common input, but have their own output, it can separate one movement into two movements, It’s main function achieve the two movement output, which the two movements  joint function each other to complete the more complicated process action. The diagram of pass the following of motion is shown in Fig 3.

   Fig.3  Transmission diagram of parallel combination mechanism for Ⅲ type 

Composite mechanisms of combination   

   This is a kind of combination modus with two degrees of freedom A and B hen an additional mechanism. This is a more complex combination type, the basic bodies have movements of the two inputs, one from body structures, and the other from the additional mechanism. There are two cases from the additional input, one is the body with additional components and access; the other is connected back through additional mechanism. 

   The type of parallel: Taking the component from the mechanism of based and additional into parallel connection, and also taking the linkages linked from them into parallel connection, one of linkages linked as input, then another linkage linked of basic component as output, the diagram of motion transfer is shown in Fig 4. 

   Fig.4  Transmission diagram of parallel join of combination mechanism 

   The two linkages linked join with the parallel manner from components of the basic and additional, the other the linkages linked, let the motion loop join the basic component to the components with complex motion. The diagram of motion transfer is shown in Fig 5. 

  Fig.5  Transmission diagram of loop join of combination mechanism  

Case Study 

   Building equation: There are two cams to complete the movement in a certain direction, the cam 1 complete the movement in X direction, the cam 2 completes the movement in Y direction. First respectively designed the two basic cams, then the combination cam mechanism can realize the purpose of any trajectory by the coordinating activities. The schematic diagram of straight moving follower disc cam is shown in Fig 6.

   Fig.6  The schematic diagram of straight moving follower disc 

   As shown the Fig 6. In the Cartesian coordinates, the coordinates of the point in the cam profile can express as:

Where e is eccentricity: 

Because of the cam 1 and cam 2 is disc cam of linear motion along the axis, and then: 

      e=0   

            S0=rb                     (2) 

Therefore, the above equation can be written as