In this Step, we add two kinematic between the Piggyback Sliders and the machine frame [Base-Part].
It is then possible to drive one of the Parts in each Dyad, and thus drive the Piggyback Sliders, with cams or servomotors. The cams and servomotors are fixed to the machine frame.
Dyads that we can use.
We can use any of the five Dyads. To keep the principle very simple, we will add in this tutorial two R-R-R Dyads.
|1.||First R-R-R Dyad: Connects the X-Slider to the Machine Frame. |
|2.||Second R-R-R Dyad: Connects the Y-slider to the Machine Frame. |
The Dyads in the model.
[Note: Below, we have changed the X and Y Motions. Now, the motions include a constant velocity segment so that the motion follows 'something'. Hence, below, the XY-Path is different to the XY-Path in Step 11.1.]
| STEP 1: ||Edit the Base-Part, Add a Horizontal Line near to where you want to join the R-R-R Dyad to the Base-Part. Close the Part-Editor.|
| STEP 2: ||Edit the Y-Slider, Add a Line where you want to connect the Dyad to it.|
We will use the Point at the Trace-Point
We can now add the 2nd RRR Dyad.
| STEP 3: ||Add Two Parts. Connect them together with a Pin-Joint|
| STEP 4: ||Add two more Pin-Joints – one with the Base-Part and the other with the new Line in the Slider.|
Question: Why a 3rd RRR Dyad?
Answer: To drive the Piggy-Back Sliders from a position that is nearer to the drive of the
Part 1st Dyad. Note the 'Bell Crank'.
| STEP 1: ||Edit the Base-Part, Add a Horizontal Line, near to where you want to 'ground' the R-R-R Dyad. Close the Part-Editor|
| STEP 2: ||Edit the Grounded Part of the second Dyad so it is used as a |
We can now add the 3rd RRR Dyad
| STEP 3: ||Add Two Parts, Connect them with a Pin-Joint|
| STEP 4: ||Add two more Pin-Joints – one to the Base-Part and the other to the Y-Slider.|
Now, the two Parts that will drive the mechanism are near to each other.
This makes it more convenient for cams and servomotors.
Please view the Video.
P = Parts; J = Joints, F = 3*(9-1) - 2*11 = 2
The new design has:
|•||6 new Parts (9 in total), and |
|•||9 new Joints (11 in total).|
F = 3(P–1) – 2J : P = # Parts ; J = # Joints
F = 3 * (9–1) – 2 * 11
F = 24 – 22 = 2
Degrees-of-Freedom = 2
Mobility = Degrees-of-Freedom – Number of Motion-Dimensions.
Mobility = 2 – 2 = 0
How do we 'Drive' the design so that we follow the 2D Planar Motion?