Add 3× R-R-R Dyads
In this Step, we add two kinematic Dyads 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.
3 × R-R-R Dyads
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STEP 1: Prepare the Parts to locate the R-x-R (Pin-Joints) 1.Edit the Base-Part: Add Horizontal Line 2.Edit the X-Slider, Add a Line STEP 2: We can now add the Parts and the Joints for the R-R-R Dyad #1 3.Add two Parts. Add a Pin-Joint 4.Add Pin-Joint 5.Add Pin-Joint |
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STEP 1: Prepare the Parts to locate R-x-R (Pin-Joints) 1.Edit the Base-Part - Add Horizontal Line 2.Edit the Y-Slider, Add a Line STEP 2: We can now add the Parts and the Joint for the R-R-R Dyad #2 3.Add two Parts. Add a Pin-Joint 4.Add Pin-Joint 5.Add Pin-Joint |
Question: Why a R-R-R Dyad #3? Answer: To drive the Piggy-Back Sliders from a position that is nearer to the drive of the 1st Dyad. Note the 'Bell Crank' |
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STEP 1: Prepare the Parts to locate the R-x-R (Pin-Joint) so it is used 1.Edit the Base-Part - Add Horizontal Line 2.Edit a Part in Dyad #2, Add a Line 3.Edit the Y-Slider, Add a Line We can now add the R-R-R Dyad #3 3.Add two Parts. Add a Pin-Joint 4.Add Pin-Joint 5.Add Pin-Joint |
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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. |
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DEGREES-OF-FREEDOM The design has 9 Parts •1 × Base-Part •2 × Slider •3 × Dyads = 6 Parts The design has 11 Joint •3 × Dyads = 9 Joints •2 × Sliders GRUEBLER EQUATION: F = 3(P–1) – 2J : (P = Parts ; J = Joints) F = 3 × (9–1) – 2 × 11 F = 24 – 22 = 2 Degrees-of-Freedom = 2 MOBILITY Mobility = Degrees-of-Freedom – Number of Motion-Dimensions. Mobility = 2 – 2 = 0 |
How do we 'Drive' the design so that we follow the XY Path?
We can drive the Dyad Parts connected to the BasePart – Parts 7P and 8P in the image above.
We can use:
•Servomotor Drives : We would need to save the motions of the driven Parts to a text file, and format it for the servo controller.
•Cams and Cam-Followers : Add the Cam-Follower 'Rollers' and Camshafts. See Tutorial 5.
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The video clip to the left shows the Piggyback Sliders driven by two 2D-Cams |
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This is a more convenient configuration. Now two cams mounted to one cam-shaft. |