Step 6A1.3: Add a Transforming-Mechanism

<< Click to Display Table of Contents >>

Navigation:  Getting Started Tutorials - MechDesigner > Tutorial 6: Cams: Flat, Barrel, Globoidal, 'Slot' > 6A1: Cam-Shaft & Follower-Roller >

Step 6A1.3: Add a Transforming-Mechanism

Summary of this Step

Add a Transforming-Mechanism to the Tool-Part.

The Transforming-Mechanism is an R-R-R dyad.

Join the Transforming-Mechanism to the Tool-Part and the Base-Part.

Edit the Base-Part to add Geometry.

MechDesigner calculates for you the motion-values of the two Parts in the Transforming-Mechanism.

This is an introduction to Inverse-Kinematics.

Terminology:

Terms :

Definitions

Transforming-Mechanism :

A derived-name for the dyad in a kinematic-chain that transforms the motion of a Tool to the motion of the Follower. The Follower is usually located at a more convenient place in the machine.

Inverse-Kinematics :

We calculate for you the motion of the Parts in the Transforming-Mechanism from the motion of the Tool-Part whose motion you design in MotionDesigner.

Dyad :

A kinematic-term for two Parts and three joints that combine as a Transforming-Mechanism.

Video of this Step

Video: Add the RRR Dyad ('Transforming' Mechanism)

tog_minusEdit the Base-Part

Why edit the Base-Part?

To add sketch-elements so that we can join the Transforming-Mechanism to the Base-Part.

Also, you need to join a Cam-Shaft to the Base-Part.

STEP 1: Edit the Base-Part

1.Double-click the Part-Outline of the Base-Part to open the Part-Editor

or

1.See also How to open the Part-Editor

GST-6A1-301

STEP 2: Add two Lines to the Base-Part.

1.Geometry toolbar > Add 2 × LinesRed-14-1bRed-14-2 - see image to the left.

2.Constraints toolbar > Add Horizontal | Click the Lines.

3.Geometry toolbar > Add Dimension | Click each Line to edit its length

Locate the two Lines with Dimensions. For each Line:

4.Geometry toolbar > Add Dimension | Click the start-Point and the X-axis. Also, do Add Dimension between the start-Point and the Y-axis.

5.Exit the Part-Editor
tog_minusAdd two Parts and three Pin-Joints  – the Transforming-Mechanism

GST-6A1-302

STEP 1: Add two Parts

1.Click Kinematic-elements toolbar > Add Part ( Shortcut : Insert key on your keyboard )

2.Mouse-button-down, drag in the graphic-area, mouse-button up, to add PartRed-14-1b

3.Do Steps 1 and 2 again to add PartRed-14-2

The two PartsRed-14-1bRed-14-2 are free Parts.

GST-6A1-303

STEP 2: Add three Pin-Joints

1.Click Kinematic-elements toolbar > Add Pin-Joint

2.Pin-JointRed-14-3: Click the start-Point of PartRed-14-1b and a Point in the Base-Part

3.Pin-JointRed-14-4: Click the start-Point of PartRed-14-2 and the start-Point in the Slider

4.Pin-JointRed-14-5: Click the end-Point of PartRed-14-2 and the end-Point of PartRed-14-1b

When you complete STEP 2 Add three Pin-Joint, the Parts in the transforming-mechanism become kinematically-defined.

GST-6A1-304

Closure...: We explain Closures in detail in Tutorial 2 Step 2.4

It is possible that the dyad assembles in a closure that you do not want. The R-R-R dyad has two closures.

Do Step 3 if the Parts do not assemble in the closure you want.

STEP 3: Change Dyad Closure

GST-Icon-ChangeDyadClosure

1.Click Kinematic-elements toolbar > Change Dyad Closure

2.Click the Part-Outline of PartRed-14-1b or PartRed-14-2

3.Click OK-tiny-11-15 in the Command-Manager

The two Parts in the dyad move to a different closure.

STEP 4: Cycle the Model with the Transforming-Mechanism

1.Mechanism-Editor: Click Run menu > Cycle

You will see that the Transforming-Mechanism (dyad) moves with the Slider.

Save you Mechanism

GST-6A1-305

If, as you cycle the model, the joints move apart, you can do one or all of these changes to your design:

•Edit the length of the Parts in the dyad - in the image the lengths of the two Parts are 160mm and 110mm)

•Edit the Base-Part to move the position of the Pin-Joint in the ground.

•Edit the Tool-Motion (in MotionDesigner) to reduce the distance the Tool-Part moves.

•Edit the Base-Value in the Motion-Dimension dialog to change position at which the Slider starts its motion.

Save you Mechanism