### What is a Slide-Joint?

 MechDesigner definition: a Slide-Joint makes a Line in a Part become co-axial (coincident) with a Line in a different Part. The two Parts can slide along relative to each other. IFTOMM Kinematic definition: a Slide-Joint makes an axis in one part become collinear with an axis in a different part, but allows the axes to slide relative to each other.
 Theme and Styling of images below:
 Edit menu > Application-Settings > General tab > Theme Options > Active Theme: Charcoal Dark Slate, Edit menu > Application-Settings > Graphics tab > Display Colours :  [Background : White] ;  [Part-Unsolved : Blue] ; [Part-Solved: Green] ;[ Joint-Solved : Green] ; [Joint-Unsolved : Blue]

 Kinematic Elements Toolbar : Add Slide-Joint icon [< Mechanism sub-menu > Add Slide-Joint Dialog-Box : None IMPORTANT: To correctly calculate reaction forces for a Slide-Joint: The lengths & positions of the Lines that define a Slide-Joint must be equivalent to the Lines that represent the Slide-Rail and Slide-Bearing in your actual design. There can be only one Line in each Part to define the Slide-Joint. There can only be one Slide-Joint between the two Parts. Thus, even if there is more than one Slide-Rail and Slide-Bearing in your actual design, you must determine the length and position of one equivalent Line in each Part for one Slide-Joint. Slide-Joint in the graphic-area: Narrow Rectangular Box - its length is equal to the length of Line '1' you select for the Slide-Joint Wide Rectangular Box - its length is equal to the length of Line '2' you select for the Slide-Joint Arrowhead to show Positive-Direction* - is at the start-Point of one of the two Lines you select for the Slide-Joint * Positive-direction becomes important when you add a Motion-Dimension FB to the Slide-Joint.

#### Preparation:

Before you can do add Slide-Joint you must have a minimum of two Parts, and a Line* in each Part. A minimum of one Part must be a free Part, which has a blue

 1 A Line* that is a child to a free Part
 2 A Line* that is a child to:
 • a different Free-Part

- or -

 • a kinematically-defined Part.

In this image: line is in the Base-Part [Rectangular Part-Outline is not-shown], which is always a kinematically-defined Part, and Line is the CAD-Line along the centre of an Added-Part.

STEP 2: Click the two Lines:

 1 Click a Line in a Free-Part
 2 Click a Line in a different Part

If the Select-Elements dialog-box opens, you have clicked more than two Lines.

 1 CTRL+Click the two Lines [in two different Parts] in the Select-Elements dialog box.
 2 Click to close the Select-Elements dialog-box

STEP 3: Complete the command

If the two Lines do not snap together:

 1 Click the graphic-area

The two Lines become collinear.

Assembly-Tree

A new Slide-Joint

Kinematics-Tree

In this image, the new Slide-Joint belongs to an Unsolved Mechanism .

A Part in the Slide-Joint is not kinematically-defined, and has a Blue Part-Outline.

### VIDEO: Add Slide-Joint - Simple-Case

#### Kinematics-Tree

 Assembly-Tree A new Slide-Joint Kinematics-Tree In this case, the new Slide-Joint in an Unsolved-Mechs as the Part-Outline is Blue in the model above

#### Special Case: Two or more collinear Slide-Joints

Frequently, a machine design has two or more Slide-Joints between three or more Parts

We must decide which two Lines from which of two Parts we want to select for each Slide-Joint.

For example:

There are a total three Parts and we would like to join all three Parts to one sliding axis. We must add two Slide-Joints:

If, say, Slide-Joint#1 is between Lines 1 & 2 [in Parts 1 & 2], there are two options for Slide-Joint#2:

Option A: Slide-Joint#2 between Lines 3 & 1 [in Parts 3 & 1]

Option B: Slide-Joint#2 between Lines 3 & 2 [in Parts 3 & 2]

When to do Option A or Option B becomes important when you need to also add Motion-Dimension FBs to specify the motions of the two Parts.

Preparation for this example:

 A. Slide-Joint: a joint of two collinear Lines :
 • Line is in a kinematically-defined Part [obviously] as it is coloured Green
 • CAD-Line along the centre of Part, which is collinear with Line
 B. Completely-Free Part, which includes a CAD-Line along its centre.

Note:

A minimum of one Part must be a free Part.  However, one Part, two Parts, or all three Parts may be free Parts.

 STEP 1: Click Kinematic-elements Toolbar > Add Slide-Joint

 STEP 2: Click the CAD-Line along the center of the Completely-Free Part

Note:

The Slide-Joint does not need to be with the CAD-Line.

Generally, a Slide-Joint can be with any Line in a Part.

 STEP 3: Click the two Lines in the Slide-Joint

Notes:

Now we have clicked a total of three Lines.

The Slide-Joint is between two Lines only.

Thus, there is ambiguity as to which two Lines you want for the Slide-Joint.

'Ambiguity': when MechDesigner is not sure which element to select.

Select-Elements dialog-box

When there is ambiguity as to which two Lines you want to select, the Select Elements dialog-box opens.

Top-tip

If you can anticipate that there might be ambiguity as to which elements you need to select, we recommend:

 • If possible, click first an element that does not have ambiguity
 • Then, click an element that might have ambiguity.

In the Select-Elements dialog-box, the element at the top of the list is always the first element you select.

When we follow our recommendation, the Line at the top of the list is CAD-Line - it has the element-name of CAD-Line2

We definitely want to select CAD-Line2 for the new Slide-Joint.

The ambiguity is which Line from the other two Lines we want to select for the new Slide-Joint.

To select the Lines

 1 key down - do this before you click the Lines in the box.
 2 Select all of the Lines we want to use for the new Slide-Joint

Generally, mathematically, you can combine two elements from three elements in three possible ways. 1&2; 2&3; 3&1

However, MechDesigner will select only those elements that you can combine to add the new element.

Thus, you can select:

 • CAD-Line2 and Line3 [image above]

- or -

However, you cannot select:

Why? MechDesigner knows there is a Slide-Joint between these two CAD-Lines already.

In the Select-Elements dialog-box.

 STEP 3: Click the two Lines
 1 key down
 2 Click to select all Lines in the Select-Elements dialog-box to do Add Slide-Joint
 STEP 5: Click in the Select-Elements dialog-box.

The Select-Elements dialog-box closes.

The two Lines become collinear.

If they do not become collinear...

 STEP 6: Click the graphic-area

The two Lines become collinear to add a new Slide-Joint,

Now, there are two Slide-Joints and three Lines that are collinear.

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd