What is a Slide-Joint?

MechDesigner definition: A Slide-Joint makes a Line in one Part to be collinear with a Line in a different Part. The Lines can move along 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 along each other.

Note: Styling: Charcoal, Dark,  Edit menu > Application-Settings > Graphics tab > Display Colours :  [Background : White] ;  [Part-Unsolved : Blue] ; [Part-Solved: Green] ;[ Joint-Solved : Green] ; [Joint-Unsolved : Blue]

Add Slide-Joint

Add Slide-Joint icon

Kinematic Elements Toolbar : Add Slide-Joint icon [<<left of graphics-area]


Add menu > Mechanism sub-menu > Add Slide-Joint



IMPORTANT: Slide-Joints and Force calculations : to correctly calculate reaction forces, the length of the two Lines in a Slide-Joint should equal to the Slide-Rail and Slide-Bearings in your actual machine design.


The Slide-Joint symbol in the graphic-area is:

two[2] rectangles - a wide and a narrow rectangle.

1s-red Narrow Rectangular Box - its length is equal to the length of Line '1' you select for the Slide-Joint

2s Wide Rectangular Box - its length is equal to the length of the other Line '2' you select for the Slide-Joint

3s Arrowhead to show Positive-Direction* - is at the start-Point of one of the two Lines you select for the Slide-Joint

* Positive-direction is important when you add a Motion-Dimension FB to the Slide-Joint.

See Positive direction of Slide-Joints and Motion-Dimension

See Also: Add Pin-Joint, Add Ball-Joint, Add Motion-Dimension FB


Before you can do Kinematics-elements toolbar > add Slide-Joint you must have a minimum of two Parts, and one Line* in each Part. A minimum of one Part must have a blue Part-Outline.


1.A Line*1s-red that is a child to a Free-Part
2.A Line*2s that is a child to:
a different Free-Part

- or -

In this image: line2s is in the Base-Part [Rectangular Part-Outline is not-shown], which is always a kinematically-defined Part, and Line1s-red is the CAD-Line1s-red along the centre of an Added-Part.

* Line or CAD-Line

Add Slide-Joint:



STEP 1: Click Add Slide-Joint


Add menu > Mechanism sub-menu > Add Slide-Joint

Kinematic Elements Toolbar : Add Slide-Joint icon

STEP 2: Click the two Lines:

1.Click a Line1s-red in a Free-Part
2.Click a Line2s 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 OK-tiny-13-17 to close the Select-Elements dialog-box

See also Slide-Joint Special Case.

STEP 3: Complete the command

If the two Lines do not snap together:

1.Click the graphic-area

The two Lines become collinear.



A new Slide-Joint


In this case, the new Slide-Joint in an 'Unsolved Mechanism' .

One of the Parts in the Slide-Joint above is not kinematically-defined, and has a Blue Part-Outline.

VIDEO: Add Slide-Joint - Simple-Case


How to...

Add a Slide-Joint






A new Slide-Joint


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

tog_minusSpecial Case: Two or more collinear Slide-Joints

Frequently, a design needs two, or more, collinear Slide-Joints.

To add a Slide-Joint, we must select two[2] Lines, with one line for two different Parts.

However, we must be careful as to which two Lines we select when we want the new Slide-Joint [#2] to be collinear with a different Slide-Joint [#1].

From a total three Parts and Lines, we must decide which two Lines we want to select for each Slide-Joint.

Assuming that Slide-Joint #1 is between Lines 1 & 2 [in Parts 1 & 2], then there are two options for Slide-Joint#2

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

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

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


The image to the left shows:

A. Slide-Joint: a joint of two collinear Lines
Line1s-red is in a Part [obviously] but its Part-Outline is not in the image.
CAD-Line along the centre of Part2s, [but we can see because it is collinear with Line1s-red]
B.Completely-Free Part3s , which includes a CAD-Line along its centre.


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-Line4s along the center of the Completely-Free Part


The Slide-Joint does not need to be with the CAD-Line4s.

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


STEP 3: Click the two Lines5s in the Slide-Joint.


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': term to use when MechDesigner cannot be sure as to which elements you want to select.


Select-Elements dialog-box

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

Notes: Very frequently, to add a new element you must select other elements.

If you anticipate that there might be ambiguity as to which elements might be selected, we recommend, whenever possible, you:

click an element that does not have ambiguity before
click an element that does have ambiguity.

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



As we did follow our recommendation, the Line at the top of the list is Line4s is at the top of the list of elements - it has the element-name of CAD-Line2

We definitely want to select CAD-Line2 [at the top of the list] for the new Slide-Joint.

The ambiguity is which of the other two Lines5s we want to select for the new Slide-Joint.

To select the Lines

1.Ctrlb 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 -

CAD-Line2 and CAD-Line [image left]




However, you cannot select:

CAD-Line2 and CAD-Line [image left]

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


In the Select-Elements dialog-box.

STEP 4: Select the two Lines:
1.Ctrlb key down
2.Select all Lines in the Select-Elements dialog-box to do Add Slide-Joint
STEP 5: Click OK-tiny-11-15 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