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-Side of graphics-area]


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



IMPORTANT: Slide-Joints and Force calculations : to correctly calculate reaction forces, the lengths of the two Lines in a Slide-Joint should be 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 one Line you select for the Slide-Joint

2s Wide Rectangular Box - its length is equal to the length of the other Line 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 Lines* in the model. A Line* in two different Parts. A minimum of one Part must have a blue Part-Outline.



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

- or -

The Base-Part is always a kinematically-defined Part. All sketch-elements you add to the Base-Part are also kinematically-defined.

This image has one line* in the Base-Part, and the CAD-Line 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, see 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 co-linear.



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

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 co-linear Slide-Joints - the Select-Element dialog-box

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

We always need to select two[2] Lines [from different Parts] for a Slide-Joint.

However, we must be careful as to which two Lines we select for Slide-Joint #2 when we want it to be co-axial with Slide-Joint #1,

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

Assuming that Slide-Joint#2 is between Points 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 & 1]

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


The image to the left shows:

A.Slide-Joint: a joint of two co-linear Lines
1.Line1s-red in a Part that is not in the image
2.CAD-Line along the centre of Part2s

Note: A minimum of one Part must be a Free Part.  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'


STEP 3: Click a Line5s in the Slide-Joint.

There is ambiguity as to which is Line you want to select.


Select-Elements dialog-box

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

The element at the top of the list is always the first element you select. See Line4s above in STEP 2.

This is why we should select the Point that does not have ambiguity before the elements that do have ambiguity. it is at the top of the list in the Select-Elements dialog-box.


To select the Lines

1.Ctrlb key down - do this before you click the Lines in the box.
2.Select all of the Lines in the list to do the Add Slide-Joint command


There are two selections that are possible:

CAD-Line2 and Line3


- or -

CAD-Line2 and CAD-Line



CAD-Line2 and CAD-Line are not possible.

Why? Because these two Lines are joined together with a Slide-Joint already.


In the Select-Elements dialog-box.

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

The dialog-box closes.

The two Lines become co-linear.

If they do not become co-linear...

STEP 6: Click the Graphic-Area

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

There are now two Slide-Joints that are co-linear.

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