What is a Slide-Joint?

A Slide-Joint makes a Line in one Part to be co-linear with a Line in a different Part. The Lines can move along each other.

Add Slide-Joint.


Mechanism Local Toolbar : Add Slide-Joint icon


Mechanism menu > Add Slide-Joint


No dialog-box

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 the real design.


The Slide-Joint symbol in the graphic-area.

There are two rectangles - a wide and and a narrow rectangle.

1s-red Narrow Rectangular Box - its length is equal to the length of one of the Slide-Joint's selected Lines

2s Wider Rectangular Box - its length is equal to the length of the other Slide-Joint's selected Line.

3s Arrowhead to show its Positive-Direction*

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

See Positive direction of Slide-Joints and Motion-Dimension



Before you can add a 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 Free-Part

- or -

[* Line or CAD-Line].

Add Slide-Joint:



STEP 1: Click Add Slide-Joint


Mechanism menu  > Add Slide-Joint


Mechanism Local toolbar > Add Slide-Joint

STEP 2: Click the two Lines:

1.Click a Line1s-red in a Free-Part
2.Click a Line2s in a different Part


It is not necessary for the Lines to be CAD-Lines along the centre of an Added-Part.  You can select ANY Line in a Part.

STEP 3: Complete the command

If the two Lines do not snap together:

1.Click the graphic-area

The two Lines become co-linear.



MechDesigner adds a new Slide-Joint to the Assembly-Tree.


In the Kinematics-Tree , a Slide-Joint is the 'P' Joint in a Dyad. P is for Prismatic-Joint.



How to...

Add a Slide-Joint

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

tog_minusSpecial Case: Two or more co-linear Slide-Joints

'A Slide-Joint makes a Line in one Part to be co-linear with a Line in a different Part. The Lines can move along each other'.

Frequently a design has two Slide-Joints, that make co-linear a total of three Lines in three different Parts.

When there are three Parts, with a Line in each Part (Lines 1,2,3), the two Slide-Joints may make co-linear:

A.Lines 1 & 2 and Lines 1 & 3

- or -

B.Lines 1 & 2 and Lines 2 & 3

The selection of A or B becomes important when you also need to add one or more Motion-Dimension FBs to specify the motions of the different Parts/Lines relative to each other.


The image to the left shows:

A Slide-Joint : a CAD-Line in Part2s is joined to a Line1s-red in another Part.
oThe CAD-Line (hidden by Line1s-red) is a child to Part2s, which has a Blue Part-Outline, it is a Free Part .
oLine1s-red is Green - it may be in the Base-Part.
A Completely Free Part3s.

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  Add Slide-Joint in the Mechanism Local-Toolbar


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 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 to do Add Slide-Joint command
STEP 5: Click OK 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.

Help Files for MechDesigner and MotionDesigner 11.1 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd