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 colored Green

•CAD-Line along the center of Part, which is collinear with Line

B.Completely-Free Part, which includes a CAD-Line along its center.

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 Select Elements dialog-box.  

2.Select all of the Lines we want to use for the new Slide-Joint

Generally, 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 are compatible to add the new element.

You can select:

•CAD-Line2 and Line3 (image above)

- or -

•CAD-Line2 and CAD-Line (image left)

However, you and MechDesigner cannot select:

• CAD-Line2 and CAD-Line (image left)

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.