The source files for this tutorial are installed in the [BricsCAD Installation folder]\Samples\Mechanical\piston folder.

Assembly design is a typical application where constraints are commonly used. BricsCAD Platinum allows users to assemble mechanisms and run a kinematic analysis.

This tutorial shows you how to start working with assemblies in BricsCAD. You will learn how to assemble the different parts in a 3D model, which lets you control the final result.

There are two approaches in MCAD (Mechanical Computer-Aided Design) to build an assembly: top-down and bottom-up.

In the top-down approach, you start with an empty assembly and the geometry of each component is then created, one by one, in the assembly.

In the bottom-up approach, each component is first created as a single entity. All components are then inserted into the assembly. The position of each component is controlled through 3D constraints.

We will now assemble a simplified - in comparison with a real-world engine - a model of a piston engine.

Step 1: Preparing for the exercise

1. You need a BricsCAD Platinum license for this tutorial.
2. Make sure the Assembly and 3D Constraints toolbars are open.
   
   
   
   To open a toolbar: move the cursor over an open toolbar, then right click and select the required toolbars from the toolbar list.
   Toolbars that are already open are marked in the list.
   
   
3. Make sure that the Quad cursor menu is active.
   
   Click the Quad field in the Status bar if necessary.
   
   
4. Make sure that the Exclude entities in Xrefs option of the PREVIEWFILTER system variable is switched off.
   
   
   
5. Open the Mechanical Browser dialog box.
   Do one of the following:
   • Click the Mechanical Browser tool button () on the Mechanical | Tools panel in the ribbon.
   • Click the Mechanical Browser tool button () on the Mechanical toolbar.
   • Choose Mechanical Browser in the Mechanical menu.
   • Type MechanicalBrowserOpen in the command bar.
   
   
   
6. Make sure Selection Modes = 3
   Do one of the following:

   • Type selectionmodes in the command bar, then type 3.

   • Set the Selection Modes toolbar as indicated below.
     

Step 2: Creating the assembly drawing

1. Click the New Component tool button () on the Mechanical | Create panel in the ribbon.
   A new drawing of the name Component_1.dwg is created and Component_1 is added in the Mechanical Browser.
2. In the bottom part of the Mechanical Browser, click the Name field and rename the main component: Piston Engine.
   
   
   The drawing name automatically matches the main component name.
3. Save the drawing.

Step 3: Adding the components

1. Click the Insert Component tool button () on the Mechanical | Modify panel in the ribbon.
   The Insert Mechanical Component dialog displays:
   Open the [BricsCAD Installation folder]\Samples\Mechanical\piston folder.
   
   
   
2. Select the crankshaft.dwg, then double click or click the Open button.
   The component is attached to the cursor with its origin point.
   Dynamic dimensions display distance from the origin of the current coordinate system.
   
   
3. We will consider the crankshaft as the anchor component of the assembly and therefore insert it at the origin (0,0,0).
   Please make sure the insertion point is exactly at 0,0,0, otherwise the kinematic analysis in step 5 might fail.
   
   
   
4. Use the Look From widget to adjust the view orientation.
   
   
5. Repeat the previous steps to insert the other components: cylinder (1), piston (2), pin (3) and connecting rod (4).
   Avoid visual intersection of the components.
   

Step 4: Positioning the components

1. Click the Fix tool button () on the Solid | 3D Constraints panel in the ribbon.
   You are prompted: Select an edge, face or 3D solid:
   
   
2. Move the cursor over the largest cylindrical face of the crankshaft. Click when the face highlights.
   
   
3. Repeat the DmFix3d command.
   Move the cursor over the currently obscured circular face of the crankshaft.
   Hit the TAB key until the face highlights and click when the face highlights.
   
   
   The position of the selected faces of the crankshaft is now locked, as indicated in the Constraints tree in the Mechanical Browser.
   
   
   
   Clicking a constraint highlights the solid, face or edge it applies to.
   
   
4. Place the connecting rod near the crankshaft.
   
   
5. Click the Coincident tool button () on the Solid | 3D Constraints panel in the ribbon.
   You are prompted: Select a pair of subentities or [Autoconstrain] <Autoconstrain>:
   
   
6. Move the cursor over two planar faces of the crankshaft (1) and the connecting rod (2) as indicated in the image below.
   Click when the correct face highlights. Hit the TAB key to select the obscured face of the connection rod and click when the face highlights.
   
   
   
7. Click the Concentric tool button () on the Solid | 3D Constraints panel in the ribbon.
   You are prompted: Select the first entity:
   
   
8. Move the cursor over two cylindrical faces of the crankshaft (1) and the connecting rod (2) as indicated in the image below.
   Click when the first face highlights, then select the second face.
   
   
   The connecting rod is automatically moved to the right position according to our design intent.
   
9. Click the Concentric tool button () on the Solid | 3D Constraints panel in the ribbon.
   You are prompted: Select the first entity:
   
   
10. Move the cursor over two cylindrical faces of the piston (1) and the pin (2) as indicated in the image below.
    Click when the first face highlights, then select the second face.
    
    
    
    
    
11. Click the Tangent tool button () on the Solid | 3D Constraints panel in the ribbon.
    You are prompted: Select the first entity:
    
    
12. Move the cursor over two cylindrical faces of the piston (1) and the pin (2) as indicated in the image below.
    Click when the first face highlights, then select the second face.
    
    
    
    
    
13. Click the Coincident tool button () on the Solid | 3D Constraints panel in the ribbon.
    You are prompted: Select a pair of subentities or [Autoconstrain] <Autoconstrain>:
    
    
14. Move the cursor over two planar faces of the connecting rod (1) and the piston (2) as indicated in the image below.
    Click when the first face highlights, then select the second face.
    Hit the TAB key to select the interior face of the piston.
    
    
    
15. Click the Concentric tool button () on the Solid | 3D Constraints panel in the ribbon.
    You are prompted: Select the first entity:
    
    
16. Move the cursor over two cylindrical faces of the connecting rod (1) and the pin (2) as indicated in the image below.
    Click when the first face highlights, then select the second face.
    
    
    
    
    
17. Click the Concentric tool button () on the Solid | 3D Constraints panel in the ribbon.
    You are prompted: Select the first entity:
    
    
18. Move the cursor over two cylindrical faces of the piston (1) and the cylinder (2) as indicated in the image below.
    Click when the first face highlights, then select the second face.
    
    
    
    
    
19. Click the Distance tool button () on the Solid | 3D Constraints panel in the ribbon.
    You are prompted: Select the first entity or specify [measurement Mode]:
    
    
20. Move the cursor over the cylindrical faces of the crankshaft (1) and the planar bottom face of the cylinder (2) as indicated in the image below.
    Click when the first face highlights, then select the second face.
    Hit the TAB key to select the bottom face of the cylinder.
    
    
    Type 120 in the dynamic distance field.
    
    
21. (optional) Edit the Expression field of the distance constraint in the Mechanical Browser panel to adjust the vertical position of the cylinder.
    
    
22. Click the Fix tool button () on the Solid | 3D Constraints panel in the ribbon.
    You are prompted: Select an edge, face or 3D solid:
    
    
23. Click the outside cylindrical face of the cylinder.

Step 5: Kinematic Analysis

In this assembly the crankshaft is the driving component. To run the kinematic analysis we will rotate the crankshaft around its axis, which in this case is the Y-axis of the WCS.

1. Move the cursor over the crankshaft, then choose Rotate () in the Model command group in the Quad cursor menu.
   
   
   You are prompted: Select axial entity or define axis by [2Points/Xaxis/Yaxis/Zaxis] <2Points>:
2. Do one of the following:
   
   • Type Y, then press Enter.
   • Choose Y axis in the prompt menu.
   You are prompted: Pick start point in the rotation plane:
   
   
3. Pick a point in the drawing, then move the mouse to define the rotation angle.
   The piston and the connecting rod move dynamically along with the rotation of the crankshaft, while the cylinder stays at its fixed position.
   

Step 6: Material assignment

1. Select the piston on the Mechanical Browser.
2. Click Open () on the right click menu.
3. In Property of the Mechanical Browser select the Material field, then click  button and specify the Steel material in the Physical Materials dialog box. Click the OK button.
   
4. Save piston.dwg file.
5. Return to Piston Engine.dwg file.
6. Click Update button () on the right click menu for the piston. The value of the Material setting has changed.
   
7. Repeat the 2-8 steps for the other components: crankshaft, cylinder, pin, and connecting rod.

Step 7: Mass properties

1. Open the Settings dialog box.
2. Expand the Property units settings under Drawing | Drafting | Drawing units.
   
3. Check the Format mass properties checkbox to enable formatting of mass values with appropriate units.
4. Select the Mass units field, then click the Browse button () and specify the desired mass units in the MASSUNITS dialog box.
5. Check the Slugs checkbox.
   
6. Specify the 0.00 precision in the Linear units precision and Mass precision fields.
7. Close the Settings dialog box.

Step 8: Drawing generation

1. Select all components.
2. Click the Base Views tool button () on the Annotate | Drawing Views panel in the ribbon.
3. Enter new or existing layout name or click Enter to take <Layout1>.
4. On the VIEWBASE menu select the Projection type | First angle.
5. On the VIEWBASE menu select the Orientation | Front.
6. On the VIEWBASE menu select the Scale | Custom scale.
7. Enter scale: 0.005.
8. Select positions for base views.

Step 9: Exploded view

1. Switch to model space.
2. Click the Explode tool button () on the Assembly | Tools panel in the ribbon.
3. In the BMEXPLODE dialog box select Table by Level.
4. In the BMEXPLODE dialog box select Generate drawing views.
5. Enter new or existing layout name or click Enter to take <Layout1>.
6. Select position of the exploded representation.
7. Freeze "Drafting Viewports" layer in the drop-down Layers control menu on the Home | Layers panel in the ribbon.

Step 10: Bill of Materials

1. Click Bill of Materials tool button () on the Annotate | Assembly panel in the ribbon.
2. On the BMBOM menu select the Configure | Volume, Mass, Materials.
3. Select the insertion point.
4. Enter EXPLORER command in the Command line.
5. On Drawing Explorer menu select Text styles.
6. Change Standard style:
   • Font: Isocpeur;
   • Width Factor: 0.8.
7. Close Drawing Explorer menu.
8. Select Bill of Materials Piston Engine table. Use the knobs to align the width of the table to the width of the layout.

Step 11: Balloons

1. Click the Balloon tool button () on the Annotate | Assembly panel in the ribbon.
2. Select a first component on the View ports with Exploded view. Pick a point to place balloon.
3. Repeat the previous step for the other components.
4. Select balloons the 2-5 numbers. In Property panel select Leader arrow | Dot small.
   
   

Back to Tutorial Overview