Ken YoussefiMechanical Engineering Dept., SJSU 1 Introduction to Fundamentals of Assembly

Ken YoussefiMechanical Engineering Dept., SJSU 2 Bottom-Up Design (Modeling) The components (parts) are created first and then added to the assembly file. This technique is particularly useful when parts already exist from previous designs and are being re-used.

Ken YoussefiMechanical Engineering Dept., SJSU 3 Top-Down Design (Modeling) The assembly file is created first and then the components are created in the assembly file. The parts are build relative to other components. Useful in new designs In practice, the combination of Top-Down and Bottom-Up approaches is used. As you often use existing parts and create new parts in order to meet your design needs. Parts can be modified in assembly or in part file.

Ken YoussefiMechanical Engineering Dept., SJSU 4 Assembly and Exploded View Assembly View Exploded view

Ken YoussefiMechanical Engineering Dept., SJSU 5 Degrees of Freedom An object in space has six degrees of freedom. Translation – movement along X, Y, and Z axis (three degrees of freedom) Rotation – rotate about X, Y, and Z axis (three degrees of freedom)

Ken YoussefiMechanical Engineering Dept., SJSU 6 Assembly in NX5 Open a new file and call it an Assembly Select Assemblies from the Application menu Make Work Part Add Existing Component Mate Component Position Component

Ken YoussefiMechanical Engineering Dept., SJSU 7 Assembly in NX – Mate option Mate Two selected surfaces become co-planar and face in opposite directions. This constrains 3 degrees of freedom (two rotations and one translation)

Ken YoussefiMechanical Engineering Dept., SJSU 8 Assembly in NX – Mate option Align Two selected surfaces become co-planar and face in the same direction. Can also be applied to revolved surfaces. This constrains 3 degrees of freedom (two rotations and one translation). Center This constrain can only be applied to two revolved surfaces in order to make them coaxial (coincident).

Ken YoussefiMechanical Engineering Dept., SJSU 9 Assembly in NX – Mate option Parallel Two planar surfaces are made parallel, not necessarily co-planar. Distance (Offset) Two surfaces are made parallel with a specified offset distance.

Ken YoussefiMechanical Engineering Dept., SJSU 10 Example Select Add Existing Component → select the file containing the first component in the assembly Select Absolute for positioning and choose a point on the screen.

Ken YoussefiMechanical Engineering Dept., SJSU 11 Example Select Add Existing Component again → select the file containing the second component in the assembly Note that Mate option is automatically selected

Ken YoussefiMechanical Engineering Dept., SJSU 12 Example Select the bottom face Then select the top face to mate the two surfaces

Ken YoussefiMechanical Engineering Dept., SJSU 13 Example

Ken YoussefiMechanical Engineering Dept., SJSU 14 Add the third component (bolt) and Mate the bottom of the bolt head with the top surface of the base

Ken YoussefiMechanical Engineering Dept., SJSU 15 Select Mate Component option → select Center → select the bolt cylinder surface and the hole surface

Ken YoussefiMechanical Engineering Dept., SJSU 16 Exploded Views Select Exploded Views from the Assemblies menu Choose Create Explosion option Name the explosion and select OK

Ken YoussefiMechanical Engineering Dept., SJSU 17 After creating an explosion, select Assemblies and choose Auto-explode Components

Ken YoussefiMechanical Engineering Dept., SJSU 18 Select components and specify the distance

Ken YoussefiMechanical Engineering Dept., SJSU 19 This option may not produce a perfect exploded view the first time; it is intended to give you a good start towards a perfect explosion. After using Auto- Explode Components, you can follow up and refine your explosion by choosing Edit Explosion and editing the parameters with the Explode Component dialog. The Exploded View

Ken YoussefiMechanical Engineering Dept., SJSU 20 Select Assemblies → choose Edit Explosion → select the object to be moved Drag the object to the new position or move it according to a specific distance

Ken YoussefiMechanical Engineering Dept., SJSU 21 Assembly in SW Select to open an assembly file

Ken YoussefiMechanical Engineering Dept., SJSU 22 Assembly – Inserting Components Select Insert → Component → Existing Part Assembly Toolbar Mate – positions components relative to each other Move component Rotate component

Ken YoussefiMechanical Engineering Dept., SJSU 23 Assembly Select the first component to insert into assembly.. Browse to find your component if it is not open. For bottom-up assembly, insert the base component, in this case the Block.

Ken YoussefiMechanical Engineering Dept., SJSU 24 Assembly – Mate Command Insert the plate, click any place on the screen to drop the plate Select Mate Mate window

Ken YoussefiMechanical Engineering Dept., SJSU 25 Assembly – Mate Command Select Coincident Select Face 1 Select Face 2 Options after selecting the Coincident Mate

Ken YoussefiMechanical Engineering Dept., SJSU 26 Assembly – Mate Command Coincident, two surfaces facing each otherTwo surfaces parallel to each other Two surfaces perpendicular to each other Two surfaces offset at a specified distance

Ken YoussefiMechanical Engineering Dept., SJSU 27 Assembly – Mate Command Two surfaces at a specified angleAlign two surfaces Undo Accept

Ken YoussefiMechanical Engineering Dept., SJSU 28 Assembly – Mate Command Use Concentric option to line up cylindrical surfaces Select cylindrical surface 2 Select cylindrical surface 1

Ken YoussefiMechanical Engineering Dept., SJSU 29 Exploded View Select Exploded View option from the Insert menu Select each component and drag to a desired location

Ken YoussefiMechanical Engineering Dept., SJSU 30 Creating an Assembly Example The example assembly requires three mates to fully define it. First constrain: Mate between the hollow faces as shown. This removes three degrees of freedom. Hollow faces

Ken YoussefiMechanical Engineering Dept., SJSU 31 Example Second Constrain: Align the right faces of both components. Third Constrain: Align the top faces of both components. top faces The assembly is fully defined Right side faces One degree of freedom left

Ken YoussefiMechanical Engineering Dept., SJSU 32 Example – Switch Plate Switch plate consists of two components, plate and fasteners.

Ken YoussefiMechanical Engineering Dept., SJSU 33 Example – Switch Plate First Constrain: Concentric select the cylindrical face of the fastener and the cylindrical face of the switch plate. Two degrees of freedom remains, the fastener can still move in and out and rotate inside the hole.

Ken YoussefiMechanical Engineering Dept., SJSU 34 Example – Switch Plate Second Constrain: mate the flat circular back face of the fastener and the flat front face of the switch plate.

Ken YoussefiMechanical Engineering Dept., SJSU 35 Example – Switch Plate Parallel could be used to line up the slot on the screw head with the flat top face of the switch plate. The assembly is fully defined