When component objects are added to the assembly part file, each component object is mated with the corresponding objects. By putting mating conditions on components of an assembly, you establish positional relationships, or constraints, among those components. These relationships are termed mating constraints. A mating condition is made up of one or more mating constraints. There are eight mating constraints as shown below.
• Mate – Planar objects selected to mate will become coplanar and the direction of the normal's will be opposite to each other
Align – Planar objects selected to align will be coplanar but the normals to the
planes will point in the same direction. Centerlines of cylindrical objects will be in line with each other.
• Angle – This fixes a constant angle between the two object entities chosen on the components to be assembled.
• Parallel – Objects selected will be parallel to each other.
• Perpendicular – Objects selected will be perpendicular to each other.
• Center – Objects will be centered between other objects, i.e. locating a cylinder along a slot and centering the cylinder in the slot.
• Distance – This establishes a +/- distance (offset) value between two objects
• Tangent – This establishes a tangent relationship between two objects, one of which has to be curved such as a free form surface, a circle, a
sphere, or a cylinder.
The Mating Conditions dialog box is shown below
There are two basic ways of creating any assembly model.
• Top-Down Approach
• Bottom-Up Approach
Top-Down Approach
The assembly part file is created first and components are created in that file. Then individual parts are modeled. This type of modeling is useful in a new design.
Bottom-Up Approach
The component parts are created first in the traditional way and then added to the assembly part file. This technique is particularly useful, when part files already exist from the previous designs,and can be reused.
Mixing and Matching
You can combine these two approaches, when necessary, to add flexibility to your assembly design needs.
This chapter introduces assembly modeling. Every day, we see many examples of components that are assembled together into one model such as bicycles, cars, and computers. All of these products were created by designing and manufacturing individual parts and then fitting them together. The designers who create them have to carefully plan each part so that they all fit together perfectly in order to perform a function.
OVERVIEW
NX assembly is a part file that contains the individual parts. They are added to the part file in such a way that the parts are virtual in the assembly and linked to the original part. This eliminates the need for creating separate memory space for the individual parts in the computer. All the parts are selectable and can be used in the design process for information and mating to insure a perfect fit as intended by the designers. The following figure is a schematic, which shows how components are added to make an assembly.
TERMINOLOGIES
Assembly
An assembly is a collection of pointers to piece parts and/or subassemblies. An assembly is a part file, which contains component objects.
Component Object
A component object is the entity that contains and links the pointer from the assembly back to the master component part.
Component Part
A component part is a part file pointed to by a component object within an assembly. The actual geometry is stored in the component part and is referenced, not copied by the assembly
The Drafting Application is based on creating views from a solid model as illustrated below.
Drafting makes it easy to create a drawing with orthographic views, section views, imported view, auxiliary views, dimensions and other annotations.
Some of the useful features of Drafting Application are:
1) After you choose the first view, the other orthographic views can be added and aligned with the click of some buttons.
2) Each view is associated directly with the solid. Thus, when the solid is changed, the drawing will be updated directly along with the views and dimensions.
3) Drafting annotations (dimensions, labels, and symbols with leaders) are placed directly on the drawing and updated automatically when the solid is changed.
Reference Features
These let you create reference planes or reference axes. These references can assist you in creating features on cylinders, cones, spheres and revolved solid bodies.
Click on INSERT → DATUM/POINT to view the different Reference Feature options:
Datum Plane, Datum Axis, Datum CSYS, and Point
Swept Features
These let you create bodies by extruding or revolving sketch geometry. Swept Features include:
• Extruded Body
• Revolved Body
• Sweep along Guide
• Tube
• Styled Sweep
To select a swept feature you can do the following:
Click on INSERT → DESIGN FEATURE for Extrude and Revolve
or
Click on INSERT → SWEEP for the rest of the options
Remove Features
Remove Features let you create bodies by removing solid part from other parts.
Click on INSERT → DESIGN FEATURE
Remove Features include,
• Hole
• Boss
• Pocket
• Pad
• Slot
• Groove
You can also select the features by clicking on the icons
User-Defined features
These allow you to create your own form features to automate commonly used design elements.
You can use user-defined features to extend the range and power of the built-in form features.
Click on INSERT → DESIGN FEATURE → USER DEFINED
Extract Features
These features let you create bodies by extracting curves, faces and regions. These features are widely spaced under Associative Copy and Offset/Scale menus.
Extract Features include:
• Extract
• Sheet from curves
• Bounded plane
• Thicken Sheet
• Sheet to Solid Assistant
Click on INSERT → ASSOCIATIVE
COPY → EXTRACT for Extract options
Click on INSERT → OFFSET/SCALE for
Thicken Sheet and Sheets to Solid Assistant
Click on INSERT → SURFACE for
Bounded Plane and Sheet from curves
Features are objects that are associatively defined by one or more parents and that retain within the model the order of its creation and modification, thus capturing its history. Parents can be geometrical objects or numerical variables. Features include primitive, surface and solid objects,and certain wire frame objects (such as curves and associative trim and bridge curves). For example, some common features include blocks, cylinders, cones, spheres, extruded bodies, and revolved bodies.
TYPES OF FEATURES
There are six types of Form features: Reference features, Swept features, Remove features, User defined features, Extract features and Primitives.
Click INSERT on the Menu bar As you can see, the marked menus in the figure on the right side contain the commands of Form Features.
The Form Feature icons are grouped in the Form Features Toolbar as shown below. You can choose the icons that you use frequently.
Click on the drop down arrow in Form Feature Toolbar
Choose ADD OR REMOVE BUTTONS
Choose FORM FEATURE
