Pro/ENGINEER - Assembling Parts

In this mini-tutorial, we will look at bringing components - either parts or other assemblies- together into assemblies. Like the creation of features in a part, parts in an assembly have to be brought together in relation to each other in such a way as to fully constrain them. That is, the relative rotation and location of the parts to each other has to be specified in all three dimensions. This done through two primary types of constraints:

Mate - Two planes, faces or datums are oriented parallel to each other in opposing directions. Opposing in that the 'outside' faces of objects face each other or the specified sides of datums face each other.

Align - When two planes are aligned, they are oriented parallel to each other in the same direction. For faces of objects this means they would 'be on the same side' of a datum plane. For datums, it means that the specified sides are facing the same direction. Axes and edges can also be aligned. Since axes/edges don't have a vector orientation, alignment simply makes the the axes/edges collinear.

With both of these constraints there is an alternative offset option. With the offset option, an offset distance for the two datums/faces/edges/axes is specified. In addition to these primary constraints, there are also other constraint options such as orient, edge on surf, and tangent.

Beginning the Assembly

Before you begin, there are a couple of things to keep in mind:

Just as with constructing a part, prior planning is critical to creating a functioning assembly. As with features in a part, components in an assembly are constrained in a hierarchy with each new part depending on the part(s) it is constrained to.

Selection of the first component is important since it is at the top of the hierarchical 'tree' and, therefore, should have the most components attached to it and be the least likely part to be removed from the assembly.

All of the parts in the assembly need to be available for the assembly to load. Be careful not to delete/rename any parts used in the assembly.

Assemblies are created in assembly mode. As with parts and drawings, you can either retrieve an existing assembly or create a new one. Once you open an assembly, the model tree window opens, but instead of listing features, it will list components brought into the assembly.

Begin the assembly by bringing in the first component. This is considered the base component.

component>assemble

Unfortunately, there is not a search/retrieve option, so you must know the names of your components (e.g., part or other assembly files).

Since there are no other parts in the assembly yet, you do not need to constrain it. This part now is listed in the model tree window. If you needed to orient this base part in a certain way, you could have used

create>datum plane or datum axis or coord sys

first to create assembly level features to which to constrain the base component to. These features will be listed on the model tree and named beginning with the letter A (e.g., ADTM1).

Bringing More Components in

The second and each successive component will have to be constrained to one or more of the existing parts or assembly level features in the assembly. Start as you would for the first component:

component>assemble

This time, once you've entered the file name, the component placement dialogue box opens (Figure 1). New components (parts or assemblies you want to bring into the current assembly) need to be constrained by means of geometric constraints relative to the existing assembly geometry. You can see the new component temporarily placed in the assembly window, but it will not be placed until it is fully constrained.

Figure 1.

 

The main elements of the component placement dialogue are:

Display component. Normally set to assembly. This means you can see the component in the assembly window as you constrain it.

Constraints. This window gives you the current status of constraints (including any offset distance). Constraints currently being created are listed as defining. The Add and Remove buttons allow you add or remove constraints from the constraint list.

Constraint type. This pull-down box allows you to choose the type of constraint to apply. The two most important constraints are:

o Mate - Two planes, faces or datums are oriented parallel to each other in opposing directions. Opposing in that the 'outside' faces of objects face each other or the specified sides of datums face each other.

o Align - When two planes are aligned, they are oriented parallel to each other in the same direction. For faces of objects this means they would 'be on the same side' of a datum plane. For datums, it means that the specified sides are facing the same direction. Axes and edges can also be aligned. Since axes/edges don't have a vector orientation, alignment simply makes the the axes/edges collinear.

Component reference. This indicates which entity on the component you have chosen to apply the constraint to. You can use Pick menu options such as query select to help with selection.

Assembly reference. This indicates which entity on the component you have chosen to apply the constraint to. You can use Pick menu options such as query select to help with selection.

Offset. This is active when you have chosen either the align offset or the mate offset constraints. A value is typed into the box.

Placement status. This box tells you the status of the constraint process. When you have added enough constraints (usually two or three), it will tell you the component is fully constrained and can be placed.

At this point the place menu appears, and you can choose the appropriate constraint to start with. Look at the opening section above for a description of the most common constraints. A couple of comments:

Other notes of interest:

When you choose to constrain with a datum plane, you will be asked to specify the yellow or red side of the plane. Remember, if you are mating two datums, picking the yellow sides would make the yellow sides 'stick together'. If you mated the red side of one to the yellow side of the other, the two yellow sides would face the same way.

At the very top of the component placement dialogue is a tab that allows you to change between constraint definition (Place) and transforming the temporary copy of the component in the assembly window (Move). The Move side allows you to choose from a number of transformation commands (i.e., translate, rotate) to better place the component for constraint definition.

Once you have fully constrained the component, choose OK. If after you have placed a component and you decide it was done improperly, you can redo it with:

component>redefine

Once back in the component placement dialogue, highlight the constraint you want to redefine in the Constraints window or use the Add and Remove buttons.

Look in the relations mini-tutorial for information on creating relations in assemblies.