PCA design in Creo - icub-tech-iit/cad-libraries GitHub Wiki

Creating the Mechanical Assembly MPCA

ECAD assembly mode provides a dedicated environment for creating and managing ECAD assemblies. In an ECAD assembly, the board is created in the context of the assembly and IDs are created automatically for all objects relevant to ECAD. These objects include hole features, ECAD areas, and components.

You can create a Mechanical Assembly PCA as shown following:

The Create Component dialog box opens. Click assembly and select ECAD from the Sub-type list. Remember to remove the selection from use default template Click OK and on the following screen select the appropriate template:

your electronic assembly is ready

Creating the Board Shape

To create the board, open the ECAD assembly e click on the button "create board" directly inside the assembly: see the picture below for the details:

follow the same steps to use the right template when you created the assembly:

In the Model Tree, notice the following icons:

• Mechanical Assembly MPCA.
• Board Shape MPCB.

Defining the board geometry

In an open Mechanical Assembly MPCA, perform one of the following actions:

• Click Create/Edit Board.
• In the Model Tree, select the board part, right-click and choose Activate.

there are two ways to proceed: Activate the prt directly from the assembly or open the prt. In any case, the PWB-Profile can only be created from the ECAD assembly.

The Model tab appears and the board opens in the graphics window.

• Choose a tool from the Shapes group to create the first board segment.

The PWB-profile of the circuit board must be created in the X,Y plane with the Z axis facing you. This will avoid problems when working with programmes such as PADS

• To create additional board segments or geometry, use the tools in the Shapes, Engineering, Bends, and Editing groups.

ATTENTION!!! As you can see in the ECAD assembly, the programme automatically generates the origin of the board in the bottom left-hand corner.

In order to have a stronger change control, you should edit the board origin and make it match the basic co-ordinate system of the PRT model.

Setting board Parameters and general rules

• Check that the Parameter BOARD_THICKNESS is properly compiled with the thickness of the board (e.g. 1.6).
• Check that the Material is properly set in the model tree (e.g. VT-FR4).
• Use the same description you can find in Wingst

Inserting holes

In the board model, if you need to define holes for fixing purposes, you shall use the Hole feature.

Holes are transferred to ECAD design, so you must specify if they are plated or not. To do this, the Family table HOLE-PCB is available ( see also "Placing components" section ):

choose the appropriate hole to assemble on the board assy

Each instance of this Family table includes information about hole diameter, plating, keep-out and copper area. Go to Mechanical Assembly MPCA level and for each hole place (as component) an instance of the HOLE-PCB Family table, choosing from the following list:

Use the flexibility feature to define the right PCB thickness of the surfaces of the hole

use the axe and the top plane to place the hole overlapped the feature hole

According to Electronic teams , define the right ECAD_REF_DES to identify the holes ( usually are H1, H2, H3.... etc)

Inserting ECAD areas

ECAD areas are 2D closed loop areas used for reserving space. Placement and user defined areas can have a height restriction as well. ECAD areas aid in design work by conveying specific restrictions or functions in the designated area. ECAD areas are created as cosmetic features on the board part.

Placement keep-in and keep-out areas and user defined areas can have a closed 3D volume, represented by a quilt. Use these quilts to perform a clearance and interference check to determine whether an ECAD component violates the restrictions for the keep-in, keep-out and user defined areas, even if the component is entirely within the keep-out volume.

Remember the following characteristics of keep-in and keep-out areas:

• In the ECAD Area tab, use the Name box in the Properties tab to name ECAD area features.
• You can display place restriction and user defined areas as 3D volumes provided the value of their height is greater than 0.0. Redefine the feature attributes and select or clear the 3D Volume option.

To Add or Edit an ECAD Area, choose one of the following options:

• Click Create/Edit Board.
• In the Model Tree, select the board part and right-click and choose Activate.

The ECAD Area tab opens.

The following ECAD areas are available for reserving space:

• Place restriction region.

  • Keep-in—Restricts placed components inside this region. You can specify a height above, below, or on both sides of the board to create a volume. The default height is zero.
  • Keep-out—Restricts component to lay outside this region. You can specify a height above, below, or on both sides of the board to create a volume. The default height is zero.
  • Region—Groups components with the same function.

• Route restriction region.

  • Keep-in—Reserves space specifically for routing. No drilling is allowed in this region, for example.
  • Keep-out—Reserves space where no routing is allowed.

• VIA restriction region.

  • Keep-out—Reserves space where you cannot create VIA holes.

• Flexible restriction region—Provides a region that is not rigid. Informs an ECAD user working in 2D or 2.5D where the board is flexible and not rigid. This option is available only in an ECAD assembly.

• User defined restriction region—Reserves space for a user defined area. The type and color of the area is set by a *.csv file containing a list of company defined areas. This option is available only in an ECAD assembly.

ECAD areas are defined by a normal sketch and are created in the same way as you create a curve on a surface.

it is good practice to activate the hatching to better identify the areas in 3D, in any case it is advisable to leave these features normally HIDE in the model tree.

leaving the box 'Trim to boudaries...' ticked. the keep out will be automatically created following the main profile

Placing components

With the Mechanical Assembly MPCA open, the main command to place components in Creo is Assemble:

Assemble can be used in two ways:

• assemble will use standard Creo assembly constraint type.
• assemble-relative-to-board will use Top or Bottom board sides + offset coordinates.

Use the correct method for your specific case.

ECAD Model Tree Parameters

After placing a component in an ECAD assembly or subassembly, you must assign its reference designator.

• Add in the model tree the ECAD parameter called ECAD_REF_DES.
• Assign to each component a STRING value matching with the electrical schematic design.

Best practice to add mechanical parts

Could be happen that in an electronic board we need to assemble mechanical parts in addition to electronic components, such as heat sinks or hardware. In this case, it is preferable to place the mechanical elements at the top of the model tree. The "hole" components should also be inserted at the top of the model shaft since they are considered mechanical components

However, it is very important to agree with the electronics team on the right circuit references (ECAD_REF_DES) to be included both in schematics and in the ECAD assembly

Now you are ready to start the ECAD Collaboration