top down master model[1]

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Top-Down & Master Modeling

Introduction:Top down design defines design intent in a top level model. Top down design is a methodologyrather than a specific tool and is implemented by many industries. Top down design enables theability to define geometry in context with related assembly components, and is characterized bythe use of a master model for the purpose of sharing data and propagating change throughoutan assembly. For the scope of this document Master Model will refer to a base model used as an

inheritance feature in derivative models.

Conversely, in bottom up design, assembly components are modeled independently. Nosystematic technique for sharing data, leveraging geometry, or propagating change is used. Thishas historically been the method used at Medtronic.

Top Down Design Key Points: Greatly improves change propagation; speed and accuracy

Allows true concurrent design environment

Provides stable platform for change

Master model captures and makes available key requirements and design intent.

Simplifies modeling; One to many feature relationships

Allows creation of an early virtual Intralink BOM and assembly place holder. Havinga complete virtual assembly is possible early in project, well before all the details arecomplete.

Potential Limitations: Top down design strategies can be undermined by failure to follow best practices for

modeling and for data management. For instance, decisions to work outside ofIntralink to rename parts can render the master model useless.

Lack of communication between groups and team members will lead to increased

design time

Lack of up-front planning or requirements gathering will lead to an insufficient master

model and reduced benefits

Lack of understanding regarding how the master model and top down assembly is

set up and modified will lead to problems Mirroring of an inheritance feature not possible (WF3), therefore workaround must be

used to accomplish goal.

Replacing a master model with another master model once dependencies exist can

be difficult and cause features to fail.

When a model contains an inheritance feature and the source model is brought into

session, the model with the inheritance feature is 'plussed' (shown as modified) afterregenerating even when no changes have been made to the source model. Thisissue has been resolved in Pro/ENGINEER Wildfire 3.0 date code M150.

Master Modeling Best Practices:

Naming Convention:Name the master model per the Pro/ENGINEER Best Practices CAD File Naming Convention. It'simportant to get this right since the master part is perpetuated, and there is risk involved with re-naming the master once dependencies have been built up. Do not use names like master ormaster_part; doing so will undermine the search capabilities in Intralink that depend on thedocumented naming convention.

Link to the CAD file naming convention:http://cad.medtronic.com/da_wiki/doku.php/mechanical:proe:pro_e_file_naming_convention

Medtronic Confidential Page 1 of 6 4/30/2013
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In general its a good practice to name the master with the same base number as its parent partor assembly if it is specific to that usage. If the master represents multiple configurations and willbe uses in several parts or assemblies it should be given a unique base number. Bothconsiderations require the *_m01 suffix. If multiple masters are used in the same model it isacceptable to use numerations of the base number such as *_m02, _m03 etc.

Examples:

m006688a (e-Matrix part family number)

m006688a_m01.prt (master model part)

A device EMA master can share the same base number as the EMA assembly.

A connector module (CMOD) master should have a unique eMatrix base number plus

the _m01 designation if it is generic enough to be used in multiple designs, or canshare the base number of its parent if it specific to a particular CMOD or family ofCMODS.

A Battery or Capacitor master should share the same base number as its assembly.

If a master will be used in multiple unrelated battery and capacitor designs it shouldbe given a unique part number with the *_m01 suffix.

Master Modeling Principles:There are endless techniques for creating master models and accomplishing top-down design.This document defines and recommends using the Pro/ENGINEER inheritance feature as thebasis for accomplishing both the master part design and the top-down capabilities. Inheritancefeatures have capabilities that give them an advantage over other techniques, such as the abilityto access their model tree, and perform family table like same as except variations. Presentinginheritance master modeling as a best practice also adds consistency and visibility to a complexpractice and helps to flatten the learning curve. Downstream users will know what to expect whenreceiving models controlled by a master and will have documentation to fall back on. Without aunified common technique, issues like training, support, re-use etc become difficult to manageand control.

Master Part Philosophy The master part should contain all of the important common features and information

that will need to be referenced by subsequent child parts. This includes datumcurves, datum points, axis and other features that define shape, locations, thickness,and act as references. Include only the features that are common for all or most ofyour components, including too much will overcomplicate the master.

Build the master using surface features; solid features cant be managed via layers

and therefore cant be hidden in the recipient part. I other words the solid features ofthe master model will display in the child part and cant be hidden.

Plan carefully to allow the master to control as much of the design as possible while

being careful not to assert control beyond what is useful.

If portion of a design is not driven by the master but rather drives the master,

determine how information will flow from driver to master. Example: Hybrid shape ismanaged by another group and as changes occur must be incorporated back into themaster. As a minimum a key contact must be identified and a change notificationprocess used.

Leverage data whenever possible and avoid duplicating sketches and features. Push

as much geometry from the master as possible. For example putting rounds on amaster quilt will prevent having to redundantly add them to subsequent parts asfeatures.

Reference the inheritance feature, dont act on it directly. For example, in a new part

use the master to offset a quilt, solidify the quilt and create features on the solidifyrather than on the inheritance.



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Master Part Techniques Flex every feature sketch to assure it reacts as intended, and allows a full range of

expected variations.

Creating the Master as surface model makes it much easier to use the quilt for

copies, offsets etc.

Consider splines as alternatives to tangent end arcs. Splines allow for more efficientgeometry and are far easier to modify.

Create features in a logical order so that volume can be calculated by using insert

mode, and that shape defining features are all created early in the model tree. Forexample, in a connector module you should be able to drag the insert arrow up thetree to a point where the volume can be calculated without having to add or suppressfeatures. Add lead bore cuts late and suture holes early.

Incorporate behavioral modeling and analysis features to maximize the power of the

master. Analysis features such as volume and surface area are easy to create andcan be displayed in both the model tree and in 3D notes. They are also parametricand display real time results as the model is modified.

Choose references carefully. Use the inheritance master for use edge operations,

choose the masters datums and coordinate system for references. When selectingedges be careful to select the curves from the master rather than part surface edgesetc. Hovering over the entity will show its name and feature number. Focus as manyreferences on the master as practical, this will help minimize unwanted parent childrelationships and improve the relationship to the master.

Use Edit Replace in sketcher to replace referenced entities with new ones. This is

an effective way to mitigate missing reference issues by specifying the replacementedges in sketcher.

Assembly Techniques Allow external referencing (mapkey xrefa). By default referencing external geometry

is disabled at Medtronic and must be intentionally allowed.

Use the 02_Data_Sharing layer to hide master

Assemble the master part as the first component in the model tree duringdevelopment; it makes it much easier to keep track of the master. Top down design ismost effective when the master is directly accessible in the assembly; it can beactivated and modified in context with relevant parts. Any modifications can them bepushed through the assembly through regeneration.

Regenerate the assembly often when modifying the master. Assembly components

which inherit the master part need to regenerate in order to reflect any modifications.Using the update inheritance option updates the part master per the most currentversion. Using update inheritance is a good practice when making modifications tothe master; but assembly and parts still need regeneration to synchronize changes tothe master with dependant features.

Be cautious when saving assemblies which have multiple copies or versions of

master parts. If care isnt taken to update inheritance in all of the parts, parts with

outdated inheritance features may overwrite more current versions of the master part.For example, in a 2 part assembly if you modify the master part and update theinheritance feature in one of the parts but not the other, you may find that when youretrieve the assembly that the effects of the updated master have not been applied.This is due to the failure to update the inheritance in both parts before saving theassembly. Inheritance features, like other features, need to be regenerated tobecome effective.



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Use the common coordinate system between assembly components and master to

facilitate assembly and eliminate possible variations to the assembly such asinconsistent assembly references, inconsistent offset values etc.

Inheritance Feature Capabilities:

The benefits of using an inheritance feature rather than a merge or copy geometry can be quitesignificant. In general inheritance features provide a parametric copy of a base (master) modeland allow access to vary its features. A common example is the use of an inheritance to create amachined version of a cast part. The cast part is used as the base model for the inheritance in themachined part. The machine part therefore inherits all of the geometry of the cast part, allowsaccess to the feature model tree of the cast part, and allows machined features to be added. Ifthe cast part changes the changes are propagated to the machined part upon modelregeneration. The need to create a second independent part (save as) for the machined versionis eliminated, and so is the need to coordinate and duplicate changes.

Changes in the reference part are associatively propagated to the dependent

Inheritance feature.

Creation or modification of varied items is possible without the reference part in the

Pro/ENGINEER session.

Can be used to add or remove of material geometry.

Allows the use of Relations and Family Tables with corresponding associated

parameters.

Allows the ability to control whether notes from the reference model are copied.

Allows the nesting of Inheritance features.

The monitoring of parent and child relationships between sub features of Inheritance

and other features of the part that references them.

Creating an Inheritance Feature; Step by step instructions.To create an inheritance feature you must first have a model to inherit, such as a master part,and you must enable external referencing.

Begin by creating a new part. Create an inheritance as the first feature. Select Insert SharedData Merge Inheritance. Open the master model and place it in the part as if it were anassembly component. Tip: Use default placement, it provides a quick and robust assemblyconstraint. Select the Toggle Inheritance Icon, the default is merge which offers lessfunctionality than an inheritance.

Select the green checkmark to complete the operation.

Replacing the Base Model:The Base Model of an Inheritance Feature can only be replaced with a Family Table Instance ofthe Base Model. It is possible to insert an inheritance feature before the existing inheritance andthen re-reference all features from the old inheritance to the new. This may require a high level ofskill if there are complex dependencies or if the geometries are dissimilar.

When Redefining the Inheritance Feature: Select Base Model from the Inheritance Feature Dialog



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Box, Define, Confirm, A Family Table Dialog box will be displayed listing all of theinstances in the family table, Select the desired instance, OK, OK

All of the settings in the Variable Dimension and Feature Dialog box will be transferred to the newBase Model. Note: if the Variable Dimension Table contained dimensions pertaining to a featurethat is not included in the new instance then those dimensions will become 'Locked'.

If the Base Model does not belong to a Family Table nothing will happen when selecting BaseModel from the main Inheritance Dialog Box.



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Figure 1: Example of a simple master part to be used as an inheritance base.

Figure 2: Example of multiple parts created and controlled by inheritance feature. Change tothe inheritance feature base model propagates change to the parts.


top down master model[1]

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