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NUPAS-CADMATIC’s Vision on CAD/CAM System Development in

Today’s Shipbuilding Environment

Geert Tepper, Numeriek Centrum Groningen B.V., Groningen/The Netherlands, tepper@ncg.nl

Theodoor de Jonge, Numeriek Centrum Groningen B.V., Groningen/The Netherlands, jonge@ncg.nl

Abstract

The architecture of the 3D model database in Nupas-Cadmatic has been designed in such a way that

it serves multiple purposes for all phases of the shipbuilding process. Besides advanced 3D detail and

production engineering there are various other possibilities that cover the (re)use of the 3D model

and offer significant added value for ship designers, shipbuilders and ship owners. In this paper

Nupas-Cadmatic introduces three new functionalities: Export to FEM, Compartment Modeling and

3D General Arrangement and the Work Breakdown and Assembly Tools.

1. Beyond the 3D geometric ship model

During the past few decades a variety of 3D CAD/CAM systems for shipbuilding have been

developed of which all had the same goal: to speed up, improve and optimize the different activities in

ship design, ship engineering and ship production. The advantages were, and still are substantial,

compared to traditional drawing boards. Almost every modern shipyard or ship design company uses

software in one way or the other in order to keep up in the strong competitive shipbuilding market.

High labor costs and increasing prices of materials force the shipbuilding industry to be innovative,

efficient and to respond quickly to the changing market demands.

Nupas-Cadmatic is the 3D ship design systems in the high level segment. Since its origin in the late

1980’s, Nupas-Cadmatic has become a strong player in the market with currently more than 290 users

in 35 countries. Although Nupas-Cadmatic started as a 3D production engineering tool, it rapidly

expanded to a mature and complete 3D ship design, engineering and production system.

In Nupas-Cadmatic the architecture of the 3D model database has been designed in such a way that it

serves multiple purposes for all phases of the shipbuilding process. When the first plate, profile or

pipe comes into existence, the production modules of Nupas-Cadmatic already know of its existence.

In other words, the 3D model database contains all the data and intelligence to provide a continuous

and consistent data flow for each phase of the shipbuilding process. Nupas-Cadmatic also aims to

make the life of the designer easier by offering an advanced topological model, rule-based

engineering, parametric modeling, specification-driven pipe routing, automatic part nesting, etc. in

order to avoid errors and take over boring tasks.

So what more should a 3D ship design system be able to do? We can continue to develop the

intelligent modeling and make it fancier and even more intelligent but we should also realize that

there are limits to what is considered to be necessary and useful or not.

The answer lies in developing functionality that goes beyond the 3D geometric ship model. Nowadays

Nupas-Cadmatic has many powerful functionalities and features that can easily be utilized in new

applications that offer significant added value to ship designers, shipbuilders and ship owners.

Possible new uses of the Nupas-Cadmatic 3D geometric ship model are in the field of finite element

analysis, ship life cycle management, browsing and sharing the model, 3D general arrangement,

compartment modeling and assembly management.

In this paper we introduce three of these new functionalities: Export to FEM, Compartment Modeling

and 3D General Arrangement and the Work Breakdown and Assembly Tools.

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2. Export to FEM model

Final Element Analysis (FEA) of a ship’s structure is an essential activity in the early design stage of

a new vessel. It is essential because it forms in some cases the basis to receive approval from the

Classification Societies for the structural design. Another essential objective, and these days maybe

even a more important one, is the fact that FEA helps designers to optimize the structural design.

Modern ships have to be fast and light yet stable, safer and more fuel efficient than ever before.

The general problem is that performing a finite element analysis on a ship design is an extremely time

consuming process. Besides the required CPU time to execute the actual FEA, modeling the ship

structure is the other main time consuming part of the process. The model has to be created from

scratch. About 70% of the time to perform a FEA consists of creating the model and existing FEA

software programs do not offer adequate and rapid modeling tools. In addition the fact that various

alternatives for the same ship often have to be considered, one can imagine that optimizing a design is

an extremely expensive matter for which mostly is no time available.

For special ships with particularly heavy constructions or ships that suffer from heavy and special

forces (heavy lift, dredgers) it is important for the ship owner and shipbuilder to create the most

optimal design. Class Societies require FEA proof of designs that deviate from the common structural

rules. This also applies to standard ships where a designer decides to use less or thinner structural

material. Another issue is validating an existing design. It is hardly done because of the amount of

time it takes. Overall there are enough reasons to try to speed up the FEA process.

In 2006 Nupas-Cadmatic started a new development project with German shipbuilder Flensburger

Schiffbau Gesellschaft to achieve a detailed FEA of a new design in the shortest possible time. By

making use of existing fast and advanced 3D modeling techniques of the Nupas-Cadmatic Hull

module, one will be able to reduce the modeling time dramatically and create an optimal FEM model.

Fig.1: The Nupas-Cadmatic model, the generated FEM model and the mesh model of a double bottom.

The development project consists of an ‘Export to FEM’ application. This application creates a

simplified and idealized FEM model from the 3D structural ship model. Because of the high level of

structural topology in the Nupas-Cadmatic ship model, the application is able to generate the optimal

FEM model quickly. The FEM model is stored in the ANSYS ™ file format for a smooth connection

to the actual FEA. Besides the ANSYS file format the FEM model can also be stored in a general

IGES file format.

2.2 The process of preparing the FEM model

A Finite Element Method (FEM) model in Nupas-Cadmatic Hull consists of a collection of FEM

objects created from selected construction parts from the Nupas-Cadmatic structural model database.

This selection can consist of a specific isolated construction, one or more blocks or even the complete

ship. Because you want to derive a FEM model at any given moment from the 3D structural hull

model (regardless of the level of detail) it needs to be simplified, idealized and optimized in order to

be processed by a FEA software program. The level of detail of the FEM model is handled by so-

called FEM policies. The FEM policies concept is explained in more detail in the next paragraph.

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Fig.2: The Export to FEM process

The process of the export of the FEM model is visualized in Fig.2. During 3D modeling, Nupas-

Cadmatic continuously maintains a FEM database via the Hullserver (the Hullserver is a server

process which serves several applications of the Nupas-Cadmatic system). The FEM database

contains specific data of the construction parts in order to generate the FEM model rapidly.

The user selects the construction parts via the standard Report Generator or via the Hull Viewer. The

user selects the output format, chooses the desired FEM policy and applies several specific FEM

export settings via a user interface. Before pressing the Export button the user is able to preview the

selected construction.

The FEM data of the selection is passed to a preprocessor. The preprocessor skips specific

construction elements according to the selected FEM policy and performs several idealizations to

simplify the model. The next step is to optimize the FEM model via an optimizer where the number of

node points is reduced or increased if necessary. Finally the output file is generated in ANSYS or

IGES format. Depending on the size and detail of the structural model the preprocessor and optimizer

can be rather time consuming. This process can, therefore, also be executed in batch mode.

2.3 FEM Policies

The accuracy or detail level of the exported FEM model is specified in the FEM policy. The default

FEM policies are GLOBAL, ROUGH or FINE and determine the final detail level based on various

settings. A policy is a collection of settings which control the so-called idealizations. The user can

also define his own policies.

Report

Generator

NUPAS-CADMATIC

HULL SERVERFEM

database

Structural

database

Skip small

parts

Idealization

Optimizer

Selection

criteria

FEM

policy

ANSYS

format

IGES

format

PREPROCESSOR

Skip conditions

Idealizations

Tolerances

BATCH JOB

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A FEM policy:

a. Contains the conditions for skipping “small” construction parts based on minimum area,

dimensions and weight.

b. Is used to specify in what way construction parts such as plates, brackets, profiles, cutouts and

holes are exported.

c. Determines the FEM element types (SHELL63, BEAM44, etc.) to be used to represent the Nupas-

Cadmatic Hull construction.

d. Determines tolerances such as the number of node points, vector lengths, etc.

2.4 FEM Idealizations

There are a number of standard idealizations that apply to every FEM model:

1. Plates are exported to objects without thickness (Fig.3).

2. The plate contours are modified to fill the gaps caused by reducing the thickness to zero.

3. Node points are positioned on the mould side of the plates.

4. Plates, brackets and profiles are extended to the nearest node point or to the plate contour.

5. All plates, brackets and profiles connected to a plate result in main (mesh)lines and node points

on that plate.

6. Profiles which are not connected to a plate are exported as beams.

7. Girders are handled as T-profiles.

8. If a profile is skipped the cutout is also skipped.

Fig.3: Reducing plate thickness to zero

Other idealizations that are performed by choosing a policy are:

1. Profiles are skipped, exported as (mesh)lines with 2 node points or exported as a beam.

2. Node points of profiles are connected to the nearest node points on the plate contour (possible

shift of profile plane)

3. New node points can be introduced (stationary profile plane)

4. Small parallel profiles in the same plane are connected to each other or to the nearest node point

5. Small parallel profiles in different planes are exported as one single (mesh)line with node points.

To counteract the reduction of profiles the average compensation method will be used.

6. In a global model there are no (mesh)lines with node points representing profiles. The properties

of the profiles are summarized in available element edges or via anisotropic material properties

(the torsional moment of inertia).

7. The effect of holes and cutouts can be simulated by reducing plate thickness (according to various

arithmetic formulas)

Some examples of idealizations can be found in Figs.4 - 7.

Fig.4: Shift of profile plane Fig.5: Parallel profiles in same plane

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Fig.6: Stationary profile plane Fig.7: Parallel profiles in different planes

The end result of the export process is a simplified FEM model in ANSYS or IGES format which is

ready to be processed by a mesh generator and finite element analysis software. Fig.8 shows examples

of the results of the three default FEM policies Global, Rough and Fine.

GLOBAL ROUGH FINE

Fig.8: The effect of policies on the FEM model

The top row images represent the simplified IGES models, the middle row images show the

simplified ANSYS models of the divisions due to the idealizations and the bottom row images show

the ANSYS models after meshing.

2.5 Current version and future developments

The Export to FEM feature received a lot of interest from the Nupas-Cadmatic user community after

the project was announced. There is currently a beta release available in Nupas-Cadmatic version 5.3

which is being tested at several Nupas-Cadmatic sites. The results are promising and the official

release of Export to FEM is expected to be available at the end of 2009.

Some of the future developments to enhance the Export to FEM feature are:

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• Increase the number of idealizations and fine tune idealizations

• Elaborate the optimizer functionality

• Enable batch job handling

• Include shell plates

• Realize different output file formats for 3rd

party FEA software

3. Compartment modeling and 3D General Arrangement Design

The process of designing a new ship is a complex combination of various activities, many variables

and numerous known and unknown factors. Each activity provides pieces of information which are

based on several design resources. As you probably recognize from your own experience this often

results easily in having to do work more than once, working with outdated information or even worse

working with the wrong information. The subsequent design steps will also suffer from these harmful

consequences. In this paragraph Nupas-Cadmatic presents its vision on the future development of the

concept of 3D General Arrangement Design to reduce the various drawbacks in conventional initial

design.

3.1 General Arrangement in initial design

The conventional process of initial design is represented in Fig.9. According to the ship’s

specifications the hull shape is designed, the initial compartments are defined and the usual ship

theory calculations are performed. For these activities a variety of commercial software packages are

available on the market from which the initial results are the basis for the 2D General Arrangement

drawing. The compartment definition is usually not available in a 3D model and is written down in

the ship’s coordinates.

General

Arrangement

Manual transfer of

change information

Transfer of

Hull shape data

Hull shape Design

3D Compartment

Modelling

Manual transfer of

change information

Ship Theory

(Intact , Damage stability…)

Manual transfer of

GA data

3D Compartment

model

FEM analysis

Evacuation

Fire Control

Noise & Vibration

2D General

Arrangement Design

Fig.9: The conventional process of 2D General Arrangement design

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Due to the fact that several disciplines in the shipyard use the compartment definition and give feed-

back to optimize the design, the danger of inconsistent compartment information is clearly present

during this cyclic process. As a consequence of communication failures design mistakes are made and

valuable time is lost.

3.2 3D General Arrangement Design

The solution to the various drawbacks of the conventional way of working is the concept of 3D

General Arrangement Design. Nupas-Cadmatic is currently investigating the development of the

solution to support the initial design phase in a more efficient way than existing software tools. The

aim is to quickly develop a 3D compartment model, optimize that model and most importantly: to

provide accurate and essential design information to the various subsequent engineering stages. This

approach clearly differs from traditional methods of working where compartment modeling, general

arrangement design and detail design are separate activities. The process of 3D General Arrangement

Design is shown in Fig.10.

Fig.10: The process of 3D General Arrangement Design

3.3 The 3D Compartment Tool

As Nupas-Cadmatic already has very enhanced 3D structural modeling capabilities, the 3D

compartment model can be created in the same flexible manner as in basic and detail design. Making

use of the existing Nupas-Cadmatic modeling functionalities offers a number of advantages:

1. Modeling with the use of structural topology

2. Calculations of volumes, sizes, weights, paint areas etc.

3. Applying attributes, properties and rules

4. Generate 2D general arrangement drawings from the model

5. Seamless connection to the detail design phase

NUPAS-CADMATIC

3D General

Arrangement Design

Transfer of

Hull shape data

Hull shape Design

Ship Theory

(Intact, Damage stability …)

FEM analysis

Evacuation

Fire Control

Noise & Vibration

NUPAS-CADMATIC

3D Constructional &

Outfitting Design

3D Compartment

model

Import/Export

Interfaces

Transfer of

Compartment model

3D Structural

model

General

Arrangement

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6. Export the 3D model to 3rd

party software for various purposes

3.3.1 Modeling with the use of structural topology

A compartment is a closed space (volume) which is defined by planes. In Nupas-Cadmatic these

planes are defined topologically. The advantage of a topological definition is its extreme flexibility

when creating and modifying compartments. There are four methods to define the planes:

a. By grid: The system supports a grid definition in 3 directions (length, breadth and height). Each

grid is identified by a unique name. It is possible to have more than one grid definition for height

and breadth.

b. By structural entity: The system supports the creation of construction plates in an arbitrary plane.

The construction plate has a thickness and thickness direction.

c. By hull shape group: The hull shape database contains the surfaces of the shape of a ship. Each

closed surface has a unique group number and is identified by that group number.

d. By manual plane: Besides the above mentioned methods, the user can define a manual plane

where the plane is defined by a minimum of 3 points (or 2 points and a direction).

By using (a mixture of) all 4 above-mentioned methods the user is able to define any compartment

irrespective of the complexity of its. Adjacent compartments are related to each other due to the

topological properties of the compartment model. See also ‘3.4 Operations on compartments’.

3.3.2 Calculations of volumes, sizes, weights, paint areas etc.

Calculations such as determining volumes, areas, weights etc. will be executed on the fly when a

compartment is defined. The results are stored as attributes in the compartment database and are

available for other functions.

3.3.3 Applying attributes, properties and rules

Compartments have attributes. Attributes can be properties, rules and values and play an important

role in determining logistical data (volumes, paint areas) and during rule-based engineering. For

instance: the compartment property ‘watertight’ determines the rule to use scallops and apply a

minimum thickness of protective coatings in tanks. The same applies to the use of specific material

types or minimum material thickness in specific compartments. The overall advantage is that a high

level of automatic determination can be achieved. The process of compartment modeling will be more

goal-oriented and decisions which are now made by the user can be made (semi) automatically by the

software.

3.3.4 Generate 2D general arrangement drawings from the model

The definitions of the compartments are stored at the ‘ship level’ so that the ship block boundaries do

not create any restrictions and the definitions will be available for all blocks. It is therefore possible to

generate views of the 3D compartment model for use in drawings. Due to the permanent link between

the model and the views, the drawings are updated automatically according to the changes in

compartments.

3.3.5 Seamless connection to the detail design phase

As the compartment definitions are available for all blocks, the compartment information can be used

during detail design. Attributes that apply to the compartment will also apply to the blocks which are

situated (partly) in the compartment area. This inheritance of attributes will be of use during rule-

based engineering and adopting shipyard standards. Attributes can be used in type definitions of for

instance brackets, profile end types, holes and cutouts. In this way Nupas-Cadmatic assists the

engineer in making the right decisions.

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3.3.6 Exporting the 3D model to third-party software for various purposes

It must be possible to export the compartment model data in a format that can be used by third-party

software systems for use in for instance ship theory applications, simulation of evacuation, onboard

logistics, fire control, noise and vibration engineering etc. The compartment model geometry can be

exported in a geometric format which is surface-based, for instance IGES or SAT format. These

formats can be used for visualization purposes.

3.4 Operations on compartments

In addition to the above-mentioned functionalities a number of specific operations on compartments

will be developed:

a. Modifying

If one of the definitions of which the compartment consists is changed (for instance a new deck plate

is selected or a new grid value is chosen) the compartment will be determined again, recalculated and

visualized accordingly. Due to the topological model, modifications can influence adjacent

compartments as well.

b. Copying

Compartments can be copied throughout the ship (with a certain offset value). Definitions with a

relation to the hull shape will be maintained and can be adjusted manually if necessary. Attributes,

properties and rules will be included.

c. Checks

• The final definition of a compartment can be visually checked by presenting the compartment

in distinguishing colors.

• The 3D Compartment Tool gives a warning when the compartment is not a fully closed space.

• It is possible to have overlapping compartments or undefined (void) spaces in the ship that do

not belong to any compartment. It will be possible to check and visualize these situations.

• The 3D Compartment Tool gives a warning when a definition related type (construction plate,

hull shape, and grid value) has been removed from the model. The compartment will keep its

current shape and will not change until the user determines a new definition.

d. Reports

The 3D Compartment Tool will be equipped with a report generator to supply various reports such as

compartment sizes, volumes, paint areas etc. It will also be possible to list (the position of) equipment

and machinery from the initial outfitting model.

3.5 The spin-off of 3D General Arrangement Design

Many systems offer compartment modeling only for ship theory computations, calculation of volumes

and capacities etc. In Nupas-Cadmatic we have advanced integration between the various stages in

design, engineering and production by means of the versatile 3D modeling system. Introducing the 3D

compartment model will surely strengthen the integration and reuse of information for each

discipline’s specific needs.

4. Work Breakdown Management and Assembly Tools

One of the most important goals of computerized ship modeling is to produce the (blocks of the) ship.

This means that the structural parts (plates, profiles, brackets, shell frames, etc.) have to be produced

and assembles in a block or section.

Due to the fact that each shipyard has its own specific production and building methods we developed

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an intelligent Work Preparation Manager (WPM) to streamline and manage the complex process of

work breakdown. The goal was to automate this process as much as possible and still offer enough

flexibility to comply with the shipyard’s working methods.

In Nupas-Cadmatic part production (nesting, cutting, grinding, beveling of plates and profiles) is

taken care of by the plate nesting and profile modules. The assembly management is carried out by

the (semi) automatic work breakdown functions which will be explained in more detail in this

paragraph.

Fig.11: The Nupas-Cadmatic Work Preparation Manager

4.1 The overall process of the building sequence in Nupas-Cadmatic

Managing the assembly order or building sequence of hundreds or thousands of parts is a complex

process which requires a lot of man hours if done manually. Nupas-Cadmatic reduces this laborious

process to a minimum by the use of the built-in intelligent Work Preparation Manager. The 3D model

contains all the information that is needed to assist in determining the work breakdown sequence as

automatic as possible. The user can define up to 12 levels in the work breakdown tree. Four of these

levels are automatically determined by Nupas-Cadmatic and form the base of the work breakdown.

With use of the interactive Work Preparation Manager the CAM engineer finalizes the work

breakdown sequence manually by inserting levels, dragging and dropping parts, sub panels or panels

freely in the work breakdown tree. Besides the tree structure view the model is also visualized in a 3D

view to assist the CAM engineer with his decisions. Once the work breakdown sequence is fixed

Nupas-Cadmatic produces the complete production documentation according to the work breakdown

sequence. This production documentation consists of various automatically generated reports and

lists, 3D panels and assembly sketches, 2D and 3D combination sketches of panels and parts, 2D

panel drawings, jumbo panel sketches and work breakdown animations. Panels and subpanels receive

work breakdown names which are automatically marked on the individual plates. If desired, the CAM

engineer can even renumber all parts according to the new work breakdown sequence.

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The fact that Nupas-Cadmatic also determines the process codes and job codes for each part, means

that the work preparation department receives a full package of detailed information to assemble the

block in the most efficient way. It is of course also possible to transfer all the production data to the

shipyard’s ERP or MMS system for further processing.

4.2 Automating the work breakdown structure from the 3D model

The automatic work breakdown process starts with the automatic numbering of all the parts and

panels. A panel is a plate with all its attributes (profiles, lugs and brackets). There are several levels of

automatic numbering. The easiest one consists of assigning a unique panel number or name to each

plate. The highest level determines all plates situated in the same plane and then divides the panels in

the same plane into sub panels, Fig.12.

The naming convention in this case is according to the plane values, i.e. frame, breadth and height

values. The sequence of determining the planes in the model can be set in various ways by the user,

for instance from aftship to foreship, from portside to starboard and from bottom to top. During this

process the user can apply several settings to influence the behavior of the automatic numbering.

Fig.12: Automatic panel and subpanel naming

Besides this it is also possible to use the 3D grid system values and naming. In this case

(sub)assemblies and panels receive more comprehensible names such as deck6000, bulkhead-fr146

etc. etc. An important advantage is that the naming convention is also used as text on the individual

parts, panels and assemblies in production. The steelworkers and welders will easily recognize how to

assemble the panels.

The result of the automatic numbering and naming is a reasonable work breakdown structure that is

suitable for manual finalization by the CAM engineer with the help of the Work Preparation Manager

Tool.

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4.3 The Work Preparation Manager Tool

The Nupas-Cadmatic Work Preparation Manager (WPM) is a built-in work breakdown tool to

complete the final assemblies and assembly sequence of a block. Once the automatic part numbering

process has created the basic work breakdown structure, the CAM Engineer is able to compose the

final (sub)assemblies and panels depending on the shipyard’s building method. The work breakdown

structure is visualized by means of a tree structure and the actual 3D model of the block, Fig.11. The

CAM Engineer can add additional levels in the tree, rename and compose new assemblies, change

assemblies by dragging and dropping single parts or complete (sub)assemblies and determine the

building order for each assembly or panel. During the process of creating the final work breakdown

the Nupas-Cadmatic logistical database is updated on the fly.

Fig.13: The Work Breakdown Tree View

An important feature is that the CAM Engineer is also able to decide upon the building sequence of

each panel and (sub)assembly. The order in the tree automatically represents the sequence of

assembling the individual parts, Fig.13. The sequence can be simulated directly via the built-in work

breakdown animation feature. The animation can be saved as an AVI file to support the steelworkers

in the workshop.

4.4 Concurrent production engineering: working offline

The WPM offers 2 ways of working: online and offline. In the online mode the WPM communicates

directly with the Nupas-Cadmatic logistical database meaning that changes in the work breakdown are

stored immediately in Nupas-Cadmatic. In the offline mode the changes in the work breakdown are

stored locally in the WPM tool and synchronized automatically at a later stage with the Nupas-

Cadmatic logistical database. The latter method can be used in situations where design and production

are executed in geographically different locations i.e. a design company working as subcontractor for

the shipyard. The design office does the block detail and production engineering while the shipyard

determines the work breakdown. After synchronizing the work breakdown data the design office

generates all production documentation according to the shipyard’s work breakdown. The same

principle can also be applied between the shipyard’s design and production departments, Figs.14 and

15.

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Fig.14: WPM at the shipyard Fig.15: WPM used in teamwork in offline mode

Fig.16: Automatic created 3D work breakdown views

Fig.17: Automatic generated 3D Work Breakdown sketch

Engineering

Work Preparation

management

Part production

Assembly of

construction

Work Breakdown

definition

Production

documentation

SHIPYARD ENGINEERING OFFICE

SYNCHRONIZE

Engineering

Work Preparation

management

Part production

Assembly of

construction

Work Breakdown

definition

Production

documentation

SHIPYARD

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4.5 Production documentation

Another main advantage of using the intelligent Work Preparation Manager is that all required

production documentation will be generated according to the work breakdown structure at each

desirable level. Most of the documentation is generated automatically in the form of reports, lists, 3D

and 2D panel sketches and drawings. Besides the 3D model presentation, the sketch contains a variety

of information such as labels, weights, CoG, a part list, welding lengths etc, Figs.16 and 17.

The production documentation is derived directly from the Nupas-Cadmatic logistical database and is

always consistent with the status of the actual 3D model. Modifications in the structural 3D model are

reflected directly in the production documentation thereby saving time and avoiding errors.