cad geometry import in flux : principle and best practices · · 2014-09-12interest the main...

CAD package for electromagnetic and thermal analysis using finite element

CAD geometry import in flux : principle and good practices

Flux Table of contents

CAD geometry import in flux : principle and best practices PAGE A

Table of contents

1. Introduction ..............................................................................................................................1

2. The models ..............................................................................................................................3 2.1. The CAD model.............................................................................................................................4 2.2. The finite elements model .............................................................................................................7 2.3. CAD model vs. finite elements model ...........................................................................................8

3. The proposed CAD import in Flux ...........................................................................................9 3.1. Formats 10 3.2. Process of standard/advanced import mode ..............................................................................12 3.3. Options of CAD import in advanced mode..................................................................................15 3.4. Import rapport..............................................................................................................................20 3.5. Influence of the coefficient for the assembly tolerance...............................................................22

4. Good practices with CAD imports in Flux ..............................................................................24 4.1. Good practice: Some general rules ............................................................................................25 4.2. Good practice with collisions between solids..............................................................................27 4.3. Good practice with parasite faces...............................................................................................29 4.4. Good practice with two tangent faces .........................................................................................31 4.5. Best practice with a solid into an other solid ...............................................................................32 4.6. Best practice with problems about coordinate systems..............................................................33

Table of contents Flux

PAGE B CAD geometry import in flux : principle and best practices

Flux Introduction

CAD geometry import in flux : principle and best practices PAGE 1

1. Introduction

About FLUX software has the ability to communicate with other software packages

and to carry out the transfer of data from CAD tools to the Finite Element (FE) analysis tools. This document deals with the CAD imports. Its main objective is to bring the users the best practices to adopt for an optimal use of the CAD geometry import in the Flux software. This specific document completes the documentation on CAD imports of the user guide (consult the help from the supervisor).

Interest The main interest to use the import of a CAD geometry file into FLUX is to

take into account projects possessing complex geometries with “twisted” surfaces). These types of surfaces cannot be generated directly using the available tools in FLUX. The import also permits to simply avoid recreating the geometry in Flux if the device has already been created with a CAD tool*.

* It is however necessary to prepare the CAD model specifically for import in Flux

Introduction Flux

PAGE 2 CAD geometry import in flux : principle and best practices

Flux The models


2. The models

Introduction This section permits to carry out several reminders necessary to understand

the use of the CAD model import in the Flux finite elements software. Indeed, the geometric modeling of the Flux software is based on points, lines, faces and volumes. Each of these entities can bring mesh information or be associated to regions permitting to describe the model appearance. Moreover, the coordinates of the points can be parameterized. This structuring of the data permits the software to propose a very fine adjustment of the model, as well as an efficient parametric resolution. Nevertheless, the approach used is quite different from CAD software approach, which is based on operations of assembly of solids. The automatic generation of an assembly of coherent points, lines, faces and volumes starting from CAD data is sometimes difficult.

Contents This section covers the following topics :

Topic See Page

The CAD model 4 The finite elements model 7 CAD model vs. finite elements model 8

The models Flux


2.1. The CAD model

Introduction This paragraph presents the principle of a geometric model created by means

of a CAD tool.

CAD model The CAD model contains :

Description Illustration

Solid A solid represents one part.The parts are independent from one another.

Part 1 Part 2

Part

One part permits to isolate a solid. There are as many parts as solids.

Part1.part Part2.partPart1.part Part2.part

Assembly The assembly of the parts permits to build the geometry.

Part1.part Part2.part

Assembly.asm

Flux The models


Mates The mates permit to position each of the solids in relation to the others.

Assembly.asm

Fixed Coaxial

Distance

Angle

Assembly.asm

Fixed Coaxial

Distance

Angle

Continued on next page

The models Flux


Defining a CAD model

Here are the main stages in the creation of a CAD model.

Step Action Illustration

1 Create parts

Part1Part1 Part2Part2

2 Create solids in the parts

Part1Part1 Part2Part2

3 Create an assembly

AsmAsm

4 Insert parts in the assembly

AsmAsm

5 Position parts in the assembly

AsmAsmAsm

Flux The models


2.2. The finite elements model

Introduction This paragraph presents the principle of a geometric model created by means

of a finite elements tool such as Flux.

Finite Elements model

The « Finite elements » model contains :

Description Illustration

Volume

One volume represents one part. There are as many volumes as independent from one another parts.

Volume 1 Volume 2

Footprint

To be able to create the equivalent of an assembly (CAD model), there must be a common print of the parts to be assembled. If there is no print, the geometry is not compatible with Flux as it does not have geometric defects (intersection of lines, superposition of faces ...)

Volume 1 Volume 2

Common topology

The contact between volumes is valid if the print has been correctly taken into consideration over each volume to be assembled. This is a common interface.

The models Flux


2.3. CAD model vs. finite elements model

Introduction This paragraph aims to show the differences in modeling of a geometry between the « CAD » and the « Finite Elements » tools.

Differences between models

The main differences between the « CAD » and the « Finite Elements » models are presented in the table below.

CAD model Finite Elements model (Flux)

Solid Volume

Part No part, the geometry is described in one project only

Assembly

No assembly phase, the assemblies between volumes are taken into consideration in the construction of the geometry (print for common interface)

No print necessary over the solids to be assembled

Mandatory print over each volume to be assembled

No common interface necessary for the validity of the geometry

Mandatory common interface for the validity of the geometry

Constraints permitting to position the solids in relationship with one another

No constraints, the positioning of the geometry is carried out by creating different geometric elements (points, coordinate systems...) by defining the coordinates

Flux The proposed CAD import in Flux


3. The proposed CAD import in Flux

Introduction This section permits to the user to find out about the operating principle of the

CAD import that Flux proposes.

Contents This section covers the following topics:

Topic See Page

Formats 10 Process of standard/advanced import mode 12 Options of CAD import in advanced mode 15 Import rapport 20 Influence of the coefficient for the assembly tolerance 22

The proposed CAD import in Flux Flux


3.1. Formats

Introduction Flux takes into consideration different import formats : Import formats named « in standard mode » Import formats named « in advanced mode »

Import in standard mode

The geometry import in standard mode consists in importing geometric elements generated by the CAD by turning them into compatible entities with the finite elements environment of Flux. With the standard import, Flux uses the Open Cascade technology (implemented only in 32 bits). With this import, the assembly operations are not carried out at the moment of the import. It is the user’s task to verify the imported geometry and to correct the defects if the need arises.

Import in advanced mode

The geometry import in advanced mode consists in importing the geometric elements generated by the CAD by converting them into entities compatible with the finite elements environment of Flux. The advanced imports correspond for the most part to the « native » formats of the CAD software. In principle, there are less losses of information if they are used as we do not pass through an intermediate format. With the advanced import, Flux uses the ACIS modeler. With this import, the assembly operations are carried out at the time of the import. The user can choose the entities that he wishes to import and can specify the automatic corrections options to be applied at the time of the import. After the import, theoretically it is not necessary to manually correct the geometry. The corrections are carried out during the import.



Different formats

The following table summarizes the different file formats accepted by Flux in function of the import type.

Import type File format Extension System

IGES (Initial Graphics Exchange Specification) *.IGES, *.IGS 32 bits

STEP (Standard for Exchange of Product) *.STEP, *.STP 32 bits

DXF (Draw eXchange File) *.DXF 32 and 64 bits

STL (STereo Lithography) *.STL 32 and 64 bits

Geometry import in « standard mode »

FBD (géométrie de Flux 2D historique) *.FBD 32 and 64 bits IGES (Initial Graphics Exchange Specification) *.IGES, *.IGS 32 and 64 bits STEP (Standard for Exchange of Product) *.STEP, *.STP 32 and 64 bits SAT *.SAT 32 and 64 bits CATIA V4 *.MODEL 32 and 64 bits

CATIA V5 *.CATPRODUCT *.CATPART

32 and 64 bits

INVENTOR *.IPT 32 and 64 bits

Geometry import in « advanced mode »

PROE (Pro Engineer) *.ASM , *.PRT 32 and 64 bits

To activate the 32 Bits system

Open Cascade is compatible only in 32 bits system. The standard STEP and IGES formats use open cascade, therefore they can be used for the import of CAD only in 32 bits. For the users having a 64 bit system that wish to use one of these import formats, it is possible to use Flux in the 32 bits version starting from a 64 bit system. To do so, one must go to the options starting from the supervisor (Menu Tools Options) and in the tab Memory tick the case « Version 32 bits ».



3.2. Process of standard/advanced import mode

Introduction This paragraph presents the different processes of the CAD geometry import

in Flux according to the mode used : standard mode advanced mode

Process : Standard import

This is the direct transfer process of the CAD model to the « Finite Elements » model corresponding to an import in standard mode.

Phase Description When ? Where ?

1 Preparation of the CAD file (done with the CAD tool used)

Before the import

Out of Flux

2 Reading the solids During the

import In Flux

3 Translation of the solids into volumes in the « Finite Elements » model

During the import

In Flux

4

Correction if necessary (within the context of correction of the CAD geometry) in order to make the geometry appropriate (see the possible defect types in the example below)*

After the import

In Flux in the CAD

healing context

* Attention: it is possible to be unable to manually correct the geometry after the import. In particular, in the case when the geometric defects are on the distorted faces. In this case, it is necessary to use the CAD import in advanced mode that will permit to take into consideration the assembly import containing distorted faces. It is possible to correct the geometry in the correction context only if the geometry defects are on the faces that Flux is able to rebuild (flat, cylinder, conic…).




Example : Standard import

The example below underlines the defects that can exist with the import of a geometry using the standard mode.

CAD

IntersectionLine / Line

IntersectionFace / Face

FE

The model isnot OK for

FE computation

Reading of solids

CAD

IntersectionLine / Line

IntersectionFace / Face

FE

The model isnot OK for

FE computation

Reading of solids

The user will have to use the context healing of the CAD geometry available in Flux to make the necessary corrections to obtain a geometry in accordance with the finite elements model.

Process : Advanced import

This is the transfer process of the CAD model towards the « Finite Elements » model with the imprinting of the assembled solids in an « advanced » import.

Phase Description

1 Preparation of the CAD file (carried out with the used CAD tool) 2 Reading of solids 3 Creation of imprints on the assembled solids 4 Translation of the solids into volumes in the « Finite Elements » model




Example : Advanced import

The example below points out to the phase of imprint creation on the assembled solids automatically generated during import in advanced model.

CAD FE

Reading of solids

Create printson solids

Creation of news- points- lines- faces

The models isOK for FE

computation

CAD FE

Reading of solids

Create printson solids

Creation of news- points- lines- faces

The models isOK for FE

computation

As the prints are generated automatically, the geometry is automatically in compliance with it.



3.3. Options of CAD import in advanced mode

Introduction This paragraph aims to present and explain the different available options

during an import of geometry in advanced mode.

Import box The import box is automatically open when the user chooses to make a CAD

import in advanced mode. This box has 3 tabs: General tab Entities tab Healing tab

« General » Tab

The different options under the General tab are described in the table below.




Part Function Illustration

Coordinate system for geometry attachment

The CAD model has its own coordinate system. Flux can have several coordinate systems. The user must therefore choose the coordinate system for attachment among the Flux project coordinate systems. If no coordinate system is given, a centered coordinate system, domain to which all the points are attached, is created during the import.

CAD model coordinate system

Flux model coordinate system

CAD model coordinate system

Flux model coordinate system

Scale factor

The scale factor permits to reduce or increase the dimensions of the geometry to be imported. For instance, the CAD model unit is the millimeter, while in Flux the unit chosen by the user is the meter. In this case, a scale factor of 0.001 will have to be applied during the import in order to remain in accordance with the dimensions of the geometry. By default the scale factor is at 1.

CAD FLUX

Center the geometry

It is possible to center the geometry on the chosen attach coordinate system. By default the geometry is not centered.

Centeredgeometry

No centeredgeometry

Centeredgeometry

No centeredgeometry




« Entities » Tab

The different options under the Entities tab are described in the table below.


Import solids The user can choose to import or not the solid entities. By default the solids are imported.

Import free faces

The user can choose to import or not the free faces. One free face is a face that does not belong to any solid. By default the free faces are not imported.




« Entities » Tab (Continued) Part Function Illustration

Import free lines

The user can choose to import or not the free line entities. One free line is a line that does not belong to any face. By default the free lines are not imported.

Import invisible entities

The user can choose to import or not the invisible entities. By default the invisible entities are not imported.

CAD FLUX

« Healing » Tab The different options under the Healing tab are described in the table below.


CAD FLUX

1 seule face

CAD FLUX

Single face




Automatic healing

This automatic healing permits to identify and repair the small gaps in segments, creating one straight line.It equally permits to delete all the small entities that can be « parasite » (small stops, fine faces, fine spaces …). To carry out the correction, all the variations to be corrected must be inferior to the accuracy of the authorized geometry (defined in the options of the Flux project geometry). By default this correction is made.

d d

CAD FLUX

Free faces stitching

This operation permits to identify the faces in contact and to create a common edge to the faces. This operation is applied only if the distance between faces is inferior to the stitching tolerance. By default the faces are not imported, so this operation is not activated.

Coefficient for stitching tolerance

User coefficient permitting to adjust the stiching tolerance. By default the coefficient is at 1. Stiching tolerance = initial tolerance * coeff (the initial tolerance is set in Flux at 1e-6 m)

Edges

Faces without common edges

CAD FLUX

Edges

Faces without common edges

CAD FLUX

Solids assembly

This operation permits to identify the solids in contact and to create the necessary prints in order to take into consideration the assembly. To create the prints, points, lines and faces are created. This operation is only applied if the distance between the solids is inferior to the assembly tolerance. By default this operation is made.

Coefficient for assembly tolerance

User coefficient permitting to adjust the assembly tolerance. By default the coefficient is at 1. Assembly tolerance = initial tolerance * coeff (the initial tolerance is set in Flux at 1e-6 m)

CAD FLUXCAD FLUX

Self intersection healing

This correction permits to detect the contact of a piece of a part to another piece of the same part. (different from the assembly correction that is the contact of a part onto another part). By default this correction is not made, as this type of contact is rare and the operation takes long to perform.

auto-contactauto-contact



3.4. Import rapport

Introduction This paragraph presents the report obtained after the import of a geometry in

advanced mode. This report permits to the user to know the different operations that have been made during the CAD import.

Structure of the rapport

The report comprises the following parts : Reading file Entities analysis Correction operations Assembly operations Entities conversion

Part Contents

Reading file The name of CAD file to import The name of file where the import rapport is stored :

IMPORT_REPORT.LOG The unit contained of CAD file

Entities analysis The number of « solid” entities of the CAD model The number of « wire » entities of the CAD model The number of « unknown » entities of the CAD

Correction operations A message indicating whether the correction operations have been correctly executed

Assembly operations The number of successful assembly operations The number of failed assembly operations The initial number of solids before the assembly The end number of solids after the assembly The list of possible warning message

Entities conversion The number of Flux points created after the conversion The number of Flux lines created after the conversion The number of Flux faces created after the conversion The number of Flux volumes created after the conversion The list of possible warning message




Example (1) Here is a first example of a CAD import rapport. CAD model Rapport after CAD import in Flux

Number of solids : 1

Entities analysis - Solid body: 1. - Wire body: 0. - Unknown body: 0. Assembly operations - Succesfull number of operations: 0. - Failed number of operations: 0. - Initial number of solids: 1. - End number of solids: 1. Entities conversion - Points created: 8. - Lines created: 12. - Faces created: 6. - Volumes created: 1.

Example (2) Here is a second a CAD import rapport. CAD model Rapport after CAD import in Flux

Number of solids : 2

Entities analysis - Solid body: 2. - Wire body: 0. - Unknown body: 0. Assembly operations - Succesfull number of operations: 1. - Failed number of operations: 0. - Initial number of solids: 2. - End number of solids: 1. Entities conversion - Points created: 12. - Lines created: 20. - Faces created: 11. - Volumes created: 2.



3.5. Influence of the coefficient for the assembly tolerance

Introduction This paragraph permits to understand the influence of the coefficient on the

assembly tolerance during a CAD import in advanced mode.

Assembly tolerance

The assembly tolerance corresponds to the minimal distance under which the assembly of two solids is carried out.

This tolerance is obtained by the following relation : Assembly tolerance = initial tolerance * coefficient

where : the initial tolerance is set in Flux at 1e-6 m. the coefficient corresponding to the assembly tolerance that the user has

chosen during the import of the CAD file.

Coefficient influence

This is an example that permits to show the influence of the coefficient for the assembly tolerance.

d d: distance between both solids.

It is considered that : the initial tolerance is of 1.0e-6 m the assembly coefficient is of 1 which results in an assembly tolerance of 1.0e-6 * 1 = 1.0e-6 m Then : If d is inferior to the assembly tolerance ( d < 1.0e-6 m) the solids are assembled

If d is superior to the assembly tolerance ( d > 1.0e-6 m) the solids are not assembled




Overlap Example

Here is an example with overlapped solids.

Modele CAO Rapport after CAD import in Flux

ZOOM

V1V1V2V2

V3V3

dd

Nombre de solides : 2

(sectional view of a 3D

geometry)

Entities analysis - Solid body: 2. - Wire body: 0. - Unknown body: 0. Operations de correction - Operations terminees Assembly operations - Succesfull number of operations: 1. - Failed number of operations: 0. - Initial number of solids: 2. - End number of solids: 1. WARNINGS - One or more solid collisions have been

detected Entities conversion - Points created: 14. - Lines created: 22. - Faces created: 13. - Volumes created: 3. WARNINGS - One or more lines have not been created:

1- Lines shorter then epsilon – Please decrease geometric epsilon before reading file

Owing to the collision between solids, Flux generates a third volume that corresponds to the intersection of two imported solids. Theoretically this 3rd volume is not wanted, it can appear when the solids are wrongly positioned in the CAD model. Owing to its small thickness, this volume can generate difficulties during the meshing process.

Best practice To solve out this type of problem, it is suggested to :

1 – adjust the assembly tolerance by modifying the assembly coefficient in the import options ( see Erreur ! Source du renvoi introuvable.)

2 – modify the model directly in the CAD tool, to correct the abnormal overlap.

Good practices with CAD imports in Flux Flux


4. Good practices with CAD imports in Flux

Introduction This section gives the user some good practices in order to face different

situations, in view of improving the use of the CAD import in Flux.

Contents This section covers the following topics:

Topic See Page

Good practice: Some general rules 25 Good practice with collisions between solids 27 Good practice with parasite faces 29 Good practice with two tangent faces 31 Best practice with a solid into an other solid 32 Best practice with problems about coordinate systems 33

Flux Good practices with CAD imports in Flux


4.1. Good practice: Some general rules

Introduction This paragraph refers to the main good practice rules for the CAD import in Flux.

General rule With the majority of failed CAD imports, the cause is the inaccurate modeling of the geometry in CAD as regards the needs of the finite elements model. The adjustment of the different options proposed during an advanced CAD import can permit to correct the possible abnormalities of the CAD model at import. In general, if the import still fails after the proposed options have been modified, then the only solution is to take the CAD model again and to correct the imperfections in the CAD tool.

Check and simplify the geometry

The majority of the CAD software items have commands permitting to check the geometry and specially to detect the collisions. It is recommendable to activate such a command and to carry out the necessary adjustments in the CAD software before the import. To optimize the use of the CAD import in Flux, it is better to simplify the geometry to the maximum before the import. Some parts of the geometry do not have any influence on the physical operation modeled by Flux (such as for instance fastenings, hole, text …), and they have to be deleted in order to avoid to uselessly make the mesh heavier.

Prefer native formats

As far as possible, it is better to use native formats of the CAD software used (ProE, Catia, Inventor, …) rather than the standard formats Iges and Step.

Prefer import of solids

It is better to import the solids of a CAD rather than the faces. Indeed the import of faces requires a supplementary stage which is the « stitching » operation of the faces to ensure the junctions. This operation is very time-consuming.



Prefer import of assembly

Theoretically, to import the different parts of the device successively in Flux or to import the assembly directly gets the same result. During a part by part import no assembly operation is carried out. Therefore, the user will have to build the different prints manually after the import. But they will be able to do it only on the faces that Flux is capable to rebuild (flat, cylindrical, conical,…). In the case of the distorted faces, this manual operation is not possible. It is therefore preferable to import the assembly directly. In this case, all the assembly operations are made during the import.



4.2. Good practice with collisions between solids

The collision A collision means that the solids (volumes) have common parts.

During the imports of CAD geometry in Flux, collisions are the most frequently encountered problems.

Example An example of a collision is presented below.

2 solids

CAD FLUX

3 volumes

In the case above, it is initially wanted to import two parts in contact. The CAD import in Flux has generated 3 volumes, which is incorrect, taking into account the wanted device.

Automatic healing

Certain collisions can be automatically corrected during the import of CAD in advanced mode, by acting on the import options on the assembly tolerance coefficient (see Erreur ! Source du renvoi introuvable.). In this case, there is no collision conflict and the 3rd volume is not created by import.




Advice 1 Depending on the tolerance coefficient for the assembly, certain collisions

can be corrected automatically at the import. In case of defects of collisions at import, these are some tests that the user can make in order to try to solve out certain conflicts and to manage to carry out a correct import.

Step Action

1 To make the CAD import in advanced mode with the coefficient of tolerance for the assembly by default (at 1)

2 If the import was not successful : Change the coefficient by setting it at 10 (this will permit to

correct the collisions or the spaces between the volumes whose defect size is the biggest)

Import again 3 If the import was still not successful :

Change the coefficient setting it at 0.1 (this will permit to correct the collisions or the spaces between the volumes whose defect size is the smallest)

Import again 4 If the import was still not successful :

Rework the CAD model in the CAD tool to correct the imperfections

Advice 2 In general, it is preferable to avoid importing solids in collision (if this is not

wanted). This can generate very small volumes, which are very difficult to mesh. Therefore, it is a priority to make sure that the CAD model is well built.



4.3. Good practice with parasite faces

Parasite faces problem

Some not wanted faces may appear after an import has been made after the faces were built. These are parasite faces that modify the initial geometry of the CAD model. They must not be taken into consideration. Flux has inevitably built these faces, but they can be considered as « ignored » by changing their form into « NO_EXIST ». The « Build faces » operation is necessary when the user does not use the infinite box (IB) but an all-encompassing box with the user limit conditions. In the case of the IB, it is possible to use the command « Complete the infinite box » that permits to construct only the faces of the IB. The difficulty consists in detecting the parasite faces. By default, all the faces are of the same color, and it is not easy to detect the parasite faces that were constructed and that are not part of the initial geometry of the CAD model. To remove this problem an artifice is given in the « Procedure » section.

A parasite face

A parasite face

The face in yellow should not have existed as it has a hollow tube.



Process This is a procedure that permits to detect the parasite faces and to turn them

into « ignored ».

Step Action

1 Import the geometry 2 Modify the color of all the faces, different color from turquoise 3 Construct the faces New faces could be created and they have tourquoise by default. 4 Change the form of the new faces into NO_EXIST (operate a

selection in relationship with all the turquoise faces) 5 Build volumes The geometry is in accordance with the imported CAD model.



4.4. Good practice with two tangent faces

2 tangent faces « Two tangent faces » means that one face is assembled to another face by

tangency. This is named « hyper tangency ».

Problem Hyper tangencies are very difficult to mesh (even impossible to mesh in

certain cases).

Solution To solve the mesh problems associated with hyper tangencies, a delay must

be created (a chamfer or a blend for example) by slightly modifying the geometry in the CAD software.

Before correction After correction

tangency Delay createdby the user

Before correction After correction

tangency Delay createdby the user



4.5. Best practice with a solid into an other solid

Problem There can be conflicts during the import of a geometry that has a solid at the

interior of another solid.

Solid 1

Solid 2 inside solid 1

Cross section (2D)

Solid 1

Solid 2 inside solid 1

Cross section (2D)

Solution This is the solution proposed to solve this problem. Etape Action Illustration

1 Import only solid 1

2 Perform a Build Volumes

The 2 volumes are present, the geometry is valid and it conforms to the initially wanted volume



4.6. Best practice with problems about coordinate systems

Problem It is possible to import a CAD geometry in Flux and then to modify the

location of the geometry. The geometric accuracy is calculated in function of the biggest diagonal of the project. If the geometry is constructed far from the « global » coordinate system in the CAD software, after the geometry import it will be far from the global coordinate system of Flux. As the project diagonal is big, the geometric accuracy will not be adapted to the real size of the geometry. The user can displace the geometry at any time in order to center it again on the global coordinate system in Flux, but this does not modify the accuracy that will still remain unadjusted. There are conflict risks: Detection of unwanted superposed points Detection of superposed lines Failure of the commands to build faces, to build volumes …

Solution To avoid distorting the geometrical accuracy it is advisable to construct the

CAD model (with the CAD tool) on the wanted coordinate system in the end in Flux.

cad geometry import in flux : principle and best practices · · 2014-09-12interest the main...

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