Timber NC-operations - Background & general modelling aspects


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Last updated April 16, 2020 by Construsoft NL ts-support@construsoft.com

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Timber NC-operations - Background & general modelling aspects

Construsoft developed and implemented several Timber NC-export tools in Tekla Structures.
Each of these export tools is dedicated to a specific Timber NC-file format, each with their own scope and definition.

The scope of some of the formats is such that Tekla can unambiguously determine the operation from the geometric information. These are categorized as basic formats. There are however also formats for which, for volumetric operations, it is not possible to unambiguously determine which operation is meant. In those cases the user needs to provide additional non-geometrical information in the form of the name of the operation. These file formats are categorized as advanced formats.
Another way to categorize the file formats is by considering the type of objects they can describe.
Next table illustrates these categorizations:
 

    Single-piece   Framing  
Timber NC-File format Type Beam Plate Beam Plate
BTL Advanced Yes Yes Yes Yes
Hundegger-BVN (K2) Advanced Yes No No No
Hundegger-BVX (SC3) Advanced Yes No No No
Hundegger-BVX2 Advanced No Yes No No
GT_Hechttechniek Basic No No Yes Yes
HM (M311 ; HMT ; HMZ) Basic Yes No No No
Randek Basic No No Yes Yes
Tigerstop Basic Yes No No No

This document is meant for end-users that want to model and export single parts to any of the advanced file formats. It is not a manual on how to apply the related Timber NC-Export tool.  Instead, it aims to provide handles that will help the end-user to model in such a way that the export to the chosen advanced Timber NC-file format can be performed without problems.

Not every operation can be described by all advanced file formats. This document handles the direct sum of available operations that are available in the several advanced file formats.

As a final remark, this document does not pretend to be complete with regard to all details, properties and scope of all operations of each one of these advanced file formats.

For a full description, please review the official document(s) from the developers of the format.

1. Categorization of Timber NC-operations

There are many ways to categorize the operations that a Timber NC-file format supports.
The most coarse way is to categorize an operation as:
A. Changes geometry of a part
B. Does not change geometry of a part
 
Operations that change geometry of a part can be subdivided in operations that are:
A.1 Separating
A.2 Profiling
A.3 Discrete
 
Operations that do not change geometry of a part are in general denoted as Annotation operations such as 
B.1 Marking
B.2 Text
 
This categorization of a Timber NC-Operation can be depicted as:


 

A. Operations that change geometry

This type of operation changes the geometry of the solid of its parent.
 

A.1 Separating Timber NC-operations

This type of operation can change the length of a part.

Note that one of these operations is planar, all others are volumetric.
In the advanced Timber NC-file formats, the negative volumes that model the volumetric operations must be given the appropriate name.

Note that for certain cases a combination of negative volumes may be necessary to achieve the required result. Each of those negative volumes must have proper shape and name.
 

A.2 Profiling Timber NC-operations

A profiled part is prismatic and has a non-rectangular cross sectiongeometrical form of a part sectioned perpendicular to its axis

.

When a non-profiled part is subjected to a profiling operation it renders that part profiled.

A profiling operation has the following properties:
• The system line of the operation is parallel to the system line of the part it operates on
• The operation stretches throughout (at least) the complete length of the part it operates on

Note that all profiling operations are volumetric.
In the advanced Timber NC-file formats, the negative volumes that model the volumetric operations must be given the appropriate name.

Note that for certain cases a combination of negative volumes may be necessary to achieve the required result. Each of those negative volumes must have proper shape and name.
 

A.3 Discrete Timber NC-operations

A discrete operation is an geometry-changing operation that is neither separating nor profiling.

Note that, except the bolt holes generated by the Bolts command, all geometry-changing discrete operations are volumetric.
In the advanced Timber NC-file formats, the negative volumes that model the volumetric operations must be given the appropriate name.

Note that for certain cases a combination of negative volumes may be necessary to achieve the required result. Each of those negative volumes must have proper shape and name.
 

B. Operations that do not change geometry

This group of operations contains annotative operations. These operations do not remove material. They add information that can be helpful during production and erection.
 

B.1 Marking Timber NC-operations

A marking indicates where on a part other parts must be positioned. This prevents that parts are positioned in wrong location on their parent.


 

B.2 Text Timber NC-operations

This operation does not need any modelling effort from the user.
Hence, there is no image to show.
 

2. Tekla Structures entities

For modelling the operations, Tekla Structures offers three types of entity:

C. Negative Volume
D. Plane
E. Bolt

A negative volume can be:
C.1 based on a beam object
C.2 based on a contour platepart whose outline form the user defines by picking three or more points

The user can define the shape of the contour plate parallel to the work plane. The profile in use defines the thickness. The corners of the contour plate can be chamfered.

object
C.3 based on polygon Cutcut that is defined by a polygon

A Plane can be a:
D.1 Fit-plane
D.2 Cut-plane

A bolt holesmall hollow open throughout a part or assembly that is usually used for fastening parts with bolts or other such objects

Hole is created in the same way as bolts and hole properties are defined in the bolt properties.

can be modelled using either the Bolts command or a cylindrical negative volume.

Next image provides an overview of these entities:


 

C. Tekla entities – Negative volume

The majority of operations is volumetric.  A volumetric operation must (*) be modelled with a negative volume.
 
(*) Exception to this rule is for modelling bolt holes.
Bolt holes can be modelled using either a negative volume based on a cylindrical beam part or by applicationpart of Tekla Structures functionality that is developed in order to extend the capability of Tekla Structures but that is not included in the Tekla Structures installation

of the Bolts command.
 
In Tekla, a negative volume can be modelled using either:
a) Part cutcut that is defined by a cutting part

based on beam
b) Part cut based on contour plate(1) part that represents a flat structure

(1) In some contexts, for example in analysis, the term plate object may be used to refer to plates.

(2) plate that represents a steel structure

(2) Plate is mainly used as a connection piece or as a floor plate.


c) Polygon cut  
 
The majority of volumetric operations is rectangular and prismatic.
 
Using a polygon cut or contour plate, the user needs to specify the location of all the vertices. Using those methods, the chance that the final result does not meet this shape restriction is quite large. Therefore it is advised to only use either of these two methods when the required result cannot be achieved by using the beam method.
 
In the advanced Timber NC-file formats, the negative volumes that model the volumetric operations must be given the appropriate name.
 
Note that for certain cases a combination of negative volumes may be necessary to achieve the required result. Each of those negative volumes must have proper shape and name.

 

C.1  Negative volume-Based on Beam object

While modelling volumetric operations, the following requirements should be met:
• The volume enlarges the bounding boxrectangular border with the smallest measure within which all the selected points that position the model objects lie

In Tekla Structures two-dimensional bounding boxes are used in drawings and three-dimensional bounding boxes in models.

of the virginal part in all directions that the required operation allows.
• The shape of the volume must be definable using the set of parameters that the file format defines for the operation. In general this means that the negative volume must be rectangular and prismatic.
 
Next images show some examples that illustrates these recommendations and restrictions.


 

C.2  Negative volume-Based on contour plate object

While modelling volumetric operations, the following requirements should be met:
• The volume enlarges the bounding box of the virginal part in all directions that the required operation allows.
• The shape of the volume must be definable using the set of parameters that the file format defines for the operation. In general this means that the negative volume must be rectangular and prismatic.
 
Furthermore it is advised to model the contour plate in such a way that the first (=yellow) point lies outside the virginal solid. This first point represents the tip of the tool on the machine and the machine cannot start the operation from within a solid.

Next images show some examples that illustrate these recommendations and restrictions.


 

C.3  Negative volume-Based on polygon cut

All remarks given in paragraph C.2  are applicable for this method of modelling a negative volume.
 

D. Tekla entities – Planes

Tekla Structures offers two types of planes. A fit plane and a cut planeplane whose position is defined by a cut surface

.

A fit plane rotates the end face of a solid so it matches the orientation of the specified fit plane. 
A cut plane actually removes a portion of the solid.

If there is only one Planar operation on an end face, Tekla Structures prescribes to use a Fit plane.
If there is more than one planar operation on an end face, Tekla Structures prescribes to first apply a Fit plane and a Cut plane for all other.

For modelling the planar timber NC-operations these same rules apply.
 

E. Tekla entities – Bolt holes

All bolt holes can be modelled using a negative volume based on a beam with a cylindrical cross section.
In the advanced Timber NC-file formats, these cylindrical negative volumes must be given the appropriate name.

Full depth bolt holes can be modelled with the in-built Bolts command as well.

 


Tags: 
Timber
BTL
Hundegger
GT
HM
randek
tigerstop

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