About this documentation file

This is file README.md

README.md is the documentation for a software library centred on file eights.py (see "Description" section below).

README.md was written by Dr. Daniel C. Hatton

Material up to and including release 0.2 copyright (C) 2017-2018 University of Plymouth Higher Education Corporation

Changes since release 0.2 copyright (C) 2020-2021 Dr. Daniel C. Hatton

This program, including this documentation file, is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation: version 3 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License, and the GNU General Public License which it incorporates, for more details.

You should have received a copy of the GNU Lesser General Public License [in file LICENSE] along with this program. If not, see https://www.gnu.org/licenses/.

Daniel Hatton thanks Dr. Justin E. Rigden, Specialist Intellectual Property Advisor, for authorizing, on behalf of the University of Plymouth Higher Education Corporation, the release of this program under the licence terms stated above.

Contact

Daniel Hatton can be contacted on [email protected].

Description

File eights.py is a Python module intended for use with the open-source 3D computer-aided design package FreeCAD (FreeCAD version 0.15 user manual, n.d.). The module automates the construction of a page of 2D axonometric drawings in first angle projection, in a style consistent (to the best of the module author's ability) with the BS 8888:2011 standard (Technical product documentation and specification BS 8888, 2011).

Statement of need

The creative process behind detailed engineering design now typically takes place in 3D CAD packages (Quintana et al., 2010). However, for this creative process actually to lead to an embodiment of the design being manufactured, this creative process must be followed by communication of the content of the design to a manufacturing facility. There are two necessary requirements for success: firstly, the communication must include information on all those aspects of the design that are necessary to complete manufacture, and to verify by inspection that the completed, manufactured artefact matches the design (Quintana et al., 2010); secondly, the communication must be in a well-defined (usually graphical) language, so that it can be understood at the manufacturing facility in a way that permits successful manufacturing and inspection (Quintana et al., 2010; Dobelis et al., 2018). The drive to meet both of these requirements has led to the development of published standards for design communication (Dobelis et al., 2018), of which BS 8888:2011 (Technical product documentation and specification BS 8888, 2011) is one. These standards are in a very advanced state of maturity for 2D engineering drawings, but despite efforts in recent years to develop similar standards for 3D models, the standards for 3D models remain somewhat less mature (Quintana et al., 2010). As a result, 2D drawings remain a crucial medium for communication of design information to manufacturing facilities, and possessing the capability for automated generation of standards-compliant 2D drawings from a 3D model is an important criterion by which the technical quality of 3D CAD software packages is assessed (Kannan & Vinay, 2008; Hughes, 2013). Hence, by automating the process of producing certain standards-compliant 2D drawings, the eights module offers the opportunity for the FreeCAD CAD package (FreeCAD version 0.15 user manual, n.d.) to be more favourably assessed against this criterion in future.

One automated tool, for generating 2D drawings in first angle projection from a 3D model in FreeCAD, already exists: the FreeCAD Automatic Drawing Macro (Macro Automatic Drawing, 2016). A full analysis of the relative advantages and disadvantages of the Automatic Drawing Macro, and the eights module announced here, can be found in the "Comparison and contrast with other software of similar purpose" section of this documentation file. For the purposes of this statement of need, it is sufficient to mention two of the relative disadvantages of the Automatic Drawing Macro:

• the Automatic Drawing Macro does not attempt to comply with BS 8888 as regards the format of the drawing sheet and its title block;
• the Automatic Drawing Macro does not offer the ability to include first angle pro jection sets for multiple 3D objects on the same drawing sheet.

It is not only in the manufacturing sector that standardized axonometric drawings have proved important to clear communication: scholarly research has also benefited from this language. For example, in the study of human anatomy, standardization of axonometric drawing sets to the BS 8888 standard has been used to reduce both cumulative uncertainty in position co-ordinates and difficulty of interpretation associated with the presentation, in published papers, of geometric data on the human skeleton (Magee et al., 2012); and in archaeology, the standard first-angle projection set has been used to facilitate unambiguous description of the laboratory methods used to infer manufacturing methods from surface profilometry of ancient monumental artefacts (Moitinho de Almeida & Barceló, 2014). In scholarly research in physics, one finds a cautionary tale concerning the consequences when no standardized language is available for engineering drawings: in foundational seventeenth-century experimental research in hydrostatics, the discovery of effects, in the force balance on columns of water and air, due to the solubility of air in water and to adhesion between water and solid surfaces, was for some time hotly contested due to a lack of reproducibility of results between subtly different sets of apparatus (Shapin & Schaffer, 2011). In the absence of a standard for engineering drawings, attempts to communicate between different research groups, using a combination of text and schematic diagrams, what the differences between their respective apparatus were, proved fruitless, and consensus on the experimental facts was eventually achieved only by the long-range transport of actual experimental rigs, across international borders, for side-by-side comparison (Shapin & Schaffer, 2011). So deep did the confusion run that, more than three centuries later, Shapin & Schaffer (2011) still found themselves with much work to do, in attempting to understand exactly what were the relevant differences between the respective experimental rigs.

Prerequisites

For this module to be useful, it will be necessary to have a working installation of FreeCAD. FreeCAD is available in the standard repositories of most Linux distributions, and for Windows and MAC OS X systems from https://www.freecadweb.org/wiki/Download. The module has been most thoroughly tested on FreeCAD 0.16 under Scientific Linux 7.3 and Scientific Linux 7.5, but also to some extent on FreeCAD 0.15 under Windows 7 Enterprise, on FreeCAD 0.16 under Fedora 28, and on FreeCAD 0.18.4 under Ubuntu 20.04.

Installation

To install, create a subdirectory called eights in your module directory (~/.FreeCAD/Mod on Linux, %APPDATA%\FreeCAD\Mod on Windows), and place the file eights.py in that subdirectory.

On some systems (at least, FreeCAD 0.16 under Scientific Linux 7.5), placing the file eights.py in the working directory from which FreeCAD is to be started can also be an effective installation method, although there are reports that this method does not work on all systems.

Details

The module provides:

• a class "create_eights_drawing_sheet", whose purpose is to provide the method "create_it", which adds, to an existing FreeCAD document, a TechDraw::DrawPage (if the FreeCAD version under which the module is being run is 0.19 or later) or Drawing::FeaturePage (if the FreeCAD version under which the module is being run is earlier than 0.19) object ("the sheet") whose formatting is intended to be consistent with the BS 8888:2011 standard for a drawing sheet, and populates the title block of the sheet, again in a way intended to be consistent with BS 8888:2011;
• a class "add_first_angle_projection_symbol", whose purpose is to provide the method "put_it_in", which adds the standard BS 8888:2011 symbol, indicating that a set of drawings are in first angle projection ("the symbol"), to an existing TechDraw::DrawPage or Drawing::FeaturePage object ("the sheet"). The method put_it_in also creates a new FreeCAD Document ("the dummy document"), containing various objects that are created as intermediate steps on the way to adding the symbol to the sheet, but which do not need to exist in the same document as the sheet. The method put_it_in also modifies the parent document of the sheet, by adding to it two TechDraw::DrawViewPart (if the FreeCAD version under which the module is being run is 0.19 or later) or Drawing::FeatureViewPart (if the FreeCAD version under which the module is being run is earlier than 0.19) objects, which are intermediate steps on the way to adding the symbol to the sheet, and which have to exist in the same document as the sheet in order to add the symbol to the sheet; and
• a class "add_third_angle_projection_symbol", whose purpose is to provide the method "put_it_in", which adds the standard BS 8888:2011 symbol, indicating that a set of drawings are in third angle projection ("the symbol"), to an existing TechDraw::DrawPage or Drawing::FeaturePage object ("the sheet"). The method put_it_in also creates a new FreeCAD Document ("the dummy document"), containing various objects that are created as intermediate steps on the way to adding the symbol to the sheet, but which do not need to exist in the same document as the sheet. The method put_it_in also modifies the parent document of the sheet, by adding to it two TechDraw::DrawViewPart (if the FreeCAD version under which the module is being run is 0.19 or later) or Drawing::FeatureViewPart (if the FreeCAD version under which the module is being run is earlier than 0.19) objects, which are intermediate steps on the way to adding the symbol to the sheet, and which have to exist in the same document as the sheet in order to add the symbol to the sheet; and
• a class "first_angle_projection", whose purpose is to provide the method "fap", which takes any object ("the shape") which can be assigned to the "Shape" property of a Part::Feature object, and adds a set of axonometric drawings ("the views") of the shape in first angle projection to an existing TechDraw::DrawPage or Drawing::FeaturePage object ("the sheet"), following the conventions in BS 8888:2011. The method fap also creates a new FreeCAD Document ("the dummy document"), containing various objects that are created as intermediate steps on the way to adding the views to the sheet, but which do not need to exist in the same document as the sheet. The method fap also modifies the parent document of the sheet, by adding to it six TechDraw::DrawViewPart (if the FreeCAD version under which the module is being run is 0.19 or later) or Drawing::FeatureViewPart (if the FreeCAD version under which the module is being run is earlier than 0.19) objects, which are intermediate steps on the way to adding the views to the sheet, and which have to exist in the same document as the sheet in order to add the views to the sheet.
• a class "third_angle_projection", whose purpose is to provide the method "tap", which takes any object ("the shape") which can be assigned to the "Shape" property of a Part::Feature object, and adds a set of axonometric drawings ("the views") of the shape in third angle projection to an existing TechDraw::DrawPage or Drawing::FeaturePage object ("the sheet"), following the conventions in BS 8888:2011. The method tap also creates a new FreeCAD Document ("the dummy document"), containing various objects that are created as intermediate steps on the way to adding the views to the sheet, but which do not need to exist in the same document as the sheet. The method tap also modifies the parent document of the sheet, by adding to it six TechDraw::DrawViewPart (if the FreeCAD version under which the module is being run is 0.19 or later) or Drawing::FeatureViewPart (if the FreeCAD version under which the module is being run is earlier than 0.19) objects, which are intermediate steps on the way to adding the views to the sheet, and which have to exist in the same document as the sheet in order to add the views to the sheet.

Invocation

The methods provided by this module can be invoked either from the FreeCAD Python console, or from a Python script opened in FreeCAD. In both cases, before invoking the methods from this module, it will be necessary to invoke

import FreeCAD
import Part
import eights

To create a BS 8888:2011 drawing sheet, as a TechDraw::DrawPage (if the FreeCAD version under which the module is being run is 0.19 or later) or Drawing::FeaturePage (if the FreeCAD version under which the module is being run is earlier than 0.19) object to be stored in "any_var_name":

any_var_name = eights.create_eights_drawing_sheet(<doc>, <shorttitle>,
                                                  <pagesize>, <orientation>,
                                                  <creator>,
                                                  <longtitle>,
                                                  <legalowner>,
                                                  <approver>,
                                                  <doctype>,
                                                  <docstatus>,
                                                  <sheetnum>,
                                                  <totalsheets>,
                                                  <inversescale>,
                                                  <partlist>,
                                                  <drawingnum>, <year>,
                                                  <month>, <day>, <rev>)
any_other_var_name = any_var_name.create_it('putanyoldrubbishhere')

where:

• <doc> is the FreeCAD document to which the drawing sheet will be added;
• <shorttitle> is a string giving a short title (suitable to appear in the tree view in the FreeCAD GUI) for the drawing sheet;
• <pagesize> is a string indicating the size of paper on which the drawing sheet should appear, in the same format used in the file names of the SVG files for FreeCAD's built in ISO7200 templates;
• <orientation> is a string indicating the orientation of paper on which the drawing sheet should appear, in the same format used in the file names of the SVG files for FreeCAD's built in ISO7200 templates;
• <creator> is a string giving the name of the creator of the design (suitable to appear in the on-sheet title block) ;
• <longtitle> is a string giving a longer title (suitable to appear in the on-sheet title block) for the drawing sheet;
• <legalowner> is a string identifying the legal owner of the design (suitable to appear in the on-sheet title block);
• <approver> is a string giving the name of the approval person for the design (suitable to appear in the on-sheet title block);
• <doctype> is a string identifying the document type (suitable to appear in the on-sheet title block);
• <docstatus> is a string identifying the document status (suitable to appear in the on-sheet title block);
• <sheetnum> is an integer identifying which number sheet this is in the overall series of drawing sheets of which it is a member;
• <totalsheets> is an integer identifying how many sheets there are in total in the series of which this drawing sheet is a member;
• <inversescale> is an integer identifying the reciprocal of the scale to which the drawings are to be drawn (BS 8888:2011 indicates a preference for this number being either 2 or 5);
• <partlist> is a string containing a comma-separated list of the part identifiers of the parts that will appear on this drawing sheet;
• <drawingnum> is a string indicating the drawing identifier of this drawing sheet;
• <year> is an integer representing the year in which the design was created;
• <month> is an integer representing the calendar month in which the design was created;
• <day> is an integer representing the day of the month on which the design was created; and
• <rev> is a string indicating the revision identifier of the version of the design that will appear on this drawing sheet.

To add the first-angle projection symbol to a drawing sheet:

some_name = eights.add_first_angle_projection_symbol(<largediam>,
                                                     <smalldiam>,
                                                     <spacing>,
                                                     <xpos>, <ypos>,
                                                     <thepage>)
some_other_name = some_name.put_it_in('putanyoldrubbishhere')

where:

• <largediam> is a floating-point number, representing the diameter at base of the truncated cone from which the symbol is generated (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD);
• <smalldiam> is a floating-point number, representing the diameter at truncation plane of the truncated cone from which the symbol is generated (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD);
• <spacing> is a floating-point number, representing the spacing between the two axonometric projections of the truncated cone that form the symbol (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD);
• <xpos> is a floating-point number, representing the horizontal position ordinate, on the drawing page, at which the symbol is to be placed (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD);
• <ypos> is a floating-point number, representing the vertical position ordinate, on the drawing page, at which the symbol is to be placed (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD); and
• <thepage> is a TechDraw::DrawPage orDrawing::FeaturePage object, representing the drawing sheet to which the symbol is to be added.

To add a first angle projection set for a 3D shape to a drawing sheet:

a_name = eights.first_angle_projection(<partnum>, <theshape>,
                                       <spacing>,
                                       <xpos>, <ypos>,
                                       <scale>, <thepage>)

another_name = a_name.fap('putanyoldrubbishhere')

where:

• <partnum> is a string containing a comma-separated list of the part identifiers of the parts included in the 3D shape;
• <theshape> is an object capable of being assigned to the Shape property of a Part::Feature object, representing the 3D shape to be drawn;
• <spacing> is a floating-point number, representing the spacing between the individual axonometric projections of the 3D shape (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD);
• <xpos> is a floating-point number, representing the horizontal position ordinate, on the drawing page, at which the first angle projection set is to be placed (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD);
• <ypos> is a floating-point number, representing the vertical position ordinate, on the drawing page, at which the first angle projection set is to be placed (on the systems where the present module has been tested, it's in millimetres, but this may depend on some configuration option of FreeCAD);
• <scale> is a floating-point number, representing the scale at which the first angle projection set is to be drawn (BS 8888:2011 indicates a preference for this number being either 0.5 or 0.2); and
• <thepage> is a TechDraw::DrawPage or Drawing::FeaturePage object, representing the drawing sheet to which the first angle projection set is to be added.

Example scripts (test cases)

Twelve example python scripts that make use of this module are provided, in the directory EXAMPLES. In each case, one can run the example script by opening it in the FreeCAD GUI and pressing the GUI "Execute the macro in the editor" button. The expected functionality of the example scripts is as follows:

• Single_part.py creates a drawing sheet showing, in first angle projection, a single part (a cube of side 100 mm), with intended output as follows: .
• Two_parts.py creates a drawing sheet showing, in first angle projection, two separate parts (a cube of side 100 mm and a sphere of diameter 100 mm), with intended output as follows: .
• Assembly.py creates a drawing sheet showing, in first angle projection, two parts (a cube of side 100 mm and a sphere of diameter 100 mm) fused into an assembly, with intended output as follows: .
• Anisotropic_part.py creates a drawing sheet showing, in first angle projection, a single part (a rectangular parallelepiped of sides 50 mm, 100 mm, and 150 mm), with intended output as follows: .
• Assembly_side.py creates a drawing sheet showing, in first angle projection, the same assembly as in Assembly.py, but in a different orientation. This has been added because previously, all the test cases had reflection symmetry about the same planes, which had caused a particular bug (now fixed) to remain undetected through multiple releases. The intended output is as follows: .
• Assembly_back.py creates a drawing sheet showing, in first angle projection, the same assembly as in Assembly.py and Assembly_side.py, but in a different orientation. This has been added because previously, all the test cases had reflection symmetry about the same planes, which had caused a particular bug (now fixed) to remain undetected through multiple releases. The intended output is as follows: .

In addition to the six scripts listed above, there are six additional scripts, with _third inserted into the filenames, which represent the same objects in third angle projection.

Comparison and contrast with other software of similar purpose

The present module is not the only available contributed Python script for FreeCAD intended to produce a drawing sheet containing a first-angle projection set: there is also the "Automatic drawing" macro. There are a number of differences between the operation of the Automatic Drawing macro and the operation of the present module. Some of these differences can be classified as advantages of the present module, some can be classified as advantages of the Automatic Drawing macro, and some are neutral (including differences that may be either advantages of the present module or advantages of the Automatic Drawing macro, depending on the use case).

Advantages of the present module

• The present module has separate methods for the creation of the drawing sheet and the addition of a first angle projection set, whereas the Automatic Drawing macro performs both tasks in a single procedure; this means that only the present module offers the ability to include first angle projection sets for multiple 3D objects on the same drawing sheet.
• The present module attempts to follow the conventions of BS 8888:2011 for the format of the drawing sheet and its title block, and for the thicknesses of lines in drawings, whereas the Automatic Drawing macro does not.
• In the present module, the scale of the drawings is an option that can be set by the user, whereas the Automatic Drawing macro automatically computes separate scales for its first angle projection set and its isometric drawing, in an attempt to produce fixed drawing sizes, and neither reports those computed scales to the user, nor automatically prints them in the title block of the drawing sheet.
• In the present module, the size and orientation of the drawing sheet are user-selectable options, whereas in the automatic drawing macro, they are fixed and can be changed only by editing the macro source code.
• In the present module, the spacing between the individual axonometric views is a user-selectable option, whereas in the Automatic Drawing module, it is fixed by an algorithm that can be changed only by editing the macro source code (and is sometimes fixed in such a way that the individual views overlap).
• In the present module, the location on the drawing sheet of the first angle projection set is a user-selectable option, whereas in the Automatic Drawing module, it is fixed by an algorithm that can be changed only by editing the macro source code (so too is the location on the drawing sheet of the isometric drawing, and they are sometimes fixed in such a way that the first angle projection set and the isometric drawing overlap).
• The present module can automatically populate the title block of its drawing sheet with user-supplied information, whereas the Automatic Drawing macro cannot.
• The present module clearly states the identity of its copyright holder and the licence terms under which it is released, whereas the Automatic Drawing macro does not.
• The Automatic Drawing macro can only add its drawing sheet to the currently active document, whereas the present module can add its drawing sheet to any document.
• The Automatic Drawing macro can only produce drawings of the currently selected 3D object, whereas the present module can produce drawings of any 3D object.

Advantages of the Automatic Drawing macro

• The Automatic Drawing macro adds fewer extraneous TechDraw::DrawViewPart or Drawing::FeatureViewPart objects to the parent document of the drawing sheet than the present module (although it still adds some).
• The Automatic Drawing module can be straightforwardly launched either from menus and dialogue boxes in the FreeCAD GUI or from Python commands, whereas the present module can be straightforwardly launched only from Python commands.

Neutral differences between the present module and the Automatic Drawing macro

• The present module produces a full set of six individual axonometric views, whereas the Automatic Drawing macro produces only three. This is an advantage of the present module if one is in the sphere of influence of the British Standards Institute, since as the author of the present module understands it, including all six views in a first angle projection set is mandatory in BS 8888:2011. It is also an advantage of the present module if one's design is sufficiently asymmetric that it cannot be successfully manufactured from just three axonometric projections. Otherwise, it is an advantage of the Automatic Drawing macro, which can thereby produce a less cluttered drawing sheet.
• The Automatic Drawing macro, in addition to the first angle projection set, adds an isometric drawing to its drawing sheet. If one actually wants an isometric drawing, this is an advantage of the Automatic Drawing macro; however, the behaviour cannot be switched off (other than by editing the macro source code), so if one does not want an isometric drawing, it is an advantage of the present module.
• In the present module, the dimensions and location on the drawing sheet of the first angle projection symbol are user-selectable options, whereas in the Automatic Drawing module, they are fixed and can be changed only by editing the macro source code.
• The Automatic Drawing macro takes as its input 3D object a Part::Feature object, whereas the present module takes as its input 3D object an object capable of being assigned to the Shape property of a Part::Feature object.

Bugs

This module attempts to implement BS 8888:2011, which is not the latest edition of the BS 8888 standard.

The drawings produced by the fap method in the first_angle_projection class do not include explicit dimensions, tolerances or labels associating part numbers with the drawings of particular parts; some of these features may, under some circumstances, be mandatory in BS 8888:2011. All of these features can be added using the GUI of the FreeCAD Drawing Dimensioning Workbench, supplied by github user hamish2014; however, the author of the present module has been unable to find a convenient way of scripting the Drawing Dimensioning Workbench in Python.

The create_it method in the create_eights_drawing_sheet class doesn't trap any attempt by the user to select a combination of paper size and orientation that doesn't exist in FreeCAD's collection of ISO7200 templates. When this happens, the method goes ahead and creates a TechDraw::DrawPage (if the FreeCAD version under which the module is being run is 0.19 or later) or Drawing:FeaturePage (if the FreeCAD version under which the module is being run is earlier than 0.19) object, to which content can be added by other methods, but which cannot be viewed in the FreeCAD GUI. The only subsequently-visible (to the user) clue as to what's wrong is that hovering the mouse over the manifestation of the relevant drawing sheet in the Tree View produces pop-up text "Cannot open file path_to_non-existent_template_file.svg".

The create_it method in the create_eights_drawing_sheet class doesn't trap any attempt by the user to insert inappropriately typed data into the fields of the title block (e.g. drawing sheet numbers that are not integers, creator names that are not strings, ...).

BS 8888:2011 indicates a preference for drawing scales of 1:2 and 1:5 over such intermediate scales as 1:3 or 1:4; however, this module contains no such preference, instead making it equally easy for the user to select any drawing scale.

BS 8888:2011 inherits its specifications for the title block of a drawing sheet from ISO7200. To implement these specifications, the create_it method in the create_eights_drawing_sheet class makes use of FreeCAD's built-in template for ISO7200 drawing sheets. However, the layout of the title block in the FreeCAD ISO7200 template (at least in FreeCAD version 0.15) is not identical to either of the ISO7200 example layouts given in BS 8888:2011. It is not clear whether this represents:

• an error in the FreeCAD template;
• a change in the ISO7200 standard since the publication of BS 8888:2011; or
• a degree of flexibility in ISO7200.

The fap method in the first_angle_projection class was written assuming that the input solid shape would be positioned in such a way that the solid shape is entirely contained in the positive-x, positive-y, positive-z octant of space, but that all three of the planes bounding that octant are tangent to the solid shape. When that's not the case, the method produces sets of projections which are not wrong in any technical sense, but which do look decidedly odd.

In setting the widths of lines in the drawing to comply with BS 8888:2011, both the put_it_in method in the add_first_angle_projection_symbol class and the fap method in the first_angle_projection class assume that FreeCAD will interpret floating-point numbers, assigned to the LineWidth and HiddenWidth properties of a TechDraw::DrawViewPart or Drawing::FeatureViewPart object, as being in millimetres. This assumption has so far proved correct on the systems on which the present module has been tested, but there may be some FreeCAD configuration option that can render it incorrect.

(This bug is fixed as long as the module is being run under FreeCAD version 0.18.4 or later.) The dummy documents created by the put_it_in method in the add_first_angle_projection_symbol class and by the fap method in the first_angle_projection class are a waste of RAM and clutter up the GUI, and ideally should be closed just before the respective methods exit. Unfortunately, adding commands to the end of the methods to close the dummy documents causes a segfault, at least under FreeCAD 0.16 on Scientific Linux 7.3 (and in some cases under FreeCAD 0.16 on Fedora 28). The segfault doesn't happen under FreeCAD 0.18.4 on Ubuntu 20.04, so the present state of the code is that the dummy documents are closed in a conditional code segment that is executed only if the FreeCAD version under which the module is being run is 0.18.4 or later.

Citing

If you use the eights module to produce published work, please cite

• Hatton, D. C. (2019). eights: BS 8888:2011 first angle projection drawings from FreeCAD 3D model. J. Open Source Softw., 4(33), 974-1-974-3. doi:10.21105/joss.00974

References

• Dobelis, M., Polinceusz, P., Sroka-Bizon, M., Tytkowski, K., Velichova, D., & Vansevicius, A. (2018). Is the constructional drawing an international language for engineers? In L. Cocchiarella (Ed.), ICGG 2018 — proceedings of the 18th international conference on geometry and graphics, Advances in intelligent systems and computing (Vol. 809, pp. 1542–1552). Milan: Springer International Publishing. doi:10.1007/978-3-319-95588-9_137
• FreeCAD version 0.15 user manual. (n.d.). Retrieved from https://github.com/FreeCAD/FreeCAD/releases/download/0.15/FreeCAD-0.15_manual.pdf
• Hughes, N. (2013). CAD for the workshop. CROWOOD metalworking guides. Ramsbury: Crowood Press.
• Kannan, G., & Vinay, V. P. (2008). Multi-criteria decision making for the selection of CAD/CAM system. Int. J. Interact. Des. Manuf., 2(3), 151–159. doi:10.1007/s12008-008-0045-5
• Macro automatic drawing. (2016, September). World-Wide Web page. Retrieved from https://www.freecadweb.org/wiki/Macro_Automatic_drawing
• Magee, J., McClelland, B., & Winder, J. (2012). Current issues with standards in the measurement and documentation of human skeletal anatomy. J. Anat., 221(3), 240–251. doi:10.1111/j.1469-7580.2012.01535.x
• Moitinho de Almeida, V., & Barceló, J. A. (2014). Measuring and describing 3D texture. In F. Giligny, F. Djindjian, L. Costa, P. Moscati, & S. Robert (Eds.), Proceedings of the 42nd annual conference on computer applications and quantitative methods in archaeology CAA 2014 — 21st century archaeology (pp. 519–528). Paris: CAA International; Archaeopress.
• Quintana, V., Rivest, L., Pellerin, R., Venne, F., & Kheddouci, F. (2010). Will model-based definition replace engineering drawings throughout the product lifecycle? A global perspective from aerospace industry. Comput. Ind., 61(5), 497–508. doi:10.1016/j.compind.2010.01.005
• Shapin, S., & Schaffer, S. (2011). Leviathan and the air-pump: Hobbes, Boyle, and the experimental life. Princeton classics (Paperback reissue, with a new introduction.). Princeton: Princeton University Press.
• Technical product documentation and specification BS 8888:2011. (2011). (Sixth edition.). London: British Standards Institution.