Drawing Generator

Local web application that creates ISO drawings from STEP files. Each drawing has an ISO 5457 frame, an ISO 7200 title block, first-angle Front / Top / Right views, section A-A through the part centre and an isometric view. Dimensions, notes and ISO 286 tolerances are added interactively. Output is PDF, DXF, SVG and FCStd (FreeCAD / AstoCAD document with a TechDraw page). AstoCAD is not used at run time. Projection and hidden-line removal use OpenCascade through build123d.

1. Installation (Windows)

1. Install Python 3.10 to 3.14 from python.org (64-bit). py -0 lists the versions known to the py launcher.
2. Unzip the drawgen folder with all files in the same folder.
3. Double-click start.bat.

start.bat uses the py launcher and selects the newest installed version from 3.14 to 3.10. The first start creates the environment in %LOCALAPPDATA%\drawgen\venv and installs build123d, flask, ezdxf and reportlab (approximately 400 MB, internet connection required). Later starts use the existing environment. The server runs at http://localhost:8765 and the browser opens automatically. Close the command window to stop the server.

Manual installation:

py -3.14 -m venv %LOCALAPPDATA%\drawgen\venv
%LOCALAPPDATA%\drawgen\venv\Scripts\python.exe -m pip install -r requirements.txt
%LOCALAPPDATA%\drawgen\venv\Scripts\python.exe run.py

run.py --port 9000 sets a different port and run.py --no-browser does not open the browser. The server listens on 127.0.0.1 only.

2. Files

File	Function
start.bat	Creates the environment on first start and starts the server
run.py	Starts the server
config.json	Defaults: sheet, scale, views, line widths, sheet sizes, frame, title block layout and field values
requirements.txt	Python packages
drawgen/project.py	Hidden-line removal, section cut, hatching
drawgen/drawing.py	Views, layout, sheet and scale selection, title block values
drawgen/titleblock.py	Frame and title block
drawgen/render.py	SVG, PDF and DXF output
drawgen/fcstd.py	FCStd output
drawgen/annotate.py	Dimensions and notes
drawgen/fits.py	ISO 286 limits
annotations/	Saved dimensions and notes, one JSON file per drawing
drawgen/web.py	Web server
drawgen/static/	Web interface

3. Use

1. Drop STEP files on Models, or enter a file or folder path in the path field and press Open. Each solid in a STEP file is listed as a part, named from the STEP labels.
2. Select the parts.
3. Set Sheet size, Scale, Mode, views and title block values.
4. Press Preview.
5. Press Export.

Control	Function
Sheet size	A4 (portrait), A3 to A0 (landscape), or Auto. Default A3
Scale	Auto or an ISO 5455 scale. Auto uses the largest scale that fits the sheet
Mode	One drawing per part or One drawing per file (all selected parts of a file on one drawing)
Section A-A, Plane normal, Offset, Reverse	Section plane normal to X, Y or Z, offset in mm from the bounding box centre, viewing direction reversed
Hidden lines	Hidden lines in the Front, Top and Right views
Tangent edges	Edges between tangent faces
Isometric scale factor	Isometric view scale relative to the drawing scale. A value other than 1 adds the isometric scale below the view
Density (kg/m^3)	Mass in the title block is volume x density when > 0
Title block fields	Values for this run. Empty Title, Identification number and Date of issue are filled with the part name, the title in upper case and today's date
Output folder	Files are written to this folder. Empty: the browser downloads one file, or drawings.zip for several files
Write to a drawings folder next to each opened STEP file	Writes to <STEP folder>\drawings for files opened by path
Save as defaults	Writes the current settings and fields to config.json. Title, Supplementary title, Identification number, Date, Mass and Material are not stored

Output file names are <STEP file>.pdf for a STEP file with one part and <STEP file>_<part>.pdf for several parts. With Auto sheet size the smallest sheet from A4 to A0 is used where the scale is >= auto_sheet_min_scale (default 1:1).

4. Title block editor

The Title block editor tab edits config.json > title_block and border.

Control	Function
Width, Height	Title block size in mm (default 180 mm x 40 mm)
Label height	Text height of the cell labels in mm
Font	Font family for SVG output. PDF uses Helvetica
Logo cell, Projection cell	x, y, w, h in mm
Binding edge, Other edges	Frame margins in mm (ISO 5457: 20 mm and 10 mm)
Logo	PNG or JPG placed in the logo cell (PDF and SVG only)
Cell table	One row per field: Key (field name), Label, x, y, w, h, Text h (value text height in mm)
Add cell	New row. A new key adds a field to the title block fields
Update preview	Shows the sheet and the title block
Save title block	Writes to config.json

Cell coordinates are in mm from the top-left corner of the title block.

5. Views and layout

View	Direction
Front	Looking along +Y, X to the right, Z up
Top	From +Z, placed below the front view
Right	From +X, placed left of the front view
Section A-A, plane normal X	Cutting plane shown on the front view, viewed in +X (Reverse: -X)
Section A-A, plane normal Y	Cutting plane shown on the top view, viewed in +Y (Reverse: -Y)
Section A-A, plane normal Z	Cutting plane shown on the front view, viewed in -Z (Reverse: +Z)
Isometric	View direction (1, -1, 1)

Two layouts are evaluated and the one giving the larger scale is used:

A:  Right | Front | A-A          B:  Right | Front | A-A | Iso
          | Top   | Iso                    | Top   |     |

Line widths follow ISO 128 in config.json > line_widths_mm (visible 0.5 mm, hidden, chain and hatch 0.25 mm, frame 0.7 mm). Hatching is 45 deg at 2.5 mm spacing on paper (hatch_angle_deg, hatch_spacing_mm).

6. Dimensions and notes

Press Preview, then Dimensions and notes on a drawing (or the Dimensions and notes tab).

Tool	Key	Picks
Select	S	Click a dimension or note to edit it. Drag it to move it. A linear dimension follows the mouse across (dimension line position) and along (text position); text dragged beyond an extension line gets an extended dimension line. Text centred between extension lines returns the text to the centre
Horizontal	H	First point, second point, dimension line position
Vertical	V	First point, second point, dimension line position
Aligned	A	First point, second point, dimension line position
Diameter	D	Circle or arc, then text position. In a side view of a shaft or bore: first edge point, opposite edge point, dimension line position (Ø added to the measured distance)
Radius	R	Arc or circle, text position
Note	N	Text position, then the text in a text box (Enter = new line, Ctrl+Enter or OK = place)
Leader note	L	Arrow point, text position, then the text in a text box (Enter = new line, Ctrl+Enter or OK = place)

Views are moved by dragging them with Select:

View	Movement
Front	Moves Front, Top and Right together
Top	Vertical only (stays aligned below Front)
Right	Horizontal only (stays aligned beside Front)
Section, Isometric	Free

Dimensions and notes move with their view. View positions are saved in annotations/<drawing name>.layout.json as offsets in mm from the automatic layout and are used for PDF, DXF, SVG and FCStd export. Reset views returns all views to the automatic layout. Shift+drag or the middle mouse button pans.

Points snap to line end points (red square), line mid points (green square) and circle and arc centres (circle). Both points of a dimension are picked in the same view. The isometric view has no snap points. Line widths in the editor are shown at a fixed screen width at every zoom level. Curves stored as B-splines that lie on a circle are recognised as circles for Diameter and Radius. Mouse wheel zooms, dragging empty space, Shift+drag or the middle button pans, F fits the sheet, Esc cancels the current pick, Delete removes the selected item, Ctrl+Z undoes.

Existing note text is edited in the Text field of the properties panel (Enter = new line). The markers \n and /n in note text are also converted to line breaks.

Properties of the selected dimension:

Field	Function
Prefix	Text before the value, for example 4x
Text override	Replaces the measured value
Tolerance	None (general tolerance from the title block), ISO 286 fit, Symmetric ±, Upper / lower deviation
Class	ISO 286 tolerance class, for example H7 (hole, upper case) or g6 (shaft, lower case). Grades IT5 to IT11, letters D to S, sizes up to 500 mm
Show deviations	Adds the limit deviations of the class next to the class

Dimensions are stored in view coordinates and follow the view when the sheet, scale or layout changes. They are saved in annotations/<drawing name>.json and are included in PDF, DXF (layer DIM) and SVG exports. Dimension text height is dim_text_height_mm (3.5 mm).

7. DXF

DXF R2010, units mm, drawn at sheet size 1:1 (model coordinates are scaled by the drawing scale). Layers: VISIBLE, HIDDEN (ISO_HIDDEN), CHAIN (ISO_CHAIN), HATCH, TEXT, FRAME, TITLE, with lineweights from line_widths_mm. Circles and arcs in the projection plane are written as CIRCLE and ARC. Other curves are written as LWPOLYLINE.

8. FCStd

The .FCStd file contains:

Object	Content
Part	The part (or the selected parts as a compound) as Part::Feature, hidden in the 3D view
Page	TechDraw page with the same sheet size and scale as the PDF
Template	SVG template with the frame and title block. Field values are editable texts (double-click the field on the page)
Front, Top, Right, Isometric	TechDraw views (DrawViewPart) at the PDF positions
Section	Section view A-A (DrawViewSection), base view Front
SectionCaption	Annotation "A-A"

TechDraw computes the view geometry when the file is opened. Dimensions, centre lines and annotations are added with the TechDraw tools. The section cut surface is a grey fill. A 45 deg hatch is set by changing Cut Surface Display of Section to SvgHatch (the hatch file is included). View positions can differ from the PDF by a few mm because TechDraw centres views on the 3D bounding box.

9. Limitations

• Input is STEP only. AstoCAD models are exported with File > Export > STEP.
• Dimensions and notes are not written to the FCStd file.
• Dimensions in the DXF are lines and text, not DIMENSION entities.
• One section view per drawing.
• Projection time depends on the number of B-spline faces (approximately 10 s to 30 s per part for a 7 MB STEP part with 234 faces on a 2-core machine). Views are computed in parallel on machines with more than 2 cores.