TechDraw General Examples

Introduction

The TechDraw workbench has many tools, but what are the required elements to turn a piece of paper into a proper drawing? This page is intended to give some explanation and some examples about what TechDraw is already capable of.

Drawings

A drawing consists of one or more views to describe a part geometrically... But you know that already, don\'t you?

Let\'s have a look at the basic elements.

Manually created drawings

Sheet of paper

Paper sizes are standardized and to be able to print without scaling the format of our sheet should match the desired printing format.

Frames

When drawings were drawn by hand they had to be pinned or taped to a drawing board. Puncher holes were added to the finished drawing to attach the folded drawing to a file or folder. This outer area is separated by a rectangular frame. Another rectangular frame inside the first one defines the drawing area. There is usually a set of indexes and separators between both frames used to locate certain drawing elements.

Title block

The title block contains written information about the part and the drawing such as part number, title, author, owner, etc.

Bill of materials

Optionally assembly drawings can have a bill of materials (BOM) included. The BOM can also be placed on a separate drawing sheet or a spreadsheet.

Change log

Changes to the part or the drawing are protocolled in a log on the drawing or in a separate document and linked to the drawing by corresponding indexes.

Views

Views contain the geometrical description of a part from a certain direction. Most parts need at least two views to be properly described.

Annotations

Additional texts that don\'t belong to the elements mentioned above.

Drawings made with TechDraw

Techdraw uses a Page object as a container for all drawing related elements; this cannot exist on its own, but has to contain a template. That is why there is no New page command and a new page object is created automatically whenever a template is inserted.

Templates

A Template object is an SVG image file and its code holds all information needed to create a virtual sheet of paper with matching frames and title block, and optionally a BOM.

SVG images are not parametric. This means that for each format a separate template has to be created, such a set of templates is needed for any variation of frame or title block objects. That is quite a lot to code and manage but on the other hand templates cannot change accidentally inside FreeCAD.

There are several ways to create a template:

1. Draw it with Inkscape, see How to create a custom TechDraw template.
2. Type it manually, see Template explained.
3. Use a macro, see TechDraw TemplateGenerator and Macro TemplateHelper.

Result of Template explained

Result of macro TemplateHelper, ISO A3 + bill of material

The drawing so far

Up to this point it is safe to say that TechDraw in connection with embedded SVG templates can provide a proper drawing sheet with a frame and a title block. Some entries can be altered after creation thanks to editable texts, and some content can be inserted automatically if macros are involved.

Views

Views contain the geometrical 2D description of an object. The content of a TechDraw view can be derived from 3D geometry or obtained from another workbench like Arch Views and Draft views.

Since FreeCAD is a 3D modelling application TechDraw\'s key function is deriving 2D views from 3D geometry. Let\'s have a look at an easy example, the part from the Basic Part Design Tutorial that is also used with the Basic TechDraw Tutorial:

Part from the Basic Part Design Tutorial

Active View

An Active View is more or less a screen shot of the 3D view in its own kind of TechDraw view.

The item displayed in an Active View with No background option enabled

View

A View is TechDraw\'s basic view object to derive proper drawings. In contrast to an Active View it is not restricted to visible objects on the screen, but also displays selected objects outside the screen. The preferred scale depends on the available space and the level of detail that has to be displayed.

The item displayed in an arbitrary View like the Active View above

Projection Group

A Projection Group is a set of views. Each view direction is perpendicular to its neighbor and all depend on the 3D window\'s direction by default. TechDraw provides six views matching with the Navigation Cube sides, and four isometric views.

The item displayed in a Projection Group consisting of three views (in first angle projection mode)

Section View

TechDraw provides tools to create a Simple Section View or a Complex Section View. Both depend on a base view and on tools to define a section line and to derive the view direction. Have a look at TechDraw Section Examples for an overview.

The cut item displayed in a Section A-A based on the Front view

Auxiliary View

If we need a view of a tilted plane to see its true lengths we would define the view direction in a base view and place the Auxiliary view accordingly, but TechDraw provides no tool for Auxiliary views yet.

Good news: It is quite easy to emulate using the Simple Section View tool:

1. Select a base view.
2. Create a Simple Section View with default settings.
3. Use Insert Angle Dimension to measure the angle of the plane.
4. Edit the section view angle in the Set View Direction area of its task panel.
5. Edit the section view coordinates in the Section Plane Location area of its task panel. Use small steps to move the section line outside the object or FreeCAD may crash.
6. Hide unwanted annotation elements such as section line, section arrows, and section name.
7. Add needed items like view arrow, and view name.

A default section view based on the Left view displaying the section line angle

Section view with section line angle set to {{value|218,93° (38,93° plus 180° to flip direction)}}

Section view with relocated section line → Finished Auxiliary view

Detail View

A Detail View is a copy of an area of a base view usually to magnify hardly visible geometry.

Detail (view) Y based on Section A-A

Imperfections

• Detail views according to ISO standard do not have a frame/border (the upper part of the enclosing circle). Editor\'s note: what is meant here?? Frames are not printed...
• The break line that cuts the detail off from the rest should be a thin freehand line or the cad equivalent, a thin zigzag line. FreeCAD/TechDraw do not provide freehand/zigzag lines (yet).
• Hatched areas in the base view should be hatched in the detail view, too.

Arch View

An Arch View displays a view of an Arch SectionPlane. Its content is rendered by the BIM workbench.

Draft View

A Draft View displays a view of a selected Part-based object or Group object. It is intended for 2D objects. Its content is rendered by the Draft workbench.

Some Draft elements in the 3D view → The same elements displayed in a Draft View on a drawing

Spreadsheet View

A Spreadsheet View displays a view of a Spreadsheet Workbench sheet.

Spreadsheet element displayed in a Spreadsheet View

The views so far

TechDraw needs some additions like break lines, and a proper auxiliary view tool and also some improvement of the Detail View tool. But even in this state we can describe our objects visually quite well:

This is how a drawing with a set of views of the example item could look

Dimensioning

Now that our item is described geometrically, dimensions will be added to further define the shape, and tolerances to define the allowed deviation. TechDraw supplies several tools to apply dimensions to the 2D representation of our item:

• [Length Dimension](wiki-test2.php?gitpage=TechDraw_LengthDimension)
• [Horizontal Dimension](wiki-test2.php?gitpage=TechDraw_HorizontalDimension)
• [Vertical Dimension](wiki-test2.php?gitpage=TechDraw_VerticalDimension)
• [Radius Dimension](wiki-test2.php?gitpage=TechDraw_RadiusDimension)
• [Diameter Dimension](wiki-test2.php?gitpage=TechDraw_DiameterDimension)
• [Angle Dimension](wiki-test2.php?gitpage=TechDraw_AngleDimension)
• [3-Point Angle Dimension](wiki-test2.php?gitpage=TechDraw_3PtAngleDimension)

They have in common that they measure the projected shape of the item. If you have learned drafting the manual way, you know how to use auxiliary views to turn the item into a position where projected lengths equal true lengths. For visualization other than this old school way, dimensions can be linked to 3D geometry using TechDraw DimensionRepair to display \"true dimensions\".

Two other tools measure the overall length horizontally or vertically respectively:

• [Insert Horizontal Extent Dimension](wiki-test2.php?gitpage=TechDraw_HorizontalExtentDimension)
• [Insert Vertical Extent Dimension](wiki-test2.php?gitpage=TechDraw_VerticalExtentDimension)

These cannot be linked with 3D geometry (yet).

See Dimension dialog (and the following properties section) for all settings that are not mentioned in this overview.

Simple dimensions

The dimension text depends mainly on these properties:

• Format Spec

• Format Spec Over Tolerance

• Format Spec Under Tolerance

: By default their defaults are {{Value|%.2f}}

To \"cheat\" we can use these two properties:

• Arbitrary

:

:   Set to `False` to use the content of the **Format Spec** to format the actual dimensional value.
:   Set to `True` to use the content of the **Format Spec** to be displayed as text instead if the dimension value.

• Arbitrary Tolerances: Like Arbitrary, but for the tolerance.

If we only need the dimension value there\'s nothing to do but to change the number of decimals if desired.

: For example: {{Value|%.2f}} → {{Value|%.3f}} to display 3 decimals, or {{Value|%.2f}} → {{Value|%.0f}} to display whole numbers.

Length dimension

There are three tools to add length dimensions: Length Dimension, Horizontal Dimension, and Vertical Dimension.

Left: Two views of an object with length dimensions applied → Right: The same Front view rotated by 20°

This shows that it is important to rotate a front view in the Projection Group dialog or otherwise the connected views will not follow. On the other hand that would restrict us to 90° turns.

If a dimension has to run parallel to an edge it needs another selectable line perpendicular to the edge and the Length Dimension tool, that can find the shortest (= perpendicular) distance between a point and a line. An edge will not be automatically extended by an imaginary line and so we need to create an auxiliary (cosmetic) line manually. (A cosmetic point could be used as well, but that requires even more work).

• The black (point to line) Length Dimension depends on a cosmetic line that doesn\'t rotate with the view. (A cosmetic point wouldn\'t be helpful either.)
• The Horizontal Dimension and Vertical Dimension (red and green) stay with the page orientation and change their values accordingly.
• The blue is a point to line Length Dimension, too but rotates with the view as there is no cosmetic geometry involved.

Angle dimension

TechDraw provides two tools to add angle dimensions: Angle Dimension and 3-Point Angle Dimension.

Two Ways to to add an angle dimension

• Blue: an Angle Dimension between two edges.
• Red: a 3-Point Angle Dimension using both end points and the center point of an arc.

Chamfer dimension

A chamfer dimension can be applied as a length dimension with a manually edited Format Spec property or by using Create Horizontal Chamfer Dimension and Create Vertical Chamfer Dimension to create a size and angle dimension for a chamfer.

Left: Chamfer dimensions applied to an object with horizontal and vertical sides → Center: The same view rotated by 10° → Right: Object tilted by 10°, view is at 0°

The chamfer tools work well for objects with horizontal and vertical sides as long as they are parallel to the view\'s = the page\'s X and Y axes, but many parts won\'t do us the favor of being perfectly aligned.

The angle values are not parametric! They do not change if the view is tilted. The last page shows the correct angles, but dimensions positioned like this are pointless.

To align the chamfer dimension along an edge we need an auxiliary (cosmetic) point where the unchamfered edges would meet and have to use Length Dimension; but cosmetic point won\'t follow the edges if the view is tilted. (also see Length dimension.)

Radius dimension

A Radius Dimension adds a radius dimension to a circle or circular arc, no more no less.

Two ways to add a radius dimension, the red one with flipped arrowheads

To change the arrowhead direction just set the Flip Arrowheads property to {{true}}.

Diameter dimension

Diameter dimensions can be added as a Diameter Dimension or one of the length dimensions Length Dimension, Horizontal Dimension, and Vertical Dimension. (Or in connection with a leader line pointing to a circle center or a center line - not displayed.)

Several ways to place a diameter dimension (please ignore the missing center line)

• Blue: a length dimension in the side view of the hole needs a \"⌀\" prefixed to distinguish this from a rectangular hole.

: Insert \'⌀\' Prefix is an easy way to do this, but the Format Spec property can be edited manually as well.

• Green: a simple length dimension.

: It needs some auxiliary geometry (cosmetic points) as it cannot be applied to circles directly.

• Red: a diameter dimension. In case you look along the hole axis and can see the circular shape of the hole the \"⌀\" may be omitted. To remove it edit the Format Spec property manually.

Thread dimension

Thread dimensions can be applied just like diameter dimensions, but they require some auxiliary geometry created beforehand: Add Cosmetic Thread Hole Side View, Add Cosmetic Thread Hole Bottom View, Add Cosmetic Thread Bolt Side View, or Add Cosmetic Thread Bolt Bottom View.

A countersunk thread with several ways to place a thread dimension (and a counter sink diameter)

All Thread dimensions are applied to auxiliary (cosmetic) lines or circles (in connection with cosmetic points) and all Format Spec properties need to be edited manually to prefix the \"M\" for metric threads.

Tolerances

Tolerances express how much a measured dimension may deviate from the dimension value on the drawing. To suffix a tolerance values to the dimension value simply set the Over Tolerance property to a value other than {{Value|0}}, this results in a symmetric tolerance such as {{Value|±0,5}}.

For an asymmetric tolerance set Equal Tolerance property to {{false}} and specify also a lower value for the Under Tolerance property.

The values can be set in the Dimension dialog or directly in the Property editor.

Hole/shaft fit

Fit tolerances can be added by suffixing tolerance classes to a dimension. A tolerance class consist of a tolerance field specifier (letter, upper case for holes, lower case for shafts) and a tolerance grade specifier (number) and can be suffixed in three ways:

1. Set the Arbitrary Tolerances property to {{true}} and specify both tolerance classes in the Over Tolerance and Under Tolerance properties.
2. Use the Add hole or shaft fit tool. This suffixes only one tolerance class but adds the related values to the Over Tolerance and Under Tolerance properties.
3. For a single tolerance simply suffix the tolerance class to the format specifier in the Format Spec property.

Thread fit

Thread fit tolerances can be suffixed like described above for hole/shaft fit tolerances, except method 2. The thread tolerance classes display the tolerance grade specifier (number) in front of the tolerance field specifier (letter, upper case for internal threads, lower case for external threads).

Inspection dimensions

Inspection dimensions (test dimensions) are not yet implemented.

: (Maybe obsolete already. See ...test dimension was withdrawn... on the forum)

To fake an inspection dimension we set the Format Spec property to \" \" (one space - no character at all and we would have no handle to grab the dimension line to move it) and then set the Arbitrary property to True; this results in a dimension without value. The value can now be substituted with a balloon without leader line. This only works with horizontal dimensions since we cannot rotate balloons.

The example item with an inspection dimension. In this case 100% of the production items have to be checked if they are within the tolerance

Geometric dimensioning and tolerancing

The system of geometric dimensioning and tolerancing (GD&T) aims at describing shapes more precisely than toleranced dimensions alone can do. It is built on datums, theoretically exact dimensions, and tolerance indicators.

Datums

Datums are virtual surfaces, planes, lines, and points used as references to describe geometrical features with theoretically exact dimensions and tolerance indicators. They can be used to built a theoretically exact virtual coordinate system.

Datum feature

A datum feature is a geometric feature of an object corresponding with a certain datum. Datum feature symbols are added using Balloon annotations.

Example item with datum features. Both views display exactly the same datum features

The Kink Length property has to be set to {{Value|0}} for vertical leader lines. On {{VersionMinus|0.21}} this results in a portion of the line shown within the frame.

Now the leader line starts on the frame which is perfect for horizontal ones, but now it is impossible to draw vertical leader lines correctly

Datum target

Datum targets are points or relatively small areas that denote where to derive a datum from. Most common use is to create a theoretically exact virtual coordinate system from a set of six datum targets.

This kind of datum target is not implemented yet

There is no known workaround at the moment.

: Special point symbols to indicate the reference point of the datum target are not yet included in the options of leader lines. : The circles have to be derived from 3D geometry and are hard to handle in projection groups.

Theoretically exact dimensions

Theoretically exact dimensions are added the same way as simple dimensions and the Theoretically exact checkbox makes the difference: It sets the Theoretically Exact property to {{true}} which adds a rectangular frame to the dimension value and deactivates tolerances and all tolerance settings.

Tolerance indicator

A tolerance indicator, also called \"feature control frame\", is a frame containing tolerance information about:

• which geometric characteristic is tolerated
• the shape and size of the tolerance field
• the datums to be referenced
• some more symbols to describe the features even more precisely.

Theoretically exact dimensions (red) and tolerance indicators with reference to datum feature A (blue)

Tolerance indicators are like datum feature symbols added using Balloon annotations but using the {{value|Rectangle}}option. Use Customize format label to insert special characters.

In most cases tolerance indicators are aligned with a dimension line which is impossible in TechDraw except for horizontal dimensions since, as already mentioned, balloon annotations can not be rotated.

Annotations

Leader lines

A Leader line points to a vertex, edge, or face where the attached information is valid.

: Tools that provide information and attach to a preselected leader line are RichTextAnnotation, and WeldSymbol.

Balloons

A Balloon is a combination of a leader line and a short text. It requires a preselected view, or an item belonging to a view or the command will return an error message. The leader line starts horizontally without exception and turns towards the selected item after a short distance defined in the Kink Length property. Its value can also be set to {{Value|0}}.

Text

Techdraw supplies two tools to add text to a drawing:

• [Insert Annotation](wiki-test2.php?gitpage=TechDraw_Annotation) adds a plain text block as annotation to a page. Annotations use the same default settings as dimensions, some parameters can be changed, and they can be edited and rotated, but they cannot be attached.
• [Insert Rich Text Annotation](wiki-test2.php?gitpage=TechDraw_RichTextAnnotation) adds a rich text block as annotation to a page, a leader line, or a view. Annotations attached to a leader line or a view move synchronously with the view or leader line when their positions change.

Weld symbols

The WeldSymbol tool attaches to a preselected leader line and adds information about how to create a certain seam between two objects to avoid modelling the seam faces on the raw parts. The fork text determines which welding or soldering process has to be used for the seam.

: It seems like the weld symbols demand an integrated leader line to get a fork symbol that matches the size of the text, otherwise the symbols on the leader line have to be scalable.

A weld symbol for a circumferential V-seam, 111 meaning manual arc welding - Don't beat me if I have cited the internet wrongly

Surface finish symbols

[Add Surface Finish Symbol](wiki-test2.php?gitpage=TechDraw_SurfaceFinishSymbols) adds a surface finish symbol to the page, which means these symbols do not move with their referenced geometry.

A surface finish symbol in comparison with a dimension

These symbols cannot be customized regarding line width and font type to match with the dimensions and they can hardly be edited after creation.

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