10. Dimensioning

Making a drawing in a certain scale, as a rule, is not sufficient for the exact manufacturing of the designed object. Most of the technical drawings should be supplemented with information about the dimensions of objects, angles, distances, etc. The method of applying information about dimensions is determined by the technical drawing standards appropriate for a given design industry, defining it with the term "dimensioning".

AlfaCAD offers the user four basic types of dimensioning:

Dimensioning can be done using graphic primitives such as line, triangular areas (dimension line delimiters as points), circles (points as delimiters), and text (dimension numerical value). However, AlfaCAD allows you to automatically generate dimension blocks based on the calculated values of a given dimension, which greatly shortens the time of drawing preparation with minimal effort.

10.1. Basic information

Dimension line

A straight line or an arc ended with terminators (limiters) in the form of oblique segments, points or arrowheads indicating a given dimension. The dimension line is always parallel to the given dimension direction. Dimension lines as arcs are used to dimension angles and arc lengths.


Dimension lines are ended with limiters in the form of oblique segments, points or arrowheads (the selection of the type of terminators depends on the user or depends on the dimensioning type; e.g. when dimensioning a diameter, the dimension line is limited by arrows, while dimensioning a radius, the beginning of the dimension line indicating the center point of the circle is limited by point and the end point - touching the arc - is limited by the arrow).

Diagonal lines are drawn at an angle of 45 ° to the dimension line. The length of the oblique segment is 4.24 mm (the length of the projection on the X and Y axes is 3 mm). The arrowhead length is 2.5 mm and the arrowhead angle is 20 °. The diameter of the points constituting the limiter is 1 mm.

Extension lines

When dimensions are placed outside the outline of the object, it is necessary to use auxiliary dimension lines perpendicular to the dimension lines. Extension lines can be of any length, the starting point of the line can be automatically snapped to the contour of a dimensioned object.

Dimension text

Dimension text is a numeric representation of a dimension. It can be drawn with a font of a given height. The numerical value of a dimension can be presented with a given precision.

Dimension variables

The dimensioning procedure is based on the values of system variables that can be modified by the user in the option / Settings / of the auxiliary menu / Dimensioning /. These variables include:

/ Direction /

/ New/ - start new associative linear dimensioning also, with shortcut key {End}

/ Remove / - removing last dimensioning block, with shortcut key {Del}

/ Edit / - editing existing dimensional block, by context, with additional shortcut key {F10}

/ Settings /

/ Arc / - options of arc dimensioning

/ Circle / - options of circle dimensioning

The values of dimensioning variables are saved in each drawing and restored when it is re-edited.

10.2. Associative linear dimensioning

The dimensioning function is available from the main menu under the / Dimensioning / option .

After initiating the function, the program waits until the first point of the object to be dimensioned is indicated by the pickbox. At the same time, the program provides an additional option in the auxiliary menu / Dimensioning / which allows for the proper selection of dimensioning variables.
When indicating a point, you can use the point location procedure in relation to an object, available from the level of the auxiliary menu.

If a line or any other linear object (solid or trace edge, polygon side etc.) is located in the pointfinder frame after pressing {LMB} or {Enter}, the program will assume by default that linear dimensioning is performed. If the option of dimensioning in the horizontal, vertical or at a given angle to the global coordinate system is active, the first auxiliary line is drawn. If the option of dimensioning parallel or at a given angle to the indicated direction is active, the program waits for the indication of the next point in order to define the dimensioning direction. The first two points of the associative linear dimension sequence determine the dimension direction.

If, instead of a line or linear object, a circle or an arc is located in the pointfinder frame, the linear dimensioning will be interrupted and the program will dimension the diameter or radius of the arc, unless selecting a circle or arc is preceded by calling the auxiliary function of locating a point in relation to an object (this allows, for example, to determine the distance between the ends of the arc etc. .).

If a line has been selected without calling the location function (and without the permanent point location mode in relation to the object active), the program first searches for a possible line intersection in the pointfinder frame .
If an
intersection point is found, it is treated as a dimension point. Otherwise, the program searches for the closest end of the indicated line using this point as a dimensioning point.

The sequence of associative linear dimensions is interrupted by selecting the / New / auxiliary menu / Dimension option / or (easier) by pressing the {End} key . After completing the sequence, the program waits for the indication of the next point constituting the beginning of the next dimensioning sequence.

10.3. Circle dimensioning

If a circle is located in the target window (any point on the arc of a circle), the program will measure the diameter of the circle or its radius , depending on the current mode , unless the indication was preceded by calling the point location function in relation to the object (e.g. the center of the circle), which allows for capturing this point in the associative linear dimensioning.

The selection of the circle dimensioning mode (diameter or radius dimensioning) is made in the option / Circle / auxiliary menu / Dimension / .

In both dimension modes, the dimension line passes through the circle point closest to the center of the target.

10.4. Arc dimensioning

If an arc is located in the pointfinder frame (any point on the arc), the radius or length of the arc will be dimensioned depending on the current mode, unless the indication was preceded by calling the point location function in relation to the object, which allows to include the third point in the complex linear dimensioning sequence.

The selection of the arc dimensioning mode (radius or arc length dimensioning) is made in the option / Arc / auxiliary menu /Dimensioning/.

In radius dimensioning mode, the dimension line passes through the arc point closest to the target center.

In the arc length dimensioning mode, a dimension block is made up of an arc dimension line delimited by arrowheads, extension lines with extension points of the arc, and dimension text drawn horizontally or tangentially to the arc at its midpoint.

10.5. Angle dimensioning

In order to dimension the angle, in the option / Direction / auxiliary menu / Dimensioning / choose the option / <) / . In the angle dimensioning mode, the program waits for selecting three points defining the internal angle.

A dimension line in the form of an arc with a radius equal to the set value in the option / [J] line offset / of variables of dimensioning, is ended with arrowheads.

The dimension text is placed tangentially to the dimension arc in the middle of the arc length, or horizontally (depending on the value of the variable / [K] text direction / ).

In order to restore the associative linear dimensioning and dimensioning of a diameter or an arc, select one of the other options in the menu / Direction /.

10.6. Editing a dimension block

If a dimension line of any dimension block (created in any sequence of linear dimensioning, radius, diameter or arc length dimensioning) is located in the pointfinder frame instead of any other object, the procedure will be switched to the dimension block editing mode. In this mode, the entire dimension block can be moved in parallel, including the extension lines and text. Moving the dimension block with the horizontal or vertical movement of the mouse or the cursor handling keys takes place until the {LMB} or {Enter} key is pressed.

If an auxiliary line of any dimension block is located in the pointfinder frame, the procedure will be switched to the edit mode that allows you to freely shorten or stretch the auxiliary line. The direction of the auxiliary line is maintained.

If the text describing the numerical value of the dimension (the so-called dimension text) is located in the pointfinder frame, the dimensioning procedure will be switched to the text editing mode, which allows you to freely move the dimension text and after pressing the {Tab} key also change the text value.

After finishing the edition, the procedure returns to the standard dimensioning mode waiting for the indication of the next dimension point.

The dimension line can be cut (using the standard edit function / Break / and the text shifted to the dimension line axis.

Editing of a dimension block can also be performed during the associative linear dimensioning, which allows for the correction of a dimension block already at the stage of its creation (e.g. moving the entire dimension block when it turns out to be necessary during the dimensioning). Subsequent segments of the dimension block will be coaxial with the shifted dimension line.

A dimension block can be exploded using the / Explode / block function and each element of a dimension block can be modified independently (this way you can perform half dimensions, etc.).

If an element of a dimension block coincides with another object, or there are obstacles to correctly selecting an element of a dimension block in order to edit it, use the {F10} key instead of {LMB} or {Enter}. In this case, the priority of searching for objects in the pointfinder frame will be given to elements of dimension block.

Texts of dimension blocks (values) are subject to the / Edit text / and / Modify / editing functions, similarly to " Text " type objects .

10.7. Deleting a dimension block

Deleting a dimensional block (or multiple blocks) is performed in a manner generally accepted for other objects and blocks.

Deleting the last dimension block (or the last sequence of associative linear dimensions) can also be performed during dimensioning (without the need to interrupt the function) by selecting the / Delete / auxiliary menu / Dimension / or (easier) by pressing the {Del} key .