Skip to main content

Advice on working with sketch constraints in the standard sketch mode

In this article, DesignSpark staff provide advice on changes in standard sketcher behaviour and functionality when an imported design contains constraint-based sketch planes. There is also commentary on new DSM v6 constraint-based sketcher features.

When we refer to standard sketcher, we mean the classic user interface with all your sketch tools in the Design tab. The constraint-based sketcher is newer and you will have a separate Sketch and Design tab. The Sketch tab contains the sketch and constraint tools. This constraint-based sketch mode can be toggled via File -> DesignSpark options -> Advanced.

Image 1: Standard sketcher - all sketch tools within Design tab

Image 2: Constraint-based sketcher - sketch tools in a dedicated Sketch tab

1. About the v6 Constraint-based Sketcher:

The Constraint-based sketcher adds advanced ways to associate sketch curve geometry to Solids and Faces during sketching - these can be Automatically applied with an 'AutoConstrain' tool, or discretely applied to unconstrained geometry. In the case of Layout Sketching, where geometry is not converted to a face, any constraints to solid faces and edges are maintained for alteration in both 3D mode and 2D sketch mode. Layout sketches can be copied and pasted to other components or files with full editability.

If you are a long-term user of DSM, you may have noted that in version 5 the standard sketcher was the default mode. This could be changed in DSM options to enable the then-new Constraint-based sketching. Via File -> DesignSpark options -> Advanced.

Image 3: Enable Constraint-based sketching by checking the box and click OK. Remove check to disable it.

In v6, initially, the Constraint sketcher was default installed with the Standard sketcher as the option choice. This change caused some confusion with users.

In v6.0.2 the program reverted to install the Standard sketcher as default. The Constraint-based sketcher will be an option unless the user has set a preference for the Constraint sketcher, which is recorded in the user configuration file.

2.a. Complications in v6 Sketch Menu presentation:

The introduction of the Constraint-based sketcher has resulted in a new Sketch Tab menu for Constraint-based sketching (see Image 2 above).

If you use the standard sketcher and open a design containing constraints, a menu change automatically adds in the Sketch Tab to edit or remove those constraints. Users should note that this 'Hybrid' menu with Sketch and Design tab menu configuration will be persistent whilst DSM is open, only reverting to Design tab after closing and starting DSM again (new session). Users with the Standard sketcher should also note that whilst the familiar Design Tab does not change, continuing use may add subtle constraints which requires opening the Sketch Tab to fully appreciate and control.

Therefore, the 2 possible menu variations for sketch tools are:

  • Design Tab ONLY: Standard sketcher (disable constraint-based sketcher via DesignSpark options -> Advanced)
  • Sketch Tab + Design Tab: Constraint-based sketcher or a constrained design opened with the Standard sketcher (Hybrid menu).

You can identify a constrained design by looking for 'Sketching Planes' in the structure tree and also sketch curves which will be in blue colour.

constraint based planes

Image 4: Enable Constraint-based sketching by checking the box and click OK. Remove check to disable it.


2.b. Advice on working with Hybrid menu in Standard Sketcher

Conditions under which a Hybrid menu (Sketch tab + Design tab) will be shown in the Standard Sketcher mode (constraint-based sketching disabled):

  • Opening a file containing a Constraint-based sketching plane will invoke an additional Sketch Tab in the menu.
  • Also, Importing an external reference file with any Constraint-based plane, will also Invoke a Sketch Tab.

If you encounter this hybrid menu, you can handle it one of these ways:

  • To restore 'Design tab ONLY' menu: Click on Constraint-based Sketcher plane in structure tree > convert to Face/Curves ( Use 30 ) > Delete Sketching Plane > Save> Close and Restart DSM (Design Tab only appears). 
    Users not requiring Constraints may sketch in the Design Tab sketcher with fast efficient sketching as per all previous DSM versions. Note that only the standard sketcher has access to the Equation curve tool. If files are saved without an open constrained sketch or any constraint-based plane in structure, then the Sketch Tab will never open given that the 'Constraint-based sketching' option is disabled via Advanced DesignSpark options (see Image 3 above).
  • Or, you can continue working with this hybrid menu (Sketch + Design tabs). This is suggested so users can experiment and become familiar with Constraint-based sketching. Use the built-in software help and tutorials to learn the new functionality in v6 - Constraint types, Label Names and Expressions, Constrained Layout sketches to bodies and faces, Remove Interiors and 'Use 3D'.

Further illustration:

The below diagram highlights the differences between Standard and Constraint-based Sketching menus and what to be aware of when a Sketch Tab becomes added.

differences between Standard and Constraint-based Sketching

Menu Behaviour


Sketcher plane


Differences constraint based toggleThe below-noted changes should also alert the user to a constrained sketch loaded in the standard sketcher mode:

  • Automatic Constraint option added to options panel:

automatically create constraints

with constraint-based sketching ON and also all curve connectivity ON. The user is advised to open the Sketch Tab thereby accessing all Constraints functionality.

post curve placement

  • Post curve placement, no active dimensions are available upon further curve selection unlike in standard sketching. New sketch planes appear with bright red green X,Y reference axes in long dash dash style.
    no active dimensions xyz axis


  • An opened file with a Constraint based plane in Structure tree, always opens the Sketch Tab.

Sketch menu

  • All curves drawn in either Sketch Tab (above) or Design Tab (below) are always originally in Blue unless user changed.

draw in sketch

Note: Curves creation commands in the Design Tab can be connected and constrained or not depending upon 'Automatically create constraints' setting.

Trim, Split, Corner, Tangent Arc and Offset always adds Constraints when Sketch Tab is present.

Design menu


Any curve selection directly in Design Tab opens a Sketch directly without reverting to the Sketch Tab menu. The standard functionality of sketch connectivity is replaced by 'Automatically Create Constraints' or 'not' option. Curves will be drawn in Blue and X,Y axes in bold Red and Green long dash dash styles indicating 'Constraint-based sketching' is active and standard sketching is not active. However, only by accessing the Sketch tab menu will all the constraint sketching functionality and modification tools be available. Curve length entry is only by moving the curve end, grid snap or dimensional constraint only - a length dialogue box is not offered post creation for easy length / distance alterations unlike in the standard sketcher.

A Sketch commanded by the shortcut 'K' or by the icon will always open the Sketch Tab accessing the full range of Constraint functionality.

NOTE: DSM does support Standard sketching on pinned planes - shown below in comparison to Constraint based sketching.

Sketching on planes and faces

RS DesignSpark is the go-to platform for students, makers, hobbyists and professional design engineers, providing design resources such as the award winning DesignSpark PCB and DesignSpark Mechanical CAD software. Join the community today at
DesignSpark Electrical Logolinkedin