Sketcher Workbench/ru

Инструментарий Эскизов используется для создания 2D геометрии используемой Инструментарий Проектирования Деталей и другими инструментариями. Он обладает решателем ограничений позволяя создавать геометрически-ограниченные 2D формы. Модуль эскизов обладает базовыми строительными блоками необходимыми для создания параметрической 3D геометрии.



The Sketcher Workbench is used to create 2D geometries intended for use in the Part Design Workbench and other workbenches. Generally a 2D geometry is considered the starting-point for most CAD models - a simple 2D sketch can be 'extruded' into a 3D shape, further 2D sketches can be used to create pockets in the surface of this shape and sketches can be used to define 'pads' (extrusions) on the surface of 3D objects. Along with boolean operations, the sketcher forms the core of generative solid shape design.

The Sketcher workbench itself features constraints - allowing 2D shapes to be constrained to precise geometrical definitions. And a constraint solver which calculates the constrained-extent of 2D geometry and allows interactive exploration of sketch degrees-of-freedom.

Основы ограничений эскиза
Чтобы объяснить как работает модуль эскизов, может быть полезно сравнить его с "традиционным" способом черчения.

Traditional Drafting
The traditional way of CAD drafting inherits from the old drawing board. Orthogonal (2D) views are drawn manually and intended for producing technical drawings (also known as blueprints). Objects are drawn precisely to the intended size or dimension. If you want to draw an horizontal line 100mm in length starting at (0,0), you activate the line tool, either click on the screen or input the (0,0) coordinates for the first point, then make a second click or input the second point coordinates at (100,0). Or you will draw your line without regard to its position, and move it afterwards. When you've finished drawing your geometries, you add dimensions to them.

Ограниченные Эскизы
Sketcher отходит от этой логики. Объекты не нужно чертить так как вы планируете чтобы они располагались, так как они будут заданы позже с помощью ограничений. Объекты могут быть нарисованы свободно и до тех пор пока они не связаны, они могут быть изменены. Они находятся в "плавающем" состоянии и могут быть перемещены,растянуты, их можно вращать, масштабировать и.т.д. Это делает процесс проектирования более гибким.

What are constraints?
Instead of dimensions, Constraints are used to limit the degrees of freedom of an object. For example, a line without constraints has 4 Degrees Of Freedom (abbreviated as " DOF "): it can be moved horizontally or vertically, it can be stretched, and it can be rotated.

Применение горизонтального и вертикального ограничения, или углового ограничения (относительно другой линии или одной из координатных осей), ограничит её способность вращаться, тем самым оставляя линию с двумя степенями свободы. Блокировка одной из её точек уберет ещё одну степень свободы, по сравнению с первоначальным. И применив ограничение "размером" уберем последнюю степень свободы. Линия будет считаться полностью ограниченной.

Multiple objects can be constrained between one another. Two lines can be joined through one of their points with the coincident point constraint. An angle can be set between them, or they can be set perpendicular. A line can be tangent to an arc or a circle, and so on. A complex Sketch with multiple objects will have a number of different solutions, and making it fully-constrained means that just one of these possible solutions has been reached based on the applied constraints.

Существует два вида ограничений: геометрические и размерные. Они подробно описаны ниже, в разделе.

What the Sketcher is not good for
The Sketcher is not intended for producing 2D blueprints. Once sketches are used to generate a solid feature, they are automatically hidden. Constraints are only visible in Sketch edit mode.

Если вам только нужно создать 2D виды для печати и вам не нужна трехмерные модели, посмотрите Чертежный модуль (имейте в ввиду что Чертежный Инструментарий также может быть использован для создания не доступной пока в Sketcher  геометрии, например B-Splines.)

Sketching Workflow
A Sketch is always 2-dimensional (2D). To create a solid, a 2D Sketch of a single enclosed area is created and then either Padded or Revolved to add the 3rd dimension, creating a 3D solid from the 2D Sketch.

If the Sketch has segments that cross one another, places where a Point is not directly on a segment, or places where there are gaps between endpoints of adjacent segments, Pad or Revolve won't create a solid. The exception to this rule is that it doesn't apply to Construction (blue) Geometry.

Inside the enclosed area we can have smaller non-overlapping areas. These will become voids when the 3D solid is created.

Инструменты
Инструменты эскизного инструментария располагаются в меню Sketcher которое появляется после загрузки инструментария.

Best Practices
Every CAD user develops his own way of working over time, but there are some useful general principles to follow.


 * A series of simple sketches is easier to manage than a single complex one. For example, a first sketch can be created for the base 3D feature (either a pad or a revolve), while a second one can contain holes or cutouts (pockets). Some details can be left out, to be realized later on as 3D features. You can choose to avoid fillets in your sketch if there are too many, and add them as a 3D feature.
 * Always create a closed profile, or your sketch won't produce a solid, but rather a set of open faces. If you don't want some of the objects to be included in the solid creation, turn them to construction elements with the Construction Mode tool.
 * Use the auto constraints feature to limit the number of constraints you'll have to add manually.
 * As a general rule, apply geometric constraints first, then dimensional constraints, and lock your sketch last. But remember: rules are made to be broken. If you're having trouble manipulating your sketch, it may be useful to constrain a few objects first before completing your profile.
 * If possible, center your sketch to the origin (0,0) with the lock constraint. If your sketch is not symmetric, locate one of its points to the origin, or choose nice round numbers for the lock distances. In v0.12, external constraints (constraining the sketch to existing 3D geometry like edges or to other sketches) are not implemented. This means that to locate following sketches geometry to your first sketch, you'll need to set distances relative to your first sketch manually. A lock constraint of (25,75) from the origin is more easily remembered than (23.47,73.02).
 * If you have the possibility to choose between the Length constraint and the Horizontal or Vertical Distance constraints, prefer the latter. Horizontal and Vertical Distance constraints are computationally cheaper.
 * In general, the best constraints to use are: Horizontal and Vertical Constraints; Horizontal and Vertical Length Constraints; Point-to-Point Tangency. If possible, limit the use of these: the general Length Constraint; Edge-to-Edge Tangency; Fix Point Onto a Line Constraint; Symmetry Constraint.

Tutorials

 * Sketcher Tutorial
 * Sketcher tutorial for beginner
 * Sketcher Micro Tutorial - Constraint Practices