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In addition to dimensions, defining sketch entities relations is very important. It can later save you time in dimensioning (for instance if you have equal line you would only need to define a length once) and also help you to “completely define" your sketch – preventing unexpected problems when changing dimensions and rebuilding the part.
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The relations are of several types:
- Single line relations
- Line to point
- Point to Arc
- Line to line
- Line to arc or circle (here and further, circles are considered as arcs.)
- Arc to arc
Other useful relations
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Single Line relations
Horizontal – line is parallel to construction plane X axis
Vertical – line is parallel to construction plane Y axis
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Coincident – the point lies on the line or its continuation
Mid-point – the point lies exactly in the middle of the line
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Coincident – the point lies on the arc/circle
Concentric – the point lies in the center of the arc/circle
Mid-point – the point lies on the line that passes through line center and middle point.
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Equal – two lines are of equal length
Parallel - two lines are parallel
Perpendicular – two lines are perpendicular
Colinear – two lines lie on the same “virtual line"
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Tangent – the line (or its continuation are tangent to the arc/circle
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Equal – the arcs (or circles) are of equal radius – but not length
Concentric – the center point of the arcs (or circles) are coincident
Tangent – the arc is tangent to another line or circle
Coradial – the arcs lie on the same “virtual" circle.
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Other useful options
- Fix – at any time you can decide that certain sketch entity would not change when you are moving/changing other entities. To do that – select the entity and press “Fix. The selected line/arc will become black – as it cannot change and is now “completely defined".
- For construction – you can define sketch entity to sere only for sketch definition purposes. The Cut/Extrude feature will ignore it – but it can be helpful to completely defining your sketch.
- Infinite Length – sometimes you would like to set the line as infinite length – and define certain sketch entities relative to it (for instance – angles)– this would of course be the construction line. You actually have 2 unlimited lines present on every sketch – the X and Y axis of the construction plane.