Concentric circle dimensions
Forum rules
and Helpful information
and Helpful information
IMPORTANT: Please click here and read this first, before asking for help
Also, be nice to others! Read the FreeCAD code of conduct!
Also, be nice to others! Read the FreeCAD code of conduct!
Concentric circle dimensions
In Sketcher, is there a way of constraining the radii/diameter of two concentric circles relative to each other?
Basically something similar to the bottom right annotations illustrated here:
Basically something similar to the bottom right annotations illustrated here:
Re: Concentric circle dimensions
There are basically 2 simple ways.
The first is to use expressions.
The second is to place 1 point on each circle, constrain them to be horizontally (vertically) aligned with the common center, then fix the horizontal (vertical) distance between them.
The first is to use expressions.
The second is to place 1 point on each circle, constrain them to be horizontally (vertically) aligned with the common center, then fix the horizontal (vertical) distance between them.
Re: Concentric circle dimensions
Add construction lines and equality constraints:
- Attachments
-
- Snip macro screenshot-957c94.png (4.48 KiB) Viewed 5715 times
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
- MisterMaker
- Posts: 746
- Joined: Mon Sep 21, 2020 7:41 am
- Contact:
Re: Concentric circle dimensions
I ended here after searching if this was really how I should do it.
Freecad is the only CAD software that I know off that cannot place a dimension between to circles.
I don't think this is on purpose.
Should I make a feature request for this?
Freecad is the only CAD software that I know off that cannot place a dimension between to circles.
I don't think this is on purpose.
Should I make a feature request for this?
Re: Concentric circle dimensions
three ways were just mentioned, by the way we are talking about constraints not dimensions, two different things.MisterMaker wrote: ↑Mon Nov 23, 2020 11:19 am Freecad is the only CAD software that I know off that cannot place a dimension between to circles.
- papyblaise
- Veteran
- Posts: 8024
- Joined: Thu Jun 13, 2019 4:28 pm
- Location: France
Re: Concentric circle dimensions
or you place a point on each circle tangent to the circles and to an axis line and you measure the space from point to point
I will thus have faith in my life to use the point tool
I will thus have faith in my life to use the point tool
- Attachments
-
- dot points.PNG (14.09 KiB) Viewed 5529 times
Re: Concentric circle dimensions
there is often a lot of confusion between constraints and dimensions, they are different things.
no, this topic is about constraining a radius with a constraint, one specific set of constraints are described as dimensional constraints but not all and even those are still constraints that constrain geometry.
To put it simply, a dimension object/tool in FreeCAD reads a value from something, the constraint forces something to have a value or do something else of a non-numerical value, like tangent etc. Depending on context a dimension could be an aspect of an item e.g. a line length could described as its dimension, but something else creates or forces that dimension (a property, a constraint, etc.).
Re: Concentric circle dimensions
that is not right, you can not apply a tangent between a point and the circle edge in sketcher. You would use "point on object" constraint.
Every way has advantages and disadvantages.
Point requires you to add a distance constraint between each point, if the circles radii increase by the same amount as the OP asked then a construction poly line is better like Chris said, because you can just add a set of "equals" constraints.
Also tangent has a relatively high computational cost, better to use something else if possible. Same with point on object, better to use only use "point on object" for the points or poly line nodes to the circles and only one of them to the axis, the rest of the points or line segments can then just be constrained with a "Horizontal" constraint.
of course an Expression applied to their radii has a lot of flexibility, as the Expression can read a value from anywhere and even apply maths to it.
- papyblaise
- Veteran
- Posts: 8024
- Joined: Thu Jun 13, 2019 4:28 pm
- Location: France
Re: Concentric circle dimensions
What is your remarkthat is not right, you can not apply a tangent between a point and the circle edge in sketcher. You would use "point on object" constraint.
I place the point on the circle, then I made this point tangent to the OX axis, and the proof by the image is correct