## Turbo Talk => General Discussion => Topic started by: WhtHawk on June 06, 2012, 08:14:48 AM

Title: Question about Constraining Circles & Arcs
Post by: WhtHawk on June 06, 2012, 08:14:48 AM
Hello,

I've decided that I would like to do some of my own CAD drawings at home.  My primary use is for mechanical drawings.  I am finding some very powerful features and am very happy to see constraints for a 2D sketch.  I am having difficulty finding a way to constrain the center of either a Circle or Radius to a dimension or construction geometry.  Coming from CATIA at my day job, I find thhis type of constraint very useful.  Hopefully, I'm overlooking a button somewhere.

I am currently using a trial of TurboCAD Pro V19 Platinum, 64-bit, on Windows 7.

Thank you for your time and assistance,
Matt
Title: Re: Question about Constraining Circles & Arcs
Post by: wd on June 06, 2012, 08:58:35 AM
If chose a rectangle explode one time than try the Concentric and Auto dimension constraints individually .If want to go wild with the dimension constraint window around it and will dimension the whole object.If you care to make adjustments also that can be done in the Selection & Calculator Palette
Title: Re: Question about Constraining Circles & Arcs
Post by: Dean on June 06, 2012, 10:43:26 AM
Not sure if this helps you but for starters try using a point which is concentric  to a circle or arc then use point coincident  on the end or ends of a reference line to the point. This will constrain the geometry. Constraints are highlighted in yellow.
as a note: As WD stated,you can't use constraints on an pre-drawn polylines.They need to be exploded prior to using a constraint. If you wish to constrain a polyline while drawing you need to enable auto add constraints
Title: Re: Question about Constraining Circles & Arcs
Post by: WhtHawk on June 08, 2012, 09:19:47 AM
It sounds like I can't directly attach a constraint to the center of an Arc or Circle.

Thanks for the help.  I was hoping that I had just overlooked a button.
Title: Re: Question about Constraining Circles & Arcs
Post by: wd on June 08, 2012, 07:46:26 PM
I am having difficulty finding a way to constrain the center of either a Circle or Radius to a dimension or construction geometry. Matt
Nope probably not the way your doing it.

It sounds like I can't directly attach a constraint to the center of an Arc or Circle.
The links will clear up any confusion I hope

EDIT: maybe it would help if you post a sample tcw. file what your trying to constraint.
Title: Re: Question about Constraining Circles & Arcs
Post by: WhtHawk on June 09, 2012, 11:30:27 AM
I've attached a file I've created for playing around with this type of thing.  Basically, it is a plate, with a number of rounded slots cut from one side.  These are all the same depth and radius.  I would normally create reference geometry parallel to the face I was going to cut and set specific offset.  I would then create a coincident constraint on the center of the to the off-set construction line.  Then all of the slots would be the same depth and would be easily changed by adjusting one design parameter.

There are also a number of holes which which would benefit from the ability to have a coincident constraint applied to them.

I did figure out how to constrain the center of a circle or arc to a dimension.  I made sure Auto Add Constraints was active and used an Orthogonal dimension with keyboard shortcuts to snap to the center of the arc or circle.

Feel free to have a look at the attached file.  I am much happier with this one than previous but really feel it could be much cleaner.  Any help to make this easier to adjust and read would be most appreciated.
Title: Re: Question about Constraining Circles & Arcs
Post by: wd on June 09, 2012, 09:20:26 PM
To make the plate accept six slots would require equally space within it space and increasing its overall length.To which I have my doubts that constraints can accommodate because the one dimension is not associative to the markers and location.Ideally five slots would fit and maintain slot locations more realistically while retaining the original overall length .To make five slots work would require deleting the undesirable one and activating the connect constraint for the fifth slot.It might work with six by making adjustments with the variables but that would require a lot of wasted time when a simpler approach would expedite it more efficiently.  :)
Title: Re: Question about Constraining Circles & Arcs
Post by: Henry Hubich on June 10, 2012, 07:40:37 PM

1. Reduce the number of dimensions by making greater use of the "Equal Diameter," "Equal Radius," and "Symmetry" constraints.

2. You can constrain the centers of the notch arcs to a horizontal line by drawing that line, applying the "Horizontal" constraint plus maybe a couple of additional contraints to prevent it from wandering, then using the "Coincident" constraint to anchor several Point objects to the horizontal line. Dimension the location of those points as required, and use the "Concentric" constraint to define them as the centers of the notch arcs.

3. You can hide the layers that contain stuff that clutters up the drawing, such as dimensions and constraint markers.

4. Despite one's best intentions and efforts, Constraints are awkward and often infuriating.

Henry H
Title: Re: Question about Constraining Circles & Arcs
Post by: Henry Hubich on June 11, 2012, 09:32:52 PM
Here's a constrained notched plate, something like yours, that contains five notches. Number of notches is fixed, as is the number of circular holes and the general shape of the entity. The eleven dimensions shown are fully constrained, meaning that changing a value in the Calculator Palette will result in an immediate update of the 3D object. (A radical or unreasonable change might well screw the thing up irretrievably -- and it's the TCad Genie who decides what's radical or unreasonable.)

I've attached the .tcw file, in 32-bit v19 format, for what it's worth. Frankly, I think you'll find it isn't worth much at all, since the Constraints in any nontrivial drawing are just about impossible to untangle. This one contains 222 Constraint "Block Marks."

Henry H