Mauritz Botha of IMSI spent a few minutes last week showing me the features new to TurboCAD v10.5. Primarily, it's the addition of a constraint manager (licensed from D-Cubed, a group of brillian British mathematicians who come up with most of the features found in competing mechanical CAD packages.)
Constraints perform two tasks:
* Define how object connect to each other.
* Drive dimensions.
Constraints are not new technology. Bentley Systems added them to MicroStation a decade ago. Today, the technology is found primarily in MCAD systems.
The drawback to constraints is that it takes advance planning to implement: which objects are supposed to connect, and how do they connect? After all, TurboCAD includes more than a dozen constraints for 2D and 3D objects:
- equal radius
- equal length
- equal distance
- change chirality
- fix geometry
Take the Concentric constraint, for example. A hole is constrained by an adjacent fillet: make the fillet smaller, and the hole reduces size.
To assist in the second half of the question, TurboCAD includes AutoConstraint. Select an object, and a toolbar lists the constraints that apply to it. Toggle off the constraints you don't want. Mr Botha says this tool is excellent for bringing in drawings from other CAD packages, such as AutoCAD (which lacks constraint management) and then quickly applying constraints.
After constraint(s) are applied, icons appear signalling the type of constraint. These can, naturally, be toggled off to de-crowd the drawing. Right-click the constraint icon, and affected objects are highlighted.
As for chirality, that's a term new to us in CAD, but common in molecular chemisty -- it means "handedness" refers to structures can be mirror images, like your left and right hands. In the context of constraints, it refers to how, say, an arc connects to a line. The arc could connect facing two different ways, convex or concave.
Driving Driven Dimensions
Constraints are also involved with dimensions. These dimensions can consist of distances (like regular dimensions) or consist of forumlas. The formulas are often based on the position and size of other objects. So, dimensions change the size of objects, depending on how other objects change.
The figure shows dimensions driving objects; formulae are seen in the panel on the right. (Click thumbnail for larger image.)
Who uses constraints? I asked Mr Botha. Primarily those TurboCAD customers involved in mechanical CAD designs and even more so in CAM [computer-aided machining]. V10.5 beta testers didn't know what to do with constraints until IMSI provided them with some sample drawings, at which point the light went on.