Of late the CAD Market has been active with discussions on the 'new' technology marketed by Siemens as Synchronous Technology - a new paradigm in Mechanical CAD. Some CAD gurus term it revolutionary, path-breaking and a panacea for the ills of Parametric Technology ( not PTC !), while other seasoned users and I-have-seen-this-often CAD specialists want to be cautious and adopt a wait-and-watch approach.
One of the common thread underlying the discussions on Pro's and Con's has been that Parametric approach has been beset with two issues , namely errors during regeneration and time taken to edit a design having a long history-tree. Hence history-free modelling approach seems to offer a solution to these issues. Instead of taking extreme stand with respect to either History-based or History-free approach, a middle path trying to capitalize on the benefits of both approaches seems to be emerging. This is definitely a positive trend for the 3D CAD Industry and the user as well.
From the perspective of a Design Engineer using 3D CAD, following points remain in focus for any tool to retain its popularity and acceptance:
1. Ease of Use
2. Bi-directional Parametricity with easy-to-generate-drawings having driving dimensions
3. Tolerance Analysis for stack-up calculations
4. Knowledge Management for re-use of design procedures
5. Design Drawing Automation
6. Error-free 2D Drawing for downstream usage in Manufacturing, Inspection, Assembly, Service among other functions.
7. Dimensional Management for Fit, Form and Function
Most of these requirements would need parametricity, constraints, relations between Features of Sizes that goes well with Parametric History-based approach.
One of the points that needs to be addressed critically, is Freedom to Edit Designs developed on any CAD system. Let us look at a scenario wherein an organization develops a design and transfers the same to another manfuacturing facility for prototype development. If the Design data can be changed inadvertantly without leaving a trace of the change (read history-free) it sounds scary with obviously undesirable implications! Freedom can result in abuse !!
Every technology has its advantages and dis-advantages.
Development of 2D Drawings that enables parametric updates and changes to dimensions need to have higher focus. This gets complicated with History-free approach on account of the bi-directional facility enjoyed by the Engineering community.
Simply said, History-based technology provides a facility to Undo, Modify and Redo a design concept at any stage in design process. History-free approach necessitates correctional approach that may involve re-work. Things done in a fraction of a second may require more steps with History-free approach. Parametric dimensions on a drawing would necessarily have to be re-visited by the Designer when a model undergoes a change in History-free approach while it would not be so with History-based approach.
I guess a consensus would emerge with more players such as SolidWorks (that already has Instant3D and SWIFT to address direct editing and regeneration/re-ordering issues) working on ways to address this requirement without sacrificing on the benefits currently enjoyed by the Design community.
Convergence of methods is sure to be in focus for time to come. At the end of the day, Users would be the winners !!