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From CAD User AEC Magazine  Vol 13 No 11 - DECEMBER 2000

Release 5 is the latest incarnation of the highly popular 3D mechanical modelling application based on AutoCAD.

If you are one of the many people who visited the Computers in Manufacturing (CIM) show at the NEC recently, then you will understand what I mean by Autodesk giving Mechanical Desktop Release 5 a low profile.  Release 5 is the latest incarnation of the highly popular 3D mechanical modelling application based on AutoCAD.  Even though Autodesk have only just released this version it was hard to find it on show anywhere at the show.  Most companies showing Autodesk based products were singing the praises of the new kid on the block Autodesk Inventor.  Inventor has only been around for about eighteen months and yet it is already at version 4 with versions 5 and 6 planned to come out in the next 12 months.  Based on a completely new architecture Inventor is seen by Autodesk as their long term product for the mechanical market, not relying on what is perceived by many as the ageing AutoCAD platform.  For many people this move away from AutoCAD might be seen as a threat to their investment in AutoCAD and Mechanical Desktop based systems, but try as it might Inventor can't make the break completely.  The recently announced version 4 of Inventor has added support for DWG read and write, and is able to import intelligent parametric designs from Mechanical Desktop with no loss of data or functionality.  Inventor may be the long term future but at present it is a long way off in terms of functionality, lacking somewhat in 2D documentation and surface modelling..  For the present Mechanical Desktop is the master and looks set to stay in that position for some time yet.  Autodesk state on their web site, "we plan to enhance Mechanical Desktop for several releases beyond Release 5".  In my discussion with Autodesk personnel it sounded like they expect Inventor 6 functionality to be on a par with Mechanical Desktop.

So who should be buying Mechanical Desktop?
At present Mechanical Desktop is the first choice modelling package for the many thousands of people who have legacy 2D mechanical designs and who want to carry on working with these as well as moving forward to creating true 3D parametric designs for new work.

With a healthy number of existing users of prior versions of Mechanical Desktop Autodesk are trying hard to make this release attractive to the upgrade market as well.  As you will see there are a range of new features which address some of the weak or complex areas of the existing product.

Mechanical Desktop Release 5 - what does it do?
Release 5 has come about at least in part by the introduction of AutoCAD 2000i.  For those that have not come across it, this is the latest incarnation of AutoCAD - being an Internet souped up version of the base AutoCAD 2000 product.  Being based on 2000i you would expect Mechanical Desktop to have some improved Internet collaboration functionality and you won't be disappointed.  To start with you get access to the Mechanical Desktop Today web portal (figure 3), a source of online resources for Mechanical applications.  From the new portal you can drag and drop intelligent parts directly into your work (figure 4). This is on top of the 1.2 million standard parts and features that come with the Power Pack.  Power Pack is an additional package that is based on the old Genius product.  In addition to standard parts it also incorporates shaft, gear and bearing design components, with the option of generating three-dimensional representations.

Along with access to online resources Mechanical Desktop 5 has added support for online collaboration with the inclusion of a range of new tools giving the ability to :-

• Share Mechanical Desktop sessions with more than one user with Meet Now, the built-in Microsoft NetMeeting client.

• Deploy work management tools on project hosting sites.

• Use a live chat medium for instant consultations among your team or discussions with the worldwide user community.

• Post news, tips, and information with other users on moderated discussion groups.

Quite how useful these tools will be, or how many people will really take advantage of them is open to debate.  To my mind most people would rather email a model and then pick up the phone to discuss it, rather than spend ages typing in messages to each other.  I suspect the inclusion of these tools is more to do with keeping up with the e-crowd rather than providing high demand features and functionality.

So what about real features?
Autodesk would not get far with this version if they did not significantly enhance either the performance or functionality of the software.  If you get it right a simplified function can have significant effects on improved productivity and Autodesk appear to have found a couple of these to work on. New methods and functions can be divided into two main groups, modelling and surfacing, which I will deal with separately.

Modelling Improvements
When working with arrays of components it is now far easier to manage a specific instance of the arrayed object.  In the past it was time consuming to break the instance out of the array to edit it and consequently lose the intelligence of the array.  Now the array object maintains its form while allowing the instances to be edited (figure 3).

Sheet or plate design has been enhanced with a new feature to enable a bend radius to be defined by a theoretical cylinder which is tangent to an open profile and sketch plane.  The cylinder has a given radius, arc length, and/or angle to define the bend completely.

Enhancemnets in the ACIS 6 modelling kernel and surfacing functionality now enable modelling of complex thin features by using curves and wires as profiles that drive the wall geometry in much the same way as you would loft a surface.

Some of the best new features, and the ones that will save the most design time, are the new  web and rib creation tools.  Rather than try to fully parametrically define a web or rib, it can now be created directly from a single sketched line.  Select, draw, or copy an open profile, then select the direction of material fill (Plane) and the direction of the thickness (with a midplane option) to complete the definition of the rib. Draft angles and material depth can be specified as options to design the rib accurately.

As well as these major enhancements a range of other feature improvements include the ability to:-

• Emboss or engrave solids with text that's defined parametrically.
• Define global or part variables during modelling with the Equation Assistant.
• Easily capture design intent in extrusions, sweeps, lofts, and revolved parts-using new, flexible termination types.

Surfacing Improvements
Visually the whole of the surfacing interface has been improved by re-arranging the menus in what is though to be a more logical way - of course if you are used to old menus then it won't be logical at all! The biggest improvements in the surfacing capability of Mechanical Desktop are in the area of surface analysis.  It is now possible to interactively display the results of surface curvature and draft angle analyses using contoured colour images and reflection lines. (figure 1).

To assist in improving the quality of surfaces new spline editing and surface joining tools have been added to enable the designer to:-

• Develop models from separate surfaces with smooth transitions with control of tangent and curvature continuity at surface edges.

• Add variable-surface fillets to surface edges on quilts to ensure manufacturability.

• Create 3D splines that are tangent to existing surface edges, capturing tangency information in the new spline.

When joining surfaces the proposed surface co-incident or U/V lines are displayed on the model.  These can then be dragged dynamically to achieve the desired result.

The link from surface to solid model has also been enhanced with the ability to thicken surfaces and quilts into base parts, preserving complex surface data while creating base features.

General Productivity
In the area of general productivity there are many new features which will smooth the process of managing and documenting designs.  I have to say that many of these features are ones which first saw the light of day in Autodesk Inventor.  A re-assuring sign that development of Mechancial Desktop and Inventor are at least linked in some way.  Productivity improvements include the ability to :-

• Design without specifying structure or defining constraints, and reorganize assembly hierarchy without losing constraints and drawing references.

• Edit external parts, combined parts, and subassemblies in place without opening the external drawing, for true top-down design capabilities.

• Save drawings to earlier AutoCAD® formats as well as DXF™ format without loading drawings into AutoCAD.

• Control display of U and V lines in surfacing documentation and drawing views.

• Specify variable dimensions in a model and reference them in the BOM and parts lists so values are updated automatically when a variable changes.

• Create intelligent notes containing associative variables that update automatically in response to design changes.

• Accurately represent 3D standard parts in 2D drawing views.

• Use OSNAP points to attach reference dimensions to drawing views through the Power Dimensioning command.

• Use 3D Transparent Orbit to interact with the 3D model without leaving the modeling command.

• Focus on parts while editing them in reference by dimming the rest of the assembly.

• Zoom to the bounding box for parts and subassemblies for quick orientation.

• Use BOM variables to generate cut lists.

• Use 3D Orbit for reorienting parts in mid-command.

• Select multiple parts and subassemblies for one-click operations.

So what is the verdict?
Far from being an also ran product wallowing in the shadow of the new kid on the block Mechanical Desktop 5 comes out fighting.  There are no major surprises or huge enhancements, but you wouldn't expect these in a product which is as mature as this.  For existing users there is plenty to look at and I can imagine most users will not find it hard to find a 'must have' feature in this release.  For new users Mechanical Desktop is still way ahead of Inventor and provides a solid platform to build on.

I was disappointed by the web features in this version, doing nothing to enable true multi user access to assembly and part models.  For some users they will undoubtedly be useful but for many the menu will never get opened.

On the whole a sound product and one that Autodesk should push a bit harder - even if they plan to supersede it eventually. CU

Review

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