By Terry Wohlers
Published in Vol. 18, No. 9, September 1995 issue of CGW
Copyright 1995 by Terry T. Wohlers
Earlier this year, Parametric Technology Corp. (PTC) introduced Pro/JR, a parametric, feature-based solid-modeling system targeted at AutoCAD and other low-cost CAD users. Rather than develop an entirely new product, however, PTC took advantage of its already established solid modeler--Pro/Engineer--removing some capabilities to create Pro/JR (thus the name). The result: Instead of launching a new product with bugs and holes, PTC introduced a robust, functional program.
The next logical question is "what's missing?" Mainly, if your work requires sculptured surfaces and complex blends, you need to use Pro/Engineer or another product. That's because you can't use Pro/JR to produce freeform sculptured surfaces, 3D sweeps, and parts that require a high degree of surface control. For example, you cannot model a car body or the twisted shape of a turbine blade. Also, you can't blend non-parallel surfaces.
Additionally, you can't use Pro/JR with any of Pro/Engineer's optional modules, such as Pro/Surface, Pro/Report, or Pro/Manufacture. However if you find after using Pro/JR that you absolutely need more capability, you can receive a $6000 trade-in credit toward the purchase of Pro/Engineer. More importantly, though, is the fact that Pro/JR has more than enough functionality to handle the majority of mechanical designs. Consider, for example, the shell of a computer, monitor, mouse, or other components in your office; most of these parts are candidates for Pro/JR.
As for learning the program, Pro/JR is quite intuitive, especially compared to some CAD products I've tried. For example, Pro/JR automatically highlights the next most-logical menu selection and "grays out" choices that are not available. And contrary to what some might expect, I doubt that Pro/JR would take much longer to learn than AutoCAD and Designer (AutoCAD is required to run AutoCAD Designer). Even so, expect to spend several days of focused learning to grasp Pro/JR's concepts and menus.
For this review, I installed and ran Pro/JR on a Silicon Graphics Indy computer with XZ graphics and 32MB of memory. The Pro/JR software package comes with two CDs, one for Windows NT and the other for Unix. I didn't find the installation any more difficult than other Unix software I've installed. One problem I did encounter was core dumps, which caused the software to crash three times. Memory-related problems, such as the memory space that Pro/JR chooses to use, can cause core dumps. While this problem is irritating (and one that you may be able to correct), you won't lose data, because Pro/JR automatically stores all of your work in special trail files.
Now to the heart of Pro/JR. It didn't take long before I could see that the strength behind this product is its associativity, which gives you the freedom to design, draft, and make changes at will. You can semi-automatically create 2D drawings from a solid model; then you can edit one or more of the drawings, cross sections, or details, and the changes automatically propagate throughout the adjacent views as well as the solid model itself. Moving from one view to the next while making changes, and knowing that these changes will be reflected throughout the database, is a powerful way to design, redesign, and optimize the shape and dimensions of a part.
The 2D drawing features in Pro/JR are identical to those in Pro/Engineer. Compared to AutoCAD Designer, I found positioning the dimensions was easier and faster with Pro/JR. You also can add intelligent notes to the drawing that drive changes in the design. Suppose, for instance, that the wall thickness of your part is 0.250 inch. By adding the note ".125 wall thickness typ" to your drawing, you can change the wall thickness of the part; drawings and the solid model change automatically.
When you first create a design or add a new feature (e.g., hole, fillet, chamfer) to an existing design, you must constrain the geometry. Constraining the geometry is a simple matter of adding dimensions to a sketch. A sketch can be a 2D object consisting of line segments, and, similar to AutoCAD Designer, you don't have to be precise when adding line segments in sketch mode. Later, Pro/JR semi-automatically snaps the line endpoints into place. It also tells you if your sketch is not fully constrained by highlighting the unconstrained geometry. Overall, I found the process of sketching and constraining geometry to be straightforward.
After you've created a solid, you can view it using one of many viewing options. Pro/JR's default display of solid models shows hidden lines in gray, which can be helpful when trying to visualize the edges of a non-rendered model. (AutoCAD Designer does not offer this capability.)
Yet another great feature is the shell function. Many plastic parts, such as enclosures, are plastic shells. Pro/JR lets you design the outer shape of an object and then produce a shell simply by specifying a wall thickness. When I first saw Pro/Engineer years ago, I thought this was one of its most impressive features; Pro/JR's shell feature works the same way.
Additionally, Pro/JR supports several types of relational design features. For example, you can use Pro/JR to create families of parts, such as gears and fasteners. Pro/JR stores only the base part geometry and uses a table to describe the other versions. Pro/JR supports assembly modeling, enabling you to establish relationships between the individual parts in an assembly. (AutoCAD Designer doesn't support this type of assembly modeling.) Plus, Pro/JR lets you create relationships between features in a model.
For importing and exporting files, Pro/JR supports a range of file formats. It can, for instance, import 2D IGES drawings, and it can export IGES wireframe and trim-surface files. It can import/export 2D drawings in DXF format, and it supports the SET format as well. Plus, Pro/JR outputs the STL file type (although the User's Guide incorrectly refers to it as the SLA file format). Output of binary and ASCII STL files is important, because this is the format required by most of the 17 rapid-prototyping (RP) systems sold and used around the world. Interestingly, Pro/JR cannot read Pro/Engineer files, although Pro/Engineer can read Pro/JR files. I expect this will change in the future as customers mix the two and begin to demand two-way file transfer.
Overall, I was impressed with Pro/JR, finding it easier to use and more powerful than I had expected. I don't know if I would have called this product a "junior," a name which, to some, implies something less than the real thing. If I had to select a CAD product for mechanical design work--so long as it didn't involve the creation of certain complex geometry--I wouldn't hesitate to choose Pro/JR. CGW
Contributing editor and industry consultant Terry Wohlers counsels organizations on how to select, manage, and develop technologies for CAD/CAM/CAE, rapid prototyping, and reverse engineering.
Parametric Technology Corp.
Price: $8000; $9000 for floating license. Minimum system requirements: 32MB of RAM, 200MB of disk space, CD-ROM drive, Unix- or Windows NT-based system.
Copyright 1995 by Terry Wohlers