Now that we’ve explored the question, “Why Does 3D CAD Need PDM?,” let’s take a look under the hood and see how these elaborate systems work.
Product Data Management software comes in many varieties and from many sources – i.e., your CAD vendor, your ERP provider or some other document management system – with varying levels of usability, flexibility and capability. Some have better integrations with other business systems, but the only one that truly understands your design data (without having to reverse engineer the file formats that get encrypted with each release) is the PDM system from your CAD vendor. These systems take full advantage of the data available from the CAD system, and often have thin client add-ins that enable quick access to data structures and the complex references and interdependencies between parts in an assembly. They are also the easiest to use, although training is usually required to get the full benefits.
A CAD file can contain any type of geometry, simple or complex. It also contains references to the interdependencies between each file and data about that file (called “metadata”), which contains properties such as name, description, material, part number and project name.
When a design is checked into the PDM vault, the highest level object, usually an assembly, is opened and the data structure is interrogated. From this file, the PDM system will extract a list of each dependent subassembly or part file. Each of those files will then be opened in turn and their dependencies, such as drawings and other parts and assemblies, will be added to the assembly structure list and an accurate Bill of Materials (BOM) will be created at the same time. This process will repeat itself until no further levels of dependency exist.
Assuming all the files can be located, they are then copied to a dedicated file server over the network and all the interdependencies and metadata are stored in tables in a Structured Query Language (SQL) database. The tables in this database are configured by the PDM software during installation to exactly match the metadata created by the CAD system. This enables data to be structured and categorized so that it can be indexed, searched and easily manipulated using SQL transactions.
For a CAD file, a table may state what type of file it is, where it is stored, list all of its custom properties and have links to the assembly or project that it belongs to. A simple SQL query is able to quickly find all the information about a file and its relational hierarchy to all the other files in your database.
Once the table structure has been defined, it is not easily changed. This causes an issue with the annual upgrade cycle of most CAD and PDM systems, in that data structure changes required to accommodate new CAD features often require changes to be made to the PDM database structure. CAD vendors, therefore, attempt to keep PDM system releases in sync with CAD releases (within maybe a week or two) to minimize the impact of the downtime that is imposed on their customers.
For large databases with many files, the data structure and file version upgrade process can take a considerable amount of time and IT resources. It is also not unusual for unknown errors and model failures to be introduced when CAD files are upgraded.
Third-party PDM systems are not able to keep up with these new encrypted data structures and often have to wait and react to changes to a CAD system’s proprietary file format. New versions of third-party PDM systems are often delayed for several months after the latest release of the CAD tool, while the new file format is reverse engineered.
Vendors also have to modify their PDM solutions to be able to keep up with any new CAD capabilities. If a new feature is too difficult to implement or deemed so insignificant that it doesn’t add any value, then they may not be added at all. Delaying a new PDM implementation is not a major inconvenience for many companies, because their standard practice is to wait a few months and several service pack releases in order to test the new CAD and PDM system in a sandbox environment for bugs and other defects before rolling out company-wide.
Do You Wish There Were a “Better Way” to Manage Design Data?
According to “The State of Product Development & Hardware Design 2019,” an independent industry survey of 850 product design and manufacturing professionals, more than 7 out of 10 file-based PDM/PLM users “wish there were a better way” to prevent version control problems.
Interested in more deeply exploring the pros and cons of Product Data Management software?
Onshape’s latest eBook,“The Engineering Leader’s Guide to Data Management & PDM,” will help you evaluate your current processes and help you compare and contrast alternative solutions. Download your free copy here.