Is PDM the Unnecessary Evil?
Michael Alba posted on August 06, 2020 |
Cloud-based CAD has PDM seamlessly built in.
PTC has sponsored this post.
Screenshot of the versions and history tree in Onshape. (Image courtesy of Onshape.)
Screenshot of the versions and history tree in Onshape. (Image courtesy of Onshape.)

How many times has this happened to you: you spend hours editing a CAD model, only to discover that you started with the wrong version? Or you email a part to a supplier, and later notice it was an outdated copy. With the CAD program you’re using, these sorts of mistakes are unfortunately quite commonplace.

“I've been in engineering since 1979 and it happens regularly,” said Dave Berchowitz, founder and CTO of Global Cooling. “You have the wrong part come in, the vendor doesn't use the latest drawing. That type of problem can be incredibly expensive to correct for manufacturing companies.”

Berchowitz has left those problems behind ever since his company switched from SOLIDWORKS, a desktop-based CAD application, to Onshape, based on the cloud.

One of Onshape’s biggest selling points is that it emphatically solves the problems of files—by doing away with files altogether. Instead of files, Onshape stores a model in a database in the cloud, with a single database for the whole project. Everyone works from the same single database, which is updated with every change from everyone who shares it, instantly, with the changes visible to all.

A single database is a single source of truth, with no duplicate files and no confusion. The model you open for editing is always the latest version, and there is no doubt that the database—or document, as Onshape calls it—that you share with a supplier is always the one recently revised.

“There's always one version of the document,” Berchowitz said. “I've been a big believer in that for years and years. I don't want different documents floating around the organization.”

One Document Makes All the Difference

The Global Cooling Stirling Ultracold portable ULT25NEU ultra-low temperature freezer. (Image courtesy of Global Cooling.)

The Global Cooling Stirling Ultracold portable ULT25NEU ultra-low temperature freezer. (Image courtesy of Global Cooling.)

Global Cooling develops ultra-low temperature (ULT) freezers, which are used to store biological samples for laboratory research and clinical trials. The company’s Stirling Ultracold brand of ULT freezers hold samples at a frigid –80 °C—and those are the warm ones. Some biological samples are stored around –150 °C, and some as low as the temperature of liquid nitrogen (roughly –200 °C.) The typical ULT freezer has a volume of 780 liters and the most efficient of them consumes about 8kWh of power per day. For comparison, the average American household consumes about 30.5kWh per day.

You may have heard of the most famous occupant of Global Cooling’s ULT freezers, a coronavirus named SARS-CoV-2. Because of Global Cooling’s contribution to studying the coronavirus, the company was deemed an essential business in the early stages of the pandemic.

With Onshape, Global Cooling can design its freezers without worrying about which version is the latest. Onshape puts all design data into what it calls a document, which can include multiple tabs for all the parts, configurations, assemblies and drawings associated with a model. Each document also holds all the history of the model, with all the past states accessible down to every last adjustment. Again, this is the Onshape version of a single source of truth.

Berchowitz doesn’t care for that term, but he does care for the results. He praised Onshape’s release management system, which borrows the software engineering approach (think GitHub) of versions, branches and merges.

“All these things follow from the one document principle, but the release system works so well. It's a really beautiful system,” he said. “Onshape, because it has this one document system, the working document is always marked. You can release it and then there is only one latest release. You would have to be absolutely perverse to undermine it.”

Daniel Scoville, director of engineering for adventure tourism company OceanGate, is another fan of Onshape’s release management system. “That's one of the things I really like about it,” he said. “You can click an icon and it gives you this version tree. It's like a software tool—software versioning systems do this exact same thing.”

A rendering of the Titan manned submersible, which OceanGate plans to send off on her maiden voyage in late summer 2021. (Image courtesy of OceanGate.)
A rendering of the Titan manned submersible, which OceanGate plans to send off on her maiden voyage in late summer 2021. (Image courtesy of OceanGate.)

Scoville and his small engineering team use Onshape to design manned submersibles, the latest of which—Titan—is expected to visit the wreckage of the Titanic late next summer. As you might expect, building a vehicle capable of reaching such extreme depths (the wreckage lies nearly 4,000 meters below the surface) is a process that requires some iteration. One of Scoville’s favorite features of Onshape is its ability to quickly compare different iterations of Titan and her components.

“There's a tool you can click on, and then you can drag a little slider along and it'll highlight the changes from one [version] to the other. It’ll fade changes in and out,” he said.

Foolproof Data Management

“Our PDM [product data management] system at my last company was SOLIDWORKS PDM, and you would check in and out a drawing,” Scoville recalled. “You could roll back to the last version, but nobody wanted to do that. With Onshape, it's way better.”

In Onshape, there’s no check-in, no check-out and no versions in the traditional sense. Onshape records every change to a model in its cloud database, so users can roll back to any point in time, at any time. To help the user manage the changes, Onshape presents a tree-branch history structure.

“There's an icon you can click on, and it shows you anything anybody's ever done,” Scoville explained. “You can go through every change anybody's ever made to this part, and anytime they've actually released it, that shows up in there too. You usually just click back to a release and then make a branch on the tree out to the side and start a new version of that part from any one of those spots. And it's all captured for all time.”

Example of the history tree in an Onshape document. (Image courtesy of Onshape.)
Example of the history tree in an Onshape document. (Image courtesy of Onshape.)

Onshape’s git-like history tree, all contained in a single document, seems incontrovertibly better than the traditional approach to PDM. For one thing, it obviates any chance of mixing up versions or sending outdated models.

“The way Onshape marks the released document—and it gives it a very distinctive location in the hierarchy of the documents—is very good. It's very foolproof,” Berchowitz said.

That said, for engineers unfamiliar with this approach, Onshape can take some getting used to. “You can always jump between branches and trees. You can confuse the heck out of yourself too, but I think it's fantastic,” Scoville said.

The Best PDM is No PDM

According to Onshape CEO Jon Hirschtick, the single source of truth database approach is the very foundation of the cloud CAD platform. He’s even gone so far as to pronounce the approach Design Data Management 2.0. His customers, it seems, would agree.

“The [Onshape] system forces everyone to have one active document,” Berchowitz said. “If somebody makes a change to it, you understand that that document has been changed. Because of that, it forces the whole design process to be highly disciplined. It also avoids the absolutely classical problem [of having] more than one document of the same part.”

“Before I got here [to OceanGate], we had a release process,” Scoville recalled. “But nobody used it because it was so painful, and nobody understood it. As soon as we got Onshape I had a solution, and it was easy to use.”

To learn more about data management in Onshape, visit Onshape.com.

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