For over 30 years, feature-based parametric modeling has been the gold standard for creating complex parts and assemblies and is used in production every day by hundreds of thousands of companies worldwide. 

The beauty of feature-based parametric modeling is that engineers can create solid models with an ordered list of understandable modeling features (sketch, extrude, fillet, shell, etc.). Changing dimension values – or adding, editing, reordering or deleting features – automatically updates a part’s geometry and all associated downstream deliverables, such as assemblies and drawings. This is a huge time-saver and helps to reduce design errors.

Other modeling technologies have tried to gain market acceptance, but parametric modeling has proven to be more reliable, more robust and more powerful, enabling engineers and designers to create new products in record time. 

However, parametric modeling is not without problems. Inherent weaknesses in creating geometry and referencing other parts of a design can cause models to be flaky and unpredictable, or require more work than is necessary to complete a task. Many “best practice” documents are in existence today to educate users on how to circumvent these issues.

A good (or bad) example is designing parts relative to other parts in an assembly, otherwise known as in-context design. If a part that is being referenced changes, moves, is deleted or cannot be found, your feature-tree lights up like a Christmas tree. Features fail, or worse, they don’t fail but the geometry has changed unpredictably with no warning or indication that an update has taken place. Parts are now incorrect and may be manufactured that way. Many companies have been bitten by this once too often and have literally banned the use of in-context references altogether!

Feature tree or Christmas tree? Nobody wants a gift like this.

Those who take the risk soon regret it. An engineer at a radiation detection company recently told me he watched the holes on a back panel of an assembly “unexpectedly float around” the last time he tried in-context design with his old parametric CAD system. Needless to say, whether you’re designing a radiation detector or a ballpoint pen, models should not have minds of their own.

Six Ways Onshape’s Design Tools Are Fundamentally Better

Onshape is relatively new to the market, unburdened by decades of “best practices” and preconceived ideas. Starting from scratch has enabled us to think differently, to approach the product design process from a different perspective.

However, with parametric modeling being the methodology of choice for design professionals everywhere, using it was a no-brainer – it made perfect sense not to try to reinvent the wheel. Using the same modeling techniques that everybody is used to keeps learning curves short.

But rather than just blindly copy how other CAD systems work, we took the opportunity to revisit each design tool and fundamentally change the way they work with the goal to improve each and every design workflow. We believe we’ve got it right. The file-less architecture of Onshape is a significant enabler for these process improvements.

You’ll find all of the core elements of parametric modeling in Onshape such as sketches, extrudes, revolves, fillets, shells and lofts. If you’ve used any professional-grade design tool in the last 30 years then you’ll instinctively know how to build a robust parametric model in Onshape. Literally within a day or two, you’ll be up to speed with all the tools and how to use them. If you’re new to designing in 3D, we’ve simplified the process and streamlined the toolsets to make the transition as smooth as possible.

While many of the tools to build parts and assemblies will feel familiar, many of the workflows surrounding their application are different. Unique enough to list and explain the differences here.

Onshape delivers fundamentally better ways of modeling in many areas, such as:

  1. Multi-Part Design

  2. Configurations

  3. Standard Content

  4. Managed In-Context Design

  5. Simultaneous Sheet Metal Tools

  6. Custom Features

Let’s take a closer look..

1. Multi-Part Design 

File-based 3D CAD (literally every CAD system apart from Onshape) is constrained by the way it stores data – every part, assembly and drawing must be saved to its own unique file on your local hard drive or in the cloud. This makes things like inserting multiple instances of the same part in an assembly much easier, but the “benefits” stop there. Individual parts are not designed in isolation, so why should the CAD system force you to work that way? 

Having a single part per file, for example, does not present a holistic view of your design. Using top-down design techniques, where each part relates to the next, is the natural way engineers think. 

So what are your options? You could design everything in the assembly, but I think we’ve already established that there are problems there, too (see #4 for more details). You could design a multi-body part, but that is really tough and laborious. 

Onshape has extended the power of parametric design from one part at a time to multiple interrelated parts that are naturally treated independently in assemblies, BOMs and downstream applications. This may seem subtle, but in practice it is a huge distinction.  

In Onshape, if you want to drive multiple parts from a single layout sketch, no problem. Or if you want to fillet all the edges at the interface between two parts, you can do that in one operation. 

When using multi-body techniques in file-based CAD, you have to do each operation twice. If you then want to put these parts in an assembly and use them as independent parts, you can't do it directly. Because in file-based, on-premise CAD, a part has to be a file. So you have to derive each part into its own separate file. You end up with all these extra intermediate files that you need to maintain to use the parts in your assembly.

In Onshape’s Multi-part Part Studios, all parts related to one another are designed together in one place, where it most makes sense. This enables you to use the power of a single parametric history to build robust relationships between multiple parts and to enable true top-down design. By defining common features and inter-part relationships in one place – instead of bouncing back and forth between files – you can ensure that the results of your design changes are predictable and robust. 

Multi-part design is now a much smoother experience.

2. Configurations 

Configurations are a way to create variations of parametric models involving different sets of parameters and other options that you can switch between very easily. So a simple example would be configuring a phone in two sizes: Plus and Regular.

File-based CAD systems require all configuration options to be represented in a single table with entries for each conceivable permutation, which in some cases can lead to thousands of rows in that single table. As configurations get more complex with more options, that table grows exponentially – making it virtually impossible to understand, troubleshoot or manage.

Onshape’s approach focuses on making it manageable for users to build and use the sophisticated configurations that designers often need. To do this, Onshape lets you build complex families of parts by creating separate small tables for each set of independent configuration options. This dramatically reduces the number of required table rows and cells. No more monster tables. 

For example, in file-based CAD, a simple bracket with 5 lengths, 5 heights and 5 hole patterns would result in an enormous 375-cell table to manage in a clumsily embedded Excel spreadsheet. In Onshape, this same configuration results in 3 tables of only 5 cells each and is edited with a native intuitive user experience.

The second major difference is what you can configure. In file-based CAD, you can only configure certain things, such as specific dimension values and feature suppressions. With Onshape, you can configure practically everything, including things like continuous values and even entity selection sets.

The third major difference is when configurable parts are inserted into assemblies. In file-based CAD, users are forced to navigate a long list of text string names, one for every possible permutation, with none of the original configuration options visible. In Onshape, users are presented with a clean and straightforward menu offering the original configuration options, making it easy to find the permutation you need.

3. Standard Content

All CAD vendors offer add-ons for standard fastener libraries, sometimes free, usually at cost. These fastener libraries, however, often cause two major problems for companies:

  • Fastener parts do not have much in the way of automation to make it easier to add them into assemblies and create stackups of fasteners.

  • Finding, sharing and updating libraries of thousands of part files is a pain.

Some systems enable auto-sizing of fasteners based on hole geometry and some level of stackup automation that only works well in demos. However, the whole setup is constrained and hampered by, you guessed it, files.

Standard library files need to be installed somewhere, usually on a shared network drive so that each file’s part properties can be maintained from a central location and each user does not have to install gigabytes of data on their machine. This presents a problem when a user does not have access to the library because they don’t have a license code or they are working remote. Sharing data outside of the company also disconnects the library, so the fasteners end up being the wrong size or are missing completely. Conflicts with other copies of libraries installed on different systems is also common. Suppliers and customers suffer the most.

Fasteners in Onshape have intelligence built-in, making them much faster and much easier to use. You can easily create stacks of fasteners, such as bolt-washer-washer-nut, in any order you like. As you add any new fastener anywhere within a stack, the other fasteners shift to accommodate it without requiring you to manually delete, create or debug mates.

Standard content is presented to you right inside Onshape’s assembly insert dialog so you don't have to go hunting for it, download it, check out the license for the add-in, etc. You also don't have to manage these libraries – they are just there and ready to use when you need them – and you’re able to add your own company part numbers.

Standard content is now very easy to assemble and share with an entire team.

4. Managed In-Context Design

File-based CAD systems offer users the ability to add relationships between parts in the context of an assembly, so modifying one part will affect another. Unfortunately, changing in-context parts or their parent assemblies will often erroneously change other parts in unpredictable ways. 

This frustrating event occurs because relationships between parts are stored in the part files and are dependent upon the assembly file, making it difficult to keep track of how they are all interrelated. Updating a part file requires the assembly file to be open. Making a simple change may need the entire assembly and all its part files to be downloaded locally to your hard drive. If it’s gigabytes of data and you’re dialing in over VPN, that could take some time. If the assembly file is missing, corrupt, or a colleague has the assembly checked out of PDM and locked, you can’t update your part. Or worse, you may update the part relative to an old out-of-date assembly. Even a simple movement of a mechanism can cause the shapes of a part to change in unanticipated ways.

Designers are absolutely helpless in this situation. They have zero control over how and when these complex relationships update: Sometimes they recalculate when a part is rebuilt, sometimes when the assembly is updated, and sometimes because a seemingly unrelated part file was edited and saved sometime in the past.

Many companies that use file-based, on-premise CAD systems outright ban the use of in-context relationships because of this unpredictability. Some CAD tools even include a user-defined setting that will prevent the use of in-context relationships (an enhancement requested by their users, delivered a few annual releases later).

With its unique database architecture, Onshape has solved all these problems. Using Onshape’s Managed In-Context Design tools, designs always update in a predictable, controlled manner against immutable historical snapshots of the assembly. 

Assembly motion does not affect in-context relationships either. You can now use multiple assembly contexts to edit single or multiple parts, and you can update the assembly context (the state of the assembly) if needed. And remember, even if you make a mistake, Onshape allows you to go back to any prior state of your model – something no other CAD system can do.

It’s finally safe to end the ban on in-context relationships!

5. Simultaneous Sheet Metal Tools

Unlike file-based CAD systems that calculate flat, folded and tabular sheet metal representations in three separate unsynchronized views, Onshape computes and displays all representations simultaneously. When you edit one view, the other two are synchronized automatically using Onshape’s parallel computing architecture. Seeing the flat and folded views side-by-side allows you to visualize errors and interferences immediately.

By also allowing editing in the Table View, the designer or even the downstream manufacturer can quickly change things such as bend radii, bend order or even convert bends to rips and vice versa. When you make a change in the table, you immediately see the impact on both flat and folded views. File-based CAD systems require laboriously rolling back, suppressing, deleting and adding features to make similar changes and to see their impact.

6. Custom Features

Ever wish you could change the way your CAD system works? 

All CAD systems offer some form of macro programming language or API to let you automate the process of adding features to your design. All these macros do is to allow some user input, do some calculations on-the-fly and save you a number of mouse clicks. All they are doing is adding standard out-of-the-box CAD features of a certain size and in a certain order. They are not associative nor parametric. They don’t understand their surroundings, their application, nor their purpose. They don’t update when a design change occurs and you can’t go back and edit them.

Automation is worthwhile in many ways, to reduce repetitive design tasks, build-in company or industry specific logic or experience, and to reduce errors. But automation is no good if it is only correct at the time of application. If the features created by a macro do not update when the design changes, then they are of limited use.

Onshape solves this with custom features, built using the same tools and open-source programming language that Onshape’s developers use to create the built-in features – “FeatureScript.” 

This programming language enables every user to build custom features that appear and behave exactly like Onshape’s built-in features and are treated as first-class citizens. This gives them the intelligence to understand their surroundings so as changes are made, the feature geometry updates accordingly. FeatureScript makes it easy to build robust, industry-specific CAD features that you wouldn’t normally find as standard in a CAD system. And you don’t need to be a programmer to use a custom feature – if somebody else has created a new feature, you can just add it to your toolbar.

As one of our customers, a luxury cabinet manufacturer, recently put it, “We’re essentially programming our own CAD system designed specifically for cabinet making… A core value of our company is that we develop our own systems versus bringing in consultants to develop solutions for us. The fact that we can code and develop within Onshape makes it a really good fit for us.” 

With FeatureScript, it’s like Onshape built a parametric modeling system just for you, with features made specifically for your work. That’s the way things should be. That’s parametric modeling on steroids.

Before Onshape, the only way to add new built-in features to your CAD system was to submit an enhancement request to your CAD vendor – and wait months, years or forever for your wish to be granted. With FeatureScript, you can create built-in CAD features right now and share them securely with anyone you choose.

More to Come

Onshape didn’t invent parametric modeling, but we have fundamentally improved many of the outdated and frustrating limitations of file-based, on-premise CAD. And there’s more to come. 

Every three weeks, Onshape delivers a new update with a dozen or so new features across the entire platform. Every one of these features have been requested by our customers to improve their design workflows and make parametric modeling – plus all of their other day-to-day activities – much easier and much faster. Taking advantage of these updates requires no effort on your part as everything is taken care of automatically. Just keep an eye out for the in-app message that lets you know when a new update has arrived and what the new features can do for you.

Thank you to the many customers who have shared their incredible ideas and feedback that has helped us to develop every aspect of Onshape. Please keep ‘em coming!