Know Your Navisworks Files

Many construction firms are now using Autodesk® Navisworks Manage as a tool for collision detection and coordination collaboration with other trades working on the same project. You could even say that it has become an industry standard, which is rare considering it is a software application (that has dominated the market, nonetheless). There is nothing comparable in its class. It flies through 40MB files with 10s of overloaded external references attached like it was a simple 24KB, one-line diagram in AutoCAD®. Okay, enough about my love for Navisworks. I simply wanted to get you in the mood for the following information on the subject matter.

To collaborate efficiently, the LBC (Lead BIM Coordinator) firm will bring all trades working on the project together for weekly coordination meetings, present the collisions with other trades, share potential problems with installation based on the 3D model they will be flying around in the meeting on a projector or smartboard. This is standard, and you won’t see much give or take in this particular situation. Some might hold biweekly coordination meetings while others meet weekly. Some save the collision viewpoints as screenshots in a physical paper collision log, to inform each trade of specific objects that need to be moved out of the way, while others might email the group, listing the collisions and the proposed changes and sign-off requests.

What will change drastically from firm to firm, though, is how the after effects of these meetings are posted to an FTP server, Autodesk Buzzsaw, or something similar. Three years ago, the NWD file format was the standard, and many people didn’t know of other formats that were being used to make things easier. Today, though, after we have been working in Navisworks Manage for countless coordination and collision detection meetings, we are finally at a point where even the project managers are educated on the different file types and the technological aspects of Navisworks, thanks to Navisworks Freedom, a free viewer that most upper management, GCs, and owners are using to fly through the model themselves via a ‘Read-Only’ type of navigation.

There are three main output file extensions from Navisworks. They are:

1. NWD – This is the main export extension for Navisworks models and is the most widely accepted. You can open an NWD in all Navisworks programs (Simulate, Manage, Review) as well as Freedom. This is the typical format to send to a large group of construction firms, as some of them are most likely using the free viewer or an early release.

An NWD file will consolidate all of the merged or appended models within that file, and bind them (for our AutoCAD users) into one large and in-charge file. All loaded models, the scene’s environment, viewpoints and the current view are all saved to the current file. This includes redlines, tags, and markups. All NWD files are static—they will never change. They are not linked to any particular drawing or reference, and they are the slowest of the three file types to open. They are also the easiest.

2. NWC – These are Navisworks Cache Files. When you open or merge/append a Native AutoCAD .DWG or any other native model with Navisworks, if you pay attention you will see it automatically creates a cache file in the root folder that your native drawing is in, named the same except for an .nwc file extension. This is because it expects you to save this file off as a Navisworks model later on, and you most likely will.

Navisworks Cache Files are created mostly for ease of use and speed. When you open a model created in other programs, it creates a cache file that is much smaller in size, and you won’t even notice it. The next time that you open that same model, it will instantly load, rather than gathering the information for it. This is because it is now reading the information from the cache file rather than the model itself (so long as the original file isn’t newer than the cache file, in which case it will re-cache and replace the old one). It does this for each file Navisworks opens or merges natively. Another reason you may have heard of NWC Cache files is because that is what Navisworks Exporter uses as its main file format. If you have Navisworks 2012, you will notice that once you load Navisworks Exporters, your “NWDOUT” command no longer works in AutoCAD®.

They completely nixed this feature with the 2012 release and replaced this command with the much better “NWCOUT” command. It is much better, because you can instantly turn any AutoCAD (or similar) program file into a living cache file of itself to be merged into its master model. When the live model changes, so does your overall model. Navisworks Cache Files play a very important role in Navisworks’ new ‘real-time’ image. The only downfall is you cannot open Navisworks cache files in a previous release or Navisworks Freedom.

3. NWF – This is a Navisworks File Set. These are what you would typically want your master model saved as, linking all other models that pertain to your drawing. Your NWC Cache files are created for the NWF file extension.

With an NWF Master Model, you simply merge or append all of your NWC Cache files into the model, (or your native CAD files, which will be cached anyway). Your model then grows exponentially, only it does not contain any model geometry like an NWD, making it a much smaller file. Let’s say that you have four Navisworks Cache Files appended to your “Overall.NWF” model: “Mechanical.NWC”, “Electrical.NWC”, “Structural.NWC” and “Architectural.NWC”. You save all five (including the Overall.NWF model) in the same directory or folder, and the mechanical contractor decides that they need to move a VAV box 14’-6” west. They modify their drawing in DWG format, then save it. If you have the overall NWF file open, you can simply hit F5 (or the “refresh” button) and their changes will instantly appear, showing what collisions or installation problems that this recent change has created.

You can edit settings within your global options dialog within Navisworks Manage 2012. Future changes will be a different color making them easier to locate within your model. This is very useful when you are dealing with a massive, multi-tiered building that would likely have thousands of changes per week, especially in the beginning stages of collision detection.

A great tool recently released is Buzzsaw Sync. You can use Buzzsaw Sync in collaboration with the above named file sets to create the ultimate real time file collaboration. You can create a shared folder on your desktop, and sync it with Buzzsaw Sync. All of the other trade partners do the same, and you all essentially work to that same folder that contains the same file structure listed above. You can then have a living, breathing document formation that will show changes as they occur, rather than waiting another two weeks for that subcontractor to post their latest file to the server. You can constantly be a step ahead, working to, or behind, their latest model on an hourly basis.

A great way to post the Navisworks files from a coordination meeting’s flythrough is to first move all of the trades’ working drawings into a main Current Collaboration folder along with the NWF that is linking them all. Be sure to save viewpoints in the model, each looking at a collision or instance, labeled and numbered in the collision report to refer to and sign off in the next meeting. You can click on the viewpoint, make your changes, then on to the next. You should then save this weekly file as OVERALLMODEL20110904.NWD (dated) – 2010 version – and save it into the ‘current’ folder and then ultimately the ‘archive’ folder, so that everyone can see the current model no matter if they are using the free viewer or an older version.

You do not need to save the native working drawings into these folders, as the NWD is no longer linking them. Everything is bound within that NWD file.

You now essentially have two folders. One folder contains the overall NWF file with saved viewpoints, materials, scenes, lights, and markups along with all of the native working AutoCAD, Revit, Tesla..etc. files that it is linking (along with the .NWC Cache files that it automatically created for each). This NWF file will be automatically updated with each meeting, because as the native files update the NWF model updates with it. There is no need to save this overall file off as an archive because it would not contain anything. Instead, you would save the actual native working drawings off in a dated archive folder for safety and reference reasons.

The other folder will contain the consolidated NWD file, which has everything bound into it. Because this file is autonomous, you should save this file off as something like OVERALLMODEL20110908.NWD, and place it in the ‘Current’ folder. With every coordination meeting, you will replace this, and move the old one into the archive folder, preferably in a subfolder named ‘Navisworks Files’, while the trades’ native files will be in a subfolder named ‘Drawings’.

Of course, every company has its own way of doing things, and by no means is this the marked standard. It is simply an efficient guide to get you started off in the right direction. The above mentioned procedure works for any trade, whether you are an AE firm, a mechanical or electrical contractor, or a material handling company. If you use this procedure, you will soon see that it will make your meetings more proficient, and you will also learn that some specifics can be changed to fit your exact meeting type. Coordination has never looked so good!

Bill Campbell lives in the San Francisco Bay Area and serves as BIM Lead for national engineering and construction firm Cupertino Electric, Inc. (CEI). In his current role, he utilizes the BIMWorkFlow® Process to optimize project speed, cost, quality and safety. He formerly owned/operated a medium-sized BIM services firm in the Detroit area, and is an AutoCAD 2012-Certified Professional. He is a loyal AutoCAD, AutoCAD MEP (ABS), AutoCAD Architecture and Navisworks user and frequently serves as an Autodesk beta tester for BIM products. He enjoys developing new modeling and CAD techniques, creating customized preferences within AutoCAD MEP 2012, creating CAD standards, and traveling and surfing with his wife and dogs.

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