The 3D CAD Assembly Defined

An assembly pre-3D CAD was just a drawing represented as a schematic of the parts assembled with a variety standard, auxiliary and section views, somewhat of an illustrated parts list. It would come in a variety of forms, mostly orthographic views as shown above. But there were a few that would do isometric illustrations. The drawing was used by planning to develop assembly procedures. A good portion of the time they actually had the parts available.

The drawing below is called a detailed assembly with an isometric view showing how the parts were assembled.


Here is the above drawing recreated in ZW3D done in a single file.

Learning 3D Mechanical CAD

But that was far too time consuming. This concept continued into the CAD world with Autocad, which of course was nothing more than an electronic drafting package. Incorrectly call the “2D Drawing”, this misnomer is still hampering our industry. Manual or electronic it was still a drawing.

This is an Autocad drawing with an isometric illustration.  Yes, a bit easier than on the board but still very time consuming. Realize this is an inseparable welded assembly.

But remember assembly drawings were mostly used in-house or shared with closely monitored suppliers. The parts were denoted by the part numbers or item bubbles. Item bubbles allowed much easier part number changes. The part list was usually on the first drawing sheet but could expand to other sheets as necessary. It was delivered as a blue print. As computers showed up the the part list was also provided in the form of computer printouts showing the assemblies, sub-assemblies and used on assemblies that were available for a variety of purposes in the company.

Parts List or BOM?

Enter 3D CAD

Today we have the 3D assembly which is nothing but an associated part accumulator in the Solidworks clones. There are a few 3D CAD systems that have a single model environment and have the complete assembly in one work space, such as IronCAD, KeyCreator, SpaceClaim, SW Conceptual Design and ZW3D. The single model environment is much, much more productive when working with assemblies. All of these packages come with the option of having associated parts.

I gave the above company a presentation of 3D IronCAD. Just took an hour to create the assembly and showed them how fast they could create the AID (Associated Information Document) which many incorrectly called the drawing.


It is quite shocking to me to see the industry have such a problem with engineering documentation since it is so incredibly simple with 3D CAD.

Engineering Documentation Today!

The resulting AID, created in minutes. Yes they bought IronCAD.

Associated Assemblies in the Solidworks Clones are problematic. You have to have all the referenced parts available. So it is very important to plan the assembly. If there are standard or common parts used where the link could be lost if the assembly file itself is sent out. Onshape only imports Solidworks in the Pack and Go .zip files. My favorite import from Solidworks is exported as a Parasolid. I am not sure what format Catia, Creo and Inventor export their assemblies, more than likely STEP. I have read the native assembly files of those products without a problem. It seemed like all the associated parts were all in the same folder.

Here is a very large assembly imported into both ZW3D and IronCAD. It was created in Solid Edge and exported as a parasolid file.  I only used IronCAD and ZW3D as an example of how we can use a generic neutral CAD import, both can bring the complete assembly into one file which is much more productive. Of course, with a Solidworks clone importing these would fill a folder with all the referenced parts and sub-assemblies.


If you look at the history all of the parts and assemblies are defined, the small arrows indicate that these are linked or duplicated parts or assemblies to be used in Parts lists.


ZW3D also imports the part and sub-assembly names

Handling Assembly Files 

Now we really should not be passing assemblies back and forth. I believe they should never leave the native system due to the engineering proprietary information. But as I show you can move to IronCAD or ZW3D and actually use the assembly for new product design. With robust direct edit functionally, history becomes a thing of the past. Take a look how easy I create a complete new product line from a variety of existing products.

Reusing 3D CAD Models for a New Product Line

PDM is a bit of a tough process and can be problematic. I rarely comment on PDM since it is used only by those trained in the CAD system whether integrated or a 3rd party outside system and in my opinion should be treated like a drawing vault. We have the part file and the associated assembly file in all Solidworks Clones. The parts always have to be accessible. So how do we archive completed projects, I am sure there is a packing procedure like Solidworks Pack and go, that will include all of the parts.

The major problem with engineering is the myriad of CAD systems we use. This locks many companies into non-productive history only based CAD systems. It may have been state of the art in 1988, but as we know many technologies advance with new products. One of these products is Onshape which will get into later. But what is on the horizon? Productive increases that cannot be denied. Maybe their here now.

Is 3D CAD Productivity an Oxymoron?

We can easily archive our assemblies in a non-native neutral format and still keep the current information at the time of release available. I have defined this in this article. We just add what I call the embedded title block. Imagine this in an assembly CAD file, all parts have the necessary description.


The Embedded Title Block! A PLM Solution!

Many of those that have very little applicable knowledge think that the model is sacrosanct. It is hardly so. When you send a part to CNC they may hide or remove many features. They have very robust direct editing 3D CAD software that allows this. They can easily eliminate the "Embedded Title Block" whether engraved, embossed or added as a tab. Due to the limitations of the Pro/e clones this information has to included in the single part.

Checking, Design Review, Manufacturing and Data Extraction!

Once a standard is set up then you can use any system to modify any of these parts in the future. The future CAD system will produce basically dumb models that will be modified with smart robust direct edit/hybrid modeling systems. They will not be limited by the complex history only Pro/e paradigm.

Just think of the cost savings. A common standard file format that can be accessed by any system. Once we standardize on this paradigm we can develop much more effective processes. Here is a video of ZW3D modifying an existing product to create a new one. Realize this took less than 5 minutes with a learning curve. My associate was not familiar with Boolean design. Just think of doing this in your solidworks clone?


The Very Large Assembly 

What about very large assemblies? We never work on very large assemblies. If they even exist they are under the control of what you would call a configuration control group.

Let’s take a Boeing airplane. Airplanes are built in sections each being a separate assembly. Each is assembled in a separate process. Do we need the complete assembled Airplane? Of course, not. But we could if we were willing to waste a lot of time and resources.

Airplanes are thousands of parts flying in close proximity!


While at Boeing in 1986 I was introduced to PC based CADKEY. It was a wireframe and we would work in aircraft space. Which was at a certain WL (waterline), BL (butt line) and STA (station line). These were the 3D location of the parts in an aircraft. Looking at the left side of the aircraft, WL was y, BL was z and STA was x. We would get the loft lines (defined outer mold lines) from Catia to design in aircraft space. I am sure you can get the frames and other structure today, this wireframe design was just in the beginning. In the beginning of 3D CAD this was a problem until we could set user defined coordinate system, prior to that we only had the system X0Y0Z0.

An airplane, a car or any large assembly is broken down to specific groups. In an airplane it is primary and secondary structures, controls, landing gear, wings, payloads, avionics etc. Automotive: brakes, power train (engine, transmission and other components), body, glass, electronics, interior, etc. Each group has their documentation coordinated with the different relative groups, making assembly much easier. Actually it is a somewhat simple process with a bit of documentation logistics in design with virtual parts and assemblies available and in manufacturing with the actual parts in front of them. Manufacturing planning is much, much easier today with the availability of a virtual assembly. But they really need a much more flexible system than a Pro/e clone.

The Secret of Part Numbers

This is the Redback Spyder

Here is the scene browser: Notice even in this smaller assembly the sub-assemblies are separated. Shown here is the power train. Now these assemblies can be reference if we have different design groups making the assembly nothing but an accumulator for a configuration group that can control the overall project.

What do we "really" need?

I feel it is time for the industry to really step outside the box and evaluate how the CAD systems are being using. The major CAD companies just have too much influence over engineering and deliverable to manufacturing. We need to break the hold they have by creating a standard they must be compatible. It really is not that hard, we just have a massive amount of ignorance, laziness and vested interest standing in the way.

The ROI would be in months, not years. While the current CAD systems are a bit clunky they still can easily be the basis of a much more productive process.

Engineering Documentation Today!

The Space Between Engineering and Manufacturing

The CAD systems can be easily standardized. We have to expand the capabilities of the system to a highly productive hybrid modeling. Sadly, the current popular CAD systems are based on the dated Pro/e paradigm that “CANNOT” incorporate this hybrid functionality locking companies into a limited complex history only based system.

Once we base our engineering on such a flexible standard the possibilities are endless.

This is how I have been designing for two decades.

Next Generation 3D CAD Technology Applied!

Engineering Documentation Today!

The Worst to Best 3D CAD System and Why

Onshape! - The Future of Document Control

The Ultimate Document Control System

I had a comment on Linkedin on my Onshape Posted Article.

Onshape! A View from the Clouds

“These types of cloud based tools require your information to be stored on line. what prevents the people/company from accessing that information? I see a lot of stolen info.”

My answer

“Having the parts available on line would be just like the blue print. The AID (Associated Information Document) as a PDF with the model as a pattern. Assemblies would not include the models since it is basically an illustrated parts list. So it would be a chore to get all of the components for any assembly. Remember, all engineering is done in the native local CAD system. Now I agree doing you complete engineering on line would a too risky.”

That comment made I start thinking about assemblies and what form they are delivered.

OnShape type cloud system is a basically a bucket where any type of information can be uploaded and stored. This is the perfect Document Control system. You can upload the part in a native format if it can be imported by Onshape and/or a neutral format with an AID as a PDF.

But when we go to the Assembly we do not want to upload the complete assembly. Only the documentation. This is usually a schematic showing all the locations of the parts and a parts list. A few assembly requirements like bonding, torqueing and other rigging instructions. But it will be taken by planning and they will create planning orders. We see this in assembly line or a group of mechanics assembling sub-assemblies. Rarely do the mechanics work from the engineering documentation.

Now I don’t care how the assemblies are handled inside the 3D CAD system. I am only interested in how we present the information to manufacturing. The only viable way is by what I defined above.

The total purpose of engineering is to produce concise, complete
and unambiguous documentation to manufacturing.

Does manufacturing need a 3D CAD assembly model? I really don’t think they do. They do have all the physical parts in front of them. They will review the assembly documentation and if thoroughly defined will develop planning orders on all the necessary steps to assembly the product.

It really is that simple.

Small Update: Onshape has changed its policies which makes this concept a bit more difficult and costly. But if we created a standard where Onshape could profit it could easily be done at a very reasonable cost. Especially for large companies like Boeing.

Onshape! The Party is over!

A bit more about Cloud based document control.

With the assembly delivered only as a document, anyone one that hacks a cloud based Document Control system would have a hard time finding all the parts. Not an easy task.

OnShape, or something similar, is the future of Document Control and will soon replace the convoluted PLM system.

The Future of Document Control

Now don’t get this confused with using cloud based CAD for your design package. There are huge problems.

First, all of your engineering information is available to the hacker.

Second is that OnShape has no native file. The parts and assemblies in the native form only exist on OnShape servers. There is no way to archive or access your engineering locally except with the model in neutral file format and an associated information document in the form of a pdf. It is much better to design with a local system and using Onshape as the document control system. But Onshape is the perfect 3D CAD and engineering design training tool.

The very best engineering collaboration tool.

I suggest that everyone involved with industrial/mechanical engineering and manufacturing get an Onshape account and start using it as a collaboration tool in your engineering or manufacturing process. There is nothing that compares. It would also be worth reevaluating how you are doing your document control. It is simple and inexpensive.

You can share 3D models and virtually any information. You can work on the part and store the latest native file in the Onshape document presented as 3D model showing the changes. Just incredible. You can even provide non-engineering personnel access to the latest engineering in any level of accessibility.

This can be a free collaboration tool for a smaller company. You can have up 10 ten projects. They they go public for viewing. So if you are just collaborating you can delete the projects when the collaboration is done and not have your information on line any more than you need to.

Update: Onshape, now does not offer the 10 free projects. All work is public. If you can allow that then the collaboration option is still viable. But I am sure a few professional seats would be well worth it for large companies with large projects. Or a small group of designers with the available budget.

So assemblies are relatively simple and just need to have documentation defined in an accessible format. And remember when a project is done (if small enough) this needs to be archived in a single file. Only to be pulled out for the basis of a new product or for a future investigation as in any legal situations.

TECH-NET Engineering Services!

We sell and support IronCAD and ZW3D Products and
provide engineering services throughout the USA and Canada!

 Why TECH-NET Sells IronCAD and ZW3D

If you are interested in adding professional hybrid modeling capabilities or looking for a new solution to increase your productivity, take some time to download a fully functional 30 day evaluation and play with these packages. Feel free to give me a call if you have any questions or would like an on-line presentation.

For more information or download IronCAD or ZW3D


The Ultimate 3D CAD Program

Beyond Direct Edit: Surface and Hybrid Modeling

Reverse Engineering 2015 AK-47 Project

The Most Incredible Presentation of Hybrid 3D CAD Modeling, Ever!!

How to Design Smooth Connection Surfaces

The Very Best 3D CAD Rental Offer!!

Starting rental price of $375.00.

ZW3D Pricing

WARNING: ZW3D is a professional 3D CAD engineering package and it is not recommended for those who are not engineering professionals or students with no prior 3D CAD experience. While we will help you get started we are not equipped at this price to teach you 3D CAD from scratch or engineering design. Don't let this low price fool you.

ZW3D now imports native NX, Catia 5, Creo and Solidworks files with PMI


Four Functions that Increase 3D CAD Productivity!!

Reusing 3D CAD Models for a New Product

IronCAD vs Solidworks and the Pro/e Paradigm

Joe Brouwer