Biblus Agnostica – The CAD Agnostic Bible

[HerrTick]

What should go into a book about CAD that is CAD-agnostic? What principles transcend CAD applications?

[MJuric]

What should go into a book about CAD that is CAD-agnostic? What principles transcend CAD applications?

Doesn't that devolve into a discussion of design and engineering principles? CAD is merely a tool to implement design and engineering. Once you remove the "How" of a particular CAD system all you're left with is "What is the proper design", aren't you?

I would think, at least for now, that different CAD systems are different enough that anything "CAD specific" would not be universal from one system to another. Even basic questions like File and sub folder structure is somewhat dependent on the individual CAD system.

[matt]

What should go into a book about CAD that is CAD-agnostic? What principles transcend CAD applications?

Whoa! Very excellent topic!

CAD Agnostic Bible? I kind of love the ironic sacrilege just in the title.

I think it would include:

I'd want to start with working out a definition of what purpose CAD is supposed to fulfil. Something about figuring out shapes and finding geometrical relationships between parts. Working out the aesthetics, function and manufacturing for products. Then using the geometrical data for other downstream applications from marketing to motion analysis, running CNC toolpaths, 3D printing, assembly instructions, FEA, you name it.

- why NURBS has been such a great thing
- why we have to transcend NURBS
- why history-based modeling has been such a great thing
- why we must transcend history
- make the case for engineers/designers really needing some "artistic" skills and tools
- make the case for "artistic" tools having some analytical capabilities (put draft limits on swoops, make surfaces go through specified curve/edge, etc...)

The argument against mesh modeling has been that it isn't very accurate, but with increased compute power, maybe the mesh itself becomes so fine that it's below the tolerance levels of the tools. Until then, we really can't get rid of NURBS. And we can't forget about mesh until really great mesh-to-NURBS tools become ubiquitous, like STEP to IGES.

And the 800 lb gorilla in the CAD Agnostic dog pile is interoperability. If we could come up with an argument that shows the software conglomerates that they stand to gain more from cooperation than spending so much time trying to lock customers in, I think that's the big picture goal of CAD Agnosticism, if it can be referred to as "a thing".

[HerrTick]

I've used NX, Creo, and SolidWorks for complete product designs. I've learned and re-learned different CAD systems multiple times, as well as troubleshooting issues in other CAD systems and neutral formats.

One thing that has allowed me to switch readily between CAD systems is an understanding of "meta" principles that govern how geometry is defined in CAD systems. The most important principles are CAD agnostic (or maybe CAD pan-theist?).

I could start with my thoughts, but I started this thread to hear others'.

[mike miller]

Whoa! Very excellent topic!

CAD Agnostic Bible? I kind of love the ironic sacrilege just in the title.

I think it would include:

I'd want to start with working out a definition of what purpose CAD is supposed to fulfil. Something about figuring out shapes and finding geometrical relationships between parts. Working out the aesthetics, function and manufacturing for products. Then using the geometrical data for other downstream applications from marketing to motion analysis, running CNC toolpaths, 3D printing, assembly instructions, FEA, you name it.

- why NURBS has been such a great thing
- why we have to transcend NURBS
- why history-based modeling has been such a great thing
- why we must transcend history
- make the case for engineers/designers really needing some "artistic" skills and tools
- make the case for "artistic" tools having some analytical capabilities (put draft limits on swoops, make surfaces go through specified curve/edge, etc...)

The argument against mesh modeling has been that it isn't very accurate, but with increased compute power, maybe the mesh itself becomes so fine that it's below the tolerance levels of the tools. Until then, we really can't get rid of NURBS. And we can't forget about mesh until really great mesh-to-NURBS tools become ubiquitous, like STEP to IGES.

And the 800 lb gorilla in the CAD Agnostic dog pile is interoperability. If we could come up with an argument that shows the software conglomerates that they stand to gain more from cooperation than spending so much time trying to lock customers in, I think that's the big picture goal of CAD Agnosticism, if it can be referred to as "a thing".

Don't you think there should be a chapter on the benefits of cloud-based collaboration and the wonders of PLM?

[zxys001]

What should go into a book about CAD that is CAD-agnostic? What principles transcend CAD applications?

HerrTick,
One of the most important hopes in my year of use has been the idea of "interoperability".
The principle foundation would need to be a Central Open Kernel system (or what maybe we hoped STEP would be... ?)
The chances of this happening with all the different kernels and code...lower than average.
..but.. this makes one think.....

btw.. imho, our cad (schisms) means so many things today but within the context of the heading, the transcending principle or my own tenet is the foundation of engineering. ..which,.. is wide and varying

..however, my prejudice, creo and solidworks (and rhino3d) are generally parametric and cult driven workflows. (forgive me for I drank the koolaid)

..as a mechanical designer, CAD-agnostic would ideally allow me to use my learned design principles or methods however way I prefer and those tools (ideally) allow me to describe or define throughout the whole design process. (cad willing)

[CarrieIves]

Maybe it isn't agnostic enough, or maybe it is more about design than CAD.

As you start, spend time thinking about how things will be changed and how those changes will be controlled. Also, how are you going to communicate to others (or even just future you who hasn't looked at this things for a couple of months) what you were thinking.

Will you have time to make a rough model (maybe for ID or space constraints) that can be thrown out and redone later, or will you have to make sure to set things up right the first time?

Will have to work within certain processes (maybe your company does machining and sheetmetal in house and requires that you design using only those processes) or are all processes open to you?

And please, use feature sizes that aren't to a bazillion decimal places. It should be something rational in at least one system of measurement that the people you work with are likely to recognize.

[HerrTick]

Carrie is getting closer to what I had in mind. Model organization is vital regardless of platform.

Assembly design techniques also are a good example. Top-down design and in-context design principles are universal. So is use of layout sketches.

[MJuric]

Carrie is getting closer to what I had in mind. Model organization is vital regardless of platform.

Assembly design techniques also are a good example. Top-down design and in-context design principles are universal. So is use of layout sketches.

As I stated earlier I think a good portion of this is simply about "good design" rather than "Good CAD practice". Good CAD practice is subject to the system you're using. Making something easy to edit in the future will depend on the CAD system. "Good" model organization will be subject to the CAD system unless you just want to say "Pay attention to your model organization and make it "Good" according to the system you're using".

Assembly design technique, Top down or bottom up and layout sketches are all highly dependent on what you're designing and what the best approach to that design is. I think this is pretty evident by the plethora of different approaches people have and many are largely based on the sector they are in and what they are designing.

So in many cases "Good CAD practice" for one sector/Company/Product is not that great for another.

[HerrTick]

As I stated earlier...

Noted.

[Ry-guy]

What should go into a book about CAD that is CAD-agnostic? What principles transcend CAD applications?

One chapter in your bible might be on how CAD design software has stiffled the design process. Design is different than CAD modeling. We all know and understand that. When you have to come up with a strategy to build your CAD model you are focusing not on the design of the product. You are focused on the shortcomings of your tool set!

[MJuric]

One chapter in your bible might be on how CAD design software has stiffled the design process. Design is different than CAD modeling. We all know and understand that. When you have to come up with a strategy to build your CAD model you are focusing not on the design of the product. You are focused on the shortcomings of your tool set!

Not to mention the idea that somewhere along the line people started thinking that because they could use a CAD system they could also design. We have a WHOLE lot of CAD users out there that have a hard time actually designing something properly....and don't get me started on detailing or making a reasonable document that someone can assemble something with.

[Ry-guy]

What should go into a book about CAD that is CAD-agnostic? What principles transcend CAD applications?

Here's another one. Product design usually represents a 3 dimensional object. So why do we allow our tools to always drive us to a 2D element to make 3D objects?

Why start with a 2D sketch and then extrude that profile to get our 3D model. Why not just have a primative shape called "block"? How many parts do you create that can start their life and live their whole life as a block?

[HerrTick]

So why do we allow our tools to always drive us to a 2D element to make 3D objects?

Great question. I think there are lots of elements to the answer.

The first would be manufacturing processes, especially machining. Most press- and mill- and lathe-type work is more 2­½D than 3D.

It's difficult to train humans to think in true 3D. We see things on a "screen" (two, actually), and our brains do the math to create the 3D illusion. We also spend a great deal of our education learning to express shapes in 2D. Most 3D geometry we learn is more like "2D plus".

[Ry-guy]

Not to mention the idea that somewhere along the line people started thinking that because they could use a CAD system they could also design. We have a WHOLE lot of CAD users out there that have a hard time actually designing something properly....and don't get me started on detailing or making a reasonable document that someone can assemble something with.

I'm with you. We used to have a roles in the R&D departments likes drafter, designer and engineer. Each had their own role. Drafter made sure that the design and engineering requirements are properly communicated. The designer was taking the requirements from the engineer to create functional and serviceable designed products. The engineer was reviewing and approving the design and documenation. Oh, and possibly you had a "checker" that was validating the documentation and ensuring it met design requirements.
Over time, companies felt that CAD was going to do all these things for you! Oh what a big failure in logic that was! CAD allowed you to create more documentation quickly. Quality is a different story!

[MJuric]

I'm with you. We used to have a roles in the R&D departments likes drafter, designer and engineer. Each had their own role. Drafter made sure that the design and engineering requirements are properly communicated. The designer was taking the requirements from the engineer to create functional and serviceable designed products. The engineer was reviewing and approving the design and documenation. Oh, and possibly you had a "checker" that was validating the documentation and ensuring it met design requirements.
Over time, companies felt that CAD was going to do all these things for you! Oh what a big failure in logic that was! CAD allowed you to create more documentation quickly. Quality is a different story!

When I started down this career path people were still using drafting boards. In large companies, and pretty much everywhere, there was a progression.

You started out as a detailer. You were given simple things like blocks with holes...that were looked over by the designer and given to the checker. At some point, well most people, eventually moved on to more complex parts to detail....that were looked over by the designer and given to the checker.

After a while, for some months, others never, you became a low level designer. You were given simple assemblies to design...or just design those blocks and bits you used to just detail. Which were looked over by the project designer or engineer and checked by the checker.

You worked up, to designer or engineer and each step someone looked over your stuff and EVERTHING was checked. If you were good and after many years YOU might become the checker and STILL someone looked over your stuff.

Today it seems any person that knows how to click a few buttons can be "Design engineer" and at the same time be perfect because no one checks anything anymore.

I think people think that because we can change things so fast and remake things so much faster that there's no need to take the time to go thru any sort of checking process. The end result is that the scrap rates today are MASSIVE compared to what they used to be and we throw an ungodly amount of money into the garbage each year....because who wants to spend the money on checking things and training people?

[HerrTick]

Machinists, toolmakers, and pattern makers did a lot to cover the sins of drafters and designers.

My first 3D gig was at a company that had piles of blueprints (yes, the actual blue). There was a lot of 2D-to-3D work. More than a few parts had fudged dimensions that were impossible model. I asked around, and found that the manufacturing crew had plenty of "tricks" to get compliant parts, but never actually made those parts to print.

[Tom G]

Some of the discussion revolves around the larger business practices which drive WHY we do things the way we do, and that is most often because of some boneheaded manager or boss that expects things to be done the way it has been. Sometimes these are well sorted and orderly procedures which are reasonable for both the work path and the career path, and other times these display a regressive ignorance of better practices.

As much as such a broad topic book would have to discuss design intent and general ideology, it should also cover the varieties of professional contexts in which CAD is applied, from dinosaur to unicorn. It could also include comparison to outside consultant, which is more like a jack of all trades that is able to adapt to others' diverse procedures and practices.

[DanPihlaja]

Machinists, toolmakers, and pattern makers did a lot to cover the sins of drafters and designers.

My first 3D gig was at a company that had piles of blueprints (yes, the actual blue). There was a lot of 2D-to-3D work. More than a few parts had fudged dimensions that were impossible model. I asked around, and found that the manufacturing crew had plenty of "tricks" to get compliant parts, but never actually made those parts to print.

This kind of thing seems to happen everywhere..... *sigh*

[Ry-guy]

This kind of thing seems to happen everywhere..... *sigh*

Yes SIr! Want to know what's made...go look at the mark-ups at the machining centers or inside the routing packet!