At an abstract level, every new project is composed of three elements:

The known knowns (the things that you know you know), the known unknowns (the things you know that you don’t know), and the unknown unknowns (the things you don’t know that you don’t know)*. Stay far far away from the known gnomes. Given any opportunity, they will steal a single sock from your hamper.

The Known Knowns

After initial brainstorming I begin 3D modeling, starting with the pre-selected commercial off the shelf (COTS) components. These are the agreed upon components that will be bought, not designed. Connectors, motors, switches–all that McMaster-Carry goodness.

You can, with a few potential exceptions, consider these items as a fixed and unchanging piece of your larger overall design. Much like an unpaired, sweaty dress sock needed as part of an incantation for gnome dark magic.

Gather any information you can, including drawings, 3D models, data sheets, and photos. However, get the physical COTS items in hand, if possible, as they are the ultimate truth–Drawings and 3D models are idealized representations that may not reflect some actual details that are, for example, by-products of the manufacturing processes (e.g. flash, injector pin dimples, warp).

Sometimes, access to the real items is difficult due to cost, limited supply, or shared need. However, politely requesting a sample or loaner item from the manufacturer can help build your own stash.

I yearn for the utopian society where all CAD models are open, accurate, and accessible, freeing designers up to do the really important work of creating awesome, unique designs that add value for others. Until then, we’ll do what we can to get that data in hand. To start, here are four options to help you along your way.

Approach 1: Request a 3D Model From the Vendor

The best option is to get a 3D model directly from the vendor. Some vendors will make this easy and provide models directly through their webpage. If models aren’t directly offered, e-mail the technical department and ask if they would be willing to send one. I have a stock e-mail I send that I have tweaked over time.

Subject: 3D model request

Hello, my name is Dan Slaski with Renegade Prototyping. We are an OEM planning to incorporate your [brief item description] into our new [brief assembly description]. I need to design custom mounts for your [brief description of item]. If you have a 3D model available, it makes my life much easier. Otherwise, I have to do my best to reverse engineer the item whcih is very time consuming. A SOLIDWORKS (.sldprt) file is preferred but an .igs or .step file is also fine.

Thank you in advance.

I like to keep it brief at first as it may go to a non-technical person before it gets to the right department.

The reason companies may hesitate is because they are concerned about protecting their intellectual property. If you think there is something proprietary about the item, add a line saying: I understand you may want to protect your intellectual property, therefore, a model of the exterior surfaces or simplified model would be adequate. Coming from the vendor is the best option:

When you are hyper “selfishly” protective of your time, i.e. efficient, you can focus on higher value tasks and it’s better for everyone.

It “should” be the most accurate.

Too much detail can’t hurt but too little can.

I always measure critical dimensions on the actual part and compare. I have received models from vendors that ended up being wrong in some important way. Vendors are fallible and keeping up with the configuration management of the CAD models they provide is likely not at the top of their priorities.

Sharing models is a smart thing to do from a business perspective. Given the option of two equivalent parts, I will choose the one with an available CAD model available for selfish reasons and recommend that one to our purchasing department.

Overtime, I have developed a database of go to companies that I know make high quality products (and have available CAD). I believe there is a correlation between companies that provide CAD models and make high quality products as it is symptomatic of a high level of attention to detail at all levels.

If they come back with a no, politely ask for a 2D drawing. These models can be a design placeholder but be very cautious with the provided models! As distrusting as you would be of a gnome that knocks at your door who says their car broke down out front and is wondering if they could use your phone.

Read the rest at SolidSmack