How to Build it: Lean Prototyping Techniques for Hardware

I recently wrote on my vision for the future of 3D printers, largely on their use for manufacturing.  I wanted to expand more broadly on my thoughts on prototyping technologies, and particularly for rapid and lean prototyping for mechanical designs.

“Lean” started in the context of manufacturing automobiles, and has since been taken to describe prototyping and customer development for software start-ups.  Many software/web start-ups do not win because of a science or technology invention.  Instead, user experiences and marketing are what drive success.  I think people are realizing that this can apply for hardware as well, and the increasing ease of prototyping is helping to drive the increase in hardware based projects and start-ups such as those seen on Kickstarter’s design section.  Of course, hardware continues to have the challenge that production and distribution continues to be more difficult than for software.

I will outline here tools and methods I use in prototyping hardware.  What do you do? (please post in the comment field below)

The Dollar Store

Duct tape, super glue, spray paint, and a dollar store full of imagination are possibly the best (and maybe least expected) prototyping tools.  I’m a strong advocate of the super-alpha prototype: the more you can build quickly, the faster you can find what you don’t know.  It’s also easier to get excited about a project when you have something tangible to show people (potential customers!)

Don’t forget the spray paint!  A prototype that looks sketchy automatically throws off people you show it to.  Civilians will discount even the best features on a prototype if it looks unprofessional, unfinished, and ugly.

Amazon, electronics stores, and hardware stores are also great resources, especially once you have enough of an idea what you are building so that you can specify a specific part.  Before that, quick, cheap, and convenient should be the main criteria for finding parts and materials.

Pen and Paper

Very quick calculations can prove your idea violates the laws of physics.  Save yourself embarrassment and make sure that you are the one to do these calculations, not someone else (like an investor) and that you do them before you invest too much time into a project.  Such calculations can also help decide between design alternatives and optimize design choices.

Simple sketches can help realize ideas and form them to guide physical prototypes.  There is often a lot of different ways to build or do something.  Having different ways on paper can help deciding which direction to take.  They can also express your ideas quickly to other people.

Computer Modeling

CAD Model and Development, Image courtesy Nikola LK

A tried-and-true method for professional mechanical designers, some computer aided design (CAD) programs have come down in price a lot recently.  Alibre for instance is about the same price as Microsoft Office Home and Business, and gives probably 70-80% of the functionality of professional design software.  Entry-level CAD systems often don’t have simulation applications to test the physics of parts, but some packages are available open source that do.  Simulation also requires training to do make reliable models.

I’m not sure why CAD isn’t getting more publicity for maker, hacker, and hobbyist use – a physical model is often easy to make from a fully rendered CAD model. CAD models can be changed easier, quicker, and at less cost.  Design iteration time on CAD can be as quick as modifying software code.

However, if the final widget uses parts that interact with one another, a CAD model may not be able to prove everything works together.  This is especially true for moving parts or imbedded electronics.

2D Cutting

75mm thick steel, cut by waterjet, Image courtesy Fromthecorner

Waterjet and laser cutters etch or remove a pattern from sheet metal (and other materials).  The sheet can then be folded to a 3D final shape.  These can be very cheap and quick: for example a small part could be made in as little as five minutes and at a cost of $5.  The size of the machines makes them practical for anything from smartphone to laptop size, with exceptions either way for certain applications.

The machines are not common in people’s houses, and take a bit of a different design approach: you have to think about your 3D project on a 2D sheet.  Even if you don’t have one in your house, there should be several companies that will be able to cut your part in even a small city.

Additive Manufacturing

The fancy name for “3D printing”, additive manufacturing has become popular for hobbyists and the media.  It is fascinating to watch a part grow in front of you, and a variety of metals, plastics, and rubber-like materials are available, but generally not on the same machine.  Machines are also now small, cheap, and usable enough that they are no longer restricted to industrial use.  Assemblies that would otherwise require serveral components can be built as a single part on a 3D printer.  3D printers allow for making parts that are impossible with other processes, for instance parts with internal holes and voids.  They also can be used to make quick, inexpensive tooling for molds to make parts from.  A prototype can be made for $20-$100+ depending what it is.


Computer numeric control (CNC) usually refers to a milling machine that cuts a big chunk of metal (or other material) into a finished part.  It was probably the first type of “prototyping machine”, but is often used for production as well.  Usually people don’t have these in their house (although the hobbyist and homemade CNC group seems to be growing), and CNC parts can be more expensive than other contracted parts.  Usually parts are in the $150+ range.

Molding and Fibreglass

Carbon fibre aeroshell from a fibreglass mold, UBC Solar Car team

Molding and fibreglass are great for making irregular-shaped parts or if you need several copies of the same part.  There can be a lot more initial work to make a mold than other processes, but quick molds using hobbyist and film-industry materials can be made pretty quickly.  Some chemicals involved in fibreglass and some molds are toxic and require gloves and/or ventilation.  Materials can be quite cheap, $50-$100 is enough to make most small-medium sized parts.


Welding allows the joining of metal.  It is useful for many different parts including frames from metal tubes or making sheet metal into 3D parts.  Like molding, there can be a lot of set-up time in making jigs to hold parts in place when they are being welded.  Spot welders are good for quickly joining metal pieces and require much less skill to operate, and are particularly useful in joining 2D sheet metal projects that were cut on waterjet or laser to make 3D parts.  Often, glues are easier to use and will suffice for a prototype.


Arduino and other microcontrollers are an easy and cheap way to prototype and integrate electronics into a project.  There are lots of examples and support for the platform: someone else has probably already solved the problem you are having and is willing to help. Sparkfun and others have good sensors and other electrical accessories that work with Arduino and other platforms.

User Feedback

If making something for more than a few people to use, you have to talk to people you hope will use it.  Live demos or letting potential users play with your prototypes is important.  But it’s also important in who you pick to ask for feedback and how you let them use it.  With this feedback, you build improve the next round of prototypes, until the project is ready.  I expect there are many parallels to Lean software development here.

How I (try to) pick people for feedback:

Open to Change

Don’t take away Milton’s stapler, Image courtesy Devinpoore

If someone is too happy with what they already have, they will be resistant to change.  Even worse is if the user doesn’t want to change but they think their boss will force them to.  These types of people will think of any reason your prototype won’t work, and it can be tough to convince them differently.  Try to take away Milton’s stapler and he’ll burn the place down (reference to the movie Office Space).

Will Give a Fair Assessment

Like the above person who will only say negative things about your work, try to avoid people who will only say positive things.  Your mother is not the person to get good feedback from, assuming she is supportive of everything you do.

Some people get excited about anything just for being new.  Feedback from them can be motivating but may require coaching and interpreting to make the advice constructive.

Is Sympathetic to How Prototypes Are

Prototype for a hovercraft, Image courtesy Timothyrfries

Many people are never exposed to how things are made.  Stuff comes from Amazon or Walmart, and it better be perfect.  If it breaks, looks ugly, sounds funny, or crashes, it’s a bad product and the company that made it may never be trusted again.  Unfortunately for people looking for feedback, I expect most people fall into this category.

These people need to have their hands held if you choose them for product feedback, as they are often disappointed with what you show them. You need to manage expectations and teach them what exactly your prototype is showing.  If they understand the prototype is only testing a few features of a final product, they will be more understanding.  These people are why spray paint and making your prototype look good is so important: for early stage design, discussion should be about ideas and features, not distracted by aesthetics.


Prototyping is cheaper and easier than ever.  In my opinion, a prototype for many Kickstarter-ready design projects could be made for $1000 in parts and materials, some for even $100.  Like software development, the larger investment is in time put in by the designers. Of course, several (or sometimes many) stages of prototypes are needed to arrive at a final design.  Good user feedback is essential, and this feedback should guide making the next round of prototypes.  It is an iterative cycle.  The key to making good products is making mistakes early and learning from them.  This is best done through prototyping and getting user feedback.


Many of my ideas and views on prototyping were formed in the University of British Columbia Mechanical Engineering program, and particularly from the design faculty.  Some thoughts are inspired by work from the Center for Design Research group at Stanford and the Engineering Design Centre at Cambridge.  Any of these three groups are great places to look more in-depth on these points.



Start of some good discussion on HackerNews:

26 thoughts on “How to Build it: Lean Prototyping Techniques for Hardware

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