Cutting the Design Path

Laser sight-lines place more accurate cuts

-by Helen Shaughnessy, design engineer, D2M Inc., Mountain View, CA

The design brief that power tools manufacturer Porter-Cable, Jackson, TN, handed to our design firm was clear. The client directed us to “...put a laser on a miter saw to help the user position the cut. It must be easy to use, durable, inexpensive, require minimal changes to the existing saw, be transferable to other product lines, and meet safety guidelines.”

We responded by applying the Stanford Product Design process:

1. Accept the problem: We believe that creativity starts with commitment. At D2M, engineers get to pick projects that they are passionate about and are seldom forced to work on things outside their interests. Then they play around with the problem, put themselves in the user’s shoes, and see if they feel that they can contribute to new solutions. Only then do they join the design team and go on to the next phase.

2. Re-define the problem: The first question we asked was: How does the user currently use the saw to get an accurate cut? At first glance, representing a cut line with a laser might seem simple; however, after making many cuts — including basic chops, miters, and compound miters — we soon found that there are several variables that need to be considered, beginning with the cut itself. Most people think of a cut as a dividing line, but forget a cut has width, which is determined by the width of blade. We quickly realized that we needed to represent a cutting region with our laser in order to accurately represent the cut.

The next question became obvious when using the saw: How to most effectively project the line? Miter saws are often used at an angle to create compound angle cuts. While a laser on the top surface of the mate-rial would work for basic cuts, a top projection would be useless on compound miter cuts, like those used to do crown moldings. The best solution turned out to be a laser marking on the top and side of the material facing the user. Problem re-definition found many other hidden issues — issues that are seldom covered in the customer’s design brief. Seeing the laser in direct sunlight, factory calibration, user calibration, com-pensating for blade changes, and line generation options all needed consideration before we would have a complete solution. Only after we felt that we had truly experienced the problem and understood it well did we move on to the next phase.

3. Express solutions: As we became expert users of Porter-Cable miter saws, we set the goal of generat-ing as many solutions as possible to the problems we had identified. We thought of using special washers to clamp the blade in place that served as mirrors from which to reflect the laser beam. We experimented with adding reflectors to the blade itself to bounce the laser around. We tried generating the laser line with con-ventional optics and with holograms. Powering the laser system was a tough problem. We tried separate and integrated power sources. Lasers work best with clean power but miter saw motors kick out a ton of electronic interference. We blew up many laser diodes experimenting with various filters to condition the power. One crazy idea we had was to use the saw’s motor to charge a small super-capacitor. We prototyped several advanced versions of these ideas as the brainstorming phase wound down. When we were literally exhausted and couldn’t think of anything else we moved to the next phase.

4. Test the solutions: After brainstorming, we started evaluating our ideas. In each case, we reviewed how accurately the laser would be positioned. We were able to cost solutions quickly because of our experience putting many laser products into production. Throughout the testing process, we always came back to the user and asked how adding laser technology would effect the cutting experience. Many ideas fell into the “nice solution... but too expensive” category. Testing took its toll and many ideas died in the process — only a few survived.

5. Cycle back through the process: Ideas that died due to cost problems were re-thought with cheaper components. Concepts that missed the mark for accuracy were re-born with better mechanisms. Some new ideas surfaced late in the “Test” phase: Why not include a button to set the laser brightness or sense ambi-ent light to set the laser automatically?

The last step involved combining many of the above solutions into several product concepts for our cus-tomer to evaluate. This led to two interesting outcomes. First, a detailed prototype of one version sparked inspiration with Porter-Cable’s development team, helping them conceive the final design. Secondly, D2M proposed a radical new product that the customer’s marketing group became really excited about…and that is still under wraps.