Designing the 'Impossible' part

Once in a while, a truly challenging part comes along. This was the case with the Raymarine Rotary Unicontroller Trackpad Dial (that's a mouthful!) This rotary dial is integral to the operation of these Raymarine Widescreen Displays (of which they made about 6 models).

Unfortunately, the dials are somewhat flawed in that the flexible membrane, seen here from the inside, deteriorates over time. Eventually, they disintegrate completely rendering the entire display unit useless, allowing water to enter and eliminating the ability to press the buttons located beneath the dial.

A boater is faced with completely replacing the display unit often along with various interlinked devices such as depth sounders, wind/speed instruments, transducers and associated cabling. All this is a huge amount of work, expensive and a waste of perfectly good electronics.

As an added challenge, the clear plastic switch actuators, which reside under the dial and translate the dial presses to the printed circuit board mounted switches, also had to be produced. These are comprised of an outer body, 4 radial actuators and a central actuator. They had to be made in clear plastic so as to transmit light from LED's which are also mounted on the printed circuit board beneath the dial for illumination.

Looking at this rotary dial, you can easily see that it is not easily printable, having no orientation which would not require support structure. And, support structure underneath clear flexible plastic is not really feasible - leaving behind too much residue and distortions.

After 3 months of research, iterating through 5 different design attempts, we finally arrived at a design that worked - something that was printable, assemblable, strong and fulfilled the requirements. Manufacturing it requires 3 different types of 3D printers and a total of 6 different types of plastics. A special Independent Dual Extruder (IDEX) FDM printer is used for much of the dial, printing the main body, flexible membrane and seal lip simultaneously so that they are integrally bonded as one part. The central button is too small for regular 3D printers and had to be outsourced to SLS (Selective Laser Sintering) printers. And, a liquid plastic resin printer - what is called a Stereolithographic Printer which hardens resin by selectively exposing it to UV radiation - was purchased to print the clear plastic actuators in the fine detail and full transparency that was needed.

Many thousands of dollars in new printers and printer upgrades as well as hundreds of hours of testing and prototyping were required to perfect these dials. We are continuing to engage the latest in 3D printing technologies to produce these faster and more efficiently to meet demand.

This is an example of a part that is on the outer boundary of what is currently possible with 3D printing. But, with enough ingenuity and perseverance, it shows what is possible. The part has been a huge success and there are many happy boaters around the world now with a revitalized display unit good for another decade of use.