We often use short-hand terms around here to explain rugged design, expecting that everyone will know exactly what we mean. Stopping to think about it, the dictionary’s definition for rugged doesn’t really illustrate what we mean by rugged in the context of product design! So, we decided to outline the language of rugged product design. There could be a book written about any one of these, but below is our overview.
Equipment used outdoors is usually subject to rain and snow during typical use. Water intrusion protection is usually rated on an IP scale and ranges from protection of light splashing to full deep-water immersion for a period of time or even at varying temperatures.
Equipment used outdoors will collect dust and dirt over time. Dust intrusion protection is usually rated on an IP scale and ranges from protection from large particles to fine dust.
Crap traps are areas of a product that will collect and hold dirt and grime during typical use. There are no standard tests for this, just common-sense product design avoiding deep holes and grooves accessible from the outside of a rugged device. https://juggernautdesign.com/7-ways-to-avoid-crap-traps/
Many rugged products are used in scenarios where the user must don gloves. Gloves change the user’s interaction with tactile surfaces and controls. An industrial designer must take care to ensure that gloves will not hamper use. Tactile feedback and sharpness of surface features often need to be increased for use with gloves. http://juggernautdesign.com/the-glove-test/
Rugged equipment is subject to widely ranging temperatures and rapid temperature swings. Product designers must consider the temperature range that the device must function within, and also the range of temperatures the product might encounter in storage or transportation. Testing will insure that material expansion (CLTE), softening, embrittling and chemical degradation don’t occur in typical use.
Devices that may encounter freezing rain must be designed to ensure that the frozen rain that may adhere to it does not do damage. In many cases the equipment may still be required to function during freezing rain, so a combination of materials, coatings and geometry may be needed to insure proper function. The additional weight of ice is also a consideration.
Vibration is common and even extreme on equipment that is hand carried or mounted to a vehicle. Gear also is subject to vibration during transportation. Proper vibration testing will insure that fasteners don’t work loose; the product doesn’t squeak and rattle and that other functional issues like resonance or buttons self-actuating doesn’t occur.
Shock is similar to vibration but is a typical result of random impacts rather than regular harmonic vibration. Testing is similar.
Foreign Object Damage
Equipment used on flight decks, in overhead environments or in situations where losing a detachable component would render the product non-mission capable (NMC) or cause damage to surrounding equipment or operators must be designed to prevent foreign object damage (FOD). Tethers, hinged rather than removable covers, and captive fasteners are typical solutions to FOD problems.
Gear that must be used in covert situations where visual detection is undesirable must be designed with muted colors, camouflage patterns and non-reflective finishes. Required labels might be hidden out of sight during typical use.
Equipment used in proximity to people, especially in ground vehicles and aircraft must be protected from highly flammable materials and toxic chemicals which may be given off in case of a fire.
Products that remain unguarded for public use may be subject to vandalism by malicious or reckless persons. IK ratings give us a quantifiable range of tests that subject the product to various levels of direct impact to simulate vandalism.
UV Resistance / Solar loading
Rugged outdoor equipment will be subject to direct or indirect sunlight which can degrade materials and finishes over time and increase the temperature of the product well above ambient air temperatures. Industrial Designers must predict the UV / Solar load and plan for materials that can handle the UV light and associated extreme temperatures.
Salt Fog / Corrosion
Corrosion is a problem for any outdoor product, especially if used on the sea or in other corrosive environments. The Salt Fog test is a standard test that will help identify inappropriate materials or combinations of materials that promote galvanic corrosion. Galvanic corrosion can damage a product, or sacrificial galvanic corrosion can be used to actually protect a critical element by sacrificing a less critical part. Part geometry that traps salt water or other corrosive liquids can also negatively impact a product’s useful life.
Electromagnetic Interference (EMI) or radio frequency interference (RFI) can cause electronics to malfunction or can be used by enemy forces to detect users. Mechanical design engineers alone cannot always completely protect from EMI or RFI just with faraday cages. Typically, the product designer must work with electrical engineers to understand the sources of EMI and the components most susceptible to damage. Testing usually involves blasting the product with EM energy or running the product and using equipment to pick up on emitted energy.
Class 1 Encryption
Devices employing class 1 encryption will have exceptional features to prevent evidence tampering. They may require extreme EMI / RFI protection measures, and features that allow the user to quickly destroy sensitive information or codes if captured.
Products used on ejection seats are subject to extreme G forces and wind blasts. They must not endanger the pilot in case of ejection.
Products to be used in aircraft may be subject to extra requirements above and beyond typical rugged equipment. Flame retardant, FOD, and ability to handle harsh vibration are common. Products needing flight readiness testing will usually have a list of requirements provided by the governing authority or prime contractor.
Products used around chemicals, often uncovered during the design brief must be able to withstand typical contact with those chemicals. Temperature range and mechanical stress can magnify chemical degradation. Chemical compatibility charts may need to be consulted or testing completed.
Battlefield products may become contaminated by nuclear, biological, or chemical (NBC) weapon fallout. NBC decontamination exposes a device to decontamination chemicals and or power washing and so may require material and ingress protection consideration.
Internal versus external air pressure gradient can occur in sealed devices when there is temperature, barometric, or altitude changes. The pressure difference can cause all sorts of problems from leaking, warping, button actuation or seal rupture. Venting with waterproof membranes may be needed. In some cases where a product is fixed in location and only subject to rain, tortured path venting may be adequate.
Under certain atmospheric conditions, water can condense inside or outside of a device. That could cause problems with electronics and cameras. Desiccants, venting or sealing may need to be employed to prevent unwanted condensation.
Speakers and microphones used in wet and dusty environments may malfunction if not protected. Some speaker and mic components are designed for harsh environments. Those that are not may need protection with a light flexible membrane or a breathable expanded PTFE (Gore Vent) membrane to keep dust and water out.
Strain Relief of Cables
Cables used on portable or man carried equipment will be subject to bending and pulling. Testing can insure that the strain relief as designed will protect the cable jacket and conductors from damage.