Let's work on the fundamentals

Engineers need hard facts to do their jobs, and that's what we try to give in these pages as we report on new technology and its applications. You can help by telling us what facts you want

For example, here's some of the important design considerations in materials, electronics, fluid power, and motion control. What would you add to the list?

Materials: Tensile strength, flexural strength, tensile and flexural modulus, thermal conductivity, and coefficient of thermal expansion. For plastics and composites, there's heat-deflection temperature, specific gravity, impact strength, resistance to ultraviolet radiation, chemical compatibility, abrasion resistance, mold shrinkage, and whether the plastic is self-lubricating. For elastomers, it's durometer and percent of elongation.

Important facts about metals include fatigue strength, melting temperature, ultimate tensile strength, and yield strength.

Electronics: Important design considerations for all electronics products include heat dissipation; EMI/RFI protection; power consumption; footprint; applicable standards; ease of installation; reliability; ruggedness; and size, strength, and material of enclosures.

Fluid power: Is the system linear or rotational? Application load in lbs, and load velocity and acceleration. System operating pressure and accumulator volume. Actuator specifications such as rod diameter, bore diameter, stroke length, force capacity, velocity, and acceleration. With hydraulic motors, important facts include motor power output, motor torque, valve operating pressure and flow capacity, and output power of pumps.

Motion control: Number of axes for performing the operation. Loads, inertias, travel distances, speeds, acceleration, and move profiles for each axis. Open- or closed-loop control. Is it the drive or the controller that closes the loop? Feedback devices. Type of encoders (absolute, incremental, rotary, linear, optical, magnetic, contacting, non-contacting, open, enclosed). Positioning resolution, accuracy, and repeatability. Type of control (relay logic, microcontrollers, PCs, PLCs). Operator interface. Number of machines networked in a zone. Serial Input/Output bus technology. Data-acquisition system.

Those points just scratch the surface of facts to know. What other information do you need in these and other areas? Please let us know so we can be sure to provide it.