COTS Components & Selection
These off-the-shelf components are commonly used to join parts together
What are fasteners?
The main purpose of prototyping
What is testing form, fit, and function?
DFA stands for this
What is Design for Assembly?
What does GD&T stand for
What is Geometric Dimensioning & Tolerancing?
The purpose of gears
What is transmitting power and motion?
Name TWO key factors when selecting a spring
What are spring constant, travel, fatigue life, or material?
Name TWO common prototyping methods
What are 3D printing, machining, laser cutting, or foam models?
One DFA principle that reduces assembly time
What is reducing fasteners or using symmetry?
Purpose of tolerancing
What is controlling variation while allowing manufacturability?
What gear ratio represents
What is ratio of output speed to input speed?
Why are bearings used instead of sliding contact
What is reduced friction and wear?
One key consideration when selecting a manufacturing process
What are material, quantity, cost, or geometry?
Why should part count be minimized
What is fewer errors, faster assembly, and lower cost?
Name the THREE categories of fits
What are clearance, transition, and interference fits?
Calculate gear ratio from teeth count
What is gear ratio = driven teeth / driver teeth?
What motor characteristic matters MOST for a conveyor belt
What is torque (and duty cycle)?
Match a process to a part: sheet metal bracket, plastic bottle, machined shaft
Sheet metal → stamping/bending; bottle → blow molding; shaft → machining
Relationship between design changes and cost over time
What is the cost of changes increases dramatically later in design?
Define RC1 close sliding fit
What is very tight clearance for a precise sliding motion?
What Gruebler’s equation is used for
What is determining degrees of freedom?
You are designing a small benchtop device that must run continuously, support a rotating shaft, and allow easy replacement during maintenance.
Which type of bearing would you select and why?
A ball bearing should be selected because it provides low friction for continuous rotation, supports radial loads on a rotating shaft, is available in standardized COTS sizes for easy replacement, and requires minimal maintenance during operation.
Explain how DFM influences cost and part quality
Simpler designs reduce tooling, labor, and defects
A product design currently requires 12 parts and 18 fasteners. Propose three specific DFA/DFM changes that would reduce assembly time and manufacturing cost, and briefly explain why each change is effective.
What is combine parts where possible, replace fasteners with snap-fits or self-locating features, and standardize remaining fasteners, because these changes reduce part count, assembly steps, tool changes, and the likelihood of assembly errors?
Given a nominal size, specify hole and shaft tolerances
What is a hole slightly larger than the shaft with tight tolerances? (values per standard)
Design a mechanism for continuous motor input
What is a 4-bar linkage with the Grashof condition satisfied?