PE Industrial key terms

The ratio of a component's strength, or allowable stress, to the maximum stress it is expected to carry in service. Values above one provide margin against unexpected loads, material defects, and modeling uncertainty.

A standardized symbolic language on engineering drawings that specifies allowable variation in form, orientation, location, and size of features. Tolerance zones are defined relative to datums so parts assemble and function without ambiguous dimensioning.

The principle that a sum of money today is worth more than the same sum received later, because money can earn interest or returns. It underlies discounting future cash flows to a common point in time.

The lowest rate of return an organization requires before committing capital to a project. It reflects the cost of capital plus a risk premium and serves as the discount rate in present-worth and annual-worth comparisons.

The discount rate that makes the net present value of a project's cash flows equal to zero. A project is attractive when its IRR exceeds the organization's minimum attractive rate of return.

The time required for cumulative cash inflows to recover the initial investment. It is simple and widely used for screening, but it ignores cash flows after payback and the time value of money.

A theorem stating that the distribution of the sum or average of many independent random variables approaches the normal distribution as sample size grows, regardless of the underlying distribution. It justifies normal-based methods for sample means.

A range of values computed from sample data that is expected to contain the true population parameter with a stated probability over repeated sampling. Its width shrinks as sample size increases or variability decreases.

Rejecting a null hypothesis that is actually true, which is a false alarm. Its probability equals the significance level alpha, and it trades off against Type II error, the chance of failing to detect a real effect.

An optimization method for maximizing or minimizing a linear objective function subject to linear equality and inequality constraints. The feasible region is a convex polytope, and an optimal solution occurs at a vertex.

The marginal change in the optimal objective value caused by relaxing a constraint by one unit while all else is held constant. It shows which constrained resources most limit performance and are worth expanding.

A single-server waiting-line model in which arrivals follow a Poisson process and service times are exponentially distributed, served first-come first-served. Standard formulas give utilization, average queue length, and average waiting time.

A technique that repeatedly samples random values for uncertain inputs, evaluates the model each time, and summarizes the resulting distribution of outcomes. It handles complexity and randomness that closed-form analytical models cannot.

A production philosophy focused on eliminating waste such as excess inventory, waiting, motion, defects, overproduction, transport, and overprocessing while improving flow. Typical tools include just-in-time delivery, kanban, standardized work, and continuous improvement.

Designing products so they are easy and economical to make and assemble by simplifying part count, tolerances, features, and fastening. Early attention to process capability lowers cost and defects later in the program.

An empirical relationship, VT^n = C, linking cutting speed V and tool life T for a given tool and workpiece combination. The exponent n and constant C are found experimentally and guide speed and feed selection.

The use of programmed instructions to drive machine tools along precise paths. Programs specify coordinates, feeds, and speeds, enabling repeatable, complex, and automated machining of parts.

A statement of which end products will be produced and when, stated by item and time period over a short horizon. It drives material requirements planning and is constrained by capacity and demand forecasts.

A planning technique that explodes the master production schedule through bills of material to determine required quantities and timing of components, using lead times, on-hand inventory, and lot-sizing rules.

A sequencing procedure that minimizes total makespan for a set of jobs processed through two machines in the same order. It repeatedly schedules the shortest processing time at the appropriate end of the sequence.

For a stable system in steady state, the average number of items in the system equals the average arrival rate multiplied by the average time an item spends in the system, written L = lambda times W.

A matrix showing the quantity of material flowing from each department or location to every other one. It reveals dominant flows and is used to arrange departments so heavy traffic travels short distances.

A layout evaluation method that sums flow volumes multiplied by travel distances between departments. Lower total load-distance scores indicate more efficient arrangements when comparing layout alternatives.

The quantity of material handled as a single unit, such as a pallet, tote, or container. Standardizing unit loads permits mechanized handling, faster moves, and less damage than piece-by-piece handling.

A time-ordered plot of a process statistic with a center line and statistically derived control limits. Points beyond the limits or nonrandom patterns signal special-cause variation, prompting investigation instead of routine adjustment.

An index equal to the smaller distance from the process mean to either specification limit, divided by three standard deviations. It measures how well a stable process fits inside its specifications.

Deciding whether to accept or reject a lot by inspecting a sample rather than every unit. Plans specify sample size and acceptance number and carry defined producer's and consumer's risks.

A bar chart of problem categories ordered from largest to smallest frequency, often with a cumulative percentage line. It applies the idea that a few causes account for most of the effect.

The time a qualified worker, working at a normal pace with a specified method, needs to complete a task, including allowances for fatigue, personal needs, and delays. It supports costing, capacity planning, and incentive plans.

A system that assigns tabulated times to basic motions such as reach, grasp, and move, letting a task's time be built up without stopwatch observation. MTM and MOST are common examples.

Estimating the proportion of time spent on various activities by taking many random instantaneous observations of a work group. Statistical confidence depends on the number of observations and the observed proportion.

A tool that computes a recommended weight limit for manual lifting by scaling a load constant with factors for horizontal and vertical distance, asymmetry, frequency, coupling, and task duration.

The order size that minimizes the sum of annual ordering cost and annual holding cost under constant demand and known costs. It balances larger, less frequent orders against higher inventory carrying costs.

Extra inventory held to buffer against demand variability and lead-time uncertainty, reducing the chance of stockouts. Higher service-level targets require more safety stock and therefore more holding cost.

The amplification of demand variability as orders move upstream from customers to suppliers. Common causes include forecast updating, order batching, price promotions, and rationing during shortages.

Ranking inventory items by annual dollar usage so that a small fraction, the A items, accounts for most of the value. Control effort is concentrated on A items, with looser control for B and C items.

A ranking of hazard controls by effectiveness: elimination, substitution, engineering controls, administrative controls, and personal protective equipment. Earlier options protect everyone and depend less on individual behavior.

A structured team study that applies guide words such as no, more, less, reverse, and as well as to process parameters at each node to identify deviations, causes, consequences, and safeguards.

A deductive method that starts from an undesired top event and works backward through AND/OR logic gates to identify combinations of component failures and human errors that could cause it.