Product Design and Development 134

allowance

The intentional space left between a hole and the shaft inserted into it. An allowance must be large enough to allow mating, but not so large as to allow unintended movement.

ANSI

American National Standards Institute. One of the organizations that has set standards and practices for graphical language in engineering drawings.

ASME

The American Society of Mechanical Engineers. One of the organizations that has set standards and practices for graphical language in engineering drawings.

average roughness

The mathematical averaging of all deviations from the centerline of a surface.

baseline dimensions

A form of dimensioning that offers units of measure from one common point. The common point must be exactly located, or all dimensions will be off.

basic size

The size from which limits are derived once allowances are set. The basic size is the true measurement of a feature.

bilateral tolerance

A tolerance method using an equal plus and minus deviation from the specified dimension. Bilateral tolerances are preferred if deviation in either direction risks exceeding the absolute limits.

boundary representation

A type of solid modeling in which facets are combined to create a solid model of a part.

breach

A failure to fulfill the duty of reasonable care. The breach must be legally proven in court.

causation

Both a factual and legal link between a product defect and injuries suffered. Causation must be proved to collect damages.

centerline

A line in an engineering drawing that represents the center of a hole, shaft, radii, or arc.

chain dimensions

A form of dimensioning that offers units of measure from one part feature to the next. Chain dimensions are used when the distance between features is more important than the size of the part as a whole.

clearance fit

The difference between the largest permissible shaft and the smallest permissible hole. Clearance fits allow for easy assembly.

computer-aided design

The use of a computer to design parts. Computer-aided design (CAD) software creates a virtual model of the part.

computer-aided manufacturing

The use of a computer to manufacture parts. Computer-aided manufacturing (CAM) generates the coded instructions for machining the part.

concurrent engineering

A newer method of manufacturing that considers all aspect of development during intial design and performs multiple steps concurrently. Concurrent engineering is often known as integrated product development.

constructive solid geometry

A type of solid modeling in which solid shapes are combined to create a solid model of a part.

continuous improvement

The belief that an organization must constantly measure the effectiveness of its processes and strive to meet more difficult objectives to satisfy customers. Continuous improvement is a lean manufacturing principle.

copyright

A form of intellectual property protection. Copyrights are used to protect "original works of authorship."

cutoff

The designated sample area in which roughness spacing is gaged.

cutting plane line

A line in an engineering drawing that represents the path and position of an imaginary cut made to form a sectional view.

damages

Monetary compensation awarded to a plaintiff once actual injury is proven and all standards of liability are met.

design failure mode and effects analysis

An FMEA targeted at product design. DFMEA is used to find product elements that could lead to premature product failure, overall product failure, product safety concerns, and product manufacturability problems.

design for "X"

A term used to describe any number of manufacturing applications to which the principles of DFM can be applied. Examples include design for quality and design for coating.

design for assembly

A methodology that simultaneously considers all of the design goals and constraints for products that will be manufactured. DFA minimizes the total product cost by targeting assembly time, part cost, and the assembly process at the design stage of the product development cycle.

design for manufacture

A methodology that simultaneously considers all of the design goals and constraints for products that will be manufactured. DFM is able to avoid design choices that would prove needlessly expensive to produce.

design patent

A type of patent issued to anyone who creates a new, original design for the manufacture of a product. Design patents last for a period of 14 years.

die

A constructed metal form used to shape metal in stamping and forging operations.

dimensions

The desired measurement of a feature on a part. Dimensions typically indicate length, width and height.

direct dimensioning

A form of dimensioning that offers units of measure to the locations of specific features. Direct dimensioning can control tolerance accumulation.

Doctrine of Fair Use

An exception to copyright law whereby some copyrighted materials can be reproduced without permission if the purpose of the use is for things such as news reports, or educational materials.

Doctrine of Independent Creation

An exception to copyright law whereby if someone can prove that they came up with the same idea, without being aware of your work, they can proceed without permission.

duty

A standard of reasonable care to refrain from selling products that contain an unreasonable risk of harm. Selling defective products would violate a manufacturer's duty.

engineering drawing

A two-dimensional print that details the size and shape of a part before it is produced. Engineering drawings also specify the materials to be used in part creation.

facet

A flat plane that, along with other facets, makes up the solid shape of a part.

failure mode and effects analysis

A systematic process to assure that potential problems are identified and risks are mitigated throughout product design and development. FMEA is a form of continuous improvement.

first-angle projection

The European standard for engineering drawings. In first-angle projection, the top view is under the front view.

front view

The view that shows the most of a part's relevant features. Each subsequent projection view is considered to be a 90° rotation, unless noted.

fused-deposition modeling

A rapid prototyping technology that involves supplying thin layers of thermoplastic to an extrusion head that is mounted above a part outline.

geometric modeling

A modeling process in which a designer creates lines and text that represent the shape of a desired part. Geometric modeling is the first step in CAD.

hidden line

A line in an engineering drawing that represents a hidden edge of a part not directly visible in the current view.

house of quality matrix

A QFD method for matching specific production design elements to customer requirements. A house of quality matrix is a visual tool used to plot the customer needs that best align with production values.

infringement

The violation of the rights of a patent holder. A patent is infringed when each and every element of one of the patent claims is present in an accused product or process.

integrated product development

A newer method of manufacturing that considers all aspect of development during intial design and performs multiple steps concurrently. Integrated product development is often known as concurrent engineering.

intellectual property

Any unique creation of the mind. Intellectual property is protected in the United States through patents, copyrights, and trademarks.

interference fit

A tight fit designed where the smallest permissible shaft is larger than the largest permissible hole. Force is required to assemble parts with an interference fit.

inventorship

The term applied to the person who initially conceives an invention. Even if you contribute to the development of a product, only those who had conception of invention are credited with inventorship.

laminated object modeling

A rapid prototyping technology that uses a laser to cut thin 2-D cross sections of a base material that is then precisely dropped onto a table.

lay

The overall direction of the pattern created by the production process. Each common lay has a corresponding drawing symbol.

least material condition

The point at which a feature contains the least amount of material within its acceptable size limit. The largest acceptable hole and the smallest acceptable shaft are examples of LMC.

legal causation

Proving that the defect that caused a plaintiff’s injury was reasonably foreseeable by the defendant during the design or manufacturing process. Legal causation is often known as proximate cause.

limit

The extreme allowable size for a feature. Any dimension that exceeds a limit leads to a defective part.

limit dimension

A tolerancing method using an absolute maximum and minimum allowable dimension. Limit dimensioning specifies a range of acceptable measurements instead of a target dimension.

material condition modifier

One of three modifiers that further define the tolerance of a feature in relation to its acceptable size limits.

maximum material condition

The point at which a feature contains the greatest amount of material within its acceptable size limit. The smallest acceptable hole and the largest acceptable shaft are examples of MMC.

negligence

The failure to exercise the standard of care that a reasonably prudent person or company would have exercised in a similar situation. Negligence can lead to liability.

nominal size

The stated designation used to provide general identification, which may not represent an item's true size. A 2x4, which is actually 1 1/2 x 3 1/2, is an example of a nominal size.

object line

A line in an engineering drawing that represents a visible edge of a part. Object lines have precedence over all other lines.

patent

A document that allows the issuant the legal right to "exclude others from making, using, offering for sale, or selling" the product or idea in the United States for a set number of years. Patents do not guarantee your right to produce a product.

patent claim

The design characteristics that make an invention unique and serve as grounds for patent application. A patent is infringed when each and every element of one of the patent claims is present in an accused product or process.

primitive

Basic shapes such as cubes, spheres, cylinders, blocks, and cones that are combined in solid modeling to create a model of a part.

process failure mode and effects analysis

An FMEA targeted at process design. PFMEA is used to identify problems and risks associated with process functions, process- and product-related failures, and manufacturing failures.

product liability

A manufacturer’s or seller’s legal responsibility for any damages or injuries suffered by a buyer, user, or bystander as a result of a defective product. There is no strict standard for liability and each case must be argued in the courts.

projection system

A set of standards for providing multiple views of a part in an engineering drawing. There are two main standard projection systems.

proximate cause

Proving that the defect that caused a plaintiff’s injury was reasonably foreseeable by the defendant during the design or manufacturing process. Proximate cause is often known as legal causation.

punitive damages

A form of damages awarded to a plaintiff designed to punish the defendant or to deter future conduct. A plaintiff can only collect punitive damages if the plaintiff proves that the defendant’s conduct was outrageous, reckless, or malicious.

quality function deployment

A method to determine customer requirements early in the development process and translate them into production requirements. QFD is a customer focused methodology.

rapid prototyping

A general term for any means of creating a physical, 3-D model of a part directly from the CAD data.

reasonable person

A legal benchmark by which negligence claims are judged. Courts constantly analyze and define what a reasonable person would do or expect.

risk priority number

The sum of scores for severity of effect, likelihood of occurrence and probability of detection for a failure mode. The result of performing a failure mode and effects analysis is the generation of an RPN for each possible failure mode.

roughness spacing

The average of the space between each peak of roughness within a sample area of a part's surface.

selective laser sintering

A rapid prototyping technology that uses powder to gradually build thin layers of a part.

solid ground curing

A rapid prototyping technology that uses a water soluble wax to support the layering of a photocurable resin.

solid modeling

A type of geometric modeling based on solids in which all visible surfaces of a part are shown. In addition, solid modeling describes interior volume, mass, and weight.

stereolithography apparatus

A rapid prototyping technology that uses liquefied plastic to gradually build thin layers of a part.

surface modeling

A type of geometric modeling based on geometry only, in which all visible surfaces of a part are shown regardless of volume definition.

surface texture

Any variation from the 0 plane in a part's surface. Almost every part has some texture.

third-angle projection

The American standard for engineering drawings. In third-angle projection, the front view is under the top view.

tolerance

An unwanted but acceptable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design.

tolerance accumulation

The tendency of a part to be more and more out of tolerance with each progressive dimension. When the starting point of a measurement is already out of tolerance, it follows that the next cut may be even more inaccurate.

toolpath

The series of coordinate positions that determine the movement of a tool during a machining operation. CAM is typically used to generate toolpaths.

trademark

Any word, name, symbol, device, or any combination thereof, adopted and used by a manufacturer or merchant to identify goods and distinguish them from those manufactured or sold by others.

transition fit

A fit in which the limits of size overlap, so that the resulting parts may have either clearance or interference. Transition fits provide for flexibility in assembly.

unilateral tolerance

A tolerancing method using a deviation in only one direction, either plus or minus, from the specified dimension. Unilateral tolerances are used if variation in only one direction risks exceeding the absoulte limits.

utility patent

A type of patent issued to anyone who creates a new or significant improvement upon an existing machine, process, or product of manufacture. Utility patents last for a period of 20 years.

view

One two-dimensional perspective or angle of a part on an engineering drawing. Third-angle projection has six principle views.

waviness

The repeating irregularities with spacing greater than roughness marks that result from machine deflections and vibration.

waviness height

The maximum variation in the repeating irregularities from the 0 plane of a surface.

waviness spacing

The average distance between wave peaks in a part's surface.

wireframe modeling

A type of geometric modeling in which the edges of a part are represented by solid lines.