When we start designing any product we start by drawing from an outline of the idea to which we are shaping by adding details, measurements and precision to the final drawing. 

• A sketch is a drawing that serves as a first approximation to an object or idea. It is done by free hand as usually with little detail, measurements are not included and it is not necessary to scale.

• A diagram is a more elaborated drawing than the sketch, made also freehand, but with greater detail, using the views of the object, although it can also be represented in perspective in order to make it clearer. It must be proportionate and it must incorporate all kinds of annotations that complete drawing information measures explanatory notes and so on.

• The final drawing is called technical drawing and is made with drawing instruments: ruler, squares, angle protractor or computer program design. It normally has a scale applied. It must be properly bounded. This type of technical drawing defines the object in detail. And presented in a technical plan with title box and framed. 

Technical drawing is a means of communication, can humans communicate by drawings? for example, any person can understand the meaning of the wifi symbol, or traffic signals...

Standardisation is the set of rules in order to ensure common understanding can be objects, drawings, symbols, techniques, formats, protocols...These standards are agreed by agencies. (AENOR: Asociación Española de Normalización y Certificación), (UNE: Una Norma Española), (ISO: International Organization for Standardization), (DIN: Deutsches Institut für Normung (Instituto Alemán de Normalización).

In the case of the technical drawing, the rules refer to the size of the paper, the way of bending the planes, the scales suitable for the representation of each object, the type and thickness of the line to be used for each type of data, the way of limiting the pieces.... 

Dimensioning is the process of indicating or determining size measurements or position in a technical drawing or plan. 

It consists of a series of elements lines, figures, signs and symbols, predefined by standarised rules. This rules are applied and understood by everyone.

The purpose of dimensioning is to provide a clear and complete description of an object. A complete set of dimensions will permit only one interpretation needed to construct the part can be. The guidelines for dimensioning are:

• Accuracy:   correct and real values must be given.

• Clearness:    dimensions must be placed in appropriate positions.

• Completeness:  nothing must be left out, and nothing duplicated.

• Readability:   the appropriate line quality must be used for legibility.

Dimensioning elements

• Auxiliary lines: These are lines that start from the drawing perpendicular to the surface to be dimensioned. They should protrude (extend) slightly from the height lines, approximately in 2 mm. 

• Dimension reference lines: They are used to indicate a dimensional value, or an explanatory note in the drawings, by a line that links the text to the piece. The reference lines shall end:

  • • In arrow, those that end up in an outline of the piece.

    • At one point, the ones that end up inside the piece.

    • No arrow, no dot, when you’re done on another line.

    • The part of the reference line where the text is labeled, will be drawn parallel to the element to be bounded, if this was not well defined, will be drawn horizontal, or without support line for the text.

• Symbols: Sometimes the dimension figure is accompanied by a symbol indicating the formal characteristics of the piece, which simplifies its dimensioning, and sometimes reduce the number of views needed, to define the piece The most common symbols are diameter, radius, square section.