PREPARE AND INTERPRET TECHNICAL DRAWING

TECHNICAL DRAWING

-is the act and discipline of composing drawings that visually communicate how something functions or is constructed.

BASIC SYMBOLS USED IN TECHNICAL DRAWING

STRAIGHTNESS

-The symbol for straightness is a short horizontal line, much like hyphen. The second block contains the type of tolerance zone, the tolerance value, and material modifiers (e.g. maximum material condition) if any.

FLATNESS

-Flatness is a common symbol that references how flat a surface is regardless of any other datum's or features. It comes in useful if a feature is to be defined on a drawing that needs to be uniformly flat without tightening any other dimensions on the drawing.

CIRCULATITY

-The circularity symbol is used to describe how close an object should be to a true circle. Sometimes called roundness, circularity is a 2-Dimensional tolerance that controls the overall form of a circle ensuring it is not too oblong, square, or out of round.

CYLINDRICITY

-The geometric characteristic block houses the symbol for the type of geometric tolerance in a feature control frame. The cylindricity symbol is a circle enclosed by parallel lines on each side.

PROFILE OF A LINE

-Profile of a line is a 2-Dimensional tolerance range that can be applied to any linear tolerance. If it is called out on a surface, like a radius on a part profile of a line would specify how much that cross-section could vary from a true curved radius.

PROFILE OF SURFACE

-The profile of a surface symbol is a half-circle with the curved edge facing up and the flat edge on the bottom.

ANGULARITY

-Angularity is the symbol that describes the specific orientation of one feature to another at a referenced angle. It can reference a 2D line referenced to another 2D element, but more commonly it relates the orientation of one surface plane relative to another datum plane in a 3-Dimensional tolerance zone.

PERPENDICULRITY

-Perpendicularity is measured using a height gauge, similar to flatness, however, the gauge (or part) is locked to a 90° datum to measure how perpendicular the surface is. The entire surface has to be measured if it is a flat feature.

PARALLELISM

-Parallelism is a fairly common symbol that describes a parallel orientation of one referenced feature to a datum surface or line. It can reference a 2D line referenced to another element, but more comm surface plane parallel to another datum plane in a 3-Dimensional only it relates the orientation of one tolerance zone.

POSITION

-It locates features of size while also controlling orientation. Paired with the size tolerance of that feature, they control Size, Location, Orientation and Form. It cannot however control the location of surfaces, which is where profile of a surface steps in.

CONCENTRICITY

-The symbol for the concentricity control is the same in both the current ISO and former ASME standards; two concentric circles along with, at a minimum, a value for the tolerance, and a reference datum.

SYMMETRY

-The Symmetry Symbol is a focus on symmetry over a datum plane. Both symbols focus on the theoretical center datum being constrained within a specific limit to ensure that the entire structure is uniform.

CIRCULAR RUNOUT

-Circular run out, commonly known as just 'run out' is a 2D measure of a circular profile in relation to a datum axis. It inspects how well a circular cross-section conforms to a perfect circle much like circularity. The tolerance zone is between the outer and inner rings on a 2D plane.

TOTAL RUNOUT

-It is a characteristic that is generally called out when you have a part that must rotate around a central axis and have all points on the entire surface of the part be in spec.

FLOWCHART

FLOWCHART

A flowchart is a diagram that represent the logical sequence in which a combination of step or operations is to be performed. It consists of labeled geometrical symbols that are interconnected to provide a graphical representation of a data processing procedure.

Flowchart Symbols

1. Input / Output Symbol (Parallelogram)

-This symbol represents an instruction to an input of an output device.

2. Processing Symbol (Rectangle)

-This symbol is used to represent a group of program instruction that perform a processing function of the program such as to perform arithmetic operations or to compare, sort, etc.

3. Decision Symbol (Diamond)

-The diamond shaped box denotes a decision or point in a program where more than one path can be taken. The particular path that is chosen depends on the answer to a question or result of a test. The question is inserted in the symbol, and the arrows leaving the symbol are labeled with the alternative, e.g., yes or no, true or false, or negative and positive. When two alternative courses of action are possible, it is termed a two-way branch. Three-way branch has three alternatives. Multiple branches are also possible.

-This symbol is used to represent an instruction or group of instructions that will alter or modify a program's course of execution. It is commonly used to specify operations such as control, index register, initialization, switch setting, and indicating loops.

4. Preparation Symbol (Hexagon)

This symbol is used to represent an instruction or group of instructions that will alter, or modify a program's course of execution. It is commonly used to specify operations such as control, index register, initialization, switch setting, and indicating loops.

5. Terminal Symbol (Oval)

-The symbols are used to designate the beginning and the end of a program, or a point of interruption. It can also be used elsewhere in the flowchart for specifying error conditions, such as parity error checks of detection of invalid characters.

6. Predefined Process Symbol (Rectangle with Two Vertical Bars)

-This symbol is a specialized process symbol that represents a named operation or programmed step not explicitly detailed in the program flowchart. As a subroutine symbol, it can be used when a procedure needs to be repeated several times. Rather than write the instructions for the procedure each time it is needed the predefined process symbol is used.

7. On-page Connector (Small Circle)

-This is a non-processing symbol which is used to connect one part of a flowchart to another without drawing flow lines. It denotes an entry or an exit from another part of the flowchart and also used to change the reading sequence of a flowchart on the same page. On-page connectors conserve space by keeping related blocks near one another, reduce the number of flow lines in complex programs, and eliminate cross lines from taking place. It aids in developing a clearer, better, organized, and more simplified flowchart.

8. Flow Direction Indicators (Arrowheads)

-Arrowheads are used to show the direction of processing or data flow. These are added to flow lines if a flowchart appears confusing in its layout.

9. Off-page Connector (Small Pentagon)

-This type of connector is used instead of the on-page connector to designate entry to or exit from a page when a flowchart requires more than one page. The off-page connector is commonly used in complex flowcharts which often require a detailed diagram

extending over several pages.

10. Flow Lines (Horizontal/Vertical Lines)

-Flow lines are used to show reading order or sequence in which flowchart symbols are to be read. Flow lines are sometimes drawn with arrowheads. The commonly accepted practice is to indicate an arrowhead if the logic flow is from right to left or from bottom to top. Arrowheads are not required when the logic flow is from top to bottom or from left to right.