As a kind of engineering language, engineering drawings can clearly express the technical informations. but what kind of informations are in the drawing and how dose other engineer clearly understand the drawing? In this blog, we will talk everything about engineering drawings.

What is a Engineering Drawing?

An engineering drawing is a kind of technical drawing that is used to show all informations of a product including size, shape, surface finishing, materials, dimensions, tolerances and more that needed to manufacture the product.

benefits of Engineering Drawing

Clear Communication

Engineering drawings can standardized the technical informations of specifications and requirements. They convey information about the size, shape, tolerances which can make all the team members on the same page for all the technical informations.

Visualization of Design

Engineering drawings can help engineers understand the design concept clearly, they can see the where are the function areas of each component and how each component fit with other component. So when in the manufacturing process, engineers will take care of these area.

precise dimensions

Engineering drawings can define dimensions on the drawing precisely. with section view and detail view, the dimensions which are critical to the functions of component can be shown clearly to the manufacturing engineers. for example, Geometric Dimensioning and Tolerancing can be showed in the engineering drawings.

Quality Control

Engineering drawing is a standard documents needed in the quality control process. manufacturing engineers will use these drawings as a reference standard to check the produced parts, only the parts meet the specifications list on the drawings can be qualified. in this case, engineers drawings help to control the quality of parts and avoid errors in production.

Types of Engineering Drawings

Assembly Drawing: 

Assembly drawings show how multiple components connect together in their designed positions to form a complete product. these components are manufactured separately, assemblely drawing help engineers to understand fit and match relations between these components.

Schematic Diagrams Drawing: 

Schematic diagrams present a simplified representation of a system or process using symbols, lines, and labels. They focus on conveying the functional relationships and connections between components without detailing their physical appearance. Schematic diagrams are commonly used in electrical, electronic, and hydraulic systems.

Part Drawing: 

Part drawings provide an in-depth representation of individual components. They feature exact measurements, material details, tolerances, surface finish requirements, and production notes. These drawings are essential for production, directing manufacturers and machinists making a good quality product.

Main Components of an Engineering Drawing

Title Blocks 

In an engineering drawing, the title blocks are located in the lower right-hand corner. the title blocks show many informations like the part’s name, the company’s name, the drawing number and name of designer and reviewer. Furthermore, this block provides technical informations such as unit measurements, projection angle, surface finish standards, drawing scale, and the material used.

Drawing Views

  • Basic Views: Place the part in the projection system composed of six basic projectors, and projected to the six basic projectors respectively to obtain six basic views. In most cases, 3 basics views such as front view, side view and top view are used in an engineering drawing.

Regionally, the views are a little different. Compare the US and ISO layouts by taking a look at this image. Drawing layouts in ISO and the United States are in direct opposition to one another. The one on the left is known as a first-angle projection, on the right is known as third-angle projection

  • Directional views: A direction view indicates a view according to the projection direction on the main view or another view, it is a view that not configured according to the projection of basic views. If a view cannot be configured according to the projection, it can be drawn according to the direction view.
  • Sectional Views: Section view is mainly used to express the internal structural of the parts, it is supposed to use a section plane or surface to cut the parts, the part between the observer and the section plane is removed, and the rest of the part is projected on plane.
  • Detail Views: Detail views focus on a specific area or feature of the object, providing an enlarged and magnified view for accurate representation and dimensioning.
  • Auxiliary Views: Auxiliary views are used to display inclined or non-orthogonal surfaces that cannot be accurately represented in other views.

Dimensions and Tolerances

Due to machining stability, it is not possible the actual dimensions are exacly same with the dimensions in the 3D data of a product. this is how tolerance come from, The actual size after manufacturing should be within the specified range of the maximum and minimum limit dimensions. below explains the related definitions about dimension and tolerance.

  1. Basic size: The dimension given by the designer.
  2. Actual size: The dimension obtained through measurement.
  3. Limit dimensions: The two extreme permissible values of a dimension variation, which are the maximum and minimum limit dimensions, determined based on the basic size.
  4. Zero line: A baseline in the tolerance band diagram (limit and fit explanatory diagram) that determines deviation, i.e., the zero deviation line. The basic size is usually represented by the zero line.
  1. Dimensional Tolerance: Abbreviated as tolerance, it is the difference between the maximum and minimum limit dimensions, and it represents the allowable amount of variation in size. Dimensional tolerance is always a positive value.
  2. Standard Tolerance: In the system of limits and fits, any prescribed tolerance. The national standard stipulates that for a certain basic size, there are 20 tolerance grades of standard tolerances.
  3. Tolerance Zone: In the tolerance band diagram, the area defined by two straight lines representing the upper and lower deviations.

Geometric Dimensioning and Tolerancing

Every part is composed of points, lines, and surfaces, which are referred to as elements. After machining, the actual elements of a part always have deviations when compared to the ideal elements, including shape deviation and positional deviation. These types of deviations affect the function of mechanical products, and corresponding tolerances should be specified during design and indicated on the drawings with standardized GD&T symbols.

GD&t Symbols

The common used GD&T Symbols in the drawing as below:

Straightness – a condition where a surface element or axis is a straight line.
Flatness – a condition where a surface has all elements lying in a single plane.
Roundness – describes a condition where the surface of a revolution (cylinder, cone, sphere) intersects any plane at all points.
Cylindricity – describes a condition of a rotating surface where all points of the surface are equidistant from a common axis of rotation.
Profile of a Line – a condition that allows the variation of a profile along a line element, either unilaterally or bilaterally.
Profile of a Surface – a condition that allows the variation of a profile along a line element, either unilaterally or bilaterally, on the upper surface.
Inclination – refers to a surface, axis, or centerline that deviates from a specified angle relative to a reference plane or axis.
Perpendicularity – a condition of a surface, axis, or line that is 90 degrees to a reference plane or axis.
Parallelism – a condition of a surface, line, or axis where all points are equidistant from a reference plane or axis.
Position Tolerance – defines a feature of size in an area that allows different true (theoretically exact) locations.
Concentricity – describes a condition where two or more features of a part, at any combination, have a common axis of rotation.
Symmetry – a condition where one or more features are symmetrically disposed about a center plane of symmetry.

How to Create an Engineering Drawing

In the past, drawings are created manually, tools such as drawing boards, rulers and round gauges are used at that time. this method will take days to weeks to finish one components drawing which is slow and easy to have mistake on the drawings.

Today, Engineering drawing is created by CAD software which allows to make the drawing in computer. Various types of CAD software are available and some types of software are specific to particular industries. With CAD software, engineers can either create a drawing from nothing or create a 3D model and then translate it into a drawing.

Conclusion

Engineering drawings are one of the best ways to communicate all the technical information. At KUSLA, our team of skilled engineers and machinists is proficient in analyzing every facet of engineering drawings, providing prompt Design for Manufacturability (DFM) feedback to guarantee the finest machined components. Take the next step by uploading your CAD files and receiving a quote today!

FAQS ABOUT ENGINEERING DRAWING

Engineering drawings are composed of some key parts. read them as following step, you can quicly understand the drawing:

  • 1.Get critical product information from Information Blocks which contains the object depicted in the drawing and the people who involved creating it.
  • 2.Understand the symbols and abbreviations include specifications and dimensions.
  • 3. Read the lines and views to understand how they are reflected in the 3D data.

Some informations can not be shown in the 3D model. but engineering drawing can provide these informations such as Geometry, Tolerances, Materials, surface finish and more.

The common mistakes in engineering drawings include Inconsistency in dimension data, Over dimensioning, Critical specification missing, incorrect tolerances and more. all these mistakes will make manufacturer can not produce parts well.

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