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Blueprint Reading / GD&Trt_1011_us

Blueprint ReadingSeries

STUDY GUIDE

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STUDY GUIDE

© 2012 A. Routsis Associates, Inc – All Rights Reserved

A. Routsis Associates, Inc.275 Donahue Rd, Suite 1Dracut, MA 01826

tel: (978) 957-0700fax: (978) 957-1860

w w w . t r a i n i n t e r a c t i v e . c o m

SPE Print ReadingSupplement:BlueprintsHydraulic PrintsGD&T Prints

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Note to Participant: It is recommended that a part drawing, mold drawing, and a molding machine’s hydraulic diagram, specific to your company, accompany this article. The purpose of this document is to act as a reference and should not be used in place of a structured training program.

GENERAL LAYOUTOverview

Although most part drawings, mold drawings, and hydraulic diagrams differ in appearance, there are general guidelines that should be followed. All drawings contain a title block, and may also include a parts list, revision block, and notes section (Figure 1).

Title Block

The title block is located in the lower right-hand corner of the drawing (Figure 1). Included in the title block is a wide variety of information about the draft, such as:

• Part name• Part number• Date started• Date completed• Department• Company• Address• Approval• Draftsperson• Manufacturing method

• Scale• General tolerances• General information• Material• Finish• Heat treatment

Parts List

A parts list is used with an assembly drawing, such as a mold drawing, and shows the multiple components used. This list is generally located above the title block on the right side of the drawing (Figure 1). Information within the parts list includes the part name, part number, materials used, and the manufacturer.

Revision Block

The revision block is generally located at the upper right-hand corner of the drawing (Figure 1). This block contains information pertaining to changes that have been made to the design, such as the revision number or letter, date, authorization, and an explanation of each change. Symbols are often used next to the explanation to identify the location of the change on the drawing.

Notes

The notes section is most often located at the bottom of the drawing and is used to indicate any general information about the drawing that does not appear in the title block, parts list, or revision block (Figure 1). This information may refer to

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Society of Plastics Engineers

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dimension and tolerance information, surface finish, color, or material.

PART DRAWING AND MOLD DRAWING READING

Introduction

Part drawings and mold drawings portray a three-dimensional object within a two-dimensional draft. This is done using a variety of different views, lines, and dimensions.

Views

In the case of a flat part with minimal detail, only a single top view may be required. To fully represent a part, most cases require multiple views. There are eight views commonly used to represent a three-dimensional part (Figure 1):

• Isometric

• Top

• Front

• Left side

• Right side

• Bottom

• Back

• Sectional

Lines

When drawing, a variety of lines are required to express the different features present on the part (Figure 2). The different lines used are listed in Table 1.

Table 1: Common lines used for drawings.

Object line: Shows detail on faces seen in the particular view

Hidden line: Indicates detail not visible in the particular view

Center line: Represents the center of circular detail

Cutting plane line: Shows the direction of cut for a sectional view

Cross-hatch: Identifies a cut surface used for a sectional view

Break line: Imaginary break used to shorten long parts such as rods or shafts

Extension line: Shows an extension of a part feature for dimensioning

Dimension line: Used to indicate the distance being dimensioned, generally using arrows or hash marks on the ends

Leader: Line with arrows at the end which point to a radius being dimensioned, to point out a note, or a part feature

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Society of Plastics Engineers

Dimensions

Imperial or metric units can be used when dimensioning. In some cases, the dimensions have indicators such as in. (inches) or mm (millimeters) after the dimension. Dimensioning units can also be called out as a note in either the title block or in the notes section. Length and diameter measurements use dimensioning lines either inside or outside the lines being measured. Radius measurements use a leader that points to the inside or outside of the radius (Figure 2).

Most dimensions require a base or datum, which is used as a reference. This is typically a

center line or an extension line located at the center or edge of the part (Figure 2).

Tolerances are used to indicate an upper and lower limit for a given dimension. Tolerances follow the dimension, using a ‘+’ for positive tolerances and a ‘–’ for the negative tolerances. If both the positive and negative dimensions are equal, the tolerances are represented with a ±. For example, 12.000 ″+0.005/-0.005 can also be expressed as 12.000″ ± 0.005. The dimension here would range from 11.995″ to 12.005″.

Threads are shown on the blueprint using hidden lines around the hole and are labeled using a leader. The depth of the hole is also dimensioned

Figure 2.

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using hidden lines (Figure 3). The most common thread types are the unified, metric, acme, and pipe.

Geometric Dimensioning and Tolerancing

Geometric dimensioning and tolerancing, or GD&T, is a more concise method of calling out dimensions and tolerances. This system uses a rectangle containing the type of feature, the tolerance, maximum or lower material condition, and the reference datum when necessary. The datum is a reference line or surface, which is

indicated with a triangle and labeled with a letter in a square (Figure 4).

The GD&T system uses features that indicate the type of tolerance being used. For example, a ⊥ symbol with 0.006 in. in the feature box indicates the line must be perpendicular within 0.006 in. from the datum A (Figure 4). The other common features are listed in Table 2.

The maximum material limit, MML, and lower material limit, LML, involve the lower and highest dimension that can be achieved. These are labeled using a circled ‘M’ or ‘L’ in the label box.

Part Drawing Review

When reviewing part drawings, you should discuss with your supervisor the key aspects of the drawing such as critical dimensions, tolerances, and surface finish requirements.

Figure 3.

Straightness Perpendicularity

Flatness Parallelism

Circularity Position

Cylindricity Concentricity

Profile of a line Symmetry

Profile of a surface Circular runout

Angularity Total runout

Table 2: Common geometric dimensioning and tolerancing GD&T symbols.

Figure 4.

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Society of Plastics Engineers

Mold Drawings Review

Mold drawings typically comprise multiple drawings. The first drawing is an assembly drawing that shows all the mold components assembled from both the cavity and core sides of the mold with accompanying drawings of the various components within the mold. When reviewing mold drawings, you should be able to identify aspects such as the gate and runner location, cooling line layout, support pillars, and ejection actuation. You should also be able to identify any auxiliary connections for either hydraulic or electrical components such as motors, cylinders, and hot runner systems.

HYDRAULIC DIAGRAMSIntroduction

Hydraulic diagrams are used to display the route of the hydraulic fluid from the reservoir, through the hydraulic line and components, and back to the reservoir. Unlike part drawings and mold drawings, the hydraulic diagram is not made to scale. Hydraulics use pump powered by an electric motor to generate hydraulic flow. The resistance to flow within the system generates hydraulic pressure. Valves control the flow of the fluid and the pressure in the line. The hydraulic fluid is converted to movement using actuators such as a screw motor and a carriage pullback cylinder.

Hydraulic Lines

Different hydraulic lines are used to connect the different hydraulic components (Table 3). The main line has the high-pressure hydraulic fluid. The pilot line has a lower pressure and lower volume of flow and is typically used to control other hydraulic components such as a valve. Many hydraulic components are lubricated with the hydraulic fluid. This fluid is passes through a low-pressure drain line back to the reservoir; the reservoir line is used to indicate hydraulic fluid being passed back to the hydraulic reservoir. Intersecting, joined, hydraulic lines are represented using a dot where the lines intersect. Lines that pass by each other without a dot or semicircle indicated are not joined. Plugged hydraulic lines are indicated by an X at the end of

the line. The direction of hydraulic flow is marked with an arrow on the line. Enclosure lines are used to identify hydraulic features that are housed in a single component or grouped, such as stack or hydraulic valves.

Pumps

A wide variety of pumps are used to generate hydraulic flow (Table 3). Fixed displacement pumps use a hydraulic pump that provides a constant hydraulic flow. Variable displacement pumps are capable of adjusting the hydraulic flow with the hydraulic demands of the molding machine.

Valves

Valves adjust the flow of the hydraulic fluid within the system (Table 3). The simplest valve is the check valve, which allows hydraulic fluid to pass through the valve in only one direction. Flow control valves use a dial to adjust the amount of fluid that can flow through the valve. Direction valves use a spool, represented by squares, to alter the flow of the fluid within the valve. The more common spools available can stop the flow, allow the flow to pass through, cross two flows, join two flows, or allow fluid to change direction. These valves are moved through the use of different controls such as a spring, manual control, pushbutton, lever, pedal, mechanical latch, pressure compensation, solenoid, servomotor, or pilot pressure. Valves actuated by these devices show the symbol for the method next to the device (Table 3).

Actuators

Hydraulic motors are rotary actuators that are used convert the hydraulic flow to rotational movement. Cylinders are used to convert the hydraulic flow to linear movement (Table 3).

Other Components

Heaters and coolers control the temperature of the hydraulic fluid. Filters are used to remove contaminates from the hydraulic fluid. Electric motors are used to power the hydraulic pumps. Pressure switches are used to turn off and on electrical components. Pressure and temperature indicators are used to measure the status of the fluid. The hydraulic fluid is stored at a low pressure in a reservoir (Table 3).

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Hydraulic Diagram Review

When reviewing hydraulic diagrams, you should ask your hydraulic maintenance technician to help you identify machine components such as pumps, valves, and actuators on the diagram and the molding machine.

Main line Hydraulic cylinder

Pilot line Spring control

Drain line Manual control

Reservoir line Pushbutton control

Joined lines Lever control

Nonintersecting lines Pedal control

Plugged line Mechanical latch control

Flexible line Pressure compensated control

Direction of flow Servomotor control

Fixed displacement pump Pilot pressure control

Variable displacement pump Heater

Check valve Cooler

Flow control valve Filter

Valve spools Electric motor

Relief valve Pressure switch

Valve with controls Pressure gauge

Hydraulic motor Temperature gauge

Reservoir Enclosure

Table 3. Common hydraulic components.

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