Transcript Technical Drawing with Engineering Graphics, 14e, Chapter 22

WELDING
REPRESENTATION
C H A P T E R T W E N T Y- T WO
OBJECTIVES
1. Describe the various welding processes.
2. Draw the common welding symbols.
3. Dimension a welding drawing using standard ANSI welding notation.
4. Identify and draw a fillet weld, groove weld, back weld, spot weld,
seam weld, projection weld, and flash weld.
5. Describe the use of welding symbols in CAD drawings.
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Welding
Welding is widely used in fabricating machine parts or other structures that formerly would
have been formed by casting or forging. Structural steel frames for buildings, ships, and
other structures are often welded.
Welding symbols on a mechanical drawing provide precise instructions for the welder. The
weld type and the location of each weld must be clearly defined using standardized
symbols. CAD libraries of welding symbols can simplify the drawing process. Welding
templates can speed the process of drawing by hand.
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Welding Processes
• Arc welding (SMAW, Shielded Metal Arc Welding, GMAW Gas Metal Arc Welding, plus others…)
• Resistance welding (RSW, Resistance Spot Welding, and others…)
• Gas welding (OFW, Oxy Fuel Welding)
RSW
GMAW
OFW
An automobile frame is welded on a robotic automobile
assembly line. (Courtesy of Vladimir Pcholkin/Stone/Getty images.)
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UNDERSTANDING A WELDING
SYMBOL
A welding symbol added to the drawing has many different features that specify
each detail of the weld. The items that can be specified are:
• Type of weld
• Process
• Depth of bevel, size, or strength for
some weld types
• Groove weld size
• Finishing designator
• Contour
• Groove angle
• Root opening
• Length of weld
• Number and pitch (center to center
spacing) of welds
• Whether the weld is to be field
welded (done on site)
• All-around indicator
• Which side of the material is to be
welded
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WELDED JOINTS
Butt joint
A number of different types of welds are applicable
to each type of joint, depending on the thickness of
metal, the strength of joint required, and other
considerations.
Lap joint
T-joint
Edge joint
Corner joint
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Basic Welds and Symbols
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WELDING SYMBOLS
The basic element of the symbol is the “bent” arrow The arrow points to the joint
where the weld is to be made Attached to the reference line, or shank, of the arrow is
the weld symbol for the desired weld.
The weld symbol is placed below the reference line if the weld is to be
on the arrow side of the joint, or above the reference line if the weld is
to be on the other side of the joint. If the weld is to be on both the
arrow side and the other side of the joint, weld symbols are placed on
both sides of the reference line.
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Supplementary Symbols
Fully penetrate
End the weld at the starting
point, or ALL THE WAY
AROUND
A back strap or backing
plate is placed onto the
back of the joint
Consumable insert is melted into
the final weldment
Weld at the final construction
site (Not in the “shop”)
Final contour should be flush
(possibly by grinding or
machining)
Final contour should be concave
(possibly by grinding or machining)
Final contour should be
Convex (possibly by
grinding or machining)
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The Welding Symbol Tail
Reference to a specification, process, or other supplementary information
is indicated by any desired symbol in the tail of the arrow. Otherwise, a
general note may be placed in the tail. If no reference is indicated in the
symbol, the tail may be omitted.
UNLESS OTHERWISE INDICATED,
MAKE ALL WELDS PER
SPECIFICATION NO.XXX
Resistance Spot Weld and an Electron Beam Weld are
called out in the Tail of the Welding Symbols.
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FILLET WELDS
The size of the weld is the length of one leg, For fillet welds on both sides of a
joint, the dimensions should be indicated on both sides of the reference line,
whether the dimensions are identical or different.
.5 Leg lengths
Dimensioning of Fillet Welds
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Fillet Weld Length and Pitch
TWO inch length of weld, with a FIVE inch
pitch (center-to-center). The .25
represents the weld leg length.
THREE inch length of weld, with a TEN
inch pitch (center-to-center). The .25
represents the weld leg length.
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Surface Contour and Fillet Welds
Fillet weld with a
Convex Finish by
Machining
Fillet weld with a
Flush Finish
Fillet weld with a
Flush Finish by
Grinding
KEY:
C= chipping
G = grinding
M = machining
R = rolling
H = hammering
Fillet weld with a
Flush Finish by
Machining
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Fillet weld with a
Flush Finish by
Chipping
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GROOVE WELDS
Symbols and their Result
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BACK OR BACKING WELDS
A back or backing symbol opposite the groove weld symbol indicates bead-type
welds used as back or backing welds on single-groove welds.
Back or Backing Weld Symbols
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SURFACE WELDS
The surface weld symbol indicates a surface to be built up with single- or multiple-pass
bead type welds. Because this symbol does not indicate a welded joint, there is no
arrow-side or other-side significance, so the symbol is always drawn below the reference
line. Indicate the minimum height of the weld deposit at the left of the weld symbol, except
where no specific height is required. When a specific area of a surface is to be built up, give
the dimensions of the area on the drawing.
Surfacing (or Hardfacing)
A Plow Blade
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PLUG AND SLOT WELDS
The same symbol is
used for plug welds
and slot welds.
If it is in the arrow-side
member, place the
weld symbol below the
reference line
If it is in the other-side
member, place the
weld symbol above the
line
A plug weld is understood to fill
the depth of the hole unless
its depth is indicated inside the
weld symbol
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SPOT WELDS
The size of a spot weld is its diameter. If you need to indicate the minimum
acceptable shear strength in pounds per spot, instead of the size of the weld, place
this value at the left of the weld symbol. The pitch would be placed to the right of the
weld symbol if needed .
.
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SEAM WELDS
The seam weld symbol, with the welding process indicated in the tail, The size of the seam
weld is its width. Show this value at the left of the weld symbol, on either side of the
reference line. If you need to indicate the minimum acceptable shear strength in pounds
per linear inch, instead of the size of the weld, place this value at the left of the weld
symbol, and show the length of a seam weld at the right of the weld symbol
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PROJECTION WELDS
In projection welding, one
member is embossed in
preparation for the weld.
Projection welds are
dimensioned by either size
or strength. The size is the
diameter of the weld.
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FLASH AND UPSET WELDS
Flash and upset weld
symbols have no
arrow-side or otherside significance, but
the supplementary
symbols do.
Note that the process reference for flash
welding (FW) or upset welding (UW)
must be placed in the tail of the symbol.
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WELD SYMBOLS FROM CAD
Most CAD systems provide a way to quickly generate weld symbols to
place in your drawing.
SolidWorks Weld Symbol Dialog Box
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