Transcript
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Sheet-Metal
A large proportion ofproducts around us aremade out of sheet-metal
Electronic enclosures,white-ware, cars,hardware, computercomponents, robots, etc.
Most common metalsused are aluminium andsteel
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Sheet-Metal Manufacturing
Methods CNC Fabrication Laser cutting
Bending Hard-tooled
Spun
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Bending
Bending is a manufacturing process by whichmetal can be deformed by plastically deforming
the material and changing its shape. The material
is stressed beyond its yield strength but below its
ultimate tensile strength.
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Bending
Bending is done using Press Brakes or bendbrakes. Press Brakes can normally have acapacity of 20 to 200 tons to accommodatestock from 1m to 4.5m
The material is placed on the die, andpositioned in place with stops and/or gages. Itis held in place with hold-downs. The upperpart of the press, the ram with theappropriately shaped punch descends and
forms the v-shaped bend.
Programmable back gages, and multiple diesets currently available can make bending avery economical process
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Types of Bending
Bending
Blank
Punch
DieDie
Punch
Blank
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Types of Bending
Bottoming
Blank
Die
Punch
Blank
Punch
Die
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Types of Bending
Coining
Die
Blank
Punch
Blank
Punch
Die
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Bend Allowances
When sheet metal is bent, the inside surface ofthe bend is compressed and the outer surface ofthe bend is stretched. Somewhere within thethickness of the metal lies its Neutral Axis, which
is a line in the metal that is neither compressednor stretched
The location of the neutral line varies dependingon the material itself, the radius of the bend, theambient temperature, direction of material grain,and the method by which it is being bent, etc.The location of this line is often referred to as theK factor
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Bend Allowances
K-factor is a ratio that represents thelocation of the neutral line with respect
to the thickness of the sheet metal part.
T
t
K-Factor = t /T
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Bend Allowances
If you have a 100mm long flat bar of2mm Aluminium and bend it at 90 deg
in the middle, the 2 legs will NOT
measure 50mm each. In fact they will
measure around 51.8mm each
Length X
Length
YTotal Flat Length
STEP 1 STEP 2
Thickness
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Bend Allowances vs Bend Deductions
Lt= L1 + L2 + BA L
t= L1 + L2 - BD
where:
Lt = total flat length
L1 and L2 are shown in the
illustration
BA = bend allowance value
where:
Lt = total flat length
L1 and L2 are shown in the
illustration
BD = bend deduction value
L2
L1 BEND
ALLOWANCE
L2
L1 BEND
DEDUCTION
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Calculating Bend Allowances
BA= A(R + KT) /180where:
BA = bend allowance
R = inside bend radiusK = K factor, which is t / T
(usually 0.25-0.5)
T = material thickness
t = distance from inside face
to neutral line
A = bend angle in degrees
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Calculating Bend Deductions
BD = 2 x OOSB - BA
OSSB = tan(A/2) x T + R
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Sheetmetal Rules
Rules in SolidWorks for Sheetmetal:
Parts have a constant thickness
Thickness faces are always perpendicular to thebend faces (material is never sheared at an angle)
The bend faces are limited to cylindrical, planar,conical shapes
The exceptions are form tools and Lofted Bends
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The Flatten Test
Can it be flattened?
Why?? Or Why not??
Ans. = Yes, All cones
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The Flatten Test
Can it be flattened:
Why?? Or Why not??
Ans. = No, Spline
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Sheetmetal Functions
InsertBen
ds
FlattenBen
ds
NoBen
ds
R
ip
B
aseFlange/T
ab
MiterFlan
ge
Fo
ld
Unfo
ld
SketchedBen
ds
EdgeFlan
ge
ClosedCorn
er
He
m
Bre
ak/TrimCorn
er
J
og
LoftedBe
nd
New SchoolOld School
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Two Basic Methods
There are two basic methods SolidWorks
sheetmetal can be used:
Model the part using regular SolidWorks
functions like extrude, revolve, etc.
Generally used only for imported parts and
rolled parts
Start with an open sketch and a Base
Flange feature
Much more powerful
Way more options
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Base Flange
Base Flange requires an open sketch
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Edge Flange
Select an edge, hit the
button, pull the flange
Flange Length and
Position buttons are self
explanatory
Offset allows
you to create a
dogleg flangeYou can also
change the angle
of the flange
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Edge Flange
Edit Flange Profile allows you to change the
sketch of the flange and alter the shape
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Miter Flange
Miter Flange requires an open sketch on the
edge of the part
Sketch
Propagate to
tangent
Allowance for
flattening
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Fold / Unfold
To put a feature across a bend, unfold the bend,
put in the feature, then fold it again
Use offset entities tomake slots!
Select face to
remain stationary
Collect finds all theunfolded bends
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Tab
There are no settings for the Tab function,
it just adds a tab to the sketch face
Sk t h d B d
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Sketched BendDraw a line all the way across the part
Dont cross bend lines
Line must go all the way across
Control bend angle and direction
Black dot selects stationary face
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JogLike a double sketched bend
Allows you to keep the original length of the tab oradd material as it jogs
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HemsButtons and dimensions are self explanatory
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Corner Break
Chamfers or rounds sharp outside corners
Puts you into a selection filter model to pick short
edges across the thickness and bend faces
Selecting a face breaks all corners on face
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Forming ToolsForming tools drag and drop from the Design Library
Forming tools maintain a constant thickness (theymay add mass to the part)
Red faces create holes in the part
Only works on sheetmetal parts
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Old SchoolChamfers or rounds sharp outside corners
Build box shellRip
corners
Insert
bends
Flatten
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Finer Points
How does SW handle bend allowances?
K Factor
Bend Allowance
Bend DeductionBend Table
A very good mathematical description of
how SW handles bend allowances isavailable as a Knowledge Base article on
the SW website.
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Finer PointsHow does SW handle bend reliefs?
Tear = zero thickness cut
Rectangular = default depth is half of thickness
Obround = full round cut
These settings are kept in the Sheetmetal feature in
the tree.
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Finer Points
Sheetmetal automatically creates a link value
called thickness, which allows the thicknessof the entire part to be changed at once
Link Value symbol
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