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7/24/2019 Sheet Metal Design Guidelines
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Design for ManufacturabilityDesign for Manufacturability
-- Sheet Metal GuidelinesSheet Metal Guidelines --
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Design for Manufacturability
Design for manufacturabilityis the process ofpro-actively
designing products to
(1) optimize all the manufacturing functions: production, assembly,
test, procurement, shipping, delivery, service, and repair, and
(2) assure the best cost, quality, reliability, safety & regulatory
compliance, and customer satisfaction.
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Incorrect Correct
Guidelines for Hole/Slot Location and Size
Pierced Hole Spacing
Pierced Hole Size
Incorrect Correct
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Guidelines for Hole/Slot Location and Size
Pierced Hole/Slot Location from Edge
Spacing between Pierced Hole and Bend
Incorrect Correct
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Normal method:Not recommended,
if close hole alignment is required
More accurate method: Pierce or
Drill holes after forming
Guidelines for Hole Alignment
Alignment
Requirement
Design will be based on: Kinds of Alignment required
Process Selection
Material Thickness variation
Spring Back
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Oversize or Oval Hole allows for
misalignment
Misalignment
Blank and Pierce
before forming
Pilot Hole assures blank centered in
forming die
Guidelines for Hole Alignment
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Guidelines for Narrow Projection
Incorrect Correct
Incorrect Correct
Narrow projections causes die
punches to be narrow and fragile.
This should be avoided.
Projections should be wider ifundergo bending or forming
operations.
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Guidelines for Bends
Fillet Corner
Missing
BendingRadius
Missing
Incorrect
Incorrect
With Proper Fillet& Bending
Radius
Undercut
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Guidelines for Stiffeners
Types of Beads Types of Offsets
Embossing Depth Limits
Cross Beads
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Types of Flanges
Straight Flange Width Guidelines
Guidelines for Stiffeners
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Guidelines for Draw
Probable Number of
Reductions
Draw Examples
Drawing Guidelines
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What is Spring Back & How to Avoid ?
(B) Corner Settings
(A) Corner Settings
(C) Beads
BEADS ON BENDS
REDUCES THE
SPRING BACK
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Grain Structure (to be taken care during Mfg)
Lugs parallel tograin: may crack
(not preferred)
Lugs at angle < 45
deg, formed
diagonal to grain;
fair practice
Lug perpendicular to
grain; recommended
practice
Form lugs at right angles to the direction of grains
Grain direction
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Factors Affecting Tolerance
Tolerances on Sheet Metal parts depends on several factors:
Part Function or Feature
Size of the Part
Material to be used (kind and thickness)
Metal spring-back variations (due to material temper and thickness
variations)
Press Operations to be performed
Die accuracy, die wear
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Key Guidelines for Design for Manufacturability:
Lesson Learnt from current / past programs
Design for easy Manufacturing, processing, and assembly
Adhere to specific process design guidelines
Avoid right/left hand parts
Design parts with symmetry
If part symmetry is not possible, make parts very asymmetrical
Design Should have feature for fixturing
Specify optimal tolerances for a Robust Design
Minimize Setups for Manufacturing
Key DFM Guidelines
Burrs :
General notes like "Remove all burrs" or
"Break sharp edges" which are not possibleon sheet metal as it needs expensive
process.
Curled, folded edges should be designed so
that the burr side is on interior of the bend.
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Example of Features (Bend & Chamfer)
SIDE BEND
WITH CHAMFER,
METAL TEARING
REDUCE AT CORNER
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Example of Features (Beads)
WITH BEADS ON BENDS REDUCES THE
SPRING BACK EFFECT TREMENDOUSLY
AND ALSO INCREASES STIFFNESS
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COLLAR ADDS STIFFNESS
TO PIERCED AREAS
EMBOSS TO IMPROVE STRENGTH
OF CLAMPING AREA
Examples of Features (Collar & Emboss)
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Examples of Features (Collar & Bends)
COLLAR / BENDS TO
IMPROVE STIFFNESS
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TRIANGULAR BEAD WILL
HAVE HIGHER STRENTH(due to higher section modulus)
U-BEAD TO TAKE CARE
FLATNESS AS WELL ASBEAR THE LOAD
FEATURE TO
LOCATE PIPE
RIB CONNECTED
WITH EMBOSSING
FEATURE WILL
HAVE GOOD
STRENGTH
Examples of Features (Emboss & Beads)
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TO IMPROVE STRENGTH & MAINTAIN
FLATNESS, EMBOSSING/COINING WILL BE
DONE AROUND PERIPHERRY OF FLARED HOLE
HEMING FOR STIFFNESS& BURR PROTECTION
Examples of Features (Emboss & Hem)
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Spot Welding
Recommended:
Spot weld diameter range from 3 mm to 19.05 mm (0.125to 0.75 in)
Spot welding is primarily used for joining parts upto 2mm(0.125 in) thickness
Dissimilar materials cannot be spot welded
Min spacing between spot welds ~ 10 x Stock thickness(Recommended to have 4 spacing for air cylinder spacing)
Distance from sheet edge to edge of spot = 3mm (min.)
Weld to form distance= Bend Radius + weld diameter
Ratio between metal thickness to be welded should be nogreater than 3:1
It is preferred to have all Spot welds in same axis
EDGE DISTANCE
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Spot Welding Spot Spacing
SPOT WELD SPACING
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CONTACTING OVERLAP
SPECIAL LOWER ELECTRODE
(for Sheet to Tube)
Spot Welding Contacting Overlap
ELECTRODE CLEARANCE
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Projection Welding
Recommended:
Projection weld diameter range from 3 mm to 19.05 mm(0.125 to 0.75 in)
Projection welding is used for section thickness ranges from0.5 to 3.2mm (0.02 - 0.125 in)
Min spacing between spot welds ~ 2 x Projection Diameter
(Recommended to have 4 spacing for air cylinder spacing)
Projections are to be placed on center of overlap (refercontacting overlap table)
Weld to form distance= Bend Radius + weld diameter
Ratio between metal thickness to be welded should be no
greater than 6:1
It is preferred to have all Spot welds in same axis
Projections are designed into thicker metal to be welded
Projections are sized on thinner metal to be welded
Projections are placed on material of higher conductivity Electrode clearance same as in spot welding
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Projection Welding Spacing & Projection Design
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Projection Welding Contacting Overlap
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Projection Welding Sheet to Tube
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Projection Welding Wire to Wire Spacing
Welding at the same time
should be within 1 inch radius
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Pipe Bending
Recommended:
Minimum Inside Bend Radius should be 1.5 - 2timesPipe Outer diameter (preferably to go for 2times to avoidwrinkles at bend)
Maintain Consistent bend radius for common tooling
Minimum thickness 1.2mm required for MIG welding
If bends not in same plane, minimum 2times pipediameter to be maintained for flat distance betweenbends.
If bends are in same plane, minimum a pipe diameterto be maintained for flat distance between bends.
MINIMUM INSIDE
BEND RADIUS
MINIMUM FLAT
BETWEEN BENDS
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Thank You