Download - Sheet Metal Design Guidelines

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

Download - Sheet Metal Design Guidelines

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