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Precision Sheet Metal WorkshopTypes of press brakes

Stamping press

Press brake

The two types of press’s

Pneumatic Press BrakesAir powered

Hand Press BrakesLever powered

Hand Press BrakesScrew powered

Hammer and viceInertia powered

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Parts of the Press Brake

Courtesy of Trumpf

Parts of the Press Brake

Courtesy of Trumpf

The mechanical press brake

Forming power is provided by a clutch and flywheel assemblyand is capable of 150% of rated tonnage at the bottom of the stroke

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“A properly run mechanical press brake requires:

•Stopping just past TDC

•Stopping before entering the die space”

Mechanical are dangerous… Never run non-stop “!

“These machines have claimed more fingers, hands and arms than any other type of press brake!

“They’re still being made in India and China…

I have no idea why?”

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A Hydro-mechanical …

•Provided full power at any point in the stroke

•Reversible at any point in the stroke

•Often accompanied by early controllers

Circa: 1970’s

Hydra-Mechanical (Hydro)

Power for this style brake is provided by a hydraulic motor attached to an eccentric which drives the up and down motion

The bushing that killed the beast

Too much clearance

Gravity holds ram down. Runningclearance on bottom

Operation forces the clearanceto move to the top

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The Bell Crank

“Power is provided by a single hydraulic

cylinder”

A great design for heavy tonnage applications

Rocker style

“Mechanical leverage increases accuracy and power”

Fulcrum point

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“Torque Tube Press BrakesThe torque tube ties the two end levers

together to achieve parallelism.

Cool huh!”

“Down-acting press brakes,the hydraulic cylinders are above ram”

Up-acting hydraulic press brakes

“The ram comes up, Dude!”

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“Tandem Hydraulic Press Brakes

But you ain’t see nothing yet !”

And just when you thought you’d seen big

•50 foot bed

•2.5 inch thick material

•60,000 metric tons of pressure

Some hydraulics use a “Positive Stop” mechanism

These hydraulics work very similar to a mechanical

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Internal stop hydraulics

“ It’s like a mechanical but powered by hydraulics!This means no origin point!”

“ Both hydraulic cylinders are control and flowcontrolled by a single directional valve”

“ Independent hydraulic control and flowto each cylinder”

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How small is a Micron?

Modern ram accuracy

Servo over Hydraulic

Drive methods

Axial Piston Pump

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Direct Servo Drive

Drive methods

“Serpentine belts are used to multiply the tonnage”

Serpentine Belt

Drive methods

Riding on the up acting ram.

Free-standing

Robotics

Drive methods

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Robots

Setting the origin pressure

“The controller expects the press brake to be origin’ed correctly”

“Some controllers origin in on top of the material”

Top origin

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“Some machines see “Zero” at full open-height”

Open-height

“Be sure to have enough tooling to not violate the tons per foot rule.”

Safety first

Small tools and Press brake origin

“Even if extra tooling needs to be added to bring the press brake to the required pressure…

It’s worth the time and effort!”

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Manually adjusted Backgauge

“In the old days we had to clamp and tap !”

“Gear lash is a real concern”

Move directly to position, error (lash) works against you

Move past and then into position, error (lash) works with you

Error (lash)

Error (lash)

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Backgauge axis

Labels can vary by manufacturer

Gauge Blocks

Backgauge referencing, for standard American planed tooling

Cutting bed

The cutting head

The planer

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“Hey, here’s a tip…Use a calibrating tool!”

“Just one of the advantages of precision groundThey're completely reversible!”

Modes of operation

“What are they, which is best? Lets have a look at the differences”

Manual data input (MDI)

Angle mode

Graphics mode

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MDI: Manual data input

“MDI requires the least amount of information”

Note: the number of lit up functions (4)

Depth of penetration

Backgauge location

Backgauge position

Lower limit setting

Angle mode

“Angle mode means, the most amount of required information.

Controller makes decisions based on data and adjusted in degrees.”

Note: the number of lit up functions (14) Including:

slow bend speeds

tensile strength

die angle and radius, etc.

“Angle and graphic modes require theOpen Height to be much bigger than depth mode;

Reaction times

it needs time to react…”

Open height

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“ You know, it takes time to react!”

Manual data input (MDI) Angle mode

“Compare the amounts of required data.”

Mode comparison

Tooling and Program Libraries

“To be fair, newer controllers have the capability of using tool libraries and

data base storage.”

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Off-line programming

“Tool libraries coupled with practical working knowledge

makes off-line programming possible”

“In graphic mode the computerdraws a picture, data is adjusted in degrees.”

Selection of Material, tooling and bending method

Programming

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Information for top and/or bottom tool

Programming, cont.

Programming / Editing

Profile

View

Section

Selection

Tooling

Geometry

Editor

Collision-monitoring for every single bend

Programming, cont.

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Tool setting plan:

Programming, cont.

“Regardless of the sophistication of your controller…The simpler the program the easier it is to maintain”

“Programming the backgauge… is easy!”

The program controls

Using stepper motors

The shaft movement

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Backgauge adjustments

Moving the reference point, moves the program

What you see and what the machine sees

A) Your view 4.000B) The Machines view 0.000

A) Your view 3.000B) The Machines view 1.000

After you’ve adjusted the Backgauge

Before you’ve adjusted the Backgauge

“When all the bends are off, the reference point can be moved”

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The methods of forming

Air Forming

Bottom Bending

Coining

“All are different, all have a purpose!”

Approximant bending style accuracy

Bottom bending(+/- ½)

Air forming(+/- 1°)

Coining(+/- ¼)

10x Air forming5x Air formingLeast tonnage

Tonnage Capacity Of Your Equipment

Range Of Materials To Be Formed (Thickness & Type)

Machine Accuracy (Repeatability) Angular Tolerances

How and Were Blank Sizes Calculated ( IR Results In BD)

Considerations when choosing a forming method

Quality Grade Of Tooling Required For Adequate Performance

Standard Or Special Profile

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The Attributes of Coining

Punch is sharp

The punch tip penetrates the neutral axis

Tonnage is excessive

Only practiced now by accident

Compressive stress applied to bending region increases the amount of plastic deformation. This reduces the

amount of springback.

Coining example

Inside

Outside

Coining Advantages

Produces Highly Consistent Angles (¼°)

Realigns Molecular Structure Of Material To Eliminate Springback

Can Produce Very Sharp Inside Radii

Does Not Require Highly Accurate Machines Or Tooling

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Coining Disadvantages

Requires high-tonnage machines

The need for extreme tonnages could lead to potentially hazardoustool failure or machine damage

Specific tool sets are required for each angle and material thickness

Reduction in material thickness weakens bend

Severe part marking may require secondary operations

The attributes of Bottom bending

Works in light gauge materials

Sets the radius and angle

All the consistency of coining withoutthe excessive tonnage

Capable of reproducing inside bend radiiup to three times the material thickness

The attributes of Air forming

Least amount of tonnage

Inside radius produced as apercentage of V-die or channel die opening

When done correctly, it’s justas accurate as any other method

This is the method recommend by all major press brake manufactures!

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“A single tool set can be used to form a wide variety of material thickness’s and bend angles.”

AIR FORMING Advantages

Parts Are Formed With Relatively Low Tonnage

Extends Tooling Service Life

Reduces Stress On Machinery

Reduces Die Marking

Increases Safety

AIR FORMING Disadvantages

Material Thickness

Tensile Strength

Ram Position

Tool Accuracy

Grain Direction

Bend accuracy is adversely affected by any uncompensated variations in:

Though not recommended, there are “Coining or Bottoming” modeson many newer press brakes.

Coining mode is not coining as described here, instead both of these terms are describing “bottom bending” in practical use.

In this mode, the press brake will reverse on tonnage.

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“Inside radii will always be equal to or larger than 63% of the material thickness, including

the use “sharp” bends!”

Air forming

Air forming in action

Predictable inside radius

Sharp punch radius

Material gauges

“16 Gauge tolerance zone.053 to .067”

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Roller deflection

“Sheets will be thicker in the center than at the edges”

“Significant thickness variations canoccur within the sheet as well as

from sheet to sheet.”

“With nesting, the grain direction can vary

from part to part.”

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“Remember a sharp bend is a function of the material and not necessarily the radius of the punch tip.

Attempting to bend the material to sharp can cause many a problem”

Film follow up

“Just a few things that need a little more discussion!”

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Back-breaking

“Back-breaking caused by the wayin which the part was held.”

Back-breaking – interference

Part encounters the punch.

Forces the part to bend back.

Breaks two ways

Curves the flange.

Damages the bend angle.

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“Coining was not shown due to the possibility of damage to the press brake, the tooling and/or Bob!”

Conclusions

“Which method, type of bend or machine is right for you.. It just depends on your needs and knowledge!”