Precision Sheet Metal Workshop Types of press brakes · 20/07/2014 · Precision Sheet Metal...
Transcript of Precision Sheet Metal Workshop Types of press brakes · 20/07/2014 · Precision Sheet Metal...
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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
“Torque Tube Press BrakesThe torque tube ties the two end levers
together to achieve parallelism.
Cool huh!”
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“Down-acting press brakes,the hydraulic cylinders are above ram”
Up-acting hydraulic press brakes
“The ram comes up, Dude!”
“Tandem Hydraulic Press Brakes
But you ain’t see nothing yet !”
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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
Internal stop hydraulics
“ It’s like a mechanical but powered by hydraulics!This means no origin point!”
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“ Both hydraulic cylinders are control and flowcontrolled by a single directional valve”
“ Independent hydraulic control and flowto each cylinder”
How small is a Micron?
Modern ram accuracy
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Servo over Hydraulic
Drive methods
Axial Piston Pump
Direct Servo Drive
Drive methods
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Servo Belt 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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The stepper motor turns the ball screw while the smooth Bars guide the backgauge
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
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“When all the bends are off, the reference point can be moved”
The methods of forming
Air Forming
Bottom Bending
Coining
“All are different, all have a purpose!”
Approximant bending style accuracy
Bottom bending(+/- 1°)
Air forming(+/- 1°)
Coining(+/- 1°)
10x Air forming5x Air formingLeast tonnage
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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
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
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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
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
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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!
“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:
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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.
“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
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Material gauges
“16 Gauge tolerance zone.053 to .067”
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.”
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“With nesting, the grain direction can vary
from part to part.”
“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”
A short filmFrom the FMA , Featuring: Mr. Bob Butchart
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Film follow up
“Just a few things that need a little more discussion!”
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.
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Breaks two ways
Curves the flange.
Damages the bend angle.
“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!”