© Copyright Engineering Research Center for Net Shape Manufacturing, 2012 Stamping Group CPF Servo...

© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group

CPFCPF

Servo Press TechnologyApplications for Today and Tomorrow

Eren Billur and Taylan AltanCenter for Precision Forming

The Ohio State University www.cpforming.org & www.ercnsm.org

August 23, 2012

http://www.cpforming.org/


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Servo-Drive Presses- Outline

• Introduction• Servo-Drive Characteristics• Servo-Drive Press Mechanisms• Applications• Die Cushions• Summary/ Future Outlook


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(4) Other Process at BDC(Multi Process)

(4) Other Process at BDC(Multi Process)

(5) Prevention of noise and shock at contact or breakaway of tools

(5) Prevention of noise and shock at contact or breakaway of tools

(6) Synchronize withfeeder

(6) Synchronize withfeeder

Crank or Link pressFixed Motion

Time

Sli

de

Po

sit

ion

Cycle time of mechanical pressCrank or Link press

Fixed Motion

Time

Sli

de

Po

sit

ion

Cycle time of mechanical press

(2) Best speedfor materials


For

min

g le

ngth



For

min

g le

ngth

(3) Improve accuracy bydwelling at BDC


Standstill at BDC



Standstill at BDC

(1) Variablestrokelength

(1) Variablestrokelength M

inim

um

str

oke

leng

th

(1) Variablestrokelength

(1) Variablestrokelength M

inim

um

str

oke

leng

thCycle time of

Free motion press

Free motion press

Cycle time of Free motion press

Cycle time of Free motion press

Free motion press

The flexibility of slide motion in servo drive (or free motion) presses. [Miyoshi, 2004]

Servo-Drive Characteristics


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Servo-Drive Characteristics

• Precise ram position and velocity control, anywhere in stroke-easier set up

• Adjustable stroke length (TDC and BDC)• Ram position/ velocity can be synchronized with

automatic part transfer• In deep drawing, cycle times can be shorter than in

mechanical presses• Considerable savings in energy• Dwell at BDC/ restriking/ vibrating and variable blank

holder force (BHF)• Max. motor torque available during the entire stroke


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Servo-Drive Mechanisms

• Low Torque/ High RPM Motors Use Ball Screws or/and Linkage Mechanisms

• High Torque/ Low RPM Motors Use Existing Crank and/or Link Press Drives


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High RPM/ Low TorqueMotor Drive 1/2

Servo Motor

Ball Screw

Slide

Bolster

Linear sensor

Timing belt

Schematic of servo press with high speed-low torque servo-motors with belt and ball screw drive. [Miyoshi, 2004]


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Schematic of servo press with high speed-low torque servo-motors with linkage drive. [Miyoshi, 2004]

Servo Motor

Slide

Eccentricload

Right / Left independent control

Linearsensors

Servo Motor

Linearsensors

Slide

Eccentricload

Right / Left independent control

Linearsensors

Servo Motor

Linearsensors

High RPM/ Low TorqueMotor Drive 2/2


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a) C-Frame Servo Press (Aida)

Power Source Balancer tank Main gear

Servomotor

Capacitor

Drive Shaft

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Low RPM/ High TorqueMotor Drive 1/2

b) Stroke-Time program for warm forming of Al and Mg sheet


CPFCPFLow RPM/ High TorqueMotor Drive 2/2

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Servo-Press Drive Using Conventional Crank Mechanism Courtesy- Aida


CPFCPFHybrid Servo Press

Block diagram of a hybrid servo press (ABB)10


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Simplified 3D-view of a hybrid servo press, seen from above (ABB)

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Modern Stamping Lines UsingLarge Servo-Drive Presses

• BMW- Leipzig & Regensburg (Germany) – SCHULER 2009 - 2500 ton servo-drive drawing press - 17 SPM

• BMW – Leipzig, Regensburg and Shenyang (China) – SCHULER – 2012 – 7 tandem lines on order.

• HONDA - Suzuka (Japan) – AIDA 2009 – 2500 ton tandem line – 18 SPM

• Kamtek/COSMA – AIDA 2011 - 3,000 ton, 30 strokes/min• Honda-America – Ohio and Alabama - AIDA 2012 - 2,500

ton tandem lines• Hyundai – Korea – ROTEM 2012 – 1000 ton Tandem line• Others ?


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Improved Formability

Improved Productivity Energy-Saving

・ System with optimized press forming requirements for each product

・ Press-to-Press Loading Motion: System is optimized for each product.

・ Die cushions have an energy regeneration system

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Schematic of Servo-press tandem line (Aida/Honda)2500 ton/ 18 SPM (2009)


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Servo-press tandem line (Schuler/BMW)2500 ton/ 17 SPM (2009)

One drawing press + 5 presses for follow-up operations

Source:BMWarchive.de

Technical Data:

Total press force: 10,300 tons

Drawing press force: 2,500 tons

Total length of press line: 98 meters

Length o press: 34 meters

Strokes per minute: 17

Source:Schulergroup.com


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Servo Tandem Line at Suzuka (Japan) Plant(Honda)


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Comparison between the slide motions of an 1100 mechanical and servo drive press for identical slide velocity during forming [Bloom, 2008].

Applications- Deep Drawing 1/3(Courtesy- Schuler)


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Decrease in cycle time by reducing the stroke length and operating the servo press in “pendular” mode (progressive die stamping, 200% increase in output) [Bloom, 2008]



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Decrease in cycle time as well as in impact speed using a servo press (150% increase in output) [Bloom, 2008]



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Side Panel Outer Deep Drawing Case Example (Honda)


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Applications- Blanking/ Ironing

Slide motion used for partial and finish blanking [Miyoshi, 2004 / Komatsu]

Precision Formed Part a) partially blanked, b) finished blanked [Miyoshi, 2004 / Komatsu]


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Item : Eye glass frameMaterial : Titanium based Shape-memory Alloy

By multiple step motion,Three processes turnedinto single process.

Three processes had been required to control the springback.

Multiple step motion

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Applications- Reduction of Springback(Courtesy- Komatsu/ Hamamoto)


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IT IS POSSIBLE TO DIGITALLY SET THE OPTIMAL WORKING SPEED, THEREBY INCREASING DIE LIFE.

SUS304

PIERCING A HOLE WITH A SMALLER DIAMETER THAN THE MATERIAL THICKNESS (INCLINED HOLE PIERCING)

Al STEPPED HOLE PIERCING(80% BURNISHED SHEAR FACE)

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Applications- Blanking/ Ironing Courtesy – Aida)


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SINCE THE PRESS CAN BE RUN AT LOW SPEEDS, IT IS NOT NECESSARY TO SWITCH TO A LARGER CLASS PRESS TO FORM HARD-TO-DRAW MATERIAL.

WRINKLES CAN OCCUR WHEN THERE IS INSUFFICIENT PRESS RIGIDITY AND THE DRAWING SPEEDS ARE NOT OPTIMIZED.

DRAW WRINKLES CAN BE AVOIDED BY SLOWING DOWN THE DRAWING SPEED. (SINCE WORKING ENERGY IS ALWAYS AVAILABLE, THE PRESS DOES NOT STOP EVEN AT INCHING SPEEDS.) 23

Applications- Blanking/ Ironing (Courtesy – Aida)


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IT IS POSSIBLE TO SET THE OPTIMAL FORMING MOTION AND TIMING FOR SECONDARY PROCESSES.

(STAKING AND ASSEMBLY)

ASSEMBLY OPERATION OF A SQUARE NUT (M5) IN A BRACKET DURING A PROGRESSIVE FORMING OPERATION

STAKING A PIN ( 3.6) IN A CHASSIS ∅DURING A PROGRESSIVE FORMING OPERATION

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Applications- Auxiliary Operations (Courtesy – Aida)


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Tool and process design guidelines to improve formability

Aida Servo Press (used in warm forming of Al, Mg and Ti sheet)

Power Source Balancer tank Main gear

Servomotor

Capacitor

Drive Shaft

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Applications- Warm Forming of Al, Ti, Mg, and SS


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AL 5754- O

T (oC) LDR

RT 2.1

250 2.5

300 2.9

T (oC) LDR

RT 2.1

275 2.5

275 2.9

AL 5052-H32

Preliminary results (Velocity range : 2.5-50mm/sec)

Note : RT: Room temperature, LDR : Limit draw ratio

Cup Diameter : 40mm26

Applications- Warm Forming of Al


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T (oC) LDR

RT -

275 2.6

275 3.2

Mg AZ31-O

Preliminary results (Velocity range : 5-50mm/sec)

Note : RT: Room temperature, LDR : Limit draw ratio

Cup Diameter: 40mm

T (oC) LDR

310 2.5

Ti (Grade 1)

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Applications- Warm Forming of Mg and Ti


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Press slide motion used in warm forming processes (TDC - Top Dead Center, BDC – Bottom Dead Center)

Warm formed lap top case from Mg alloy(Courtesy – AIDA)

Applications- Warm Forming of Mg Lap Top Case


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Die

Cus

hion

For

ce (

kN)

29Elimination of Pressure Surge in the Die Cushion

Servo-Hydraulic Cushion (Courtesy-Aida)


CPFCPFCapabilities of the Self-Driven Hydraulic Servo Cushion

• pre-acceleration to reduce the impact speed between the die and blank holder

• variable pressure / force capability to control blank holder force/pressure during stroke

• prevention of momentary return of the cushion after BDC to avoid pressure on the top of the part


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SMS/M

PowerDirection

Closed Hydraulic Circuit

Power Regeneration: Approx. 70%

Pump Rotation Direction

Motor Torque Direction

Pressure Sensor

Linear Scale

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Servo-Hydraulic Cushion (Courtesy-Aida)

During Down Stroke, Cushion Pressure Generates Power


CPFCPFAdvantages of Servo- Press Technology- Applications in Forming AHSS -

1. Major Challenges in Forming AHSS (DP, TRIP, TWIP) include:

• lower formability (ductility) and higher probability of fracture• variations in mechanical properties form batch to batch• higher forming forces and high sheet/die interface pressures &

temperatures• Excessive tool wear, rapid increase in down-force and large

reverse tonnage• large springback due to large tensile strength

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2. Precise Ram Position (including dwell) and velocity control

• allows for easier die set-up• prevents noise and shock when the ram is contacting the

workpiece (hydraulic cushion with pre-acceleration)• improves formability and reduces fracture by reducing ram

velocity during deformation (drawing, stretching and bending), improves die/sheet lubrication by reducing temperature increase at sheet/die interface

• reduces shock loading and reverse tonnage in blanking, improves tool life

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3. Dwell at BDC and Pendulum Motion allows:

• dwell at BDC and restriking quickly through pendulum motion before the formed material fully strain hardens, reduces springback (die design is still very important)

4. Adjustable Stroke Length (TDC to BDC):

• provides flexibility so that in the same press, drawing, blanking and coining can be conducted with maximum productivity (high strokes/min)

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5. Ram Position/Velocity can be:

• synchronized with automatic (or robotic) part transfer to increase strokes/min

• adjusted to maximize strokes/min while maintaining lower ram velocity during forming stage

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CPFCPFServo-Drive Press TechnologySummary / Outlook

• Gap presses up to 150 ton are in production (15+ years)• Straight Side stamping presses up to 3000 ton are already

built• Direct drive (high torque) motors and energy recovering

cushions are used• High speed automotive stamping transfer presses (18

strokes/min)/ Schuler-BMW/ Aida-Honda and Cosma / Komatsu-Toyota & others

• Novel tool design techniques for servo drive technology are being developed

• Servo-drive presses will greatly contribute to improving the technology for forming AHSS and Al alloys

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CPFCPFQuestions/Comments

Taylan Altan, Professor and Director

Center for Precision Forming (CPF)

www.cpforming.org / www.ercnsm.org

The Ohio State University, Columbus, OH

Email: [email protected], Ph: (614) 292 5063

Source: Chapter 11 – Electro-mechanical

Servo-Drive Presses in “Sheet Metal Forming, Fundamentals”,

Vol. 1, by Altan/Tekkaya, ASM International, www.asminternational.org

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http://www.asminternational.org/

© Copyright Engineering Research Center for Net Shape Manufacturing, 2012 Stamping Group CPF Servo...

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