Servo Press Technology Applications for Today and Tomorrow

© Copyright Engineering Research Center for Net Shape Manufacturing, 2012

Stamping Group

CPF

Servo Press Technology

Applications for Today and Tomorrow

Eren Billur and Taylan Altan

Center for Precision Forming

The Ohio State University

www.cpforming.org & www.ercnsm.org

Webinar – MetalForming Magazine

August 23, 2012 – 2:00-3:00 pm EST

http://www.cpforming.org/


Stamping Group

CPF

2

Servo-Drive Presses- Outline

• Introduction

• Servo-Drive Characteristics

• Servo-Drive Press Mechanisms

• Applications

• Die Cushions

• Summary/ Future Outlook


Stamping Group

CPF

3

(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 with

feeder

(6) Synchronize with

feeder

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 speed

for materials

(2) Best speed

for materials

For

min

g l

ength

(2) Best speed

for materials

(2) Best speed

for materials

For

min

g l

ength

(3) Improve

accuracy by

dwelling at BDC

(3) Improve

accuracy by

dwelling at BDC

Standstill at BDC

(3) Improve

accuracy by

dwelling at BDC

(3) Improve

accuracy by

dwelling at BDC

Standstill at BDC

(1) Variablestrokelength


Min

imu

m s

troke

leng

th



Min

imu

m s

troke

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


Stamping Group

CPF

4

Servo-Drive Characteristics

• Precise ram position and velocity control, anywhere in

stroke

• 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


Stamping Group

CPF

5

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


Stamping Group

CPF

6

High RPM/ Low Torque

Motor 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]


Stamping Group

CPF

7

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 Torque

Motor Drive 2/2


Stamping Group

CPF

a) C-Frame Servo Press (Aida)

Power Source Balancer tank Main gear

Servomotor

Capacitor

Drive Shaft

8

Low RPM/ High Torque

Motor Drive 1/2

b) Stroke-Time program for warm

forming of Al and Mg sheet


Stamping Group

CPF Low RPM/ High Torque

Motor Drive 2/2

9

Servo-Press Drive Using Conventional Crank Mechanism

Courtesy- Aida


Stamping Group

CPF Hybrid Servo Press

Block diagram of a hybrid servo press (ABB) 10


Stamping Group

CPF Hybrid Servo Press

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

(ABB) 11


Stamping Group

CPF

12

Modern Stamping Lines Using

Large 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 ?


Stamping Group

CPF

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

13

Schematic of Servo-press tandem line (Aida/Honda)

2500 ton/ 18 SPM (2009)


Stamping Group

CPF

14

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


Stamping Group

CPF

15

Servo Tandem Line at Suzuka (Japan) Plant

(Honda)


Stamping Group

CPF

16

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)


Stamping Group

CPF

17

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]


(Courtesy- Schuler)


Stamping Group

CPF

18

Decrease in cycle time as well as in impact speed using a servo press (150%

increase in output) [Bloom, 2008]


(Courtesy- Schuler)


Stamping Group

CPF

19

Side Panel Outer Deep Drawing Case

Example (Honda)


Stamping Group

CPF

20

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]


Stamping Group

CPF

Item : Eye glass frame

Material : Titanium based Shape-memory Alloy

By multiple step motion,

Three processes turned

into single process.

Three processes had been

required to control the

springback.

Multiple step motion

21

Applications- Reduction of Springback

(Courtesy- Komatsu/ Hamamoto)


Stamping Group

CPF

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)

22

Applications- Blanking/ Ironing Courtesy – Aida)


Stamping Group

CPF

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)


Stamping Group

CPF

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

24

Applications- Auxiliary Operations (Courtesy – Aida)


Stamping Group

CPF

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

25

Applications- Warm Forming of

Al, Ti, Mg, and SS


Stamping Group

CPF

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 : 40mm 26

Applications- Warm Forming of Al


Stamping Group

CPF

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)

27


Mg and Ti


Stamping Group

CPF

28

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)


Mg Lap Top Case


Stamping Group

CPF

Die

Cush

ion F

orc

e (k

N)

29 Elimination of Pressure Surge in the Die Cushion

Servo-Hydraulic Cushion

(Courtesy-Aida)


Stamping Group

CPF Capabilities 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


Stamping Group

CPF

S

M

S/M

Power

Direction

Closed Hydraulic Circuit

Power Regeneration: Approx. 70%

Pump

Rotation

Direction

Motor Torque

Direction

Pressure Sensor

Linear

Scale

31

Servo-Hydraulic Cushion

(Courtesy-Aida)

During Down Stroke, Cushion Pressure Generates Power


Stamping Group

CPF Advantages 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

32


Stamping Group



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

33


Stamping Group



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) 34


Stamping Group



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

35


Stamping Group

CPF Servo-Drive Press Technology

Summary / 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 36


Stamping Group

CPF Questions/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

37

http://www.asminternational.org/

Documents

Servo Press Technology Applications for Today and Tomorrow