Electric cylinder for welding tongs used in the automotive industry

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  • SEW image
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    Bath lubrication

    Unique - maintenance free - patented

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No matter what type of welding tongs you use – X-welding tongs for spots that are hard to access, or C-welding tongs for simpler constructions – the electric cylinders by SEW‑EURODRIVE are perfectly suitable for both applications and will provide you with a repeat accurate welding power: Our electric cylinders can provide a peak drive force of up to 10 kN in C-welding tongs, and up to 24 kN in X-welding tongs.

Spot welding – A challenging task

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There's no accounting for taste when it comes to the looks of a car body – but when it comes to the importance it's greatest task, protecting the passengers from harm as good as possible, everyone will agree upon it. In order to ensure the safety of the passengers, the car body must be torsionally rigid and the other components must be firmly attached to it. In case of alternative drive and mobility concepts, the need to combine a mixture of different materials, such as steel, aluminum, plastic, and composite materials must also be taken into consideration.+

This secure connection is created by thousands of welding spots on the car body, the doors, the hood, etc. Each component contributes to the rigidity of the vehicle and thus to protecting the passengers. In car body manufacturing, the welding spot connections are performed fully automatic with consistent precision and quality.

For exactly this purpose, electric cylinders are used to evenly generate the force of the welding tongs. In order for a welding spot to meet all quality requirements, the welding electrodes must be constantly pressed together and held with the correct amount of force during the welding procedure.

Repeat accuracy, process reliability and durability are just as important quality criteria for the used welding tongs drive, as accurately positioning the welding spots so that the surrounding surfaces aren't damaged. This includes that welding spatter does not occur when a welding tong application functions optimally.

The technical solution

X-tonge
X-tonge
X-tonge

The mechanical design of our electric cylinders is variable, so that it exactly fits to the used welding tong construction, whether you use X-tongs or C-tongs.

The design of the electric cylinder is selected depending on:

  • Available installation space
  • Required stroke
  • Required welding power
  • Required speed
  • Used control system
C-tonge
C-tonge
C-tonge

More properties of the electric cylinders:

  • Maintenance-free for the entire service life due to the patented bath lubrication
  • No regreasing required throughout the entire service life
  • Very high efficiency
  • Easy to install
  • Excellent power density / enhanced heat distribution via bath lubrication
  • Twice the service life as compared to the market standard
  • Low costs throughout the service life and higher OEE as compressed air preparation of the electric cylinder is not needed
  • Easily integrated into control systems using flexible encoder systems and connector options
  • Exact positioning thanks to ball screws using servo drive technology with high-precision encoders
  • Perfect force and repeat accuracy throughout the entire service life, with no need of additional sensors
  • Very low noise as compared to pneumatically operated welding tongs

System integration via plug-and-play

Flexible options regarding motor feedback, connection assignment, and temperature sensors allow for plug-and-play operation with the market-leading control systems for welding robots.

Two variants to integrate electric cylinders are available:

  • As 7th axis in the robot controller: With this variant, the motion of the robot (6 axes) and the opening/closing motion of the welding tongs (7th axis) are defined by the robot controller, e.g. KUKA, ABB or Fanuc. An welding controller is additionally required to regulate the welding current.
  • Using the Bosch Rexroth welding control PRC7300 or PRC7400: A robot controller controls the 6 axes, but out electric cylinder and the welding current are controlled and adjusted to each other by the PRC7300 and PRC7400.

Comparison of the 3 systems

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  Convetional Market standard Future-proof
Design / selection criteria Pneumatic cylinders Planetary screw drive with grease lubrication Ball screw with
bath lubrication
Service life Depending on maintenance Depending on regreasing For the entire service life
Speed Up to 3 m/s Up to 1.5 m/s Up to 0.75 m/s
Weight and required space Low Moderate Moderate
Noise level High Moderate Low
Efficiency 7 – 10% 60 – 80% 86 - 92%
Force precision Low Force gauge required +/- 150 N
Positioning accuracy Moderate High High
Maintenance Regular tightness maintenance every 1.2 million cycles Regular relubrication
every 2 million cycles
Maintenance-free for
the entire service life
Controllability in the process (speed, power, starting behavior) No speed control Average control, slip-stick effect at the beginning of a stroke Easy and precise controllability
Environmental impact Very low efficiency1 More grease required, low efficiency Oil only needs to be disposed of after the service life ends, very high efficiency
Characteristic stability in case of temperature changes etc. throughout the service Risk of leaks in the compressed air system, speed depending on the compressed air Very high stability, independent of the temperature Very high stability, independent of the temperature
Additionally required tools Compressed air supply, pressure reduction, sensors, pneumatics controller Cables for motor feedback and power supply, servo controller, local relubrication tools Cables for motor feedback and power supply, servo inverter,
Welding spot quality Repeat accuracy, positioning and
force control depending on air
leaks, the construction cannot be controlled very accurately
High repeat accuracy, positioning
and force control
High repeat accuracy, positioning and force control
Reliability of the overall system Ca. 11 million cycles when the cylinders are regularly checked
and resealed
Ca. 11 million cycles when the cylinders are regularly checked and resealed 20 million cycles
  1. 1 Compressed air preparation required
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Technical Data

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Electric cylinder Stroke Maximum feed
speed
Peak feed force Continuous
feed force
Weight
mm m/s kN kN kg
(stroke lenght
160 mm)
Size 50 70 – 600 0.75 2.65 – 8 0.6 – 3.2 5.8 – 13.6
Size 63 60 – 600 0.45 10 2.4 – 5.2 8.8 – 18.6
Size 71 100 – 1200 0.45 18 – 24 6.2 – 12 21.6 – 48.7
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Dimensions - axially parallel

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Electric cylinder A B H Y LB
Size 50
Type S / M / L
73 217 70 / 100 / 150 / 200 / 300 / 400 / 600 221.5 / 251.5 / 301.5 / 351.5 / 451.5 / 581.5 / 781.5 Type S: 174.5

Type M: 223.5

Type L: 262.5
Size 63
Type S / M / L
88 245.5 60 / 100 / 160 / 180 / 200 / 400 / 600 235.5 / 275.5 / 335.5 / 355.5 /
375.5 / 607.5 / 807.5
Type S:
252.8

Type M:
302.8

Type L:
352.8
Size 71
Type S / M / L
115 291 100 / 160 /
200 / 400 /
600 / 800 / 1000 / 1200
326 / 386 / 426 / 686 / 886 / 1146 /
1346 / 1546
Type S:
229

Type M:
254

Type L:
304
  1. All dimensions in mm
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Dimensons - axially serial

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Electric cylinder A B H Y LB
Size 50
Type S / M / L
73 120.7 70 / 100 / 150 / 200 /
300 / 400 / 600
221.5 / 251.5 / 301.5 / 351.5 / 451.5 / 581.5 / 781.5 Type S:
156.4

Type M:
195.4

Type L:
234.4
Size 63
Type S / M / L
88 245,5 60 / 100 / 160 / 180 / 200 / 400 / 600 235.5 / 275.5 / 335.5 / 355.5 / 375.5 / 607.5 / 807.5 Type S:
163.7

Type M:
214.2
Size 71
Type S / M / L
115 295 100 / 160 /
200 / 400 /
600 / 800 /
1000 / 1200
326 / 386 / 426 / 686 / 886 / 1146 / 1346 / 1546 Type S:
211

Type M:
236

Type L:
286
  1. All dimensions in mm
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