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Spot welding – A challenging task

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

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:

More properties of the electric cylinders:

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.
 ConvetionalMarket standardFuture-proof
Design / selection criteriaPneumatic cylindersPlanetary screw drive with grease lubricationBall screw with
bath lubrication
Service lifeDepending on maintenanceDepending on regreasingFor the entire service life
SpeedUp to 3 m/sUp to 1.5 m/sUp to 0.75 m/s
Weight and required spaceLowModerateModerate
Noise levelHighModerateLow
Efficiency7 – 10%60 – 80%86 - 92%
Force precisionLowForce gauge required+/- 150 N
Positioning accuracyModerateHighHigh
MaintenanceRegular tightness maintenance every 1.2 million cyclesRegular relubrication
every 2 million cycles
Maintenance-free for
the entire service life
Controllability in the process (speed, power, starting behavior)No speed controlAverage control, slip-stick effect at the beginning of a strokeEasy and precise controllability
Environmental impactVery low efficiency1More grease required, low efficiencyOil only needs to be disposed of after the service life ends, very high efficiency
Characteristic stability in case of temperature changes etc. throughout the serviceRisk of leaks in the compressed air system, speed depending on the compressed airVery high stability, independent of the temperatureVery high stability, independent of the temperature
Additionally required toolsCompressed air supply, pressure reduction, sensors, pneumatics controllerCables for motor feedback and power supply, servo controller, local relubrication toolsCables for motor feedback and power supply, servo inverter,
Welding spot qualityRepeat 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 systemCa. 11 million cycles when the cylinders are regularly checked
and resealed
Ca. 11 million cycles when the cylinders are regularly checked and resealed20 million cycles

1 Compressed air preparation required

Electric cylinder StrokeMaximum feed
speed
Peak feed forceContinuous
feed force
Weight
mmm/skNkNkg
(stroke lenght
160 mm)
Size 5070 – 6000.752.65 – 80.6 – 3.25.8 – 13.6
Size 6360 – 6000.45102.4 – 5.28.8 – 18.6
Size 71100 – 12000.4518 – 246.2 – 1221.6 – 48.7
Dimensions - axially parallel
Electric cylinderABHYLB
Size 50
Type S / M / L
7321770 / 100 / 150 / 200 / 300 / 400 / 600221.5 / 251.5 / 301.5 / 351.5 / 451.5 / 581.5 / 781.5Type S: 174.5

Type M: 223.5

Type L: 262.5
Size 63
Type S / M / L
88245.560 / 100 / 160 / 180 / 200 / 400 / 600235.5 / 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
115291100 / 160 /
200 / 400 /
600 / 800 / 1000 / 1200
326 / 386 / 426 / 686 / 886 / 1146 /
1346 / 1546
Type S:
229

Type M:
254

Type L:
304

All dimensions in mm

Dimensons - axially serial
Electric cylinderABHYLB
Size 50
Type S / M / L
73120.770 / 100 / 150 / 200 /
300 / 400 / 600
221.5 / 251.5 / 301.5 / 351.5 / 451.5 / 581.5 / 781.5Type S:
156.4

Type M:
195.4

Type L:
234.4
Size 63
Type S / M / L
88245,560 / 100 / 160 / 180 / 200 / 400 / 600235.5 / 275.5 / 335.5 / 355.5 / 375.5 / 607.5 / 807.5Type S:
163.7

Type M:
214.2
Size 71
Type S / M / L
115295100 / 160 /
200 / 400 /
600 / 800 /
1000 / 1200
326 / 386 / 426 / 686 / 886 / 1146 / 1346 / 1546Type S:
211

Type M:
236

Type L:
286

All dimensions in mm