Electric cylinder | for welding tongs used in the automotive industry

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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:

Available installation space
Required stroke
Required welding power
Required speed
Used control system

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

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.

	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

Electric cylinder	Stroke	Maximum feed speed	Peak feed force	Continuous feed force	Weight
Electric cylinder	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

Dimensions - axially parallel

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

Dimensons - axially serial

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