Leading In Connecting Rod Manufacturing

More Than 25 Years of Experience in the Fracture Splitting/Cracking of Connecting Rods

In order to be able to assemble connecting rods and crankshafts, the “crank bore” of a connecting rod is separated during manufacturing. The separated components are then bolted together again. The separating of the “crank bore” is normally done with the inexpensive and extremely reliable procedure of “fracture splitting” or “cracking”.

During cracking, a stress riser is initially made with a laser at a defined position in the component. In the next step, a high amount of force is introduced into the work piece through a fracture mandrel. The break occurs exactly along the laser notch. The separated components do not have to be machined at the joint face, because the cracked surfaces guarantee a matching fit. The material must have sufficient brittleness in order to undergo cracking.

Conrod machining without tool change

ALFING is a pioneer in the development of procedures and technologies for the fracture splitting of connecting rods. ALFING made this technology ready for large scale production in the beginning of the 90’s and it has been used throughout the world in ALFING machines. We are continually developing this process in close cooperation with our customers, because the demands for connecting rods are growing and thus, new shapes and new materials are being used. A particular challenge is the cracking of “tough” steel materials. When separating hardened or very tough substances, the pieces are cooled with nitrogen before cracking. The very tough substances become brittle through the cooling and are therefore able to be cracked.

Rotary Transfer Machines from ALFING: Shortest Cycle Times, Highest Precision

Rotary transfer machines from ALFING are the optimal solution for cracking and assembling connecting rods. The shortest cycle times guarantee high productivity and the modular machine construction permits the execution of different process steps within a machine.

Standard Processes Include

  • Loading and unloading with type recognition
  • Making stress riser by laser
  • Cracking
  • Bolt assembly
  • Bushing press


Optional processes:

  • Bushing press
  • Bushing calibration


Optional test equipment:

  • Mismatch measurement
  • Break out detection
Conrod machining without tool change


Cracking and assembly machines from ALFING are the result of years of experience and therefore offer countless advantages when compared with other suppliers:

  • Short cycle times
  • Short changeover times through changeover flexibility
  • Use of the newest laser technology to create the stress riser (currently: fiber lasers)
  • High-speed crack equipment with process monitoring to guarantee excellent quality during the cracking process
  • High quality bolt assembly with the use of torque-controlled electric nut runners from ALFING (AMT)
  • Location-oriented bush assembly with servo controlled pressing spindles and integrated process monitoring
  • Recording and analysis of all important process parameters
  • High operator and maintenance friendliness

Loading and Unloading

The rotary table assembly machine can be loaded in different ways. Depending on the degree of automation, you can choose between simple manual loading, loading through conveyors and sliding beam transport or flexible loading with a robot.

Conrod machining without tool change

Laser Stress Riser Setup

Laser Stress Riser Setup

The pre-requisite for a precise fracture is the quality of the previously made fracture notch. Predominantly lasers are used to create this notch. The newest generation of fiber lasers are used in ALFING machines.

  • NC – controlled laser head
  • Possible depth of the laser notch up to 1mm
  • Laser notch possible with any shape (straight, arched, etc.)
  • “Perforation” possible

For new materials, it may make sense to determine the optimal parameter settings for the process through testing. ALFING, with a state of the art testing laboratory, is also an ideal partner for this.

Cracking Mandrels

The cracking mandrel is the compound that decides the quality of every fracture machine. If there is a lack of experience, a lot of bad things may happen. The result could be unclean breaks, break outs, strong deformation or partial breaks.

This cannot happen with cracking mandrels from ALFING. Due to our decades of experience and our high-speed crack equipment, we have the perfect solution for every connecting rod size and every material. Process monitoring that informs the user of the quality of the crack process at any time is also available if desired.

  • Hydraulically activated wedge system
  • Robust separating system
  • Hydraulically activated cap support with fine adjustment of the gap
  • Hydraulically activated support on the rodside and/or adjustable fixed pin inside the pin bore

Bolt Equipment

Bolt Equipment

Depending on the cycle time requirements, the bolt assembly of the connecting rods is distributed to one, two or three bolt stations. In the first step, the bolts are automatically inserted and pre-tightened. In the next step, the bolts are slightly loosened again and a vibrating unit can be activated to remove any loose particles from the joint faces. The final step is the tightening of the bolts with a defined torque.

Bush Insertion Equipment

The bushes are inserted automatically and - if necessary - aligned before insertion. The bushes are inserted with a servo pressing spindle with simultaneous monitoring of the insertion force and insertion depth.

The bush may also be calibrated.

Bush Insertion Equipment



Connecting rods are highly stressed components and subject to permanent technical development.

With our modernly equipped testing area, we support our customers during different phases of development:

  • Checking the cracking properties
  • Preliminary tests to determine the optimal parameters for the “laser notch” and “cracking” processes
  • Manufacturing of prototypes for engine tests



Alfing Support Service



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