HL 1000 – Oil hole drilling in hardened crankshafts

10/12/2008 - Oliver Hagenlocher

With its HL 1000 EMAG presents an oil hole drilling machine for soft as well as hardened crankshafts.

The advantage of hard machining: fractures and hardening cracks are safely avoided.


In the manufacture of crankshafts for passenger cars and trucks it is not only the position, dimensions and contour of the external geometry that have to be accurate. Generating the oil holes in the main and pin bearings is just as much of a precision job. It is those oil holes through which the lubricant is supplied to the contact point between con rod and crankshaft. They run at right angles to the symmetry axis of the shaft, as well as at a diagonal, and are interconnected. Only an accurate entry of the medium into and a precision exit from the oil hole guarantee the efficiency of the lubricating process. Their creation is a highly demanding job in more than one sense. To drill these holes to the required precision and to chamfer them according to drawing tolerances is a decisive part of the process. An error at this stage would make of the already extensively machined workpiece an expensive lump of scrap. The oil holes are usually drilled into the crankshaft in its soft stage, i.e. before it is hardened. As they are drilled at a very acute angle, their edges throw up a very thin projection of material. If the main and pin bearings are hardened after the oil holes have been drilled, the steel cools down too quickly at this particular spot and becomes highly porous. When the crankshaft is used, small particles could break off at this particular point and impede the running of the bearings, even damage the engine. The hardening of crankshafts after the oil holes have already been drilled could also cause quenching cracks to appear at the intersection points. Under heavy duty use this can break the crankshaft. To eliminate this source of danger right from the start, EMAG has developed a process that allows for oil holes to be drilled into hardened crankshafts. The advantage: the shaft can be hardened before drilling takes place. The oil channels are only drilled after heat treatment – the way to safely avoid hardening cracks and fractures.

The HL 1000 accommodates crankshafts of up to 1020 mm length and 265 mm diameter. With bore diameters of between 4 and 8 mm and the use of minimum quantity lubrication the HL 1000 achieves the kind of tool life that is far beyond the usual. Finally, all machining results – even those for truck crankshafts weighing up to 150 kg – are checked and logged by the control system while the workpiece is still clamped.

The HL 1000
The machine base is of Mineralit (reaction resin polymer concrete), offering excellent thermal stability and outstanding dampening qualities. (In fact, the dampening properties of Mineralit are 6 to 8 times those of cast iron.)  At the top of the machine base, and outside the machining area, are two pre-loaded linear roller guideways for the compound slide. They guarantee the highest degree of accuracy and high dynamic rigidity at all speeds.
The compound slide is equipped with two axes (X vertical and Z horizontal). The axes are driven by pre-loaded ball screws and a no-maintenance servomotor with built-in high-resolution rotary encoder. Cross slides and swivel axis (Y cross and B rotary) provide flexibility in the drilling of oil holes at variable angles. Rapid traverse speeds of up to 40 m/min reduce the idle times for tool change, workhandling and positioning. The B-axis is driven by a highly dynamic NC torque motor. A direct measuring system with high resolution guarantees the greatest accuracy in angular positioning. The 12-station disc-type magazine is equipped with HSK-A50 tool receptors. Tools are changed on the pick-up principle, using the motor spindle. The magazine remains outside the machining area and is therefore well protected against contamination. The highly dynamic, compact construction ensures time-saving tool changes.

Contact

Oliver Hagenlocher

Press and publishers

Phone:+49 7162 17-267
Fax:+49 7162 17-199
E-Mail:communications@emag.com

Images