Crankshaft machining process

Abstract: This paper introduces the current passenger car engine crankshaft production line using new technologies and new equipment for engine companies in the crankshaft production line investment planning to provide reference for crankshaft processing project managers to provide reference to improve the level of engine crankshaft manufacturing has a certain guiding significance.

Crankshaft machining process

Typical process flow of crankshaft machining for turbocharged engines of passenger cars: dynamic balancing, drilling the centre of mass → turning the 5th main journal → turning the flange → rough machining the main journal, connecting rod journal and shoulder → drilling the oil passage holes and chamfering → rough grinding the main journal, connecting rod journal journals, sidewalls and countersinking grooves → cleaning, blowing and drying → rounded rolled → precision turning and rolling of the thrust surface + precision turning of the small end → precision turning of flange end and groove → precision grinding of main journal, connecting rod journal and small end → machining threaded holes, pin holes and reaming the centre hole of the flange end of the crankshaft → precision grinding of flange end of the crankshaft → machining both ends, pin holes, pin holes and reaming the centre hole of the flange end.

and grooves → precision grinding of main journal, connecting rod journal and small end → machining of threaded holes at both ends, pin holes and reaming of centre holes of flange end → precision grinding of flange end of crankshaft → crankshaft dynamic balancing and de-weighting → abrasive belt polishing of main journal, connecting rod journal and flange outer neck → automatic checking and marking → final cleaning of crankshaft.

Application of advanced technology

(1) Dynamic balancing and drilling centre of mass holes.

The positioning reference in the crankshaft machining process is the centre hole, which can be divided into geometrical centre hole and quality centre hole according to its machining position. Use the V-shaped block or other ways to find out the geometrical centre of the crankshaft’s main support journal, and the centre hole machined on this centre is called geometrical centre hole. The centre of mass of the crankshaft is measured using special test equipment, and the centre hole machined on this centre is called the centre hole of mass. When the geometric centre hole is used for subsequent turning and grinding, the centrifugal force generated by the rotation of the workpiece will affect the machining quality, and the remaining dynamic unevenness after machining is large, which needs to be measured and de-weighted several times in the dynamic balancing process in order to meet the technical requirements, which is inefficient, affects the production beat, and results in an increase in the rate of semi-finished product rejects and the loss of positioning elements. The use of a centre-of-mass hole solves such problems and improves cycle times.

Figure 1 shows the COMAU SYMES10 crankshaft centre of mass measuring machine, the crankshaft is placed in the rat cage of the equipment, rotating with the rat cage, the measurement of the rat cage and the parts together with the amount of unevenness of M, the amount of unevenness of the rat cage (M1) is known, the amount of unevenness of the parts M2 = M – M1. through the special formula, the equipment can be automatically calculated through the M2 The coordinate position of the balance axis of the crankshaft is automatically calculated from M2. The measurement result is transmitted to the COMAUSDC700L type fully automatic crankshaft two-end machining centre, which has a measurement uncertainty of ≤40 μm. It is possible to measure several varieties of crankshafts, and the part varieties can be identified automatically, with a cycle time of 1.2 min, making the equipment simple and reliable.

(2) High-speed external milling for roughing crankshafts

High-speed external milling roughing crankshaft main journal, connecting rod journal and shoulder, than CNC turning, CNC internal milling, car – car pulling the high productivity and stable quality. For example, CNC turning – turning and pulling process to process the connecting rod journal to two processes, while CNC high-speed external milling can be completed in just one process, high-speed external milling roughing crankshaft’s distinctive features are: cutting speed of up to 350m/min, cutting time is short, the process cycle time is shorter, the cutting force is smaller, the temperature of the workpiece is low, the tool life is high, the number of tool changes are fewer, and the machining accuracy is higher, Flexibility is better, is the development direction of crankshaft main journal and connecting rod journal roughing.

The NILES-SIMMONS N20 crankshaft external milling machine (see Fig. 2) allows the simultaneous machining of crankshaft main journals and connecting rod journals. The machine is equipped with two tool spindles, each with independent motion, each with a single cutter disc, and each with an independent machining programme and its parameters. The part is placed on the auxiliary loading device, which places the part into the machining area; the chuck clamps the part flange and the centre is pressed from the rear; the part is rotated, and the left and right cutter discs rotate at a certain speed on the tool spindle while moving backwards and forwards in the radial direction to achieve the machining of the main journal and connecting rod neck.The bed (W/Z-axis) linear rolling guideway, transverse drag plate (U/X-axis) linear rolling guideway.

The CNC control system is based on the technical data of the SINUMERIK 840D sl, the milling operation modular microprocessor CNC continuous trajectory control with integrated PLC with digital complete solution SINAMICS S120.

(3) CNC crankshaft grinding machine application.

Rough grinding of main shaft journals, connecting rod journal journals, side walls and countersinking grooves. CNC crankshaft grinding machine can grind all crankshaft main journal and connecting rod journal in one clamping. This kind of grinding machine is generally equipped with double grinding wheel headstock, which can meet the requirements of multi-species, low-cost, high-precision, and high-volume production, and the application of servo-linkage control technology of workpiece rotary and grinding wheel feed can complete the grinding of all journals without changing the crankshaft rotary centre in one clamping, including the follow-on tracking of grinding connecting rod journals. The use of a hydrostatic spindle, hydrostatic guideway, hydrostatic feed screw (wheelhead holder) and linear encoder closed-loop control system ensures high accuracy in grinding journal roundness and high grinding efficiency.

MARPOSS.——-The JUCRANK 6S 10-10 CNC cylindrical crankshaft grinding machine (see Fig. 3) is used for rough grinding of crankshaft main journals and connecting rod journals as well as countersinking grooves. The robot that comes with the machine grabs the parts from the loading raceway and places them on the pre-support block inside the machine; the fixture automatically clamps the parts; the parts rotate, the two grinding wheels advance and move radially according to the programme, grinding the main and connecting rod journals at the same time; after machining, the grinding wheels retreat, the parts stop rotating, the fixture loosens, and the robot grabs the parts and places them on the discharging raceway; the positioning accuracy of the X/Z-axis is 0.004mm; Repeat positioning accuracy is 0.002mm; MARPOSS automatic diameter gauge and axial gauge are adopted to ensure precision monitoring of diameter and axial dimensions.

Precision grinding of spindle neck, connecting rod neck and small head end. The main and connecting rod journals of the crankshaft are finish ground using a JUCENTER 6L CRANK CNC cylindrical crankshaft grinding machine (see Fig. 4) with two stations, the first one to finish grind the connecting rod journals of the crankshaft and the second one to finish grind the crankshaft’s main journals. The machine’s own manipulator grips the part from the loading rollers and places it onto the preloaded support block of the first station inside the machine, where the fixture of the first station automatically.

The fixture of the first station automatically clamps the part, the part rotates, the grinding wheel corresponding to the first station advances, moves radially according to the programme and grinds the connecting rod neck; after machining is completed, the grinding wheel retires, the part stops rotating, and the fixture is loosened. The robot grabs the part and places it on the pre-support block of the second station; the fixture of the second station automatically clamps the part; the part rotates, the grinding wheel corresponding to the second station advances, moves radially according to the programme and grinds the spindle neck; after machining is finished, the grinding wheel retreats, the part stops rotating and the fixture is loosened. The robot grabs the part, places it on the discharging roller, and starts the next machining cycle. the positioning accuracy of X/Z axis is 0.004mm; the repetitive positioning accuracy is 0.002mm.

CNC horizontal lathe is widely used

DANOBAT NA750 crankshaft thrust face finish turning machine is equipped with an automatic inspection device. After the component is clamped, the measuring head automatically detects the width of the thrust face, determines its centre line, takes it as the machining reference and automatically compensates for it according to the machining of the previous crankshaft, thus realising the finish turning of the two sides of the thrust face with the centre line as the machining reference and with equal margins, and then the width of the thrust face is automatically detected after the completion of the turning.

After turning, the width of the thrust face is automatically detected, and the processing of the small end and groove is completed at the same time, after turning is completed, the turning tool is returned and the roller head is extended, and the two end surfaces of the thrust face are rolled at the same time. When rolling, the rolling surface should be well lubricated.NA500 type fine turning flange end face and groove machine tool is equipped with automatic detection device, after the component is clamped, the probe will automatically detect the distance from the thrust surface to the flange end face.The positioning accuracy of X-axis is 0.022mm, the repeatability of positioning accuracy is 0.006mm, the positioning accuracy of Z-axis is 0.008mm, the repeatability of positioning accuracy is 0.004mm.

Application of crankshaft belt sanding and polishing machine

The GRINDMASTER crankshaft belt polishing machine is used to polish the oil seal neck, main shaft neck and connecting rod neck of the crankshaft. When polishing, the workpiece is firstly sprayed and cleaned, and then polished by using abrasive belts to wrap the components. There are two rotating directions when polishing, and the final polishing direction is the same as the normal running direction of the engine (viewed from the flywheel side); after polishing, it carries out the work of drying and degreasing, and the equipment needs to be equipped with its own polishing liquid treatment system.

Crankshaft rounding and rolling machine

Regarding the HEGENSCHEIDT MFD7895 crankshaft rolling machine, the control system adopts Siemens PLC S7-300, and the machine is installed with 9 rolling units, which are used to roll and straighten the crankshafts, with a maximum rolling pressure of 30kN; pulse-type rolling of the connecting rod journals, which reduces the deformation of the workpieces; detection and monitoring of rolling pressure by means of the pressure sensors and position sensors and rolling.

The pressure and position sensors integrated in the rolling unit and the rolling depth sensor enable the detection and monitoring of the rolling pressure; the main journal runout is automatically detected after rolling and straightened by rolling; a broken tool detection device is equipped; the radial runout of all main journals of the crankshaft is measured by electronic measuring probes; and the highest point of the connecting rod necks is detected by a laser head, which allows the identification of the component type.

Crankshaft Oil Hole Machines

HORKOS Imql crankshaft oil passage hole and chamfering machine tool, the use of three steps on the oil passage hole processing, milling plane → drilling oil passage holes →

Crankshaft dynamic balancing de-weighting machine

COMAU SYME S10