The OD/ID grinding machines of the JUCAM series impress with precise grinding results in a single clamping set-up. Thanks to the control system with learning function – with which virtually all disturbing variables are compensated – camshafts, cam pieces and individual cams are given a perfect finish. The many decades of experience in grinding cams, the many special solutions and the resulting expertise in finding solutions convince engine and pump manufacturers the world over.
Grinding machines for grinding camshafts, cam pieces and individual cams combine non-cylindrical grinding for the cams and cylindrical grinding for the bearings. With non-cylindrical OD/ID grinding, the grinding wheel follows the cam contour through interpolation of the workpiece spindle (C-axis) with the grinding spindle (X-axis). CBN or diamond are used as an abrasive – for high cutting performance with a constant level of quality and a long tool life.
The cam geometry is specified in a lift table. In the process, each angle is assigned a lift value to define the cam contour and import it to the program. The software then interpolates the values automatically. The cam contour is frequently concave in the infeed and discharge area. Here the concave radius determines the maximum grinding wheel diameter that can be used.
Inside round grinding
External cylindrical grinding
When grinding cam pieces, it is essential that the exact angular reference to the inner toothing is ensured. For this reason, the JUCAM clamps the cam pieces with an inner clamping mandrel. The longitudinal and radial positioning and the C-axis with direct drive result in a smooth, transition-free shifting surface.
The workhead with two opposing clamping devices minimizes the downtime when grinding individual cams and cam pieces: While grinding is being carried out on one side, unloading and loading, clamping and positioning are carried out on the other. The only downtime: Swiveling by 180 degrees in less than 3 seconds.
The use of grinding wheels sets is ideal for grinding cams with the same orientation. Several cam contours are ground simultaneously in one operation, which considerably reduces the cycle time. Carbon base bodies are also available for saving weight.
The Erwin Junker Operator Panel was specifically developed to control grinding machines. All machine components are controlled using the operator panel – irrespective of the series and the used control system. The identical structure, intuitive menu guidance and visualization of the workpiece geometry make for extreme user convenience and flexibility in operation. Programming takes place directly using the operator panel or an external programming tool.
Grinding wheel dressing is CNC controlled. A driven diamond dressing wheel or a workpiece-dependent diamond profile roller can be used. Dressing takes place manually or using an automatic dressing program with grinding wheel compensation.
In order to generate a precise width and angular position of the main and pin bearing, the position must be precisely determined when clamping the crankshaft. For this, a touch probe measures the radial position of the pin bearing and the longitudinal position of the main and pin bearing. The measured values are automatically integrated in the grinding process by the control system.
The control system comes with automatic compensation of runout and disturbing variables such as temperature influences, grinding allowance fluctuations or material changes. Even minimal deviations between the target and actual position of the grinding wheel are automatically corrected.
The X axes, with linear roller ways with high pre-load, takes care of ultra-precise positioning of the grinding and regulating wheel head. Drive is executed by a precise, intrinsically rigid ball screw with infinitely variable servo drive and glass scale.
The B axis of the wheelheads is driven by a backlash-free gear. Every angular position is programmable; the position sensor system has a sensational resolution of 0.00001 of a degree. Extreme low noise (vibration) levels are guaranteed with the JUNKER grinding spindles with direct drive – an in-house development – complete with a structure-borne sound sensor and dynamic balancing system in one or two planes.
Torque motors are used for direct drive of the C axis. This ensures impressive quiet running, high torque rigidity and superb dynamics in the C axis. Torsionally unstable crankshafts are driven by two C axes.
The machine bed made of mineral cast provides impressive damping behavior and torsional rigidity. The temperature stability allows fluctuations in the ambient temperature to be compensated with a minimum of effort, ensuring a high level of dimensional stability throughout the whole day.
The patented 3-point mounting interface allows grinding and dressing wheels as well as work holdings to be mounted and centered on grinding spindles, workpiece spindles and tailstock sleeves in record time. Adjustment of the tailstock and, where applicable, the workhead take place using optionally using a chain wheel, a hydraulic cylinder or a CNC axis with rack and pinion drive. An airlift function simplifies position adjustment. Depending on the workpiece, in addition a wide range of clamping systems are also available
Depending on the application, the abrasive CBN or diamond is used. The basic bodies of the grinding wheels comprise steel or carbon. In conjunction with CBN, it can make sense to use a carbon base body: It is light, has vibration-damping properties and remains dimensionally stable even at high speeds.
In case of an fire, the machine interior is automatically hermetically sealed, suffocating a fire before it has a chance to spread. If required, extinguishers (CO² or water mist systems) and exhaust air purification systems can be additionally installed. A competent partner for fire protection and filtration solution solutions is LTA Lufttechnik GmbH, which also belongs to the JUNKER Group and which researches, develops and produces filtration systems for industrial air purification.
The Filtration systems
JUNKER offers both internal and external loading systems for all its machine series, depending on customer and workpiece requirements. The loading systems can be combined with different infeed and discharge systems such as conveyor belts or custom tailored systems.
The measurement systems are also individually adjusted to the various workpieces and customer specifications. The measurement processes entail evaluating the recorded measured values and utilizing them for measurement correction in line with the prepared measurement strategy. A grinding wheel measuring system to determine the diameter, axial position and width of the grinding wheel completes the wide range of systems on offer.
A swivel-in measurement probe carries out an in-process measurement of the diameters of the main and pin bearing. The control system logs the measured values, calculates the correction data and generates the precise shape. After grinding, the Machine is able to measure the entire geometry of the crankshaft – depending on requirements: from the bearing width through the lift height to the taper of each element.
As an option, self-centering three-point steadies ensure stable support. Tracking hydraulic jaws guarantee a balanced ratio of forces at all three support points, and with it a grinding process with repeat accuracy.