The SmartRevComau 60CM centering and balancing process is already deployed within a high volume production line for a top automotive OEM. Selected for its combination of innovative crankshaft machining technology and “right the first time” balancing, the dedicated solution will manage a production volume of roughly 175,000 crankshafts per year with the added flexibility to change types and lengths, according to the scheduled production batch. To do this, the multi-station machine has been fitted with an easy change-over solution to enable the OEM to meet new configurations or sudden needs.
It is standard practice to centre the cast or forged crankshaft as the first step in a crankshaft manufacturing line. The process starts with the automatic overhead loading and positioning of the raw part on the first of the two workstations. Once positioned, the raw crankshaft is secured by two chucks and the system automatically rotates the part and conducts unbalance measurements with detailed analysis to determine the axis of inertia. This data is then processed by the machine, where it is used by the second station to automatically drill centring holes on both crankshaft ends. Relying on the precise clamping and alignment capabilities of the SmartRevComau 60CM, the second station automatically corrects the relative angular and coordinate positioning of the crankshaft to the centre drill and creates the ideal alignment between the future rotational axis in respect to the inertia axis. The mass centring machine is also able to perform hollow milling and other operations on the ends, if needed, to produce a clean cut diameter on the clamping surface and reduce the cutting work on further operations. All this is done with the help of precise measuring tools, together with an accurate loading and centring capacity when manipulating the crankshaft.
The power of the SmartRevComau 60CM is not limited to its ability to handle multiple type and length configurations. The real strength of the dedicated station is the feedback and correction functionality between the final balancing machine and the mass centring machine, which allows the system to force an offset in the axis of inertia when needed to ensure a better final balance at the end of the line.
Given that the machining process itself can introduce additional imbalance to the crankshaft as it moves along the line, a manufacturer may find that the final unbalance of an individual crankshaft exceeds the acceptable tolerance. At this point, the system would correct the unbalance by drilling extra holes in the counterweights. If, however, a batch of crankshafts displays a propensity to exceed unbalance tolerances, the parameters of the centring machine can be set to alter the drilling position of the initial centring holes in the first phase of the process to preventively correct the problem.
By offsetting the initial centring hole, the final crankshaft will be better balanced than had the machine drilled at the original axis of inertia. Once on the final balancing machine, the offset crankshaft will still need to be measured and may need to be fine-tuned, but fewer holes will be drilled and any holes needed will be less deep. As a result, the SmartRevComau 60CM is able to deliver better quality and greater structural soundness in the final crankshaft. What’s more, Comau’s experience shows that, on average, 60% of the parts produced with its system are within tolerance and do not need their counterweights to be drilled. This is the true time and cost savings of mass centring, and why flexibility is as important as repeatability when it comes to crankshaft machining.
