Machining of crankshaft boring journals are extremely complex in their nature, requiring a precision machining technique to meet specifications. The quality and concentricity of bores has a direct impact on the engine’s performance in regard to efficiency and emissions.
There are a number of different methods to accurately machine a multi-journal crankshaft component, the most efficient method of which is through the use of line boring bars, allowing the tool to be supported at both ends during the machining process and therefore delivering a much higher geometric quality.
Whilst this is the case, conventional line boring solutions have their limitations. The setting process often requires a complex “trial and error” approach, putting pressure on skilled operators to accurately reach fine tolerances. Not only can this process eat into valuable machining time, but also compromise part quality through the risk of operator error in manual setting.
Rigibore’s ActiveEdge tooling allows automotive manufacturers to achieve the two most important goals, accelerate productivity by reducing machine downtime and prevent scrap through oversized bores.
Precision performance is achieved through application of a completely automated boring process known as Rigibore’s Zenith solution. This involves coupling ActiveEdge line boring bars with in-process measurement, allowing the machine control to send compensation commands directly to the tools cutting edges, without stopping the process, and without operator intervention.
The ActiveEdge tool completes the tool setting process by automatically backing the size off from nominal, running a “test cut” before accurately calculating the remaining stock requirement and adjusting for verification of a perfect finish cut.
During the machining process, crankshaft bearing journals will wear at varying rates. This can be problematic to manufacturers, in that conventional line boring bars only allow cartridges to be adjusted by the same amount, meaning compensating an undersized insert could have a negative effect on other journals.
In the production of high-volume engine blocks, operators are faced with the dilemma of keeping the tool within the required parameters, this paired with lengthy tool downtime means operators often leave inserts to run down as low as possible before making a compensation, sacrificing bore quality.
Rigibore’s line boring solution applies ActiveEdge precision cartridges for the finish cut. Not only do these cartridges posses the ability to be automatically compensated with micron accuracy, but each ActiveEdge cartridge can be adjusted independently from one another, extending or retracting to the stay within the required tolerance parameters . This unlocks a unique benefit in precision crank bore operations, with each journal set and maintained to fine tolerances throughout the machining cycle, eliminating the risk of offsetting size on another journal.
This technology has already had a significant impact on crank boring applications globally. Recently, an industry leading automotive manufacturer based in Europe was looking to reduce non-productive elements of their process, where setting of two line boring tools (10 cartridges in total) running on a multi-spindle CNC machine was leading to significant downtime. After setting, parts were ran, measured with a bore gauge and checked for size. Often several cartridges needed further tweaking to obtain the desired size.
After performing a 24 hour trial period, Rigibore’s ActiveEdge technology managed to reduced machine downtime from 60 minutes during manual adjustments, to just 10 minutes. This time saving was equivalent to an additional 66 parts in just one day.