Rigibore

This project centred around improving the production of large diameter finish bores on large, complex wind gearbox castings at ZF's production facility in Lommel, Belgium.

ZF Wind Power, industry leading manufacturer and supplier of wind turbine gearboxes, was seeking for a superior solution to certify precision bores upwards of ∅275mm to an H6 tolerance, running on horizontal machining centres (HMCs).

Prior to Rigibore's involvement, ZF was using traditional flange boring tools. In-process bore measurements were also obtained manually.

The Challenge

Due to the large casting size and restricted access, the task of manually measuring critical component features and setting large diameter boring tools with micron accuracy was a challenge, even for skilled operators. Process safeguards to ensure operator safety could also negatively affect production.

Environmental factors were significant due to the long setup and machining cycle. Ambient temperature changes meant that bore sizes could drift, leading to additional downtime to manually readjust the cutting edges during the machining cycle. This was exacerbated by differing thermal lag coefficients between the component, measuring equipment and tooling.

Whilst productivity was a primary concern, it was also of extreme importance to guarantee part quality. The initial cost of the casting partnered with the high setup cost and additional machining time meant that scrapping a part was simply not an option.

The Solution

Rigibore developed the ActiveEdge Nexus boring module for this particular application. When used with standard flanges, this tooling solution is the perfect combination for large diameter boring applications of ∅275mm — ∅1020mm.

The Nexus module supports a precision ActiveEdge cartridge that enables micron accurate cutting edge adjustment by wireless transmission. The Nexus is a flexible solution that can support both boring and overturning operations.

Advantage Through Automation

In order to accelerate productivity and minimise downtime, Rigibore suggested its Zenith solution as a means of achieving micron accurate bores through an automatic closed-loop process.

Zenith combines the ActiveEdge Nexus tool with in-process measurement to monitor bore sizes and automatically adjust when required. Specialised Rigibore macros allow the Nexus tool to be compensated for insert wear, temperature change and material inconsistency during the manufacturing cycle.

More importantly, the Zenith technology allowed ZF to implement a two-stage finish cut. This involves automatically backing off the cutting edge before a first cut is made, then measuring and adjusting precisely to the correct size for the final finish cut. In conjunction with temperature compensated measurements, this process produces precision bores regardless of changes in environmental factors.

Results

Introduction of Rigibore tooling created immediate and continuous process improvements in a number of key performance indicators.

Productivity

  • The introduction of automated bore sizing allowed in-process adjustments to be made with micron accuracy in a matter of seconds.
  • Produced a significant reduction in rewwork and scrapped parts by implementation of the two-stage bore finishing process.
  • Achieved a significant reduction in cycle time.
  • Provided the flexibility to adjust the tool anywhere in the machine, including the tool carousel, in order to maximise spindle utilisation.

Guarantee Part Quality

Rigibore's Zenith automated process guarantees precision by greatly increasing process repeatability. The automation of bore sizing also removed the risk of error in making manual cutting edge adjustments.

The micron accurate adjustment capability of ActiveEdge Nexus allowed ZF to more closely achieve nominal bore size, improving Cpk and increasing the quality of parts produced.

Health and Safety

The Zenith process has allowed the entire machining process to be completed without the need for manual intervention. Any risk to the safety of production personnel has been removed.

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