Taming the 'Nastalloys'

Published Date
January 15,2008 - 11:00:am

Interrupted turning: What to do

By Victor Cassidy

Interrupted turning is common in aero-engine machining, said Sean Holt, aerospace specialist for Sandvik Coromant Co., Fair Lawn, N.J. There, a complete, finished component is machined out of a single, large block of material (most commonly Inconel 718) in several process stages that involve accurately removing a vast amount of material to meet strict parameters for the finished part's dimensions and characteristics. Sandvik Coromant claims to have cutting tools and machining methods that greatly improve aerospace component manufacturing.

Sandvik Coromant divides the machining stages into three areas, which are characterized by different tool wear characteristics and demands made during the production cycle. Between the stages, there are stress relieving processes. Each stage puts different demands on the cutting edge.

First-stage machining begins in the foundry where skin and scale are removed from the blanks prior to heat treatment. Here, maximum metal removal is needed and large inserts with large DOC are applied.

Intermediate-stage machining generates the greatest production costs and offers the best opportunities for productivity improvement. The goals are maximum increase in metal-removal rates and savings in time and cost coupled with high process security and reliability.

Sandvik Coromant has divided intermediate stage machining in two, based upon the approach angle of the insert at the maximum DOC. When the approach angle is 90°, notch wear is a limiting factor and only PVD-coated grades can be used. When the approach angle is 45° and round inserts are used, notch wear almost disappears. This allows more temperature-resistant CVD-coated ceramic grades to be employed. (Sandvik Coromant has new geometries—round-SM, SR and Xcel-SM—to maximize the benefits of CVD-coated grade S05F.)

Final-stage machining and finishing is where the manufacturer must understand the effects of cutting and tool parameters on a component. This helps in choosing the optimal tool to increase productivity while maintaining component quality.

Sandvik Coromant offers insert grades to maximize component surface integrity. For stable components, there is the insert grade S05F in insert geometry MF or the Corocut-RO geometry. For thin-wall components, where low cutting forces are required, the new PVD grade GC1105 with sharp, ground edges is recommended.

Interrupted turning: What to do?

By Victor Cassidy

Related Link: Taming the 'Nastalloys'

Interrupted turning is common in aero-engine machining, said Sean Holt, aerospace specialist for Sandvik Coromant Co., Fair Lawn, N.J. There, a complete, finished component is machined out of a single, large block of material (most commonly Inconel 718) in several process stages that involve accurately removing a vast amount of material to meet strict parameters for the finished part's dimensions and characteristics. Sandvik Coromant claims to have cutting tools and machining methods that greatly improve aerospace component manufacturing.

Sandvik Coromant divides the machining stages into three areas, which are characterized by different tool wear characteristics and demands made during the production cycle. Between the stages, there are stress relieving processes. Each stage puts different demands on the cutting edge.

First-stage machining begins in the foundry where skin and scale are removed from the blanks prior to heat treatment. Here, maximum metal removal is needed and large inserts with large DOC are applied.

Intermediate-stage machining generates the greatest production costs and offers the best opportunities for productivity improvement. The goals are maximum increase in metal-removal rates and savings in time and cost coupled with high process security and reliability.

Sandvik Coromant has divided intermediate stage machining in two, based upon the approach angle of the insert at the maximum DOC. When the approach angle is 90°, notch wear is a limiting factor and only PVD-coated grades can be used. When the approach angle is 45° and round inserts are used, notch wear almost disappears. This allows more temperature-resistant CVD-coated ceramic grades to be employed. (Sandvik Coromant has new geometries—round-SM, SR and Xcel-SM—to maximize the benefits of CVD-coated grade S05F.)

Final-stage machining and finishing is where the manufacturer must understand the effects of cutting and tool parameters on a component. This helps in choosing the optimal tool to increase productivity while maintaining component quality.

Sandvik Coromant offers insert grades to maximize component surface integrity. For stable components, there is the insert grade S05F in insert geometry MF or the Corocut-RO geometry. For thin-wall components, where low cutting forces are required, the new PVD grade GC1105 with sharp, ground edges is recommended.

Related Glossary Terms

  • approach angle

    approach angle

    Angle between the insert’s side-cutting edge and the line perpendicular to the milling cutter’s axis of rotation. Approach angle, which is also known as cutting edge angle, is used with metric units of measurement. See lead angle.

  • physical vapor deposition ( PVD)

    physical vapor deposition ( PVD)

    Tool-coating process performed at low temperature (500° C), compared to chemical vapor deposition (1,000° C). Employs electric field to generate necessary heat for depositing coating on a tool’s surface. See CVD, chemical vapor deposition.

  • stress relieving

    stress relieving

    Annealing designed to relieve internal stresses caused by machining, welding, casting, cold working, quenching or normalizing.

  • turning

    turning

    Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.