M ATERIAL R EMOVAL P ROCESSES

For industry to operate effectively, the material that produces the final product must be machined and formed quickly and accurately. The key factors that affect the efficiency of a metal-removal process are the machine tool, the controller, spindle, toolholder, cutting tool, and CNC programming. High Speed Machining (HSM) uses high spindle speeds, high feed rates, and light depths of cut to increase productivity, reduce lead time, reduce warping, increase part accuracy, and improve surface quality.

In virtually all metal-removal operations, manufacturers are trying to reduce the amount of time a part is moved from machine to machine and perform more operations in a single workpiece setup. This has led to the development of new machine tools such as the turning center with live tooling and special workholding fixtures where both turning and milling operations can be performed in one part setup.

S INGLE -P OINT OD G RINDING

(Steve Krar, Consultant – Kelmar Associates)

Over the years, many developments helped to improve the metal-removal rate and increase the flexibility of conventional OD cylindrical grinding operations. The development of superabrasive wheels greatly increased metal-removal rates, however the parts produced were limited to the shape of the grinding wheel. Therefore these parts had straight or angular forms and it was not possible to produce contour forms  without dressing the wheel to the form required.

Single-point grinding is a process that combines two technologies - superabrasive grinding wheels and high-precision servo control - to provide a contour grinding process that resembles a computer numerical control (CNC) outside diameter (OD) turning operation. It allows one machine to perform several operations such as grinding parallel diameters, tapers, contours, and threads without removing the part from the  machine. Performing more operations on a part in one setup reduces the amount of workhandling between operations. For many medium OD grinding applications, it is a means of combining several grinding applications and machines into a single step.

THE GRINDING PROCESS

The basic idea for single-point grinding comes from the modern CNC turning center where a single-point cutting tool can be used to perform various operations. For example, one single-point tool can profile, face, plunge, and cut threads.

A single-point OD grinding machine is similar to a turning center since two axes of movement are generally involved in both metal-removal processes. On turning centers a form tool can be used to cut profiles, or a single-point cutter can be programmed to follow a desired profile through the coordinated movements of the X and Z axis, Fig. 2-2-1.

Fig. 2-2-1 Single-point grinding combines two technologies to grind parallel diameters, tapers, contours, threads, etc. (Junker Machinery Inc.)