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Fives says the new Cranfield Precision TTG machine is a radically new concept. While conventional machine tool platforms use stacked linear axes as the primary motion control system, the Cranfield Precision range coordinates two rotary axes and a short linear axis in a "twin-turret" design. It uses a unique (and patented) combination of rotary and linear axes to produce relative motion (both position and angle) between tool and workpiece over a swept working area.
Compared to conventional machines, the Cranfield Precision platform offers two main advantages:
Stiffness, because the new machine base is effectively two rotary, highly damped hydrostatic bearings that resist machining forces, and thermal stability, because the twin-turret design enables a simple non-contacting labyrinth seal, making the machine base almost immune to distortions. These are usually caused by the heat generated from constantly changing coolant return path as the grinding wheel carriage moves along the linear axis.
This design provides a common platform for multiple machine configurations and processes, including OD grinding, ID grinding, profile grinding, milling, polishing, hard turning, diamond turning dicing and in-situ metrology.
The machine is supplied in two sizes: TTG100 and TTG400 for up to 100mm-dia. and 400mm-dia. components, respectively.
The trend towards superabrasives demands a highly stiff and thermally stable machine geometry. The new design of this Cranfield Precision machine reportedly responds to the needs of the most demanding applications looking for extreme accuracy in their grinding processes:
The optics industry for grinding spherical, aspheric and free-form surfaces on a variety of materials.
Universal CNC grinding of more conventional parts held in a chuck or faceplate using aluminum oxide or superabrasives.
The experiences gained by Fives over many years for its Cranfield Precision range of products in the optic industry show that ductile regime grinding of brittle materials can deliver considerable process advantages over conventional grinding processes. This mode of operation is not possible to support unless the machine system is extremely stiff, highly damped and capable of submicron position control.
Related Glossary Terms
- aluminum oxide
aluminum oxide
Aluminum oxide, also known as corundum, is used in grinding wheels. The chemical formula is Al2O3. Aluminum oxide is the base for ceramics, which are used in cutting tools for high-speed machining with light chip removal. Aluminum oxide is widely used as coating material applied to carbide substrates by chemical vapor deposition. Coated carbide inserts with Al2O3 layers withstand high cutting speeds, as well as abrasive and crater wear.
- chuck
chuck
Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
- coolant
coolant
Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- grinding
grinding
Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.
- grinding wheel
grinding wheel
Wheel formed from abrasive material mixed in a suitable matrix. Takes a variety of shapes but falls into two basic categories: one that cuts on its periphery, as in reciprocating grinding, and one that cuts on its side or face, as in tool and cutter grinding.
- hard turning
hard turning
Single-point cutting of a workpiece that has a hardness value higher than 45 HRC.
- inner diameter ( ID)
inner diameter ( ID)
Dimension that defines the inside diameter of a cavity or hole. See OD, outer diameter.
- metrology
metrology
Science of measurement; the principles on which precision machining, quality control and inspection are based. See precision machining, measurement.
- milling
milling
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- outer diameter ( OD)
outer diameter ( OD)
Dimension that defines the exterior diameter of a cylindrical or round part. See ID, inner diameter.
- polishing
polishing
Abrasive process that improves surface finish and blends contours. Abrasive particles attached to a flexible backing abrade the workpiece.
- stiffness
stiffness
1. Ability of a material or part to resist elastic deflection. 2. The rate of stress with respect to strain; the greater the stress required to produce a given strain, the stiffer the material is said to be. See dynamic stiffness; static stiffness.
- 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.
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