To deliver the cutting performance required (accuracy, finish, extended tool life etc) turning centers need to be of a rigid construction and good design.
A polymer composite base combined with wide-spaced, heavy-duty linear guides; super-finished tracks and centrally-located, short-pitch ball screws help reduce vibration and minimize stick/slip movement.
- Slides mounted on preloaded roll bearings guide ways
- Rigid tool holders system
- Specific chucking device designed to minimize the deformation on the part
Can start with solid blank operations and produces a finished component in one machine. In hard turning you can start with pre hardened material and machine it. You can skip several steps and actually cut days of process . Choosing between these two process is purely application driven. Grinding is better suited is it against thin walled or delicate from crushing perspective. Hard turning is very well suited when you have complex figures. Complex contours, difficult radii, angles and diameters all in one part. Hard turning can do it with one setting Grind = Lot of fine particles= special filtration unit= clean regularly. Hard Turning = producing steel chips= much easier to dispose or recycle It is becoming more popular than grinding as it usually less expensive, faster, machines cost less and operator learning curve is less. Operator has to learn one machine and that machine does it all. Speed – 91 – 150 m/min. Feed- 0.13 mm/min. Depth- 0.08 mm– 0.5mm. Surface finish- 0.003mm. Roundness value -0.00025mm. Size control – 0.005mm. To the naked eye, ground surfaces appear to be smooth and free from defects. The photomicrographs to the left show the surface of ground tungsten carbide compared to Hard Turning on right show.
When considering the tooling material, it's important to understand the application and critical attributes such as size and finish requirements.
The typical brazed tip CBN insert has a cost structure 3-4 times that of carbide.
Ceramic, on the other hand, has a cost structure more similar to carbide but would not be used for applications which had a tolerance range smaller then , Parts requiring a greater accuracy would logically use CBN.
Ceramic does not perform well in the presence of high thermal shocks, so it is not generally a good candidate for coolant cutting.
How did Hard Turning provide the winning methodology for meeting critical deadlines in Turner Powertrains Systems (TPS) Engine Development Program.
Located at Wolverhampton, United Kingdom.
Turner Powertrain Systems is the world market leader in the design, development, manufacture, sales and support of off-highway transmissions (50 kW / 67 hp to 135 kW / 181 hp) for Backhoe Loaders, Telescopic Material Handlers and 4 - 9 tonne Site Dumpers
TPS produced High precision shafts by cycles of grinding and machining process, which they realized that this was taking their precious time; more Non value added activities were hampering their progress to market at faster rate.
For a standard size of shaft ASA took nearly 20 (only grinding hours) working hours and cost $ 210 prior to adoption of hard turning operations. This also includes additional cost of heat treatment, coolant and frequently changeable grinding wheels.
The company's move to integrate hard turning into its spindle shaft manufacturing process was spurred by the surface, work, machine distortion problem, right kind of tool, coolant, machine adopted etc.