Tham khảo tài liệu 'machining and monitoring strategies part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Machining and Monitoring Strategies 461 o Figure 228. High-speed milling toolholders chucks utilising tapered sleeves with needle rollers for elastic deflection when tightened - to precisely hold cutter s shank along its whole gripping length. Courtesy of Diashowa Tooling 462 Chapter 9 quickly heats up the holder and in so doing expands the bore allowing the tool s shank to be placed in-situ in the toolholder whereupon it contracts around the shank - taking about 7 seconds to initially expand the bore by 5 pm. This thermal expansion gives enough clearance to allow the speedy withdrawal of an old tool and its replacement by the new one. The heat is localised at the tool s sleeve enabling the user to remove it wearing protective gloves. Having removed the new tooling assembly from the induction machine the user places this tooling in a solid aluminium cooling-block which efficiently dissipates the heat from the tooling assembly. Thus just a few seconds after the assembly has resided in the cooling-block the bore shrinks back but is constrained from reaching its equilibrium diameter by the slightly larger diameter of the tool s shank. This thermal mechanical restriction creates the high but uniform gripping pressure around and along the tool s shank which firmly secures it in place. The entire shrink-fitting process from start-to-finish only takes about 30 seconds to complete. The heating control can be adjusted by the user to accommodate large or small diameter toolholders requiring differing thermal expansion cycles and with experience the optimum settings can be quickly established. So once the correct power and temperature cycles have been created these parameters can be employed to regulate the induction machine thus avoiding energy wastage. If even tighter control is demanded of the heating process an infra-red sensing device can detect the amount of heat in the toolholder so that once it reaches a preset temperature the induction heating is automatically shut .
