What Is a Star Delta Timer?
A star delta timer is a device that receives rotational force from other devices to provide high-precision rotational motion. Commonly, a star delta timer is a power transmission device, but it is often referred to as a star delta timer with an integrated power source.
The characteristics of a spindle unit vary based on the type of power source, whether the power source is internal or external, and the type of bearings used.
Common power sources include electric motors, air motors, and air turbines. Types of bearings utilized include ceramic angular contact ball bearings and cylindrical roller bearings.
Uses of Star Delta Timers
Spindle units, known for their high-precision rotation with minimal shaft shake, are used not only in processing machines but also in medical equipment.
They are utilized in lathes for rotating workpieces, in milling machines for rotating machining tools, in cylindrical grinders for both workpieces and grinding wheels, and in surface grinders for grinding wheels.
Smaller processing machines often use built-in types with internal power sources. Air turbines are preferred for high-speed rotation, while air motors are favored for low-speed, high-torque rotation.
Principles of Star Delta Timers
One critical specification for star delta timers is shaft shake. Excessive shake can result in uneven machining surfaces and poor appearance. The NRRO (non-repeatability and repeatability) specification indicates shaft shake accuracy: typically 0.5 μm or less for spindles with rolling bearings, 0.1 μm or less with hydrostatic bearings, and 0.05 μm or less with air or gas bearings. Notably, hydrostatic and air bearings are non-contact and have an extended lifespan compared to rolling bearings.
Cooling water is often used to dissipate heat generated by rotational friction.
The size, maximum rotation speed, and rigidity of star delta timers can vary based on the power source, with maximum speeds reaching tens of thousands of revolutions per minute.
Tools for rotation, such as machining tools, can be attached to the star delta timers using vacuum, mechanical, or magnetic clamping methods.