Basics of the machine include only simple motions such as straight, rotating/indexing and synchronized motions. When precision and super-precision machining is desired, however, unexpected problems and limits may appear, with no measurement technology, no reference, no parts, etc., to refer to. Nagase has been reviewing these problems and limits one by one and developing unprecedented element technologies. Super-precision component units are born from such processes. This is a super-precision unit with the basic structure designed to be accommodated in conventional machines or any other machines that need to be newly developed. In this instance, motions are classified into straight, rotating/indexing and synchronization. Measurement and operation units structured for respective motions are explained.
■Straightness measurement unit
In straightness evaluation, measurement by comparison with a reference straightness gauge has been the general method used. When the workpiece is a few meters long, however, a reference gauge itself may be difficult to prepare. In addition, evaluation of a workpiece, re-setting and corrective machining are time consuming. To solve these problems, a unit for measuring straightness of a long workpiece easily and accurately simply by mounting it on the machine head has been developed. Measurement with an error of 0.33μm/1m (at measurement pitch of 75mm) or 0.77μm/3m (at measurement pitch of 150mm) is achieved by absolute form evaluation. Repeatability in units of submicrons is also achieved, and the evaluation of the waviness component that enables the check of the machined workpiece feature with an accuracy of 0.1μm or less is possible.
■ Non-contact displacement sensor
■ Repeatability measurement operation result
Rotating & indexing motion
■Super-precision rotary table unit
The conventional large-size rotary table has a rotation accuracy only around a few microns to the machine, which achieves submicron straight motion accuracy even for a meter-size workpiece. Advancing from this level, Nagase developed an ultra-high accuracy and rigidity rotary table unit of max. φ2700. The rotation accuracy is 0.5μm in the radial direction and 0.2μm in the axial direction. By combining with Nagase’s large-size gate-type grinder, it allows super-precision rotary grinding. This technology is also incorporated in the super-precision rotary grinder of below φ1000 and super-precision lapping machine of φ2000 to create epoch-making machining solutions in both fields.
■ Rotary grinding by large-size gate-type grinder
■ φ2000 large-size super-precision lapping machine
■Super-precision rotary indexing unit
No other large-size indexing units have had submicron or nano-meter accuracy. Because of this, Nagase developed a super-precision rotary indexing unit to allow unconventional indexing and rotating accuracy. The minimum resolution is 0.000001°, indexing accuracy is 0.0003° and repeatability is below 0.0001°. There are both vertical type and horizontal type. The vertical type is incorporated into a processing machine for large-size (φ1300) aspherical lenses and a minute processing machine for smaller-size (φ300 – 700) with 1-nano resolution. The horizontal type is incorporated into a gear grinder for φ30 – 300 sizes and a super-precision grinder for large-size workpieces (2100mm × φ800).
■ Vertical super-precision rotary indexing unit mounted on the super-precision grinder
■ Horizontal super-precision rotary indexing unit mounted on the gear grinder
■Super–precision small-size indexing unit
Like the large-size unit, the small-size unit in the past was not equipped with an super-precision indexing function. Nagase has developed a light-weight and small-size, but accurate indexing unit. When the minimum resolution is 0.0001 deg., the indexing accuracy is 0.0003° and repeatability is below 0.0002. By mounting this unit on the existing Nagase grinder, carbide serration punches, spline gauges and punches can be machined easily. This unit is available as a single unit or can be incorporated into a machine in the development stage.
■ Super-precision small-size indexing unit mounted on the super-precision high reciprocating grinder for long workpieces
■Measurement and correction of grinding wheel dynamic balance
Conventionally, grinding wheel balance has been adjusted manually before mounting the wheel on the machine. In super-precision machining where nano-order surface roughness is pursued, however, the grinding wheel vibration of several μm level needs to be controlled. To achieve this, the grinding wheel dynamic balance automatic measurement & correction unit (NB-3012W) has been developed to measure the imbalanced grinding wheel during rotation accurately and correctly (patented world-wide). This unit is available for machining with a small to large-diameter grinding wheel.
■ New Balance Doctor NB-3012W
■Smart 3D probing
Evaluation and 3D form measurement of large workpieces have always been issues in pursuit of super-precision machining.
Nagase has developed a measurement function for the machine (equipped with a hydrostatic guide and super-precision linear motor drive method) with submicron motion accuracy, which is almost equivalent to that of the latest 3D measurement machine. As measurement accuracy, repeatability of 0.16μm is achieved when 3D form is included. Operation is easy when a joy stick is used. This technology will be applied into various machines in the near future.
■ Measurement on the grinder equipped with smart 3D probing function
■ Corrective machining is possible without dismounting the workpiece when ultra 3D machining function Smart Surfup is used
Customers who are thinking of introducing new facilities are welcome to ask us for test machining or to visit our factory. Please feel free to consult us. Inform us of your facility conditions, size and material of machining workpieces, machining time, etc., in details.
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