Test & measurement
Reducing manufacturing and maintenance costs
production cost is well known. Advanced design and manufacturing techniques can help to reduce costs, but parts with tight tolerances generally have a higher cost. Tolerance stacks occur when modules are
T
assembled from parts that must fit together. The overall tolerance stack of an assembly of parts can be calculated by summing all individual feature tolerances. Therefore, the required dimensional precision of each part can increase proportionally as the number of parts increases in the tolerance stack. By increasing the overall dimensional
tolerances of an assembly, significant cost reductions are possible, due to easing of the tolerance requirements of each component. Furthermore, the time taken to align and
fit assemblies can be reduced with faster, well-designed installation procedures that help to minimise both associated costs and product lead times.
How can QUanTic encoders increase profiTabiliTy and redUce lead Times? Optical position encoders are used in a huge variety of machines and devices. They consist of an electro-optical readhead (sensor) and a precision graduated rotary or linear scale. The
he challenge of producing machine component assemblies with ever tighter machining tolerances at low
readhead measures linear position or rotation by optically sensing the regularly spaced scale markings and outputs this information as an analogue or digital signal.
wider insTallaTion Tolerances
Consider the example of an encoder installed on a rotary drive shaft. The shaft is machined to enable an interference fit with a rotary encoder ring, such as Renishaw’s RESM40, and the readhead is mounted on a bracket above the ring such that the separation (rideheight) between the scale surface and readhead is maintained to within a tolerance of ±0.1 mm. If the rideheight tolerance is doubled, the tolerances on the shaft, ring assembly and readhead mounting bracket can also be doubled, which may result in a significant time and cost saving over a long production run. The QUANTiC encoder series combines leading-edge filtering optics and interpolation technology to create a high performance, super- compact, incremental, open optical encoder. QUANTiC encoders feature exceptional installation tolerances and excellent dirt immunity due to an advanced photodetector design and coarser 40 µm-pitch scale. For instance, readhead installation rideheight and yaw tolerances are now ±0.2 mm and ±0.9°, respectively.
fasTer macHine calibraTion wiTH less mainTenance The time taken by a skilled operator to install and calibrate multiple encoders on a machine represents a significant cost. By designing the encoder to be simple and intuitive to install and calibrate, such that a semi-skilled worker may perform this task, labour and time costs are reduced.
QUANTiC encoders feature ease of set-up
and calibration, and are supported by the Advanced Diagnostic Tool (ADT) combining both ADTi-100 hardware and ADT View software components. The ADT acquires comprehensive real-time data from the readhead to assist with quick and easy encoder installation, and in-field fault finding, potentially saving time and reducing installation and maintenance costs. During scheduled and preventative maintenance, this off-line diagnostic tool can test key performance parameters of a QUANTiC encoder system, such as signal strength, readhead pitch and Lissajous output. QUANTiC encoders also offer end users
a lower total cost of ownership due to robust design features, such as higher dirt immunity and wider operating tolerances, which may decrease the downtime required for scheduled maintenance.
design flexibiliTy Designers can specify a range of QUANTiC encoder options including resolution, signal output, scale type, reference marks and cable lengths. One benefit of the
QUANTiC encoder design is the elimination of additional bulky external interfaces, which is particularly useful for space- constrained applications. This innovative approach was first used for Renishaw’s advanced VIONiC encoders. QUANTiC readheads now offer digital or analogue outputs and are compatible with linear, partial arc and rotary scales. The choice of either a digital or analogue signal output enables direct manipulation of the signal inside the controller, which may be preferred for highly dynamic applications where refined velocity and acceleration control are required.
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August 2021 Instrumentation Monthly
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