Glass linear encoders for length machine retrofits

A low-cost retrofit digital readout and glass linear encoder package from Anilam is enabling SIP (UK) to boost the productivity of ageing SIP length measuring machines

A low-cost retrofit digital readout (DRO) and glass linear encoder package from Anilam is enabling precision machine tool and measuring machine specialist SIP (UK) to boost the productivity of ageing SIP length measuring machines (LMMs).

Costing from only 15 per cent compared with buying new, the high-performance retrofit package is based on the use of Anilam's MSA 6705 linear encoder and Z715 DRO.

The linear encoder, which boasts a highly-accurate measuring resolution of 0.1 micron, reinstates the machines' sub-micron measuring capability while the DRO effectively reduces operator fatigue and therefore speeds up the task of length measurement and calibration.

Manufactured in Switzerland by SIP (UK)'s parent, Societe Genevoise d'Instruments de Physique, LMMs measure and calibrate gauges, instruments and other master references.

They are widely used throughout the aerospace sector, for example, as well as by gauge manufacturers and calibration laboratories.

SIP (UK) is initially targeting the older LMM models, the 305M and MUL-300, of which hundreds are in use throughout the UK.

There is also a conversion available for the 214B co-ordinate measuring machine, which is used in similar environments.

According to Geoff Taylor, managing director of SIP (UK): "We're finding that the mechanical structure of LMMs made by SIP even 40 years ago are still perfectly sound and stable.

But users are finding it increasingly difficult to maintain them.

A typical LMM retrofit can be carried out within a day and can be performed on-site or at the SIP (UK) premises in Coventry.

A loan machine is available if the retrofit is likely to hinder production.

The retrofit involves removal of the LMM's electronics and measuring system - depending on model, microscope or DRO scales/rotary encoder linked by a system of mirrors, projectors and photo detectors.

The new Metric/Imperial switchable system, which has an RS232 printer interface, is then laser calibrated.

"We chose the Anilam glass linear encoder package due to the system's functionality, accuracy and cost-effectiveness," adds Doug Mynard, sales and applications manager at SIP (UK).

"In addition, the encoder's build quality is particularly good compared with alternative systems - especially the use of four mm thick glass, neoprene seals and Anilam's exclusive low force lip seal design which also eliminates any possibility of contamination.

Phil Goulding, Anilam's UK general manager, comments that accuracy is always the key denominator when comparing encoders, and was obviously at the forefront of the discussions with SIP (UK).

"Anilam ensures encoder accuracy by adding the hard chrome graduations to the glass in a vacuum, then the scale is mounted in a one-piece extrusion using elastic adhesive.

"Coupled with the fact that the roller bearing-guided reader heads consistently maintain their position relative to the grating, the result in the case of the MSA 6705 is predictable and repeatable measuring to +/- 2 microns per metre.

The LMM retrofits currently involve one-axis (measuring axis) conversions, and SIP (UK) is also developing a two-axis system involving the rise and fall of a universal table for measuring tapers.

Also for the future, the company is working with a university to satisfy a plan to provide links to a PC with measuring software and gauge management, for example.

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