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Precision measuring in the environment of machine tools is a tough job.
The most important component in providing the ultimate in both
reliability and precision is a rack and pinion linear encoding device.
A Rack and Pinion Linear Encoder or
Resolver System incorporates lengths of precision measuring racks; an
enclosed channel; and an incremental rotary encoder or resolver with an
integral pinion. Our racks are ground with a crown which
reduces the need for precision pinion alignment. As motion occurs,
the pinion rotates along the racks causing the encoder/resolver
contained within the sealed housing to rotate. This rotation
reflects the change in linear positions, and the velocity is determined
by the frequency of pulses coming from the encoder/resolver.
The channel is a piece of steel,
physically connected to the machine. Constructed of machine steel,
the channel has the same thermal co-efficient of expansion as machinery
and will expand and contract at the same rate. All channels can be
joined to give unlimited lengths. The protective seals are fitted
in one piece after all installation work is complete. This is
suitable for pinions with 1"/rev. and a total reach of 1", such as BEI
Model H25E.
The precision racks are hardened and
ground #416 Stainless Steel. The racks are mounted with pitchline
on the neutral axis of the channel and laser calibrated to avoid
cumulative errors. The rack, mounted to the channel, is surrounded
by seals over the entire length of travel to prevent contamination.
As as additional precaution against particles adversely affecting
performance, the rack's teeth are facing down. If any contaminants
do penetrate the lipped seals, they will fall harmlessly to the bottom
of the housing or are wiped away by the wiping action of the pinion and
rack teeth.
The pinion is hobbed to AGMA Q15
integral in the shaft of the rotary encoder/resolver. The pinion
is lightly spring loaded against the rack to keep the total backlash
under .0001 inches. The pinion is constructed of a metal softer
than the ground rack to allow the pinion to be honed to the rack
pattern. Once matched to the rack pattern, there will
be negligible wear on the pinion due to the light preload and minimal
encoder inertia.
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