Product category:
Linear Position Sensors
News Release from: Newall Measurement Systems | Subject: MHG-TT linear encoders
Edited by the Engineeringtalk Editorial
Team on 12 December 2005
Linear encoders aid Spanish tool builder
Unamuno gets help from Newall to help enter the world of multi-axis CNC.
Spanish machine tool builder Unamuno has nearly 50 years experience in manufacturing automatic lathes used in industrial sectors such as the automotive industry, electrical products manufacture, medical orthopaedics and the sub-contract trade To adapt to new markets, Unamuno decided to enter the world of multi-axis CNC and in 2003 started work on the design of a numerically controlled lathe designed for bar-turning
This article was originally published on Engineeringtalk on 31 Jan 2002 at 8.00am (UK)
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The twin-spindle multi-axis turning centre requires seven axes of linear feedback and linear encoders are specified for position sensing.
In previous designs, glass based linear encoders had been used but were known to have problems with contamination reaching the encoder's moving parts and proving the cause of a potential failure.
Unamuno turned to Newall Measurement Systems and to the company's inductive linear encoder, which has no internal moving parts.
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Newall's SA100 single-axis digital readout system is specifically designed to increase productivity and machine tool efficiency within the machinery and metrology industries.
Philip Wilkinson, Unamuno Project Manager, said: "This is a newly developed machine which is still under evaluation".
"A rigorous testing programme is under way and so far tests have been very good".
The main gain is the lack of problems due to contamination.
Normal coolant pressure on CNC machines is 10bar.
So far, machining tests have been carried out at 50bar without problems with contamination.
The MHG linear encoders provide a standard differential quadrature output at RS422 TTL levels.
The device has a scale diameter of 5.75mm and is compatible with most digital readouts and controls.
IP67 sealing is standard so contamination is not an issue.
Newall supplied samples for evaluation and these were subsequently fitted onto development machines and subjected to a test programme.
The encoders provide quadrature square wave or sine-cosine feedback signals that allow for direct integration to servo driven applications.
The encoders use electromagnetic induction, which means that all electrical and electronic components are sealed from harsh working environments.
Inducing a 10kHz sinusoidal current through a single drive coil within the reader head generates an electromagnetic field.
This field interacts with the nickel chrome elements contained in the scale.
Four pickup coils detect variations in the induced field that are then combined and processed by the electronic circuitry to generate a signal that varies as the head moves along the scale.
Depending on the position of the reader head as it passes over each element, the phase shift of this pickup signal relative to the drive signal will vary between 0 and 360deg.
A DSP converts the analogue signal to the differential quadrature signal and generates the periodic reference marker pulse.
The design of these linear encoders allows installation in almost any position.
Optional self aligning fixing brackets ease scale mounting, needing only one hole for each set of brackets. Request a free brochure from Newall Measurement Systems ...
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