Product category:
Control systems, DROs, etc, for machine tools
News Release from: Newall Measurement Systems | Subject: SHG-AF absolute linear encoder
Edited by the Manufacturingtalk Editorial
Team on 07 August 2007
Linear encoders enliven vertical boring
mills
Retrofitting linear encoders to the older vertical boring mills/vertical turning lathes reduces scrap and rework rates by improving machgining accuracy and repeatability.
As skilled machinists capable of operating older CNC machine tools become scarcer, either the user has to scrap the machines and buy new, or it can consider retrofiiting Retrofitting Newall absolute linear encoders to three ageing vertical turning lathes (VTLs) at a UK aerospace manufacturer has improved accuracy and repeatability of the machines and helped eliminate expensive component scrap and rework rates
This article was originally published on Manufacturingtalk on 31 Jan 2002 at 8.00am (UK)
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Established for 20 years, Wigan-based systems integrator, A-Tec Systems, recently completed a contract to retrofit three older Morando VLN12 VTLs at an aerospace manufacturer.
As the machines were being moved to a new facility, the user thought it would be an ideal oppurtunity to implement a programme of refurbishment.
Specialising in the rebuild and retrofit of CNC machine tools, ISO9001 registered A-Tec set about assessing the necessary work.
Further reading
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Featuring a novel 'ball' technology, this digital encoder is competitively priced against glass- scale encoders and significantly reduces fitting time and dramatically increases efficiency levels.
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Offering OEMs, retrofitters and end users unbeatable value for money, a compact, easy-to-use, single-axis digital readout system is specifically designed to increase productivity.
Magnetically-encoded tape scale is supple, tough
Encoder system features a supple, magnetically-encoded tape scale, which is ideal for both rotary and linear applications, including long-bed machine tools.
"The machines required a complete refurbishment as they were running Allen Bradley CNCs that were at least 25 years old," related company partner Chris Hatfield.
"From a control perspective this meant a new CNC, a new panel and new servo-drives," he said.
The bridge axis on an Italian-built Morando VTL carries the X- and Z-axis.
A fundamental flaw in the configuration of the pre-retrofit machines was that any movement of the bridge by the operator would require the DRO reading to be input manually as an offset into the CNC.
This would be prone to costly operator error, particularly over three shifts when communication problems were common.
The special aerospace alloys are expensive - some component billets at the end user cost several thousands of pounds each.
Accidently programming the quill to collide with the VTL's chuck or workpiece could destroy entire features and potentially scrap whole parts.
"The answer was to fit an absolute linear encoder to the bridge," said Hatfield.
"There were two main requirements here: firstly the encoder had to offer good resistance to potential contamination in the form of swarf, oil and coolant; and secondly it had to be easy to mount.
In both cases a conventional glass-scale type encoder didn't fit the bill".
A-Tec selected a Newall SHG-AF absolute linear encoder, which can be installed in almost any position - unlike glass-scale linear encoders, which usually need to be installed with the lip seal facing downwards to prevent contamination.
Self-aligning fixing brackets permit virtually effortless scale mounting, needing only a single hole for each set of brackets.
A-Tec's preferred CNC for the VTLs was Fanuc.
The reasons were as follows.
* The SHG-AF has a protocol that is proprietary to Fanuc and available on the majority of Fanuc control systems.
The Fanuc CNC makes a request for positional data and the encoder responds correctly with data within a strictly controlled time state.
* The SHG-AF absolute linear encoder provides a true absolute position immediately upon power-up.
The encoder does not use batteries or static memory to retain the positional data.
True position can be re-acquired once power is applied, regardless of duration or power-off movements.
* Interface software developed by A-Tec means that any offset movement of the bridge by the operator (even in-cycle movement) is now relayed to the CNC automatically.
"On each machine we mounted the Newall encoder in an unprotected position on the side of the column, safe in the knowledge that any contamination would not affect its performance" continued Hatfield.
"What's more, thanks to Newall's two-point suspension system, there was no need to provide a machined surface for mounting or create a spar using spacers." Hatfield said that since the encoders have been fitted there have been no incidents of bridge-related failures, which previously were the biggest single contributor to component damage.
A-Tec Systems successfully manage a diverse range of projects.
Varying in complexity from servo and CNC control retrofits to bespoke turnkey machines designed from the ground up.
In each case the control system, servo drives and interface software are designed specifically to meet customer needs. Request a free brochure from Newall Measurement Systems ...
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