Sealed linear encoder delivers sub-micron positioning resolution

A manufacturer of specialist production machinery has selected the Heidenhain LF481C sealed, compact, incremental linear encoder for a new micro dicing machine that has to obtain - and maintain - an axis positioning resolution of 0.1 micron.

Increasing global demands in the highly-challenging prototyping and production of silicon wafer and related substrates have played directly into the hands of Loadpoint. The company has carved a niche in manufacturing bespoke equipment for cutting, dicing, grinding, polishing, slitting and drilling components used in the semiconductor, printer head, optical, ultrasound scanning and medical diagnostic sectors.

The MicroAce 66 model 150 x 150 x 10mm capacity micro dicing machine is the latest example of how Loadpoint meets the challenges posed by bespoke high-precision equipment: the machine had to obtain - and maintain - an axis positioning resolution of 0.1 micron to consistently achieve a pitch accuracy of better than three microns when dicing across components.

To achieve this goal, the MicroAce 66 has a closed-loop feedback system for ultra-precise control over the programmed cutting process, which can involve dicing wheels as large as 75mm diameter and slitting wheels as thin as 15 microns.

By working very closely with Heidenhain (GB), Loadpoint's choice of Heidenhain LF481C sealed, compact, incremental linear encoders not only provided the required level of positioning accuracy and repeatability but also, according to Clive Bond, Chief Engineer: "Use of the Heidenhain brand effectively provides the customer with a renowned reference standard."

Customer confidence

With almost 90 per cent of Loadpoint equipment being exported, Bond reflects how one European customer challenged the company's ability to build a machine that would be able to provide such precise levels of pitch accuracy for slotting silicon wafers. He says: "Our response was to contact Heidenhain and, by utilising the Heidenhain VM182 comparator system, we put the customer totally at ease."

The VM 182 system incorporates a steel scale with two co-ordinate phase gratings and a scanning head connected to the scale by an auxiliary carriage. The scale is clamped to the table and the scanning head to the machine spindle. Bond explains: "This qualified, without any doubt and according to ISO 230-2, both linear and non-linear error curves as well as any reverse error in each of the machine axes. So successful was the trial that we now take this reference to customer sites when we check and recalibrate machines."

Custom machinery

Based in Cricklade near Swindon, Loadpoint has progressively built its business over 40 years to provide a micro-machining sub-contract operation as well as a machine, process development and prototyping facility that is said to be one of the most advanced facilities of its type in the UK. The company has a turnover of some £3million and employs 25 people. High on its agenda is the continuous development of bespoke machinery capable of working in micron and sub-micron applications.

It enjoys a long relationship with Heidenhain, having utilised and capitalised on Heidenhain linear scales 35 years ago while its competitors were still relying on open-loop stepping motors. This move became the foundation stone in its ability to achieve higher orders of precision and repeatability, and it inevitably led to a particular focus on special applications.

Loadpoint's development laboratory has seen various special machines and processes created for machining silicon, silicon carbide, glass, quartz, gallium arsenide, germanium, lithium niobate, lithium tantalate, sapphire, lead zirconate and titanate (PZT), as well as equipment for processing components such as wafers, substrates, plates, laminates, rods, blocks, tubes and assemblies.

With such a wide range of different and challenging applications, Loadpoint has become largely self-sufficient in order to meet the precise demands of the development of customised equipment - it even has its own nano control system featuring high-level diagnostics and remote communication.

Proprietary software

In addition, Loadpoint develops its own software and such is this level of expertise that in-house programs are able to monitor process quality by including the company's own Kerf Check for measuring the width of cut, size and area of chipping, while also identifying and correcting alignment offset errors. The software also monitors and display spindle current, blade wear, chuck vacuum and the co-ordinates for each of the required machine axes.

The latest MicroAce 66 machine (launched in January 2010) has X and Y axis travels of 160 and 164mm, respectively, and a Z axis able to accept components up to 10mm thick when using the maximum size slitting wheel of 76.2mm.

Each axis is fitted with the Heidenhain LF481C linear scale for position feedback, which also includes Heidenhain's mounting spar; this means that, in the event of an encoder change, there is no requirement for drawn-out clocking procedures to establish datum positions.

Sealed encoder

The linear encoder is fully protected from dust and other contaminant, and an aluminium housing and elastic sealing lips protect the scale, scanning carriage and guideway. Indeed, the significant benefit of the LF481C (pictured right) being sealed was another major factor in Heidenhain securing this business against a supplier of exposed scales.

The 1.2kW air bearing spindle has a top speed of 80,000rpm (the optional alternative is 2.4kW and 60,000rpm) and this works in conjunction with a theta-axis bearing rotary table with vacuum chuck. The table has a high-resolution, direct-drive torque motor with an axis resolution of 0.0004 degrees. A four-direction coolant delivery system has outlets for main the blade jet, side wash bars, wafer fan jets and flood jets.

Also incorporated in the full-screen display vision and alignment system is monocular video alignment that incorporates pattern recognition with a Z axis autofocus to set up the alignment of the image. Through-the-lens LED illumination and external high-intensity LED fibre ring illumination are also included.

About the Heidenhain LF481C linear encoder

Heidenhain's LF481C is one of a comprehensive range available from the company. Sealed linear encoders are available with full-size scale housings for high resistance to vibration up to measuring lengths of 30m, as well as slimline scale housings for measuring lengths up to 2040mm in applications where installation space is limited.

Follow the link for more information about Heidenhain's portfolio of linear encoders and length gauges.

Heidenhain (GB) Ltd

200 London Road
RH15 9RD

+44 (0)1444 247711

More from Heidenhain (GB) Ltd

Telescope relies on tape encoders

Posted 1 week ago

What’s your position on encoders?

Posted 1 month ago

Heidenhain compact rotary encoders with Drive-CLiQ interface

Posted 1 year ago

Heidenhain (GB) celebrates 50th anniversary

Posted 1 year ago

Compact linear encoder resolves to 2 nanometres

Posted 3 years ago

First Heidenhain control with touchscreen

Posted 3 years ago

Hollow-shaft encoders with inductive circumferential scanning

Posted 3 years ago

CNC systems, probes, encoders and motors to be promoted

Posted 3 years ago

Robust rotary encoders for arduous applications

Posted 4 years ago

New ring encoders with absolute feedback

Posted 4 years ago

ERO 2000: high-accuracy miniature angle encoder

Posted 4 years ago

Jones & Shipman switches to Heidenhain encoders

Posted 5 years ago

New representation for Heidenhain in Scotland

Posted 5 years ago

Heidenhain provides student scholarships in metrology

Posted 5 years ago

Automated quality management system for production lines

Posted 5 years ago

Heidenhain LC 200: additional important interface variants

Posted 6 years ago

Absolute encoders feature hollow shafts and integral bearings

Posted 9 years ago

Trade-in offer reduces cost of upgrading machine tool DRO

Posted 10 years ago

Linear encoders for use in high and ultra-high vacuums

Posted 10 years ago

IP64 absolute encoders for safety-related control applications

Posted 10 years ago

Electronic handwheel eases machine set-ups

Posted 10 years ago

See Heidenhain's angular, linear and rotary encoders

Posted 10 years ago

Absolute encoders are central to success of theatrical effects

Posted 10 years ago

Heidenhain to exhibit new products at EMO 2007

Posted 13 years ago

Heidenhain delivers 200,000th NC control unit

Posted 13 years ago

More applications
13 hours ago
Modular safety relay claimed to be world first
Pilz says that its all-new myPNOZ is the world’s first batch size 1 safety relay
21 hours ago
Edge computing hardware and software choices for machine builders
RDS and AAEON offer machine builders an even greater choice of hardware and software to build high performance, integrated solutions for smart applications that require vision data to be processed at the edge
3 days ago
Certified Machinery Safety Expert course on 18th January
In conjunction with TÜV NORD, Pilz Automation UK is hosting its first CMSE Course of 2021. It starts on 18th January and lasts for four days
3 days ago
Improving communication with (and between) machines
Lenze has published a White Paper discussing PackML, a programming standard defined by OMAC, the Organisation for Machine Automation & Control. Here, Lenze's Marc Vissers provides machine builders with an insight into the paper
3 days ago
Danfoss buys Artemis Intelligent Power
Danfoss says it will allow them to begin the global commercial rollout of its Digital Displacement® pump technology, a disruptive low-carbon opportunity with applications in the industrial and off-highway markets
4 days ago
Quarter turn fastener that still turns heads
Automotive manufacturers are gradually making the transition from solely manufacturing vehicles to taking on more responsibility for the performance of a vehicle over its life cycle. As a result, OEMs are increasingly looking for ways to lower installation costs, and facilitate quick repeatable access to critical vehicle components in order to enable faster service calls
4 days ago
Wave spring or coil spring?
Simon Ward is Technical Manager at Uckfield-based fastener specialists TFC. Here he offers a machine designers a comparison between wave springs and round wire coil springs 
4 days ago
New course: Safety Design Incorporating EN ISO 13849-1/EN 62061
Pilz Automation UK says that this training course is designed to enable delegates to develop a greater understanding of the processes and standards related to safety control system specification, design and validation
5 days ago
Intelliconnect moves to larger factory as sales grow
Intelliconnect (Europe) Ltd has moved to a larger facility at the Corby Innovation Hub
5 days ago
ABB industrial robots get Wizard programming
ABB is expanding it Wizard easy programming tool to encompass its industrial robot range, saying that it makes robots easier to install, programme and operate without specialised training