Largest reflector telescope in China uses custom eddy current sensors

Precision sensor specialist Micro-Epsilon has supplied 600 eddy current sensors to the Chinese Academy of Science for use on the LAMOST (Large sky Area Multi-Object fibre Spectroscopic Telescope), the largest reflector telescope in China.

The custom-developed eddy current sensors have a measuring range of 2mm and provide extremely high resolution of just 1nm (nanometre). The sensors also offer long-term stability of better than 20nm over 3-4 hours (a typical operating cycle for the telescope). The function of the sensors is to compensate for any slight movement of the lenses used by the telescope.

LAMOST is located in the Chinese observatory at Yinglong Station near Peking. The telescope is a new type of segmented reflector telescope for the spectroscopic surveying of space. The project is part of the ESO (European Southern Observatory), a European organisation that builds and operates a suite of the world's most advanced ground-based astronomical telescopes.

LAMOST (Large sky Area Multi-Object fibre Spectroscopic Telescope),

The sensors are critical to the successful operation of the telescope. The telescope comprises a series of lens and numerous hexagonal-shaped mirrors. A primary mirror receives light from space and directs it to a correction mirror, which is in the focus of the primary mirror. The corrector, in turn, bundles the light information onto an optical element (in this case a fibre optic cable).

The diameter of the primary mirror is approximately 4m. The primary mirror and corrector comprise 46 or 24 individual mirror segments, which can be moved and adjusted to receive different angles of between -10 and +90 degrees. Due to the high optical resolution of the telescope, the mirrors have to be precisely aligned with each other at all times, as well as consistently flat and uniform. The smallest movement of these mirrors due to thermal expansion means the telescope will lose focus.

The telescope is used primarily at night to scan the sky. Before it can be used, regulr calibrations of the telescope are required, which take between 3 and 4 hours to complete. For these calibrations, the sensors have to be extremely stable, as the slightest drift of the sensor can result in changes in output.

Originally, LAMOST utilised capacitive displacement sensors from another supplier. However, these sensors functioned poorly because they were sensitive to contamination (dirt and dust) and humidity (condensation), as the sensors are exposed to the elements when the telescope is in operation.

Chris Jones, Managing Director at Micro-Epsilon (UK) Ltd comments: "The way we solved the problem was to develop a completely new sensor by using special materials and components with very low thermal expansion coefficients. Using in-house electronics expertise, we also developed brand new electronics that measure 600 sensor channels. Again, these electronics were developed specifically to give extremely high thermal stability in the application."

The sensor lenses are made from ZERODUR, a zero expansion glass ceramic material that offers a very high thermal stability of 0.05ppm/degrees K. ZERODUR is an inorganic, non-porous glass ceramic that has a completely non-directional, isotropic structure. Due to the perfect balance of glass and crystal phases within the material, the thermal expansion coefficient is almost zero.
Other components inside the sensor are made from boron nitride, which has a temperature stability of 2-3ppm/degrees K. The combined temperature stability of the sensor is 0.5ppm/degrees K.

As Jones concludes: "Despite the high proportion of custom developments required for this application, Micro-Epsilon was able to complete the new developments in just nine months from initial contact with the customer."

For further information, email: info@micro-epsilon.co.uk or view website: www.micro-epsilon.co.uk    Refer to page 25

Precision cleaning and drying process

Layton Technologies, the specialist component cleaning equipment manufacturer, has developed a precision cleaning and drying process for the effective removal of flux and associated contamination from printed circuit boards.

Based on the application of the latest high solvency cleaning chemistries for removing residues from PCBs produced using 'No-clean' and 'No-lead fluxes', Layton have worked closely with Dupont and their new generation of highly effective defluxing solvents - Vertrel SFR to provide a complete board cleaning process. 

Layton developed the latest PCB cleaning systems to provide a more effective solution to manufacturers of high value electronics components destined for critical applications where cleanliness standards and validation are paramount.

The Layton Bluestone FRS system is a fully automated and enclosed system which offers the highest level of solvent containment is efficient, fast and gives controlled cleaning and drying with high standards of operator safety and environmental acceptance.

Overall the new Bluestone package provides a much faster process than many conventional cleaning methods, with significant cost savings on solvent use and superior ionic cleanliness results.

Layton have a full demonstration and testing facility at their North Staffordshire manufacturing base and offer a complete cleaning trials and evaluation service for companies who wish to test the new cleaning process on their products and to view the equipment to establish its advantages and suitability.

Layton provides a range of cleaning technologies for the electronics, semi-conductor and precision components industries. These technologies include PCB cleaners using a range of solvents, flammable solvent cleaners, wet-benches, vapour driers and aqueous ultrasonic cleaning systems.

For further information, e-mail: ianparry@laytontechnologies.com or view website: www.laytontechnologies.com    Refer to page 65

Programming robots for high speed, high precision work

'Neighbours, everybody needs good neighbours' goes that vaguely-familiar theme tune, although in this instance the neighbours are two cutting-edge businesses in trendy Totnes, Devon.

Inject Plastics is a trade injection moulder producing a huge variety of plastic parts, whilst literally across the road is Barr & Paatz, a leading industrial robotics specialist. With one company committed to high technology production and the other specialising in process automation, it was almost inevitable that their paths would cross commercially.

Not unusually, the project in question concerned programming a robot for high speed, high precision work, in a fully automated workcell. Less commonly, it involved a powerful 6-axis robot already installed alongside an injection moulding machine, rather than designing the cell layout from scratch.

A family-owned business established in 1986, Inject Plastics is based in a modern 13,000sq ft factory on the town's industrial estate, adjacent to the Barr & Paatz premises. It invests continually in leading edge technology and is equipped with the latest microprocessor-controlled Demag injection moulding machines, with clamping forces ranging from 35 tonnes to 300 tonnes, enabling it to produce plastic parts up to a kilogram in weight. Unlike many injection moulding companies, which tend to employ simple 3-axis Cartesian fixed automation systems for demoulding, Inject Plastics also boasts a 6-axis, Stäubli RX 90L industrial robot, with a reach of almost 1200mm, a maximum payload capacity of 6kg and an impressive repeatability of ±0.025mm.

Programming a robot for high speed, high precision work, in a fully automated workcell, involved a powerful 6-axis robot.

"Cartesian systems are OK for loading and unloading, but not sufficiently adaptable to perform the other operations and movements frequently required, such as rotating the moulding or assembling components," says Inject Plastics MD, Richard Bromley. "A six-axis robot, with its full range of accurate and repeatable motion over a wide work envelope, provides the ideal, cost-effective automation solution."

Industrial robots can also be reprogrammed and redeployed for other processing tasks, an inherent flexibility that was exploited by Barr & Paatz on this project. On behalf of a trade customer, Inject Plastics produces precision mouldings for scratch-resistant safety goggles and the Stäubli robot was previously used as a pick & place device in a process that involved laying paper-thin plastic film inside the moulding tool and injecting plastic onto the back. However, a product redesign necessitated adding film to both faces of the optical moulding, creating a three-layer sandwich, which meant fully automating the more complex process.

"Since Barr & Paatz is an authorised Stäubli integrator, knows the robot configuration well and has in-depth programming experience, we turned to our neighbours for expert help," says Richard. "We're more than happy with the work they've done and now they're the first people we talk to regarding other process automation applications."

Since the robot and some safety guarding were already installed, revising the whole cell layout for optimum performance was impractical, so Barr & Paatz had to work within existing parameters and add ancillary equipment for such functions as film handling, bonding and gate cropping. The robot specialists also incorporated new loading mechanisms, extra guarding and safety interlocks, as well as air filtration equipment that enables the workcell to operate in a dust-free environment.

The moulded goggle lenses are curved to eliminate optical distortion, but the robot starts by configuring the end-of-arm tooling to pick up flat plastic film, which is achieved by first docking the tool into a custom-powered drive configuration that mechanically flattens the shape. Once the tool is in the flat figuration, the robot collects two separate strips of plastic film, one on either side, then returns to the drive station to reconfigure the tool into a curved format.

When the moulding machine is open and ready, the robot rotates the end effector 90º and removes the finished product by means of vacuum cups, then flips back 90º and loads the new film onto each face of the mould, ready to produce the next three-layer optical lens. Finally, the robot deposits the finished product onto the exit conveyor and is ready to start the whole cycle again.

"The whole process is completed without the product being touched by human hand, which contributes to its optical integrity. Quite frankly, it would be impossible to produce these parts to the required standard and in the quantities involved, using manual procedures," concludes Richard. "Robotics eliminates the costly labour element from the process and it's fair to say that the operator's skill set has actually increased, since he has had to become familiar with the working kinematics of the robot."

For further information, email: s.paatz@barr-paatz.co.uk or  view website: www.barr-paatz.co.uk    Refer to page 24