Optical and analytical developments

The story this week covers viscosity measurement on-line, where Hydramotion have reported that their XL7 viscometer has been able to significantly improve the efficiency of paper recycling operations, involving the use of different grades of starch, for Amcor in Sydney. More and more on-line analysis measurement systems provide process plant control, taking the lab onto the plant: plus several systems these days are described as “At-line”, where lab techniques are automated and use alongside the flow line, giving a response in a few minutes, instead of hours or even a day. Significant examples of this style of equipment are offered by Applikon Analytical, who can even conduct titration analytical measurements at-line in a hazardous area.

Tiger Optics offer a parts per trillion analyzer system for HF and HCl gases. The Tiger-i line employs the patented Tiger Optics continuous wave cavity ring-down spectroscopy (also known as CW-CRDS!), which basically uses the attenuation of multiple laser beam at a specific absorption wavelength passes through a sample cell to monitor the gas concentration, by comparison with an ‘off-peak’ beam. It is a very clever way of making a measurement independent of the mirror state and the natural air attenuation at the time, and can be tuned for other specific gases, for anyone that needs ppt monitoring: explosives and drugs come to mind.

Just as clever, but in a pharmaceutical application, is the Malvern Instruments use of their Morphologi high sensitivity particle characterisation system to slash the time required to analyse particles in a pharmaceutical ointment, typically down to just 15 minutes. This uses an automated system to size and count the particles, rather than an operator, so improves consistency and accuracy as well as the time involved. In a similar vein, the Hosokawa Mixing Sensor uses an optical reflection measurement to monitor a mixing process by looking for variations in particle size, colour, density and roughness, to determine the optimum mixing time. Last week another report also used optical techniques, this time video smoke detection in the tunnels at the Palm Jumeirah development in Dubai: the D-Tec FireVu system analyses normal CCTV system images, automating the detection of smoke to give alarm initiation faster than a human operator.

The Farnborough air show and exhibition produced some interesting spin-off applications of Defence Technology: the ‘Hawkeye’ system used at Wimbledon actually was a spin-off from MoD work on missile tracking systems – and the latest system for measuring a child’s foot size for shoe fitting comes from a 3D camera developed by QinetiQ for battlefield applications. Perhaps showing the reverse track, engine health monitoring technology used on RR Trent engines has been developed so far that it is being used by OBS Medical for giving advance warning of the initiation of strokes and heart attacks in patient monitoring systems.

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Paper catalogues vs websites

Recent news from RS Components is the most telling of all accounts of the changes the web has made to the old-established industrial catalogue-based distribution companies, with the names we might have recognized many years ago, like Radiospares and Flowbits. Over 50% of the RS Components sales revenue in June originated from their website, a milestone achieved 9 months ahead of their predictions, ie twice as fast as the forecasts made last October (Link). Once again the growth of the use of the web in business has been faster than even the people on the front line expected. But I wonder what proportion of the engineers ordering from RS over the web, still use a paper catalogue to establish what style of product they want, and what the catalogue calls it, before searching for current product info and options available on the web? Possibly the paper catalogues will evolve into the presentation of general data and keywords, leaving detailed spec sheets and product options for website publication only. Or maybe I am wrong, have the engineers thrown away all paper catalogues?

The most interesting aspect about the growth of the on-line sales of the major distribution companies is that this web growth is achieved despite the obvious business challenge – that the product offered by the distributor is also available direct from the website of the manufacturer, or main importer, and probably is presented there at a significantly lower price, and also ex-stock. It is only because of lack of time, or laziness, that the purchasing engineer does not seek out the same product on other websites, to find lower prices and further options. The specialized suppliers and distributors, with their own niche catalogues, have also developed their own websites, and will be quickly moving into web ordering with ex-stock delivery: for example Testo has on-line webshops in 9 separate countries for their air flow and humidity instrumentation (Link). PVL, in the UK, have developed their ‘Big Kat’ catalogue, concentrating on pressure, vacuum and level switches, as a paper copy, but have a parallel website presentation for the same products. Their business is based on the free offer of knowledgeable product advice and support at the end of a phone, which is often needed when dealing with the different fluids and corrosion potential in level and pressure applications, and can take the order at the same time (Link). Nevertheless they offer on-line industrial shopping at an associated company, Plan-B Marketing, which provides more general use instrumentation kits, and compressed air devices: like the ‘Ecliptical’ valve, which is a delightful word for a device that allows occasional insertion of their ClimaAir thermal meter into a compressed air line to monitor flowrates (Link).

Greenhouse gas emissions

The potential atmospheric damage of the ‘greenhouse’ gas emissions from industrial processes are often quoted in the media, and this is an area where maybe the processing industry does not blow its own trumpet enough, over the investment and attention that goes into preventing harmful gas emissions. In June there were several developments and announcements about CO2 and carbon capture schemes. But it seems that even the Daily Telegraph is now joining in with uninvestigated scare stories: last week an article suggested that the Flatscreen TV boom is causing the production of 4000 tonnes of NF3 a year, with the conclusion that if this were all released, it would be equivalent to 67million tones of CO2, or as much as the whole of Austria.

The reality is a lot different. The gas used is very carefully controlled and neutralised. A Special Report* earlier this year, published after a visit to Edwards in Burgess Hill, mainly discussed their vacuum pumps. They are major suppliers of vacuum pumps to the plants that produce Flatscreen TVs and solar panels, as well as to the semiconductor industry. Mainly located in Korea, these plants use vapour deposition of chemical layers onto a glass substrate to create the panels. Edwards have worked with these manufacturers and have developed specialist expertise as their major supplier of “Gas Abatement Systems” – i.e the systems that catch the gases sucked out by the vacuum pumps, and that then neutralise them, so that they are not emitted into the atmosphere. From Edwards, their Chief Technology Officer, Dr Stephen Ormrod, advises that the role for the quoted NF3 is as a source of fluorine, which is used as a cleaning agent to react with any silicon deposits in the chambers, to create gaseous fluorides that can be pumped away. The excess NF3 and fluorine in the chamber also cleans out the vacuum pumps! Downstream from there, these surplus and waste gases are fed into the Edwards Abatement Systems, the path includes passing through a flame to create hydrofluoric acid, which is then captured in a water scrubber, neutralised, and probably ends up back as calcium fluoride, which is the raw material that, as a mineral, Air Products started from, in order to manufacture the NF3. Edwards have been supplying Abatement Systems to deal with the Flatscreen TV production gases like the NF3 quoted by the Telegraph, but there have been other recent reports on other similar applications. For example, also from Edwards, there was an application on solar cell production at Solsonica in Italy (Link), and AirProtekt has supplied a Regenerative Thermal Oxidation system, plus a special scrubber, to a textile manufacturer to remove fluorine contaminants from its gaseous exhaust (Link).

Effluent control is very important, whatever industry it comes from, and it is one of the areas where I am always keen to highlight good modern technology and products being used to monitor and control discharges back to the environment.

*See https://nickdenbow.wordpress.com/2008/06/05/new-techniques-in-high-vacuum-at-edwards/

A dozen Robot ‘Do’s and Don’ts’

Stirling Paatz, of robot integrators Barr and Paatz, provided tips for avoiding specification mistakes on industrial robots: these at first glance looked fairly straightforward, even back on 1 July 2008, when the article was first published.

Typically, there’s a picture of the particular model, looking sleek and stylish, unblemished by external cabling, end-of-arm tooling, feed mechanisms and safety guards.

Then there are the quoted figures: number of axes, maximum payload, reach, repeatability, maximum speed, cycle time and installation footprint.

All these specifications seem comparable, manufacturer to manufacturer, so it’s like buying a car or a TV, surely……

Actually, it’s not.

During my many years designing and commissioning robot workcells, I’ve encountered many mistakes and oversights when specifying a robot for a particular task.

Some I made myself, in the early days when robotics was still an unfamiliar technology; most I had to fix for frustrated robot buyers, whose machines wouldn’t do what they were supposed to do.

So I have assembled a dozen of the most common robot ‘do’s and don’ts’, partly to help those new to robotics avoid the worst pitfalls, but mainly to emphasise that specifying and building robot workcells is a specialist job, best left to specialists.

It’s what I do.

1) Don’t overestimate speed performance.

Although manufacturer speed data is usually honest, a robot won’t operate at full speed throughout its work cycle, nor will it interact with the workpiece at maximum speed.

You also need to allow for the gripper to secure and release the workpiece, which slows the cycle time.

True, some manufacturers do quote cycle times, based on a benchmark function, but this relates to a simple pick and place operation, not necessarily your application.

No, the only way to get an accurate estimate of speeds and cycle times is to pre-design an actual workcell simulation, which I’ll come to later.

2) Do make allowances for the end-effector.

The end-effector is the end of arm tooling that grips the workpiece, usually by means of grippers, suction or magnetics.

The gripper or vacuum cup needs to pick up the workpiece with sufficient force for the weight of the object, but without too much aggression that it marks or damages the object.

You also need to take into account the robot acceleration forces during a high speed work cycle, which can actually lever open grippers or peel the workpiece straight off the vacuum cup.

The weight of the end-effector, together with its cable or hose, needs to be added into the equation, when specifying the machine, which leads to…

3) Don’t underestimate payload requirements.

A common specifying error is to omit the weight of the end-effector and associated cabling when calculating payload.

A robotic gripper, which employs jaws or fingers to hold the workpiece, can weigh several kilos, which is why lighter vacuum cups are often specified, although they require vacuum generators and hose that must also be factored into the payload.

Kinetic forces generated by off-centre payloads, as well as torsional forces created at the extreme end of the robot arm travel, should also be accommodated in your calculations.

Remember too that the maximum payload is just that, an occasional maximum limit, not the normal operating capacity.

4) Do take the robot arm into account.

If you’ve ever played snooker in a room that was too small or tried to saw wood tight against a wall, you’ll appreciate what I mean.

A robot, especially a 6-axis articulated robot, has an arm mechanism very similar to a human arm, complete with jointed elbow.

It has a large work envelope, almost spherical in shape, and the end-effector can be manipulated to any position or orientation within that envelope.

However, when laying out the workcell, many people focus solely on the end-effector, forgetting the rest of the arm and particularly that flying elbow.

Given the speed of movement, there is great potential for mechanical damage if the rest of the arm is overlooked.

5) Don’t overlook cable management.

Cable management is a major installation issue that is often forgotten.

Although it is possible to channel cables and pneumatic hose internally through the robot base and arm, in most cases some level of external cable routing is required.

Here, the very flexibility of the robot arm and its high speed movement pose a problem, since you need to plan the cable routing to avoid snagging, tangling and stressing sensitive connecting wires.

Designing cable runs to allow unrestricted movement of the robot manipulator is quite an art and happily there are flexible cable carrying systems available, which are able to withstand the twisting movement, high-speed friction, and harsh operating environments associated with such applications.

6) Do provide for operating conditions.

The conditions in which the robot will be operating, whether it’s a dusty, greasy shop floor or a pristine clean-room environment, is an important consideration when specifying the IP rating, or ingress protection.

Levels of protection extend from a basic IP54, through the more standard water and dust-tight IP65, which is ideal when installing next to a machine or workstation, through to special versions equipped with gaiters and external coverings for laboratory, clean-room paint-shop or hazardous applications.

Enhancing the IP rating adds to the cost, so consider the application carefully; just because it’s food processing, the robot might be handling product that is already wrapped, so advancing the spec may not be necessary.

7) Don’t forget workcell safeguarding.

Often overlooked in the initial specifying and costing, yet absolutely critical from a safety compliance angle, are the mechanical and electronic safeguards.

Robots are virtually silent and extremely fast in operation and unlike conventional automated machinery, in which the operating envelope is clearly defined, most robotic workcells are individual in configuration, so bespoke safeguarding is usually required.

HSE guidelines provide standards for perimeter fencing, interlocking devices, opto-electronic systems, safety light curtains and emergency stop actuators, which we adhere to when building highly sophisticated workcell safeguarding.

8) Do factor in the peripheral costs.

Far be it for me to dissuade potential robot buyers by pointing out hidden costs, because robotic applications can, and usually do, justify themselves on financial grounds alone.

But don’t overlook peripherals, like teaching pendants, interface boards and software licenses, when budgeting for an installation.

Because if you omit these from your initial order, then run over budget and incur delays awaiting delivery, question marks are likely to be raised.

Teaching pendants cost a grand or so and you require them for programming purposes, but you don’t need one for every machine.

Software licenses are often required for every machine and you’ll need plug-in cards for network communications, so be sure to compare the competitors pricing basis.

9) Don’t confuse accuracy with repeatability.

Repeatability data always looks impressive at +/-0.02mm or so and, indeed, it is.

But don’t confuse accuracy with repeatability and expect the same precision, because repeatability figures are always better than those for accuracy.

Repeatability refers to how precisely a robot can return repeatedly to a given position, following the same approach vector.

Accuracy relates to how closely a robot can move to a specified X-Y-Z position in the work envelope.

If, say, a robot gets to within 0.5mm of that specified position, that would be its accuracy; however, once that position is programmed into the controller memory and, each time the robot is sent there, it returns to within 0.02mm of its taught position, that would be its repeatability.

10) Do exploit the robot’s full capabilities.

Current trends toward shorter product life cycles and more versatile manufacturing mean that when selecting an industrial robot, it pays to bear in mind possible future duties.

Unlike fixed automation, robots offer inherent flexibility and can be re-programmed and redeployed any number of times, over an average 15 year life cycle.

Also, modern robots, especially 6-axis models, are capable of so much more than simple pick and place duties, since the arm’s ability to reach over and around obstructions and twist or tilt the end-effector make it ideal for complex functions.

The extensive command sets embedded into the robot controller and pre-written subroutines also make programming easier and more economical.

11) Don’t buy a robot solely on price.

The fact that a modern robot costs a quarter what it did a decade ago, means that the technology is already more accessible and affordable.

So don’t be tempted to buy solely on price, but look instead for best-value performance.

The various manufacturers have different strengths in different robot classes, so check out their credentials in the payload capacity you’re buying.

Equally, it doesn’t make financial sense to over-engineer the solution by specifying functionality you don’t need.

A 6-axis robot is highly capable, for instance, but for many routine pick and place tasks a 4-axis machine would be equally capable and considerably cheaper.

12) Do request a robot workcell simulation.

When planning and specifying a new project, we invariably use an advanced 3D design package to simulate the entire workcell and verify that our initial calculations and specifications are correct.

In most cases, we use a simulation, not least because it demonstrates graphically to the client that our proposed solution will work.

It allows us to check the reachability of all positions, optimise cycle times, and generally observe the do’s and don’ts I’ve covered in this article.

So convinced are we that this is the way forward for those new to robotics, that we offer a 3D workcell simulation of any prospective application for just GBP1,500, including a video.

Then if you go ahead with the project, we’ll discount that figure off the final project price.

* Biography of Stirling Paatz, MD and joint founder of Totnes-based robotics integrator Barr and Paatz, a high technology company with an 18 year track record of automating production processes across a wide cross-section of industry sectors.

He is a qualified Engineering graduate, specialising in electronics and software, and is experienced across all mechanical, electrical and IT disciplines, with in-depth knowledge of the design, programming, build and implementation of robot work cells, automated assembly lines and materials handling systems.

His company is an official integration partner for such leading edge technology brands as Mitsubishi, Staubli and Festo, positioning itself as an early adopter of advanced automation products and bringing state-of-the-art ideas to its client base.

Stirling can be contacted on 01803 869 833, at s.paatz@barr-paatz.co.uk or via his firm’s website at http://www.barr-paatz.co.uk, (but Totnes is worth a visit – Ed: PS – while he specialises in robots, I am supposed to specialise in editing, and I am having real problems: is “Do’s and Don’t’s” correct? Or would it be understandable with the more accurate “Dos and Don’ts” – either way, i don’t reckon the option chosen, the readable “Do’s and Don’ts” is strictly correct!).