There are robots and robots. One type inhabits the popular culture of books, movies and TV, where more-or-less humanoid machines may be heroes, villains, evil or good, oppressors or slaves. Then there are the ones that actually exist, that mostly look nothing like humans.
It’s this second class that are sometimes to be found around print factories. They are still comparative rarities, primarily used for materials handling tasks of transporting, loading and unloading.
Robotics is a class of engineering that uses mechanical, electrical and other components coupled with sensors and computer controls, to automate tasks that are too time-consuming, strenuous, dangerous, precise or just plain too boring for humans to do.
Take-up of industrial robots is low in the UK, where industry in general has only 71 robots per 10,000 employees, less than the world average of 74 and well under Germany with 309 and France with 132, according to the Frankfurt based International Federation of Robotics.
An early type of robot for print was the driverless reel trucks within large web offset and gravure plants, shuttling between the paper store and the reel stands on the presses. These are officially called AGVs (automated guided vehicles), but most people call them robots.
Probably the first UK examples for print were operating at Hunterprint’s then-new Corby plant in 1989. Today’s equivalents can do more but still only make sense in very high throughput factories, otherwise humans driving reel and pallet trucks are more flexible. Likewise, highly automated reel stands with flying pasters for high-volume web offset presses can be regarded as applications of robotics, while at the other end roller conveyors combined with robot arms to move multiple stacks onto palettes and in and out of wrapping machines are used at some high-volume sites.
Robotics are now proving relevant to some lower throughput print sectors, including large format sheet loaders. For this article we’ve been taking a particular look at the articulated arm-type systems that are increasingly being used alongside very large-format inkjet printers or cutting tables.
HP Scitex and Inca Digital in particular have been working with robot manufacturers in recent years, to automate large format inkjet loading, while Esko Kongsberg has been applying robotics to the largest of its cutting tables.
Last September PrintWeek reported on the first UK-built Clinchtech robot built to load an HP Scitex 11000 flatbed inkjet, installed at Cartoneo in France. Cartoneo had previously installed a robot loader on an Esko Kongsberg C66 cutting table, which features multiple zones.
Esko can supply both gantry and arm type load/unload systems. It has a travelling beam with suction heads that picks up sheets at one end and deposits them on the cutting bed. A similar system at the other end picks up the cut sheets and stacks them ready for manual stripping.
Pick and place
The robot arm can find and pick up individual cut items from the bed and stack them neatly at the other end or at the side, removing the need for manual stripping. It can also work with multi-zone operations without stopping the cutter.
Back in 2011 Inca’s distributor Fujifilm commissioned Clinchtech to develop a gantry beam type system to load and unload large corrugated sheets onto Inca Digital Onset S20 presses (today’s equivalent is the Onset X3). However Inca Digital itself has since worked with other suppliers: the Swedish-Swiss ABB Robotics for robot arms and the German Hostert Pro for conventional beam type loaders.
We learned more about the concepts during a visit to Inca’s Cambridge HQ last year. Product manager Roger Walkley explained a lot of Inca’s experience and future thinking. He’s recently retired, so we spoke to Bjoern Schueler, acting product manager for the Onset X series.
The X series printers are configured with a vacuum bed that moves rapidly and repeatedly in and out of the printer body, building up swaths of ink as it does so. Loading and unloading take place at the front, where it is loaded from the right side of the bed and unloaded to the left.
“We have seen a migration of customers in the past year from our original offloading solution to robots,” Schueler says. “Almost 90% order with robots now, so it is a huge trend for us as a company.”
Robot loading doesn’t necessarily improve throughput, Walkley explained. “There are other benefits,” he said. “Job size times can be much shorter, down to about a minute. Also the stack heights can be much greater, especially for corrugated. As corrugated sheets are thick, you don’t get many of them on the standard 600 mm height, but we can now handle up to 1,400 mm. A standard palette truck can still work with the greater heights.”
If a conveyor is placed on the load side, it can cycle several different pallets back and forth for short run jobs or mixed media work that doesn’t need full pallets all at once. Likewise a conveyor on the unload side allows you to produce several stacks of different images or sizes.
Easier off than on
A robot arm is almost always the best solution for offloading, but it’s not quite so simple when it comes to the loading side, Schueler explains. For large display board, polystyrene or corrugated in one- or two-ups, a robot arm may be preferable. For users handling a lot of paper, and multiple-ups per bed, the non-robot Hostert Pro may be best.
“One limitation we have found using the robot arm for loading is that each sheet position has to be registered on the effector, the frame that picks up the sheets. With two-, three-, four-up the effector has to register every time to the corner of the stack. That gives you a time penalty. You want your robot to wait for the printer and not the other way round. The Hostert can do up to four-up at once. It’s a dumb solution but extremely repeatable. It’s very reliable, but a robot gives more flexibility.”
Surprisingly, a load/unload robot pair costs about the same as a Hostert Pro unit plus an unloading arm. Actually the loading robot has more complexity than the unloader. The loader needs six axes of movement (called degrees of freedom), where four is enough for the unloader.
The extra degrees are needed to overcome static and vacuum forces holding down a sheet on a stack, so the robot’s ‘wrist’ essentially twists the effector frame to peel up one edge first. After printing the bed vacuum is released so the unloading arm doesn’t need the extra twist.
A feature of the robot loading arm is that it doesn’t just release the sheet onto the bed, but it can press it down slightly. This can overcome slight warping and flatten the sheet so the vacuum takes effect. “We have a database of media types, so the robot will be programmed to press down with those prone to warping,” says Schueler. “It is completely integrated with the Onset’s GUI so the vacuum is applied at the right time too. It makes it very easy, especially in conjunction with our table zoning that says which cups to switch off and does the same thing on the vacuum bed. It’s an integration we put a lot of emphasis on.”
Another benefit of using at least one robot arm is access for humans. Lay tables or gantry loaders and unloaders fit close up to the side of the bed. Although they’re on wheels, human operators can’t quickly get in if they need to for masking or cleaning. A robot arm though, can fold itself neatly and rotate away from the bed in seconds.
Other applications for robot loaders include platemaking lines and guillotines. For example the Danish printer Inprint in Jutland is using a compact and fairly low cost Danish built Universal Robots UR10 arm to feed a plate processor originally intended for manual loading, freeing up operators to get on with something else and saving two labour-hours per day.
Another Danish company, Graphical Robots, adapts Yaskawa Levanto arm robots for a range of co-worker (‘cobot’) functions in print factories, such as multiple VLF platesetter loading. It’s paid particular attention to guillotine feeding, where a robot arm’s effectors can delicately separate a ream at a time off a high stack and pass it over to the guillotine’s air bed where the operator takes over.
Robot unloaders are also being used for picking smaller cut items off a conveyor line, typically downstream from a narrow web rotary die-cutter or a laser cutter. Here the most common robot is the spider-like overhead pantograph type, where low inertia and low weight items means it can keep up with multiple items side by side on a fast-moving belt. These robots are supplied as options with at least two laser cutters, the LasX LaserSharp and Themediahouse’s motioncutter, both demonstrated at Drupa two years ago.
Finally. the Industry 4.0 concept of a fourth industrial revolution takes in robotics in its mix of internet-connected machines, sensors and electronics (Internet of Things) with shared analytics. This extend the definition of what a robot is. For instance Heidelberg’s ‘push to stop’ concept for its automated XL presses is an example of Print 4.0. Unless there’s a problem all the operators need do is monitor it and keep the press fed with paper, ink and plates. Essentially, today’s smartest presses are robots already.