Packaging machinery in focus: Pit stop pack changes

If production managers cannot have new and improved figures to brag about, the next best thing seems to be a new and improved collection of acronyms or production philosophies.

Here, one of the newer additions is single minute exchange of dies (SMED) also known as single minute engineering downtime. First applied to the automotive industry, this could be recast rather more realistically for packing lines as 'several minutes engineering downtime'.

Of course, there are electronic size changes that can be made in seconds, but any substantial changes are likely to take longer. Some will aim for five minutes, says Kliklok International sales director Graham Holbrook, but even this is challenging.

As he says, at that level you would need the kit, preparation and probably the number of operators more suited to a Formula One pit stop. More typically, customers are aiming for 10-minute changeovers in most situations.

Importantly, says Holbrook, fast changeover requirements are no longer specific to smaller firms and co-packers managing short runs. The wider use enterprise resource planning (ERP) systems to cut leadtimes and minimise stock in the supply chain means that the largest manufacturers are also having to provide greater flexibility at the production and packing stage, he says. So for instance, the volume biscuit manufacturers are likely to make several size changes to their cartoning lines in any given day.

Size adjustments​

Size adjustments remain the most common kind of changeover. Over time, machine manufacturers have tended to reduce the number of change parts, make changeovers toolless and minimise the manual changes to guide rails and so on.

But the retailer-driven trend towards reduced packaging has introduced variants and complexities of its own. As Holbrook explains, frozen food manufacturers have traditionally used full cartons, while wraparound sleeves (needing less board) were applied to chilled products. Kliklok introduced its SFR (short footprint rotary) range of machines to allow firms to switch between formats. "I think we are the only supplier to offer this option," says Holbrook. "In this case, the end-flap glueing system can be disabled on the touchscreen, allowing changeover in about 10 minutes."

At flow-wrap, weighing and bagging supplier Ilapak UK, md Guy Levy says that similar concerns about weight reduction have made the ability for flow-wrappers to switch between supported and unsupported product a key requirement.

This first happened in the fresh produce sector, says Levy, originally with tomatoes, but now with apples, kiwis and other fruit. It is also needed where poultry packers want to wrap whole birds either with or without a tray. For the past 10 years or so, control of PC and PLC (programmable logic control) has been standard on Ilapak equipment, with manual input typically limited to two or three adjustments, which are flagged up on the control screen.

Tailor-made​

Levy emphasises the research that has to go into tailoring a machine for a particular operation. "When we're looking at a project, we take a lot of time to understand our customers' processes, and that feeds into minimising changeover times. Whether that customer is a co-packer or a brandowner running a single product, it's always going to be an important factor."

Some types of machine can manage faster changeovers. Tray sealing is a case in point, says Rick Carless, sales engineer at Proseal. "One ready meals manufacturer is facing half-hour changeover times, and it's just taking them too long," he says. But with the right equipment, he claims that a five-minute changeover will in many cases be feasible. Offline preheat stations for the sealing heads are commonly specified, he says. Similarly, Proseal's introduction of automated loading for the upper tool set began some seven years ago, with the same capability for the lower set only being introduced in the last two to three years.

At processing and tray-packing specialist Reiser UK, md Ken Mossford queries the idea of a five-minute changeover. "You can make the change, but the difficulty is in getting the machine to the point where you can start it up again," he says.

Specifically on tray sealing, he agrees that customer expectations have risen hugely over the past couple of decades from dedicated tooling sets, to changeovers that might take up to an hour, and now to changeovers of 10 minutes or less. But the sealing stage is just one component in the type of line that Reiser is likely to install. Typically, a line for minced meat, for instance, could comprise a thermoforming stage, a dosing station, tray sealing (with or without gas flush) and film cutting.

"If you were staying with the same footprint but going deeper in thermoforming, that change might take just two or three minutes," he says. "But if you're changing, say, from a six-pack format to a four-pack, you'd be looking at 30 or 40 minutes, since everything from the sealing dyes to the cutting tools also needs to be changed."

Options at the thermoforming stage have multiplied, too, with packing operations able to switch between gas-flush packing, vacuum and skin-packing.

Of course, speed of changeover means nothing if the settings are not accurate. As both Reiser and Kliklok make clear, one of the principle benefits of electronic servo-driven size change is that it is precise and consistent.

Where complementary manual changes are necessary, machine manufacturers have done all they can to simplify operations and instructions. These features range from a clearer colour touchscreen in Proseal's case, offering 'recipes' and directions in different languages to toolless change parts on Kliklok's Certiwrap wraparound sleever, which have quick-release handles and will only fit into the machine one way round.

Ilapak explains that customers are increasingly likely to keep the various product setup 'recipes' on a central ERP system, requiring the individual machine or line operator to download them from there. As Levy puts it: "A key component in changeovers has to be avoiding or minimising the possibility of human error."

Optional interface​

Domino UK's coding equipment similarly features optional interfaces with ERP systems, again with the aim of eliminating operator error during setup.

Like other coding suppliers, Domino has sought to reduce consumables replenishment downtime. In the case of its V-Series thermal transfer printer this means a 1.4km-length ribbon twice that of any other system on the market, says the company. For its A-Series inkjet coders, the result is ink cartridges that not only boast high capacity but can also be replaced during printing, with no requirement to stop the line.

Unavoidable downtime can be unnecessarily stretched when equipment is slow in coming 'up to speed'. Domino has addressed this issue in its A-Series design. Says sales manager Jim Orford: "Automatic flushing of nozzles and sealing of the nozzle plate ensure high-quality print immediately on restart, however long the idle time."

Frequently, when investing in capital equipment, manufacturers are making a trade-off between flexibility and cost. And those cost pressures have only grown over the past couple of years.

"Everyone has to do much more to justify any investment," says Levy at Ilapak. "We've responded by making our production more efficient and sourcing in a smarter way. We're also designing our machines to be more modular, which means better value for customers."

At Ishida UK, marketing manager Torsten Giese spells it out: "Flexibility will always cost you money." But downtime also costs money, and is not only incurred by changeovers.

Giese cites the example of a multihead weigher used to weigh and portion different products, including nuts. "The packer may decide it doesn't want the downtime needed to cleanafter nut products, opting instead to change the hoppers and halve that downtime from around an hour to half an hour or less," he says.

That trade-off between investment and savings is not always clear-cut. Kliklok explains, for instance, that market conditions for servo drives and controllers have not improved noticeably in recent years. The company tends to use Allen Bradley systems which, no matter how many drives are actually integrated into the line, are likely to add several thousand pounds to the price. They are used in Kliklok's high-speed Celox machine.

While that will speed up the changeover process, there are other actions such as running all the residual carton blanks out of the magazine which still have to be carried out. "So the servo drives may save you five minutes on a 10-minute changeover," says Holbrook. "And that can be a fairly marginal thing."

A question of flexibility​

Servo drives offer a similar element of speed, flexibility and accuracy on the cutting station of Reiser's tray lines. But Mossford analyses their benefits rather differently.

"In our case, if you're looking at a 30- to 40-minute change, you could save five or 10 minutes on that, and you have to think long-term," he argues. Over 20 years, the savings on production uptime could be considerable, he points out.

Then again, in the UK, where relationships with retailers may not always be as durable as those in other parts of Europe, manufacturers tend to invest more carefully, says Ishida's Giese. In some cases, this could even mean staying with all-manual operations rather than opting for automation. After all, a manual operation still remains for some smaller manufacturers at least the option for ultimate flexibility. FM

Key contacts:​

Domino - 01954 782551

Ilapak - 020 8797 2000

Ishida - 0121 607 7700

Kliklok - 01275 836131

Prosea - l01625 856600

Reiser - 01908 585300