How smart do you want your size reduction?

Photo Credit: Adobe Stock/digitalstock

Information overload can be a real problem in the internet age. We all know the feeling: stress brought on by consuming more information than we can digest and more than is needed to make decisions. And it can be a problem for plastics processors too, where large volumes of data coming at them 24/7 courtesy of smart factory technologies might make it hard to find the really important production information they’re looking for.

Which is why the idea of smart size reduction might sound like overkill. For many processors, granulators and shredders have tended to be low-tech outliers in the factory, oftentimes working separately from primary processing lines – you turn them on periodically, feed start-up scrap and off-spec product into them for downsizing for reuse in a process, and then turn them off again. And no doubt a lot of shops like it that way and don’t want to mess with a good thing. So, even with increasing interest in intelligent equipment, Industry 4.0 and equipment diagnostics, the question remains: given that size reduction is generally a price-sensitive market, how intelligent do want your grinder to be?

The answer, some experts say, depends on how important size reduction is to your production, which is usually signalled by the grinder being incorporated into a work cell or not. In a nutshell, do you want it to remain offline or – in keeping with Industry 4.0 – be brought inline with ongoing operations? That depends, in part, on what you do. For injection molders in manufacturing sectors that are data-intensive such as automotive parts and medical, or for blow molders and thermoformers for whom scrap generation is part of the regular manufacturing process, or for recyclers whose entire operation revolves around size reduction, the ability to monitor grinder operations in real time is valuable – and probably invaluable. “For larger shops that already have centralized smart factory production, it’s important to have connected grinders too, otherwise they become the weak link in the process and can hamper production,” said Jonas Wästberg, CEO of Rapid Granulator Group.

But if the only function of the machine is to downsize scrap – if the grinder is, in short, a “necessary evil” – advanced controls might not be necessary.

INTELLIGENT SHREDDING

It’s important to realize that much of today’s size reduction machinery is already semi-smart. “For some time, shredder and granulators have been able to monitor some key factors, such as amperage, heat and vibration using PLC-based systems,” said Dave Miller, general manager of size reduction with Conair Group. “This data will show when any of these factors start moving beyond normal baseline levels.” Shredder controls, in particular, have been providing some diagnostic information for years now. “Shredders already come standard with PLCs,” said Greg Parent, the Canadian sales agent for Vecoplan LLC. “Ethernet connectivity is standard on our newer styles of shredder and an option on our older models, which allows for basic monitoring of the equipment and also allows our service department to connect with the machine for troubleshooting purposes as well as making potential software changes. Pretty much all options are open, and the customer simply needs to let us know what they need.”

For shredders equipped with PLC controls, the common things to monitor are motor amperage for the shredder shaft and hydraulic pressure in the feed mechanism that pushes material into the shredder. “When shredder blades are new, motor amperage is going to run in a baseline range, such as 30 to 40 amps,” Dave Miller said. “But if motor amps are consistently running a higher-than-baseline range – say 40 to 50 amps – it’s a good indication that either new blades or other maintenance is required.”

And when it comes to shredders being connected to other equipment, customers’ demands can vary. “Some want full integration with their plant-wide monitoring systems and others simply want access to information from a single particular shredder, mainly the number of hours on a new set of cutters so they know when a rotation or change will be required,” Greg Parent said. A middle position is with a stacked shredder/granulator system – which puts the shredder on top of the granulator to decrease the load on the granulator – where the shredder communicates only with the granulator. “In a stacked system, the baseline info that the shredder needs to convey to the granulator is how hard the shredder is working – by voltage readings, temperature sensors, and vibration sensors – to keep them in sync, and this level of technology has been available for years,” said Cole Cyr, purchasing and project manager with Rotogran International Inc. “That’s still as far as most customers want to go as far as the communication between the shredder and granulator.”

GRANULATORS GET WITH IT

For granulators, meanwhile, PLCs are available now for control, but they don’t analyze data and predict outcomes based on what’s happening in the machine. “Controls can be added to stop and start a feed conveyor based on granulator motor amperage in order to maximize production and some customers asking for options or features to make the process more energy efficient, but no one is asking me yet for the ability to collect and analyze data for its own sake or to be connected to a server,” said Bob Harrison, product manager, size reduction group with Universal Dynamics Inc. “But there are other granulator features available right now that I would describe as ‘smart’: ammeters to monitor knife wear, high-level indicators for the regrind transition bin that let you know if something is going wrong with the material conveying used to remove and convey the regrind, and temperature monitoring on high-capacity machines or hot applications like blow molded trim scrap.” Italy’s CMG SpA granulators – tailored to tackle in-house blow molding scrap ranging from one-litre bottles to 500-litre tanks, and available in North America through Universal Dynamics – can be equipped with the Adaptive Motor Power proprietary motor control, which allows them to adapt to variations in container format, container thickness, the quantity of material and temperature changes. “The granulators’ controls can manage material levels in the surge bin and are Industry 4.0-compliant,” Harrison said.

Germany-based Hellweg’s GRANUmaster smart control touchscreen is available on all of the company’s granulators from the 2-5 hp, beside-the-press 150 series on up, and record a variety of operating data useful for preventive maintenance: power consumption; rotational speeds; bearing temperatures; and operating hours of bearings, blades, screens, and drive belts. This data can be communicated to a central computer via the OPC-UA interface included as standard. The granulator also can be monitored remotely or networked to communicate with upstream and downstream components. And the controller can be used to issue spare-parts requests and even automatic requests for parts that wear out on a regular basis.

Available as a package with its EcoPower and SmartPower injection molding machines, Wittmann Battenfeld’s Ingrinder system integrates an advanced granulator and sprue picker – which can be operated via the machine’s UNILOG B8 control system – with the press itself. A Wittmann sprue picker with swivel drive removes the sprue directly during the injection process and passes it through an ejection chute integrated in the machine frame to a built-in and specially modified G-Max 9 granulator. The Ingrinder works best with smaller presses that run together with molds incorporating cold runner technology with a corresponding need for scrapping or recycling sprues, Wittmann Battenfeld officials said. Processors benefit from a more efficient grind, faster use of regrind and less time for hygroscopic materials to absorb water. Also, depending on the machine model, users can see a 25 per cent savings in floor space compared with a work cell utilizing a granulator and a robot with guarding.

RECYCLERS RULE

So, for molding shops that produce very little scrap and simply toss it into bins and granulate it offline when they have time, there may not be value in a granulation system with sophisticated digital controls, sensors or alarms. On the other hand, the shops that can benefit from smart controls on size reduction equipment are those that generate scrap consistently as part of the production process or that deal with waste plastic full-time, such as high-volume film producers that run film lines at up to 3,000 to 4,000 pounds per hour and generate a lot of edge and trim scrap; blow molders that make tops and tails, and thermoformers that generate scrap in the form of “skeletons”; and recyclers.

Indeed, maintaining high throughput is everything in recycling operations. Recyclers can’t afford unexpected downtime or having to take a key shredder offline for major repairs; for them, the experts note, smart controls that feature monitors and alarms are critical for tracking performance and keeping ahead of maintenance problems. “For recyclers, size reduction machines are the only production equipment on the shop floor, rather than in a side room for just scrap reclaim, so they really understand the importance, and value, of smart technology,” said Bob Harrison. Which is why recyclers were the original market for shredders with PLCs, and why they remain among the most receptive audience for the latest smart control features, monitors and alarms for tracking performance and keeping ahead of maintenance problems. “We’re starting to some requests for long-term trending data on granulators from the recyclers,” said Cole Cyr. “Unlike granulators for processors, there’s a developing standard in the recycling sector around what technologies these machines should have. When that’s your primary piece of equipment, you want to get as much information from it as you can.”

SHAPE OF THINGS TO COME

Conair already has SmartServices, a cloud-based Internet of Things or Industry 4.0 solution for machine monitoring and data collection; and although its size reduction equipment doesn’t yet tie into it, the company is currently developing smart controls incrementally in a two-stage project. “The first phase, which is ongoing, is to equip our large central granulators with a small PLC that records data from internal sensors that monitor amperage, rpms, temperature, and vibration, all of which indicate how well scrap is being processed,” Dave Miller said. “The second phase is to develop the controllers for all granulators and shredders to the point where they scan real-time sensor data to actively predict or identify a problem – blade or bearing wear and other critical issued – and go on to recommend that plant personnel take corrective action. That type of genuinely smart grinder will be a huge advancement from where the industry is today.” Miller says that Conair has canvased its customers about the value of a smart control versus standard push-button start control, and about half have expressed interest. “Their main concern is cost,” he said. “Frankly, with HMI and PLC prices coming down, we don’t anticipate a big cost difference between a smart system and a standard control.”

Also in development is a sensor kit from Rapid Granulator. Branded as the Rapid Smart node, it will offer a wireless connection up to 150 meters inside a factory, measuring temperature, energy, vibration, running time, and more, and connects up to 100 granulators or other devices per gateway. “The granulator data from each sensor will be useful for continual monitoring and as a preventative maintenance tool, and will also tie into other equipment on the line – such as the conveyor and/ or the robot – that connects to the granulator. The data can be either sent up to the cloud where the customer can log in and review it, or it can be viewed directly,” said Jonas Wästberg. “We’re currently testing this solution with select customers, and plan to launch it during 2023.”

With the benefit of some hindsight, smart, predictive capabilities on grinders is turning out to be the last piece of the smart plastics factory puzzle. “The majority of plastics processors probably put the grinder at the bottom of their list of importance – well below the primary molding equipment – so it’s become, by default, the last piece of equipment to be brought into the smart production loop,” said Cole Cyr. Which is why smart equipment controls for grinders will be important for some types of shops, less so for others. “For the recyclers and the processors that need them, those controls will be available, but there will always be customers that want grinders they can just buy, turn on, and forget about,” Dave Miller said. “For them, the small added cost of the controls isn’t justified because they don’t need those capabilities.”

In the end, then, not every molder is going to want or need shredders or granulators with digital data and networking capabilities. But in this coming era of smart factories, at least grinders don’t have to be at the bottom of the class any longer.