MANUFACTURING | SMALL BATCH COMPOUNDING
Right: Feddem’s curved plate small-batch die head is claimed to reduce ‘curling’ of unfilled
compounds
ing the application range of screw profiles that will require even fewer screw changes in flexible, small-batch compounding,” he says.
Below: CPM Extrusion’s E-Series die uses a wedge- lock design with captive fasteners for fast removal and replacement
Ramping production Another factor encouraging small-batch com- pounding is the development of sustainable and renewable materials, according to compounding machinery maker CPM Extrusion Group. Frequent- ly applications for such materials start small but can ramp quickly, it says, adding to the list of already- established compound categories where the ability to deliver a fast response service is critical. “Any product requiring a custom formulation, such as colour and additive masterbatches, will also always be produced on a make-to-order basis, as well as high value-added compounds,” says Adam Dreiblatt, Director of Process Technology at CPM Extrusion. “Compounds involving expensive raw materials, such as PEEK, serve speciality and niche markets that are easily satisfied with small lot sizes, such as compounding applications for medical devices.” Dreiblatt highlights several issues that need to be considered when running a frequent changeo- ver small-batch compounding operation. “Consist- ency is key for any product, especially for small lot sizes that may be produced infrequently. Having standardised procedures for changeover and cleaning – with proper training – ensures that every machine operator performs each task the same way using the same tools. Including a sign-off checklist for changeover reminds the operating staff that they are responsible for the product quality that comes out of their extruder,” he says. “Safety should also be at the forefront of everyone’s mind who works with compounding lines. With high frequency changeovers – for example, screw changes once or twice per shift – there are far more opportunities for ‘incidents’ than in those manufacturing operations where
screws are never removed, and the machines run continuously at the same settings for days,” he says. Extruder OEMs such as CPM have developed
quick-change designs for screw shaft couplings, dies, side feeders, vent ports, and feed hoppers enabling their rapid removal for cleaning. The remaining challenge, Dreiblatt says, is the cleaning of screws and barrel for relatively small diameter machines. He says having several spare sets of assembled screws (with different configurations) can provide a fast turnaround if the old screw set can be cleaned offline and he points out that the cost of several sets of screws and shafts can often be justified by shortened changeover time and improved cleaning. Dreiblatt flags a number of other procedures that should be considered to ensure successful small- batch compounding. “Management tends to focus on minimising the time required for changeovers. However, there should be an equal – if not more – emphasis on yield during the time the machine is in operation. Running at maximum production rate makes sense for commodity compounds but can also produce large amounts of scrap during any process upsets. For this reason, operating staff must react quickly to processing problems when produc- ing smaller lot sizes and for those formulations with expensive raw materials,” he says. “Successful small-batch compounding, there-
fore, depends on having professionally trained operators who understand how twin-screw extrud- ers work and are provided with the right tools to perform the job requested. This not only refers to physical tools like cleaning brushes and purging compounds, but also includes intellectual tools such as basic training in twin-screw extrusion technology,” he says. Dreiblatt also spells out that customers that invest in operator training will be the ones with the highest productivity and first-pass quality. “These companies benefit from increased efficiency and employees feel better about their job performance
42 COMPOUNDING WORLD | April 2021
www.compoundingworld.com
IMAGE: CPM EXTRUSION
IMAGE: FEDDEM
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