Closed Loop Gravimetric Technology improves Productivity, Profitability and Quality

Raw material accounts for up to 70% of many plastics processing companies’ total operating costs. Clearly, if processors cannot control these costs they are seriously compromising their ability to control profit.

There are 3 basic methods to control raw material in production: centrally dosing and mixing by hand; installing devices that volumetrically dose and mix materials and gravimetric devices that dose and mix by weight.

Polymation is frequently asked, “How do I calibrate a volumetric feeder?”

The basic reasons why so many processors are making this request relates to the fact that inconsistent bulk density of materials is common place and when virgin, regrind and expensive colour and additives materials are blended together the effect is to compound inaccuracy, increase scrap and compromise product quality and consistency.

Dosing materials by volume via a cup method, or automated by an Auger Screw or Rotating Disk, fundamentally ensures there is a fixed volume for material to fill. Due to varying bulk density in size and shape of pellets this means in one volumetric dispense there could be 15 pellets but in the next 25 = built in error.

Furthermore, those companies that recognize these problems and prefer to hand weigh and mix materials introduce the potential for human error and even in countries where labour rates are considered low cost, the problems of centrally weighing and mixing materials leads not only to a high utilization of labour but also, an increased risk of redundant blends, congested production areas and a strong propensity for product inconsistency as conveying blends from large day bins leads to de-mixing over the production cycle.

Improving Product Quality and Saving Cost

Automatic calibration of each material ensures that optimum product quality is always achieved. Blow moulders and Injection moulders using gravimetric blending, automatic material handling, inline granulators and conveyor belts gain significant advantage over their non-automated competitors. A Closed Loop production principle that automatically grinds the product sprues or top and tails in the case of blow molding, and loads them into a gravimetric blender is the optimum solution for controlling production costs.

Material blends are then weighed directly in accordance with the production settings ensuring that weight rather than volume dictates the quality of the end product. Savings occur at every level of production. Colour and additives can be effectively added just to the virgin material saving as much in percentage terms as the regrind content of these expensive additives. Hidden savings of redundant blends, the mass transit of regrind and blended materials to and fro in production is also avoided, the unknown human error and the lack of production data that gravimetric control provides the producer is lost via manual or volumetric means.

Return on Investment is critical and PolyMation knows from experience that automated gravimetric Closed Loop production pays back in most cases in less than 12 months.

LineMaster Installations demonstrate dramatic payback and multiple benefits for extrusion

One major benefit that all processors reported was savings on raw materials in production – both on short and long production runs. A film extrusion company saw significant savings on yield by the ease of the gram per meter control, producing a diverse range of short run films ranging from 120 to 150 grams per meter, whilst a pipe producer making large bore PE drainage pipes likewise saw a dramatic reduction in wastage of materials, seeing a faster start-up and achieving control within 0.5% on targets ranging in between 18 to 55kg per meter. Overall typical LineMaster installations achieve a massive 4% saving on raw material consumption.

The LineMaster system monitors the kg/h consumption of raw material via a loss in weight hopper mounted directly on the throat of the extruder. This monitors materials usage and updates every second calculating kg/h. Coupled with that a digital encoder can be mounted downstream to monitor LineSpeed providing feedback on the meters per minute the line is running at. This data combined the system calculates very accurately the gram per meter or micron of the product being extruded and can lock in and adjust either the extruder drive, haul off drive or both to control the line very accurately.

This then eliminates many process variations that can lead to excessive consumption of material that cannot be tracked consistently enough by manual spot checks. Issues such as screen pack, voltage fluctuations, screw wear, and materials bulk density variations all can be managed effectively by LineMaster extrusion control keeping the line constantly trimmed within the target set.

Quality Control from several applications have reported the benefits and simplicity of the system showing consistent roll weights in blow and cast film, as well as peace of mind in terms of data on what’s been produced constantly.

A recent cable line application demonstrated enhanced productivity by having automatic control – speeding up dramatically the changing of reels and allowing operates to see in real time material consumed and product produced, reducing scrap and overall changeover time.

The LineMaster Extrusion and Yield Control System is quick and easy to install minimising the time a line is down, plus is very easy for operators to start to use – having the ability run the line as before in manual mode and then when ready simply switch to automatic control, keying in target for the product.

LineMaster runs with all free flowing materials, be they granules or powders. The system is backed with a full 5 year warranty on all electrical and mechanicals parts. Contact PolyMation to see how the system can benefit your production – be it film, sheet, cable, profile or pipe extrusion.

New Return on Investment calculator available

PolyMation have put together a simple excel calculator to review costs savings available to customers when looking at automating materials dosing and blending.

The tool allows quick and easy access to see potential savings for different processes factoring in Regrind usage and savings on Masterbatch and Additives, plus gives some good pointers on indirect savings based on scrap reduction, better productivity, consisted product quality and reductions in labour cost and handling.

Contact us now to receive a copy of how this can work for your production.