Gravimetric Dosing System GDS – Octagon Blown Film Control

What is the Gravimetric
Dosing Unit GDS?

Combining the well-proven Octagon throughput measurement unit WLS and screw feeder units, the GDS sys¬tem offers highest performance in gravimetric dosing and extruder control. Both main material and additives are measured by loss of weight, a process assuring highest accuracy and reliability.

The GDS unit is installed directly on the material inlet of the extruder, thereby eliminating any separation or de-mixing of the different materials. No additional mixer is required. An advanced dosing concept allows dosing screws to be changed without any risk of overdosing.

See the Gravimetric
Dosing GDS in action

See the Gravimetric Dosing Unit in action.
Click the button to watch the video.

Perfectly met requirements

Highest measurement and dosing accuracy

High degree of linearity over entire measuring range

Secure in functioning

Perfectly adaptable by modular design

Why use gravimetrics?

Precise proportions for all component materials

Even colour distribution

Constant quality

No separation or de-mixing of components as the dosing units are installed directly on the extruder inlet.

Octagon Dosing Modules

For highly advanced technology in extrusion control

Applications and dosing by “loss of weight” principle

The GDS, a continuous gravimetric dosing system, is based on the “loss of weight” principle which ensures the highest precision for each component.

The GDS is applied in the monolayer and coextrusion production of blown film, sheet, tubes and profiles.

It can be used as a stand-alone system or easily and rapidly be integrated as a module in an SPS or fieldbus system.

The GDS unit can be supplied for up to 6 components per extruder.

Wide range of dosing screws

Six different dosing screw sizes are available and supplied with the appropriate sleeves for an overall production range from 0.05 to 400 kg/h. For easy identification, screws and sleeves are colour-coded.

High accuracy with continuous dosing

Dosing directly at extruder material inlet to assure:

No loss of blend of the different materials
Uniform colour distribution
Highest dosing accuracy

Integrated control
systems from Octagon

Quality control, optimised products, production increase, savings in raw materials

Extruder control with the GDS Module

In addition to precise gravimetric dosing of additives required for film composition, the GDS module also precisely measures the consumption of each material by means of the patented Throughput Measuring Module WLS. This exclusive system features high quality airtight load cells, ensuring reliability and accuracy in throughput measurement of each component. In addition, a unique external hopper protects the inner weighing hopper from external influences and vibrations.

With this information on material consumption, the ScenEx process control is able to calculate and automatically control the target screw speed of mono-extruders. In case of co-extruders, the screw speed is controlled individually for each layer.

In this manner, it is possible to control the production of the extruder as well as the average thickness of each layer of film.

Simultaneously, the weight per metre of film is automatically controlled by synchronisation of the haul-off speed, thereby ensuring a constant average film thickness.

Module GDS

Gravimetric dosing of up to 6 additive components per extruder
Throughput control on co-ex lines with up to 7 extruders
Control of average layer thicknesses
Control of weight per metre

Quality in
every detail

See our photo gallery of Gravimetric Dosing. See photos of the GDS-Eco.

Present in
companies all over the world.

Large companies rely on our solutions.
We are a reference in technology for the plastic industry.

Talk to Octagon

We are a technology center which has guaranteed our customers spare parts and technical support for over 30 years. As holders of an unequalled record of keeping systems running for 30 years, 24 hours a day, we are proud of the stability of our systems and the quality in technical support.

Learn more about

Join us

Be part of one of the most innovative companies in the world.

Total Quality

Give it a go on the road to Quality Management.

Technology Centre

Industry 4.0. Together with our customers we are creating a digital future.

Partnerships

Be our business partner and we will focus on the individual needs of your process.

Frequent questions

What are the reasons for using the GDS Gravimetric Dosing Unit and how can I calculate returns on investment?

Basically there are two reasons, firstly for most accurate dosing of the plastic additives, secondly for accurate recording of the grams used per meter of film produced.

The return on investment is based on the percentage of savings of plastic additives and the accuracy of the grams per meter of the film produced.

The superior accuracy of the system allows you to work with a lower percentage of additives per screw. Example: If with your current conventional system you are using 4% of a plastic additive, with the GDS system you can reduce this percentage due to the fact that the dosing control is more accurate and the blend by dosing screws more uniform. This leads to a reduction in consumption of additives and pigments per kg of film produced.

The accuracy of the grams per meter control ensures that each kg of film produced is identical. This helps in the control of the thickness profile and the process in the final finishes. For packaging sold per unit the accuracy ensures that each kg has the same the volume of packaging.

Faults in the gravimetric control leads to several problems and most companies do not know whether the equipment is accurate or not. Without an equipment such as the regular collection of measured film samples from film reels offered by the GPA it is very difficult to identify the variations. This will result in a number of problems in the final packaging process. For this reason, accurate and reliable equipment such as the GDS Gravimetric Dosing Unit ensures stability and confidence in the extrusion process.

The equipment pays for itself in a few months. This is based on the savings made in plastic resin due to the accuracy of grams per meter produced and the reduction of the percentage of pigments and additives used in the process.

What is the difference between the Gravimetric Dosing Unit GDS to conventional blender systems?

The Gravimetric Dosing System GDS is incomparably more accurate and ensures a much more homogeneous blend of materials. This is achieved by each component having its own individual load cell and a dosing screw system fully integrated in the extruder assembly. The dosed material enters directly into the extruder assembly without going through any intermediary mixing process eliminating separation of components due to different densities and granulometry of the materials. The concept produced by Octagon gives stability and continuity and its electronic components and load cells are of the highest quality ensuring stability to the system.

The batch blender system has been developed to be inexpensive, with the concept of one single load cell for all components, i. e. additives, pigments and main materials releasing the complete volume or batch into a mixer. Variations in density and granulometry prevent this type of system from being accurate due to the physical factors of gravity itself. Additives and pigments do not have the same grain size as the resin material, the density also differs greatly between the components. So it is impossible for a mixer to maintain uniformity in the blend once the material leaves the blender and is exposed to machine vibration. We should also consider the variation caused by the accumulation of materials in the corners of the blenders. Most Batch Blenders require constant attention by the operator for load cell calibration.

In conclusion it is obvious that the GDS Gravimetric Dosing Unit is technologically superior, more accurate, more stable and more reliable.

Why does the GDS gravimetric control integrated with the SmartLip Air Ring achieve better thickness control indices?

In the extruder the gravimetric unit GDS is responsible for controlling the grams per meter in the film produced. On the other hand the SmartLip Air Ring controls the thickness profile by correcting thick and thin spots on the bubble. The algorithms included in the Octagon software integrate and synchronize the two systems ensuring an excellent result in the quality of the film produced.

Is it possible to buy a system with fewer components at the beginning and add more in the future?

Yes, our system is modular and can be enlarged up to seven components step by step.

If a component is causing problems is it possible to move the dosing screw to the component next to it?

Yes. The dosing screws are quick change and allow any change between components.

For the operator is this system more difficult to operate?

No, on the contrary. Our software is transparent and very easy to operate.

How is a change of materials carried out?

First, the respective dosing unit has be completely emptied of all materials. This is an easy job by simply opening a latch under each dosing screw. Our system is designed in such a manner that no grain of raw material gets stuck contaminating the following product.

Who we are.
What we do.

Welcome! We are Octagon, a world reference in technology for the plastic industry.

Meet Octagon!

Automatic Air Ring

Sensor de Espessura PMS-B - Octagon Blown Film Control

Thickness Sensor

GPA Evo

Width Measurement