How Does an Oil Press Work? Technology & Operating Principle Explained.

For farmers, oil mills, and food producers, the oil press is the heart of production. But how exactly does an oil press work technically – and what happens inside the machine when rapeseed, flaxseed, or sunflower seeds are turned into high-quality edible oil? As a manufacturer of professional oil presses, oleopress.com explains the functional principle step by step.

The Basic Principle: Extracting Oil Through Mechanical Pressure

The basic principle of every oil press is simple: oil-bearing seeds or nuts are mechanically compressed so strongly that the oil bound in the cell structures is released. This process is referred to as mechanical oil extraction or cold pressing – in contrast to the chemical extraction with solvents used in large-scale industry, which is not an option for quality-conscious producers.

The decisive advantage of mechanical pressing: The oil remains natural, containing all valuable ingredients, fatty acids, and aromas – thereby meeting the increasing quality requirements of retailers and end consumers.

Main Press Types in Commercial Use

The Screw Press – The Professional Standard

The screw press (also known as an expeller press) is the most commonly used type of press in the commercial sector. Its operating principle is based on a rotating conveyor screw that transports the material through a narrowing press channel, continuously compressing it. The resulting pressure – depending on the model, between 200 and over 800 bar – forces the oil out through fine gaps in the press channel. The remaining press cake is ejected at the end of the screw.

Screw presses are suitable for continuous operation, are robust, and process a variety of seeds such as rapeseed, sunflower, flaxseed, black cumin, and various nuts. The oil presses from oleopress.com are based on this proven principle and are specifically optimized for continuous use in agricultural operations and oil mills.

The Hydraulic Press – For Highest Oil Quality

In a hydraulic press, the material is pressed in a chamber by a hydraulically operated ram. This process is particularly gentle and works at low temperatures – ideal for sensitive raw materials like walnuts or flaxseeds. The disadvantage: Hydraulic presses operate discontinuously (batch processing), meaning the chamber must be refilled after each pressing cycle, which significantly reduces throughput compared to a screw press.

The Pressing Process Step-by-Step

This is how the pressing process works in a commercial screw press from oleopress.com:

Seed Preparation: Depending on the raw material, the seeds are cleaned, dried, and pre-warmed if necessary. Optimal input moisture is crucial for yield and oil quality.
Feeding and Conveying: The seeds are fed into the press via a hopper. The rotating screw continuously draws the material in and transports it through the press channel.
Pressure Build-up: Through the interaction of the screw, press cylinder, press head, and nozzle, the seed is continuously “squeezed out.” This pressure breaks the cell walls of the seeds and releases the oil.
Oil Drainage: The emerging oil flows through slits, holes, or screens in the press channel into a collection container. Coarse suspended solids are already mechanically retained during this stage.
Press Cake Discharge: The de-oiled press cake is continuously ejected at the end of the screw. It contains valuable proteins and fiber and can be repurposed as animal feed or fertilizer.
Post-Filtration: The raw pressed oil is then filtered – via sedimentation tanks, filters, or centrifuges – to obtain a clear, marketable end product.

Temperature Management – The Key to Oil Quality

The frictional heat generated during the pressing process is one of the most important quality factors. If the oil is heated too much, valuable ingredients are lost and the oil may lose its characteristic flavor.

Kambas OleoPress professional oil presses are specifically designed for the production of cold-pressed oils.

Oil Yield: What is Realistic?

Oil yield depends on the raw material, the oil content of the seeds, and the pressing conditions. Typical guide values for mechanical pressing:

Rapeseed: approx. 35–42% oil yield
Sunflowers: approx. 38–45% oil yield
Flaxseed: approx. 30–38% oil yield
Walnuts: approx. 40–50% oil yield
Black Cumin: approx. 20–28% oil yield

These values vary depending on seed quality, moisture content, and machine settings.

Conclusion: Technology That Ensures Quality

A commercial oil press is much more than a simple machine – it is a precision instrument that determines the quality, yield, and economic efficiency of your oil production. Understanding the operating principle helps you choose the right machine for your business and get the best out of your raw materials.