In a cold press oil expeller the motor turns the pressing screw through a gearbox, slowly and with high torque; selection therefore starts from the screw speed, the gearbox ratio and the torque the press needs. In cold pressing the screw runs slowly so the oil does not heat up; the gearbox takes up the difference between motor speed and screw speed.

DRG-132M1-6 4 kW 1000 rpm cast iron frame DRG three-phase motor – cold press oil expeller motor

Screw speed and gearbox ratio

To work out screw speed, divide the motor's speed under load by the gearbox ratio. For example, a motor running at about 1450 rpm under load turns the screw at about 29 rpm through a 1:50 gearbox. If a 1000 rpm motor is connected to the same gearbox, the screw slows down, output drops and the oil temperature changes too. DRG does not sell gearboxes; the input flange and shaft bore of the existing gearbox must match the motor selected. You can check the ratio and output torque with the gearbox output speed and torque calculator.

Seed type and heavy starting

Sunflower, rapeseed, walnut, sesame or flax each create different resistance inside the screw; hull content and moisture also change that resistance. The press may have to start while cold and still packed with cake from the previous run; for the motor this is often the hardest moment. The power recommended by the maker should be checked against the toughest product and a loaded start.

Oil leaks, cake dust and cleaning

If oil seeping from the press head and cake outlet reaches the motor frame, it catches dust, a sticky layer forms between the fins and cooling suffers. Place the motor outside the oil drip line and wipe the frame regularly. If cleaning water is used in the food production area, remember that IP55 protects against water jets and that direct pressure washing needs extra precautions.

Points to settle before ordering

  • Hourly capacity of the press and the products to be processed
  • Gearbox ratio, input flange and shaft bore size
  • Whether the press starts loaded
  • Daily running time

If the calculation points to a four-pole requirement of 7.5 kilowatts, the DRG-132M-4 cast iron frame model can be considered among the options; for other ratings see the food processing machine motors page.