Flour Packing and Dosing Machine Electric Motors

In a flour packing and dosing machine, electric motors turn the feed screw that pushes flour into the bag, the impeller that fills valve bags, the micro-dosing screw that meters additives such as vitamins and enzymes into the flour, the bag sewing head and the belt that carries filled bags. On 25–50 kg flour bagging lines these are mostly standard three-phase induction motors of 0.37–6.5 kW, and the DRG range covers them. Servo and stepper motors on small-pack (1–10 kg) fillers are a separate class and are not in the DRG range.

The weighing, filling and control design of the machine belongs to the packing machine builder; the motor supplier provides the motor with the power, speed and mounting that design requires. You can see suitable motors on the Buy Electric Motors Online page. For the other motors of the milling line see our article on high-torque motor supply for flour mills.

Which packing line motors does the DRG range cover?

The motors of a flour packing line fall into three groups. Knowing from the start which group is in the DRG range avoids asking for the wrong quotation:

Servo and stepper motors work together with their own drive and feedback system (encoder). When one fails, a motor of the same type matched to the drive is needed; a standard induction motor cannot do the job. On such machines DRG supplies only the line's standard motors (the feed hopper agitator, belt, screw).

Bag filling methods: auger and impeller

Fast and slow filling of open-mouth bags

Flour does not flow freely; it aerates and bridges, so open-mouth bags (25–50 kg) are mostly fed by a screw. The screw first fills most of the bag at high speed, slows as the target weight approaches and dribbles in the small remainder. On a Turkish milling machinery builder's 25–50 kg single-weigher packing system, the screw motors run with speed control drives; the bag belt motor is also drive controlled, and a vertically acting bag shaker compacts the flour in the bag. Because the inverter handles the speed change, the screw motor is a standard induction motor.

Weighing methods and their effect on the motor

In gross weighing the bag sits on the scale while it fills; in net weighing the product is first taken into a weigh hopper and then discharged into the bag. In one milling machinery builder's catalogue, a single-spout single-weigher flour bagging machine is listed with 6.5 kW of feed power for 8–15 t/h, and a single-spout double-weigher type with 5.9 kW for 15–25 t/h. The number of stops and starts per bag decides how warm the motor runs, and the motor should be chosen for that cycle count.

Valve bags and impeller filling

A valve bag has a small filling opening at one corner; the bag is slipped onto the filling spout and the product is pushed in. For fine, aerating products such as flour this is done by a horizontal or vertical impeller. The impeller throws flour from the hopper towards the spout; fill rate is set by impeller speed and gate opening. According to the brochure of a milling equipment company, impeller filling gives fast, low-dust filling of fine and free-flowing products; whether the impeller is vertical or horizontal, and its diameter, are chosen for the product. The same brochure also includes an air-type (pneumatic) valve bag filler; in that type compressed air, not a motor, does the filling.

The impeller motor carries a high-inertia load together with the impeller and belt pulley. On a Turkish packing machine builder's turbine valve filler, the motor power is 4 kW and the working speed is 300–350 bags per hour.

Micro-dosing of flour additives

Additives such as vitamin C (ascorbic acid), enzymes, iron and folic acid are added to flour in very small proportions. A micro-dosing unit feeds the additive into the continuous flour stream with a small screw. One manufacturer states that its micro-dosing unit is based on a single-screw principle and uses a frequency-converter-controlled drive to make full use of the throughput range. Another manufacturer's micro feeder range has a 0.75–1.1 kW feed motor and a 0.55 kW bridge-breaker motor inside the hopper. On some micro feeders the motor goes down to 0.37 kW. Since the DRG range starts at 0.25 kW, most of these motors fall within it; very small dosing motors below 0.25 kW are outside the range.

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How many kW is a flour packing machine motor?

A) Motor powers seen in catalogues

For this machine group, manufacturer catalogues show single motor powers of roughly 0.37–6.5 kW; on rotary packers the total feed power reaches 14–20 kW. Single motor and machine total are different things: the 20 kW feed power of a six-spout machine is the sum of several motors split across the spouts. The connected power of a packing station is the sum of screw, belt and sewing unit; for the station in the data sheet above that comes to about 4 kW.

B) What the DRG range covers

DRG Motor is an electric motor manufacturer, supplier and seller. Our range is 0.25–11 kW in aluminium frames and 0.55–355 kW in cast iron, 1000/1500/3000 rpm, 3-phase 230/400 V or 400/690 V; B3, B5, B14 and B35 mounting is specified on the order. On a 25–50 kg bagging line the feed screw, impeller, bag belt, bag shaker and dosing screw motors of 0.25 kW and above fall within this range. Outside it are servo and stepper motors of small-pack fillers, devices with integrated motors such as portable sewing machines, motors below 0.25 kW and Ex motors for explosive dust zones.

Fill time and the feed screw: a worked example

A packing line's bags per hour depend on the screw's fast and slow fill times and the time to place and remove the bag. The values are assumptions.

• Target weight 50 kg. At fast fill the screw delivers 15 t/h, i.e. 4.17 kg per second; the first 47 kg fill in about 11.3 seconds.
• The last 3 kg are completed in about 1.8 seconds with the screw slowed to 40% of its speed (1.67 kg per second).
• Allowing 4 seconds to place, close and release the bag onto the belt, the cycle is about 17.1 seconds and capacity about 210 bags per hour, or about 10.5 tonnes of flour per hour.

210 bags an hour means the screw motor speeds up and slows down 210 times an hour, and on most machines stops between bags. In this duty, the motor's ability to cool under frequent acceleration and deceleration matters as much as its power.

The feed screw's power is not calculated with the conveying screw formula. A screw conveyor manufacturer's engineering guide states that its formulas apply only to control-fed conveyors and that feeders drawing from under a hopper need additional calculations: the head load of flour in the hopper adds load on the screw. That is why the feeder motor power is taken from the packing machine builder's data. The 2.2 kW dosing screw on that data sheet can take a DRG-100L1-4, which gives 14.5 Nm at 1450 rpm.

Flour dust, hygiene and protection on the packing line

Dust and cleaning

The filling spout, where the bag is opened and sewn, is one of the dustiest places in the mill. On packing machines the filling point is usually connected to the aspiration line; one maker's data sheet requires 5 m³ of aspiration air per minute for the packing station. Because the motors stand in this dust, their fins should be cleaned often and the terminal box cover and cable glands kept tight. DRG cast iron motors have IP55 protection.

Ex motors and classified zones

The inside of the packing hopper and the aspiration filter may count as explosive dust zones in the plant's risk assessment. Such areas call for an Ex-marked motor, which the DRG range does not include.

Checklist for choosing a packing or dosing motor

• The motor's job: feed screw, impeller, belt, shaker, sewing or dosing. Is it a servo or stepper motor or an induction motor? If the nameplate says "servo" or there is an encoder connection, it cannot be replaced with a standard motor.
• The old motor's nameplate: kW, speed, voltage, current, frame, mounting (a B5 or B14 flange is often tied to the gearbox).
• Drive: if an inverter is used, the new motor's current and voltage must match it; 230/400 V winding on small motors, 400/690 V from 4 kW upwards.
• Cycle: bags per hour and stops and starts per bag.
• Mounting and shaft: gearbox input, key, shaft diameter; exact dimensions come from the machine builder's drawing.
• Zone classification: is the motor in an explosive dust zone?

DRG motor options for a flour packing line

The table shows 4-pole models in the powers seen on the feed, belt and impeller motors of a packing line. Aluminium frames can also be chosen in the 0.25–11 kW range.

DRG MOTOR motors are guaranteed against material and manufacturing defects for 2 years from the date of delivery (warranty certificate). To compare motor and gearbox flange dimensions, see the technical drawings page.

Motors in this power range

• DRG-801-4 – 0.55 kW – 1400 rpm – 80 cast iron
• DRG-90L-4 – 1.5 kW – 1445 rpm – 90L cast iron
• DRG-100L1-4 – 2.2 kW – 1450 rpm – 100L cast iron
• DRG-100L2-4 – 3 kW – 1450 rpm – 100L cast iron
• DRG-112M-4 – 4 kW – 1450 rpm – 112M cast iron

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Flour packing machine motor: frequently asked questions

Which motor is used in a flour packing machine?

On 25–50 kg bagging machines the feed screw, impeller and belt use standard three-phase induction motors driven by an inverter. On small-pack fillers the filling auger is mostly turned by a servo or stepper motor.

Can an induction motor replace a servo motor?

No. A servo motor, with its drive and encoder, provides position and dosing accuracy; an induction motor does not give this control. When a servo motor fails, use the same type of motor and drive recommended by the machine builder. DRG does not sell servo motors.

How many kW is a flour dosing motor?

For additive micro-dosing, catalogues show 0.37–1.1 kW feed motors. For the dosing screw in bag filling, one maker's data sheet gives 2.2 kW.

What current should I expect from a 2.2 kW filling screw motor?

The DRG-100L1-4 nameplate shows 4.52 A on 400 V, and the drive's output rating should not be lower; for protection settings see the overload relay, fuse and contactor selection page.

Send us your packing machine's nameplate, the motor label and the drive details, and we will work out together whether the motor has an equivalent in the DRG range. Phone +90 (542) 666 11 11, e-mail [email protected], contact page. For all models and current prices, visit Buy Electric Motors Online.