Meat Grinding Machines: Types, Design, and Operating Principles
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The main types of meat grinding machines are meat grinders (wolves), bacon cutters, mincemeat mixers, and bowl cutters. 
What are meat grinders (wolves) — purpose, classification, design and operating principle?
Meat grinders, known as "wolves" (Fig. 1), are machines designed to grind both frozen and unfrozen meat, fat-containing products, and other raw materials. Most of these machines feature mechanized feeding of raw material into the working zone.
Some meat grinders have a simplified design in which raw material is fed by gravity due to the difference in levels. The core unit of every meat grinder is the cutting mechanism, which operates on the knife–plate principle.
The cutting mechanism of a meat grinder can have one, two, three, or four cutting planes depending on the required degree of grinding. The output of a meat grinder depends on the pressure in the working section, the rotation speed of the knives, the number of cutting edges, and the contact area between the knives and the plates.
By the method of feeding raw material onto the working auger, meat grinders are divided into those without forced feed and those with forced feed. They are also built with horizontal and with inclined cylinders. 
The working chamber inside the meat grinder housing is a stationary hollow cylinder, the interior of which carries ribs that prevent the product from rotating around the auger together with it.
The braking effect of the ribs depends on their number, height, and shape. The auger — fitted with a tapering core that narrows toward the cutting section — moves the raw material through the working chamber, feeds it to the knives, and pushes it through the knife plates.
How does the grinding mechanism of a meat grinder work?
The distinctive feature of the auger's operation is that it creates enough pressure to push the meat through the cutting mechanism without squeezing out the liquid phase of the product. The cutting mechanism of a meat grinder consists of a stationary cutting plate, rotating cross-shaped knives, stationary knife plates with holes of varying diameter, and a clamping nut.
Plates 160 mm and 200 mm in diameter are the most widely used. Correct operation of the cutting mechanism requires the knives and plates to be tightly clamped together.
To achieve this, the nut is first tightened with a wrench until it stops, then loosened by 0.25 to 0.33 of a turn. Meat grinders are driven by an electric motor through a V-belt transmission and, as a rule, a cylindrical gearbox. Plates with different hole diameters are used, and these determine the degree of grinding.
The hole diameter of the plates decreases in the direction the product travels. Grinding therefore proceeds in sequence from larger sizes to smaller ones, without unnecessary energy expenditure or loss of output.
A meat grinder is made up of a loading bowl into which the raw material is fed, a feeding device (a spiral and a worm), an electric motor, a metal casing, the cutting mechanism, and the clamping nut.
The meat grinder works as follows: meat enters through the loading opening into the throat, from where the auger pushes it into the working chamber that houses the knives and plates. The pressure created by the auger forces the meat through the holes of the receiving plate, and it leaves the grinder in ground form.
The K7–FVP–82 meat grinder is intended for the direct grinding of boneless sinewy meat and other meat products. It is used in meat-processing plants and other meat-processing enterprises.
The technical output of this grinder is 175–350 kg/h. The K7–FVP–82 (Fig. 2) consists of the following parts: a welded frame (4) carrying all the mechanisms and the drive, and a loading bowl (1) for receiving the raw material.
The drive of the working auger consists of an electric motor (5), a gearbox (6), and a V-belt transmission (7). The protective and starting apparatus, housed in the motor box, is installed in a convenient location for servicing (mounting it on a wall is recommended).
This grinder operates as follows: boneless sinewy meat is loaded into the receiving bowl and fed onto the working auger (2), which moves it into the cutting zone (3), where it is ground to the required size — set by installing the appropriate set of knives and knife plates. 
Figure 2 — General view of the K7–FVP–82 meat grinder: 1 — loading bowl; 2 — working auger; 3 — cutting mechanism; 4 — frame; 5 — electric motor; 6 — gearbox; 7 — V-belt transmission. 
What are bacon cutters used for and how are they built?
Bacon cutters (shpigorizky) are used in industry to cut lard or boiled meat into cubes. Depending on the position of the feeder, bacon cutters are horizontal or vertical; in the first two cutting planes the knives may be disc-type or plate-type.
At the lard outlet, sickle-shaped knives with an internal cutting edge are installed. Plate knives require a feeding mechanism, since only disc knives provide self-feeding of the lard. Bacon cutters are built with hydraulic and with mechanical drives. 
The working part of a bacon cutter (Fig. 5) includes a drive shaft (1) with a sickle-shaped knife (2) and an eccentric cam (3) seated in the grip of the fork (4). The fork is connected to the frame (5) carrying the flat knives (6), and through an angle lever (7) that oscillates around an axle (8) linked to a second frame (9) fitted with knives (10).
The cutting mechanism is installed in the box (11), in which the pusher (12) moves, receiving continuous or pulsed motion from the feed mechanism. Two dimensions of the cut pieces are determined by the distance between the flat knives mounted in the frames; the third by the amount of feed per single revolution of the sickle-shaped knife.
Pulsed feeding of the lard under the sickle-shaped knives is advisable. In mechanical drives it is achieved by means of a crank or a Bosch device; in hydraulic drives, delayed oil feed is used.
The K7–FGShM bacon cutter is designed to cut lard into cubes of 4×4×4 mm, 6×6×6 mm, 8×8×8 mm, and 12×12×12 mm. It is used in meat-processing enterprises.
The technical output of this bacon cutter when cutting lard into 6×6×6 mm cubes is no less than 150 kg/h. The K7–FGShM (Fig. 6) consists of a welded frame (1) on which the main units are mounted: a table (9), a box (2), a body (3), a drive (4), a knife mechanism (5), a control panel (7), and a hydraulic system.
The box is intended to feed the lard into the cutting zone. Feeding is carried out by a pusher (15) connected directly to the rod of a hydraulic cylinder (16). A table (9) with a pass-through capacity that is filled with lard is attached to the box.
The capacity of the box is closed off manually by a damper (10). An interlock on the damper prevents pusher movement while the damper is open. 
Two bearing units are mounted on the wall of the body (3); one of them holds a shaft that transmits rotation to the cut-off knife (11) and the eccentric mechanism.
The eccentric mechanism transmits motion to the connecting rod (14) mounted on the axle of the second bearing unit. The connecting rod (14) drives the knife frames, arranged in mutually perpendicular planes, in reciprocating motion.
How does a bacon cutter operate?
Lard loaded into the box and closed from above by the damper is pushed by the pusher into the cutting zone, where it is cut into cubes by two knife frames moving in mutually perpendicular planes and a sickle-shaped knife.
When the pusher, after the "Feed" button is pressed, reaches its extreme position against the knife frames, the interlock is triggered and the pusher automatically returns to its starting position.
Triggering the interlock lights a signal lamp on the control panel, indicating that the cycle is complete. The interlock is provided by two limit switches mounted on the frame beneath the pusher rod. 
In the vertical bacon cutter with hydraulic feed (Fig. 7), the hydraulic cylinder and the pusher rod are connected by a plate (1), and to prevent the pusher rod (2) from bending, a bar (3) sliding along guides is attached to the plate. The power cylinder (4) houses the piston and rod (5).
The pusher enters the working section of the rotating box (6), while its second section is under loading; the box is turned manually around the axle (7). The cutting mechanism consists of an upper (8) and a lower (9) frame with flat knives and a sickle-shaped knife (10), whose free end is fitted with a slide shoe running along the guides (11).
The sickle-shaped knife is mounted on the shaft (12) of the worm wheel (13), which is connected to the worm mounted on the shaft (14) and driven by the electric motor (15) through the coupling (16). The frames are driven by a pin (17) mounted eccentrically on the shaft (12).
Oil is forced into the system by the pump (18), which receives its rotation from the shaft (14) through the coupling (19). The suction (20) and discharge (21), (22) pipes are connected to the pump and are fitted with a spool valve (23), an adjustable plug valve (24), and two safety valves (25) and (26).
What is a mincemeat mixer and how does it work?
Mincemeat mixers (farshmishalky) are used to mix mince and give it the proper consistency. The machine also carries a handle for engaging the system and a switch (27). Depending on the flow capacity, mixers of batch (periodic) and continuous action are used, as well as open and closed types (for mixing under excess pressure or vacuum). 
Each mincemeat mixer consists of a vessel (1) (Fig. 8) in which two counter-rotating helical blades (2) and (3) are mounted, driven by a shaft (4).
Helical or other blades are selected so that during their rotation the mass is moved from the edge toward the center while the flow at the bottom runs in the opposite direction (imitating hand mixing). In terms of rotation, blade (3), on the operator's side, turns 1.3 to 2 times slower than blade (2).
The L5–FM2–U–150 mincemeat mixer (Fig. 9) is intended for mixing meat mince to the required consistency with all the components specified by the recipe and the technological process of producing sausage products. The output of the mixer is 100 kg/h. 
Figure 9 — General view of the L5–FM2–U–150 mincemeat mixer: 1 — counterbalancing mechanism; 2 — control mechanism; 3 — lid; 4 — mince hopper; 5 — mince unloading handle; 6 — grip; 7 — mince unloading hopper.
What is the L5–FM2–U–150 mincemeat mixer made of?
The L5–FM2–U–150 mincemeat mixer consists of a frame, a mixing trough, an auger drive, a loading mechanism, an unloading hatch, and electrical equipment. The mince is mixed by mixing augers in the trough, which is covered by a protective grille.
The loading and unloading of mince are mechanized. To ensure safe operation, the mixing augers are interlocked so they stop when the lid is open and when the guard over the unloading hatches is removed. The mixer is operated by a single worker.
The mincemeat mixer is fitted with two three-phase squirrel-cage asynchronous electric motors. For fine grinding of meat, bowl cutters (kuter) have become the most widely used. 
What are bowl cutters (kuter) and how do they grind meat?
Bowl cutters are intended for the fine grinding of soft meat raw material and for turning it into a uniform, homogeneous mass. Before being fed into a bowl cutter, the raw material is first ground on a meat grinder, although some bowl cutter designs include attachments for grinding piece raw material.
Bowl cutters are of batch and continuous action. In a bowl cutter, meat raw material is ground by sickle-shaped knives mounted on a shaft. The knives are alternately immersed in the bowl, which moves at a frequency of up to 0.3 s⁻¹.
Grinding takes place in open bowls or under vacuum. In addition, bowl cutters combine the processes of grinding and mixing.
Figure 11 shows the schematic of a batch-action bowl cutter. It consists of an open bowl, a cutting mechanism (including the drive shaft and sickle-shaped knives), a comb, and a lid that closes off the working zone of the bowl cutter. Scrapers are attached to the lid, positioned on the outer and inner parts of the product held in the bowl.
The scrapers direct the product under the cutting mechanism as the bowl rotates; the cutting mechanism is a set of sickle-shaped knives fixed in the knife head. The number of knives in a set for batch-action bowl cutters is at least two, and they rotate at frequencies of up to 100 s⁻¹ and higher.
The knives of a bowl cutter may have a cutting bevel in the form of a straight line with a wedge-shaped grind, or of a slightly curved line. The choice of knife and the shape of the cutting-bevel grind is determined by the required grinding quality and the energy expenditure.
Among the existing grind shapes, preference is given to an asymmetrical wedge with an apex angle of 15–30°. The bowl of a bowl cutter is loaded manually or by loading devices (lifts with floor trolleys). The main indicator in a bowl cutter's technical specification is the bowl capacity.
Small enterprises use bowl cutters with bowls of 15 to 125 L; large ones use bowls larger than 125 L. The L5–FKN bowl cutter (Fig. 12) is intended for the fine grinding of meat in the production of semi-smoked, raw-smoked, and liver sausages, frankfurters and small sausages, and pâtés from meat, fish, and poultry.
The bowl cutter consists of a frame, a bowl, a grinding mechanism, an unloader, a protective lid, and an electric drive. The drive and process units are mounted on the frame. The grinding mechanism has a knife shaft, on the cantilever part of which a sleeve with sickle-shaped knives, set in place by means of rings, is mounted.
The mince unloading mechanism is mounted on a bracket attached to the lower part of the frame. Its working element is an aluminium disc driven by an electric motor through a worm gearbox. The unloader mechanism swings freely on a special axle.
In the raised position, the unloader is held in place by its own weight. The unloader shaft passes over the working space of the bowl through a tube, one end of which is rigidly connected to the housing of the unloader gearbox; on the other end is fixed a metal scraper for removing mince from the outer surface of the disc and directing it into a chute.
The electric motor of the unloader mechanism switches on and off automatically: with the disc raised it does not run, and it switches on only after the disc is lowered into the machine's bowl. The unloading mechanism does not empty the bowl completely, so additional manual cleaning is required. 
Figure 12 — Kinematic schematic of the L5–FKN bowl cutter: 1, 2, 7 — electric motors; 3, 4 — V-belt transmissions; 5, 6 — worm gearboxes; 8 — unloader; 9 — knife shaft; 10 — bowl.
The protective lid provides safe working conditions and prevents processed raw material from being thrown out of the bowl. Special scrapers are attached to the underside of the lid, directing the raw material being ground under the knives. Raw material is loaded into the bowl while the machine is running. It is fed onto the knives by the rotation of the bowl.
The duration of mince processing in a bowl cutter depends on the grade of meat, the degree of its preliminary grinding, the bowl loading factor, the distance between the outermost knives and the bowl (a minimum of 2 mm), the number of knives, and their rotation frequency.
The knives are assembled in strict sequence so that the outermost points of their edges describe, in the diametral cross-section, a circle of the same diameter. This achieves the balancing of the knife head.
