Centrifugal Feeder Design

Centrifugal Feeder Design

Tutorial

A centrifugal feeder, or ‘rotary feeder’, has a conical central driven rotor surrounded by a circular bowl wall. The feeder separates parts utilizing centrifugal force and the parts revolve with high speed and are pulled to the outside of the bowl. The design shown in this tutorial is a more sophisticated concept where an inclined revolving disc brings bring s the parts to the rim of a revolving bowl. b owl. This concept allows for a series of qualifiers to gently orient the parts for transfer to a downstream process.

Warning – This tutorial tutorial is to serve as a guide covering most design areas. User is to consult and respect local government regulations where the unit is to operate.

Phase 1: General geometry Phase 2: Drive design Phase 3: Structure / Tooling www.packexone.com

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Phase 1 – General geometry (1) Operation:  Parts are metered from a prefeeder on the rotating disc. The disc carries the parts to the rim of the rotating bowl in a single lane. Fixed mechanical or pneumatic qualifiers orient and qualify the parts. Improperly oriented parts are ejected from the rim to the disc for recirculation. Properly oriented parts moved out of the rim and out of the feeder. Feed rate is affected mainly by:  The part size, its ‘natural’ orientation and the desired orientation. The disc and bowl speeds. Part speed shall not exceed 100 meters/min to prevent damages. BOWL RIM

DISC BOWL

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Phase 1 – General geometry (2) Calculated rate:  The feed rate, R, can be approximated using: L : the part longest dimension. V : the part speed (or the bowl rotating speed x 3.14 x bowl rim diameter). P : the percentage of parts that will be in the desired orientation. R=PV/L A large bowl rim diameter will give time and space for the parts to be qualified and oriented. So bigger bowl means higher rate.

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Phase 1 – General geometry (3) Components (exploded view)  Tooling support

Tooling backup ring

Outer shell

Cone Rotating disc

Disc hub

Rotating bowl

Bowl hub

Shell attachment

Base

Leveling foot

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Phase 1 – General geometry (4) Components (section view) 

The bowl has a spherical inner surface. This allows the disc to rotate in an inclined orientation and maintains a small gap with the bowl around its perimeter

Static hub fixed on base

Ball bearings

Roller chain & sprocket

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Phase 1 – General geometry (5) Components (section view) 

Roller chain & sprocket

Bowl gearmotor

Torque limiter Disc gearmotor Chain tensioner

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Phase 2 – Drive design (1) Drive  The drive is the assembly of components which rotates the disc and the bowl. The disc rotates within the bowl at a speed that may be equal, higher or lower than the bowl speed. A speed difference between bowl and disc is used to improve loading of the bowl rim. Chain tensioner

Torque limiter

Bowl gearmotor

Torque limiter

Chain tensioner

Disc gearmotor

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Phase 2 – Drive design (2) Drive  The static hub is bolted on the base. The bowl is bolted on the bowl hub which rotates over the static hub. A large sprocket drives the bowl hub. Through the static hub, the drive shaft rotates the disc.

Disc hub Steel: UNS G10200

Ball bearing Static hub Steel: UNS G10200

Bowl hub Steel: UNS G10200 Ball bearing

Large sprocket

Base

Torque limiter Small sprocket Drive shaft Steel: UNS G86200

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Phase 2 – Drive design (3) Disc drive  The gearmotor drives in rotation all items listed below and the parts carried by the disc. Gearmotor output speed , Sd = (maximum part speed) / (3.14 x disc diameter) = {rpm} Gearmotor output torque , Td = (Id + (Wp D2 / 4)) Ad + T f = {N*m or lbs-in} where: Id : total rotational inertia of the items listed below Wp : weight of the parts carried by the disc. D : disc diameter Ad : required disc acceleration after a complete stop. Ad = 3.14 Sd / (30 td ) td : time to accelerate (below 2 sec.) T f : frictional torque in the bearings Torque limiter and roller chain are to be selected using this data. Cone PVC

Disc hub

Disc PVC

Driveshaft

Torque limiter Sprocket

Gearmotor

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Phase 2 – Drive design (4) Bowl drive  The gearmotor drives in rotation all items listed below and the parts carried by the bowl. Gearmotor output speed , Sd = (maximum part speed) / (3.14 x bowl diameter) = {rpm} Gearmotor output torque , Td = (Id + (Wp D2 / 4)) Ad + T f = {N*m or lbs-in} where: Id : total rotational inertia of the items listed below Wp : weight of the parts carried by the bowl. D : bowl diameter Ad : required disc acceleration after a complete stop. Ad = 3.14 Sd / (30 td ) td : time to accelerate (below 2 sec.) T f : frictional torque in the bearings Torque limiter and roller chain are to be selected using this data.

Bowl Cast aluminum

Bowl hub

Bowl floor Aluminum: UNS A96061

Sprocket

Gearmotor

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Phase 3 – Structure/Tooling (1) Structure  The structure supports all the rotating components and the outside shell. Its construction is made of painted carbon steel (UNS K02600). The triangular geometry allows easy mounting for most components.

Shell attachment Base plate

Post

Leveling foot

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Phase 3 – Structure/Tooling (2) Tooling  The tooling is all the components that qualify/orient the parts: mechanical stoppers, air jets, pneumatic actuators, rotating wheel, …. These components are mounted on the tooling backup wall which serves also as an external guide. This wall is mounted to the tooling support, and the tooling support is mounted on top of the outer shell.

Tooling support

Outer shell

Tooling backup wall

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