REV A MDR Spiral - Installation and Maintenance Manual
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OVERVIEW 1
1.1
Zero Pressure Accumulation (ZPA)
An MDR conveyor with accumulation is composed of several ‘zones’, as shown in the image
below. Each zone is powered by a motorized drive roller (MDR). The MDRs are controlled by
a communications network, allowing the zones to communicate with each other to achieve
the desired accumulation method. The rollers in a zone do not rotate until product has been
detected in the adjacent upstream zone. In other words, the rollers in Zone 2 do not rotate
until the photo eye sensor in Zone 1 detects a product. The rollers in Zone 3 do not rotate
until the photo eye sensor in Zone 2 detects a product.
There are two types of accumulation release: Singulation release and Slug release. Singulation
release allows one product to be released at a time after the downstream zone has cleared.
Slug release allows a predetermined amount of product to be released at one time after the
downstream zone has cleared. Slug release is typically used in Palletizing or Machine loading
conditions. The type of release to be used is usually determined at design time.
Accumulation begins when a product is forced to remain in Zone 4. The photo eye sensor
in Zone 4 detects the product and turns o the motorized drive roller in Zone 4, stopping all
the rollers in that zone. When a second product is detected by the photo eye sensor in Zone
3, the motorized drive roller in Zone 3 is turned o, stopping all the rollers in that zone.
This accumulation sequence is repeated for each succeeding zone as long as the product
in Zone 4 is forced to remain in position.
When the product in Zone 4 can be released, the motorized drive roller is turned on and the
product moves down the conveyor system. When the product clears the photo eye sensor
in Zone 4, the motorized drive roller in Zone 3 is turned on and the product moves from
Zone 3 to Zone 4. This release sequence is repeated for each succeeding zone as long as
product is not intentionally stopped in any given zone. The subsequent gap between products
is approximately equal to one zone length. This accumulation sequence may be started
anywhere along the length of the conveyor.
The MDR accumulation is a true zero--pressure accumulation (ZPA). This means that
the product being conveyed never comes in contact with any other product; provided
it is dimensionally compatible with the zone (product length is less than the zone length).
K1
MOT1
IN1
X1
MOT2
IN2
X2
K1
MOT1
IN1
X1
MOT2
IN2
X2
TO ZONE 2 PHOTOEYE
TO ZONE 2 MOTOR
TO ZONE 4 PHOTOEYE
TO ZONE 4 MOTOR
TO ZONE 3 PHOTOEYE
TO ZONE 3 MOTOR
TO ZONE 1 PHOTOEYE
TO ZONE 1 MOTOR
DOWNSTREAM
CONVEYOR
INTERCONNECTION
UPSTREAM
CONVEYOR
INTERCONNECTION
FLOW
