Section 3 --Operation and Adjustments 3- 9
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purity of the accepted product while leaving throughput at the same level, the yield
will decrease (a greater percentage of product will be rejected). If throughput is
reduced you may be able to have this higher purity without reducing the yield.
With these relationships in mind, evaluate your product samples considering the
following possible adjustments to the sorter setup:
Product Feed - It is important that all chutes receive the same product flow. Visually
evaluate the product feed for consistency. The height of the metering gates on the
hopper outlets should be the same. The balance pots on the Feeder Driver PCB
should be used to equalize the vibration of the feeders. As discussed in Section
3.2.8, weigh timed samples from each chute to confirm that product flow is the
same across the sorter.
Product Handling/Flow - Excessive good product in the reject stream, or defects
which are missed in the accept stream, may be caused by bouncing in the feed
stream. Any product which runs high in the chute may bounce on the ejector bar
and disturb the flow. This will cause product to fall into the reject flow without
being sorted, and will change the velocity (timing) for defects which would be
targeted for removal, causing them to be missed. Look down into the sorting
section while the ScanMasterII is running and evaluate the flow. Virtually none of
the product should be running high enough to bounce on the ejector bar. Rejected
product should hit the reject deflector and be turned down. Streams of product
from each channel should be centered between the alignment marks on the ejector
liner plate. These marks define the edges of the channels for each chute. If you see
product handling problems, and are unable to resolve them, contact your service
representative.
Separation Point - The adjustable baffle on each accept tube defines the dividing
point between the accepted product and the rejected product. Generally, primary
sort accept tubes will be set to a “closed” position to maximize purity of the
accepted product. The resort accept tubes will be set to an “open” position to
minimize the product removed, and thus to maximize the yield.
Ejector Dwell - Excessively long dwell can result in too much good product being
removed, while excessively short dwell can result in defects being missed. It is
recommended that dwell be set at a middle point and all other fine tuning
adjustments be completed, then tests be conducted for shorter dwell to determine if
good product in the reject flow can be further reduced.
Note: The timing logic of the ScanMasterII ejector fire is to time out the delay
setting and then fire the ejector for the time of the dwell setting (or longer if the
defect is large and dwell extension is on). When making changes to the dwell
setting, remember that the effective “center” of the valve’s fire pulse is moved as
dwell is changed. For the ScanMasterII, for each 0.2 ms of change in dwell, the
delay setting should be changed by 0.1 ms in the opposite direction in order to keep
the effective center of the valve’s fire at the same point. For example, if dwell is
decreased from 1.4 to 1.0 ms, the delay should be increased by 0.2 ms.
Ejector Delay - Incorrectly set ejector delay, either long or short, will result in both
missed defects in the accepted product and excessive good product removal. Tests
can be conducted by turning delay up one millisecond at a time and evaluating
finished product for missed defects, and then turning delay down one millisecond
at a time and conducting the same evaluation. Usually, the optimum delay setting is
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