Fume extraction system avoids thermal shock in reflow and wave
soldering
Purex International has incorporated a unique vacuum control capability
in its Purex Powerflow fume extraction systems. By automatically
keeping air flow constant, accurate temperature profiles can be maintained
in reflow ovens and wave soldering machines. The risk of thermal shock
is therefore minimised, which improves product quality and reduces reject
rates.
Using conventional fume extraction systems, the air flow will vary as
filters fill up with solder particles through their life and become partially
blocked. With the Purex system, Purex International's microprocessor-controlled
IPCP (Intelligent Purification Control Program) monitors the vacuum in
the system and automatically varies the pump's motor speed to keep a constant
vacuum. The air flow rate is therefore kept constant, to within a variance
of less than 1% throughout the filter life.
Due to the cooling effect of the extraction air flow, conventional extraction
systems require frequent and time-consuming manual adjustments to the
heating elements of the reflow oven or wave solder machine. These adjustments,
with the resultant potential for operator error, are necessary to maintain
the required temperature profile. The Purex system avoids this
problem completely, with automatic control taking the place of operator
modifications.
With a new, unblocked filter, the IPCP's motor control capability allows
the motor to be run at a lower speed. This saves power, leading to lower
running costs, and extended motor life. The flexibility of the IPCP also
means that the motor can be driven at higher speeds when required, enabling
higher pressure extraction to overcome the increased resistance as a filter
blocks.
The Purex system also solves the problem of fume build-up in the reflow
oven caused by extraction speeds dropping. The fume build-up leaves debris
on the products, the heating elements and the inside surface of the oven.
This debris makes the oven less efficient, and leads to higher product
reject rates. It also requires maintenance to remove it, leading to down-time
and lost production.
The IPCP allows the Purex extraction system to be easily linked to the
reflow oven control system via an industry-standard RS423 interface. The Purex system can then automatically switch off the oven if extraction
is insufficient, and the oven can automatically switch on the Purex system
at start-up. An optional feature is the Intelligent Purification Network
(IPN) which allows remote diagnostics and adjustment of a group of extraction
systems from an office PC.
For further information please call Purex International on 00
44 (0)1709 763000.
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