There are sound economic and operational arguments in favour of making
piecemeal upgrades to existing machinery. Les Hunt discovers how
selective use of modern pneumatic components can lend a new lease of life
to largely mechanically-based assembly systems
Standex Electronics manufactures reed switches on a big scale, the
majority of which is exported to the USA, Europe and the Far East. The
Tonbridge factory has a production capacity running into tens of millions
of units per year, placing considerable demands on production machinery
and processes throughout the factory. The company boasts a unique and
ingenious method of assembling reed switches, which enables it to
manufacture in these impressive volumes. Understandably, the process is a
closely guarded secret as it gives Standex a significant manufacturing
advantage over its competitors, and not surprisingly, it is highly
automated.
Over the years, a strong in-house production engineering department has
designed and built assembly and grading lines, which are a credit to its
ingenuity and resourcefulness. Initially, these machines were entirely
electro-mechanical in operation, hugely reliant on cams for positioning
during assembly and other downstream process operations. These mechanical
systems have served - and continue to serve - the company extremely well,
so like any other sensible assembly line operator, Standex saw no reason
to change things for change's sake, reasoning that if it ain't broke,
don't fix it! However, mechanical systems wear, no matter how well they
are maintained, and since this was beginning to compromise accuracy and
elevate rejection rates, some new thinking was required. Product
engineering and QA manager, Edward Palmer, picks up the story.
About ten years ago we began to replace cam-driven positioners and
gating devices with self-powered pneumatic slides. We sourced components
from a variety of suppliers at the time and some of these are still very
much in use. They made a great difference, and provided a relatively easy
and cost-effective method of replacing worn and wearing elements within
the mechanical system. Among those suppliers was SMC Pneumatics, who
later came to us with a range of miniaturised pneumatic components, which
appeared to be years ahead of the competition. Admittedly, we were
sceptical at the time that these small devices would have sufficient flow
capacities to cope with the applications, but SMC persuaded us to try
them out. A trial on one machine was enough to convince us of their
capabilities. We were particularly impressed by the low power consumption
of the solenoids - some of the competitor products were drawing up to 8W
per coil!
The first major upgrade using SMC components was to the actuator
mechanism, which presents the glass tube and contact assembly for
nitrogen purging and final sealing. This arrangement now comprises a CXS
type linear actuator with MH series gripper, which is much faster and
more repeatable, as well as being more reliable. The pneumatic system is
also much cleaner and less of a maintenance burden. Further upgrades
around the factory have made good use of CXS linear and CRB type rotary
actuators in various combinations. Mr Palmer believes these two products
working in combination have had the biggest impact to date on the machine
upgrade programme. Controlling these and other devices are SMC's SY
series valves, many of which have now been installed around the factory.
Mr Palmer says the indicator LEDs on these valves, plus the manual test
buttons, became a major factor in helping overcome any prejudices or
resistance to change, because they are so useful when troubleshooting!
We have a good customer/supplier relationship with SMC, says Mr palmer.
They have been very helpful with advice on new products and how these
might be incorporated to improve our processes, and we have