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 Reverse
Engineering
Industrial Case Studies
High Speed Centrifugal
Compressor
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--- The
problem ---
This compressor was a very high speed, high output unit, specifically
custom designed for the application it is used in. These factors were
also the driving reasons for its very large price tag. Another
condition in this equation was its age. The OEM that manufactured the
blower was no longer supporting the unit, and therefore had no spare
parts available.
As is
the case with many mechanical systems, this unit had worn out over the
years, but the need for its services had not. The OEM had given an
extremely high price tag and long lead time to manufacture a new
compressor wheel, which was the part that failed first due to extreme
load and erosion (wear). This was very devastating news to the
customer, as their plant operations depended on this unit to keep the
product chain, and subsequently their lively hood, in operation.
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Lets add the
clincher to this disturbing yet very common situation. And this, as
they say, "is where the plot thickens". Upon disassembly,
the destroyed compressor wheel, the obvious reason for the unscheduled
outage, was removed from the unit. There was another used wheel in the
warehouse that had previously been removed from service because it too
had worn beyond its ability to produce the required pressure, but had
been replaced before it was completely destroyed, as was the case with
the failed wheel.
They were contemplating
whether or not they might use the worn spare wheel to try to squeak by
until they could get an OEM replacement, when someone made a grim
discovery. The mating wear surface of the volute was worn over .125 of
an inch (more than
twice the total running clearance of.059"), so now not only was
there no hope of making adequate pressure with the worn wheel, but even
with a brand new OEM wheel, they would not be able to get the pressure
that the unit was designed to produce. |
| The volute
assembly was so large that just removing it would cost a
tremendous amount of man hours, then there would be shipping and
substantial repair costs, and the labor to reinstall. The chances of a
repair being successful, without the proper engineering geometry of
the involute curve on the blade edges and the wear surface of the
volute itself, was very poor indeed, and extremely expensive. This was
a risk and expense that just could not be justified. |
(Digitized points from worn
volute) |
(New surface geometry for
blade edges)
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--- The Answer ---
The answer was to go to the customers
site and accurately digitize the worn surface of the volute. The Laser
Tracker was the logical choice, as it had both the portability and
accuracy needed to successfully acquire the data. We then take that
reverse engineered surface and make a new wheel that will precisely
fit the worn volute, thereby maintaining the running clearances and
the factory fresh performance of a new machine.
The worn wheel that was still in tact would supply us with the proper
geometry and curvature of the wheel hub and the curvature of the
double reverse curve blades. All these curves must be reproduced
precisely in order for the flow and pressure characteristics to be as
they were before.
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The term
"match machining" means to machine one part to match the
profile of the mating part that it will operate with. This is often
the best and sometimes the only way to insure a complete and correct
fit between parts, especially when the tolerances are tight and the
profile is complex. Digitizing one part allows us to use precision
manufacturing techniques to insure the mating part will function as
intended.
After digitizing the
volute and match machining our newly manufactured wheel to fit the
wear in the mating volute surface, the high speed / pressure
compressor functioned as well as a new unit, saving the customer tens
of thousands of dollars not having to buy a new unit. And substantially
more money than the initial purchase savings in not having to wait
months for a new unit to be designed and manufactured, all the while
losing many thousands of dollars in profit for every day that the unit
was down.
This high speed high
accuracy method of reverse engineering and manufacturing has literally
saved some of our customers from going out of business due to the loss
of their mission critical components (down time), and the lengthy lead
time of the OEM's in getting a replacement or re-manufactured unit
back to the customer. This is the value-add
of our services that cannot even be quantified in just monetary
savings, saving jobs and even entire companies is a satisfaction that
goes way beyond just liking what we do, and our customers are
extremely pleased with the results. |
Finished CAD model
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