Experiencias usuarias -Industrial equipment manufacturer optimizes new equipment design with Working Model -
In designing this industrial smelt spout cleaner, Clayton Abel, a
product engineer for Anthony-Ross, used Working Model to determine
dynamic loads for parts moving along a complicated path.
From concept to completion, designers of automated industrial
equipment face a significant challenge when they implement proposed
features into a new product design. How does an engineer know with
complete certainty that he is producing the optimum design for a product
that must withstand rigourous operating requirements? Clayton Abel, a
product development engineer with Oregon-based Anthony-Ross Company, an
industrial engineering firm that designs paper mill equipment, recently
found the solution to this challenge. When Abel was given the project of
designing a complex piece of machinery, he realized that the key to
achieving flawless automation would be found in the repeated testing of
the model in the early stages of the design.
Unfortunately for most engineers, the extensive testing of
anticipated stresses upon their designs means either developing costly
prototypes, or spending valuable time developing an endless series of
geometric equations. Abel knew that he could bypass both of these
obstacles by using Working Model 2.0, desktop motion analysis software
made by San Mateo-based MSC.Software. Abel saw an ad for Working Model
and sent away for information. At the time, he was using a similar
product, so he was familiar with desktop motion analysis software. But
once he purchased Working Model and realized its capabilities, Abel
never used the old software again.
"It was a good program, but not as convenient as Working
Model," said Abel, who used Working Model to help him customize
designs for Anthony-Ross? trademark product. For more than ten years,
Anthony-Ross has manufactured Automated Port Cleaners (APCs), devices
that clean ports in recovery furnaces used in the pulp and paper
industry. Recovery furnaces are the chemical recycling centers of pulp
and paper mills.
It takes large quantities of expensive chemicals to break down wood
chips into pulp. The pulp created from this procedure goes in one
direction to be made into paper, while the spent chemicals and leftover
organic matter are sent to a recovery furnace to be burned. These
boilers are ninety-nine percent effective in recovering chemicals for
recycling, so there is little pollution or waste involved in the
process.
Smelt Spout Cleaner.
The heat from the furnace reduces the chemicals, which fall to the
bottom of the burner and melt into a black liquid called smelt.
Recently, Anthony-Ross decided to expand its line of automated equipment
with a smelt spout cleaner, an apparatus for cleaning spouts that drain
smelt from the bottom of the furnaces. If smelt is not drained regularly
and thoroughly, it freezes and forms a crust that clogs the smelt spout,
which causes the level of smelt inside the furnace to rise. This
decreases the amount of chemicals that can be recovered and increases
the amount of noxious chemicals released. Before the smelt spout cleaner
was introduced, the only effective method of spout cleaning involved
workers inserting long rods into the spout to dislodge char and
encrusted material. This is a physically demanding job that exposes
workers to potentially hazardous fumes and the danger of being splashed
by the molten smelt.
Abel faced several challenges in the creation of the new smelt spout
cleaner. The product had to sit well away from the furnace so it
wouldn?t be exposed to corrosive fumes and so that it could be
repaired or relocated quickly without disturbing the burning furnace.
The cleaner had to be able to sense any misalignment between itself and
the spout, as well as any thermal expansion taking place within the
spout, so it could follow spout movement. In addition, since different
boilers have different spout designs, Abel wanted to create a cleaner
that would not have to be customized for each installation.
The proposed design involved a long horizontal beam attached to a
camming track. The beam would move back and forth over the spout and
rake loose the frozen smelt. Then paddles attached to the beam assembly
would unfold, lock into place, and scrape out the loosened materials.
DXF IMPORT. Abel created the design in AutoCAD, then separated it into
sections and exported them in DXF files to Working Model. He then
assigned properties such as mass, density and coefficients of friction
to the different components to control how they interacted with each
other.
Before he could begin testing the parts, Abel linked them together.
"Working Model provides all the built-in actuators, motors,
springs, dampers and pin joints needed to construct realistic
models," he said. "With my old software, I had to write
equations for all those devices and create them from scratch within the
program. With Working Model, just click on an icon to select a device,
and place it on the object by dragging it there with the mouse."
Once the parts were joined, Abel imposed anticipated working loads
upon various components of the smelt spout cleaner. "My goal was to
reduce the stress on machine elements as much as possible," he
said. "Too much stress will cause parts to wear out quickly."
One of the most challenging aspects of the smelt spout cleaner design
was the moving beam assembly supported by cam rollers in a track. The
track had an almost roller-coaster shaped design. It had to be precisely
shaped so the beam could move freely without coming in contact with the
spout. Not only did the track have to support the weight of the beam,
but it had to allow for extensive cam roller movement as the beam moved
in a simultaneous up-and-down, in-and-out fashion.
"It would be difficult to manually calculate the loads on the
track," said Abel, "but Working Model did it automatically. It
allowed me to look at eight or ten different track configurations in a
day, and I came up with the ideal shape. Without Working Model, it would
have taken me a week or more to calculate that many geometries."
Another load Abel considered was the external force of the frozen
smelt upon the beam and the cleaning paddles. "I modeled the smelt,
added it to the simulation and looked at how it affected beam
movement," said Abel. "This test made it obvious what size cam
roller to choose." Abel used Working Model?s built-in actuators
to model air cylinders. "I positioned the actuator at the base of
the beam and ran a simulation," said Abel, "I was able to
measure the forces required to reverse the direction of the beam as it
raised and lowered above the spout. This allowed me to properly size the
air cylinder for the job."
Quick & Accurate.
All these tests were accomplished quickly in Working Model.
"It?s easy to determine what the loads are for static tracks and
rollers," said Abel. "Working Model is unique because it
allows me to determine what the dynamic loads are as parts move along a
complicated path." As Abel?s simulations ran, he watched graphs
of the changing forces on the screen as well as compiled the recorded
data in a tabular form, which he then printed for closer examination.
Once Abel located the maximum forces, he entered the information into a
finite-element analysis program. The results allowed Abel to
substantially reduce the size and weight of the proposed product design.
"Working Model saved Anthony-Ross a significant amount of time
in the development process," said Abel. "In addition, it gave
us the assurance that the product we finally chose to produce is the
best that we can do. If I had to manually do what Working Model did, I
could not have looked at nearly as many configurations and might not
have come across the best combination of geometries. Working Model is
easy to use and very useful."
Abel is now in the process of designing another new product for
Anthony-Ross. "The next project on the board is a port-damper
assembly, which will control the air flow entering the recovery
furnace," said Abel. "The product will have several links,
pivots, spring tensioners and air cylinders, so it?s a natural design
to analyze with Working Model."
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