Thermwood

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hermwood Corporation was established in 1969 as a plastic molder of
wood grained parts for the furniture industry, hence the name “Thermwood”.
From the beginning Thermwood incorporated a high level of technology in its
business.
For example, to mold its plastic parts
Thermwood developed a unique molding
process, and much of the plastic molding
and trimming machinery Thermwood
used was designed and built in house. In
the mid-1970s, it developed the first commercial CNC machine tool
control and used it to build machinery to trim its plastic parts. Thermwood began selling this trim equipment for plastics and woodworking
applications and the CNC router was born. Thermwood is the oldest
CNC router company and continues to offer products for the woodworking, plastics and aerospace industries. In addition to numerous
applications in the wood, furniture and cabinet industries, Thermwood
machines have also been used to process a wide variety of well-known
products.
Thermwood
Volumetric Compensation
Means Better CNC Routers
The interiors of most commercial jet airliners are processed on Thermwood machines, as are many helicopter blades, structural parts for military aircraft and tile underlayment for the space shuttle. Thermwood
machines produce parts from bowling alleys to bicycle helmets, spas,
motorcycle parts to truck bodies. Many of the sets on Broadway were
built on Thermwood machines, as were sets for movies such as Batman, Jurassic Park 3 and the latest Star Wars. Thermwood machines
helped rebuild both Windsor Castle and the Opera House in London.
Even NASA has used Thermwood machines to build the Mars Flyer
and Mars Lander.
Thermwood is deeply involved in CNC technology and technology development, incorporating a high level of next generation control technology in its products. It remains the only major CNC router company
in the world that designs and builds its own high-end CNC control and
has more patents on CNC router technology than all other CNC router
manufacturers combined. Thermwood’s control has become a worldwide standard in certain aerospace and defense applications.
thermwood
First in CNC Routers
P.O. Box 436, Dale, IN 47523 United States
Phone: 800-533-6901 Fax: 812-937-2956
www.thermwood.com
thermwood
MADE IN THE U.S.A
Thermwood Volumetric Compensation
Means Better CNC Routers
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hermwood has developed and is using
advanced new technology that dramatically
improves the accuracy and quality of CNC
routers without increasing cost. This new
technology impacts all Thermwood CNC
routers but is especially meaningful for large
envelope five-axis machines.
Here are some charts showing each axis of a three-axis
machine before and after compensation. Note that the
compensation process dramatically improved positioning
accuracy along each axis.
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The second requirement is a machine control that can process data fast enough to handle three-dimensional compensation at high block processing speeds. After over two
years of development, Thermwood’s new Gen2 SuperControl has the speed and has been given the capability of processing this volumetric data.
So, volumetric compensation is now a reality and Thermwood is the only CNC router manufacturer that has it. Here
are some charts showing typical readings before and after
volumetric compensation.
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As machine size increases it becomes ever
more difficult to achieve accurate positioning. Even miniscule deviations at the very limit of what
can be built today, when multiplied by the large structure
size become meaningful errors.
he traditional method of dealing with mechanical
variations is to use a laser interferometer to measure the
exact position of each axis as it moves along its linear path,
compare this to machine position and create a compensation table. This compensation table is used to correct for
mechanical error as the machine is running. This is a much
more practical approach than trying to make the structure
and mechanics absolutely perfect and it works well.
This is because the current compensation method only corrects for errors ALONG each axis. For example, if you move
along the X axis, the compensation system makes sure the
position along the X axis is exactly correct. Moving along
the X axis, however, can cause variations in the position of
the Y and Z axis for a variety of reasons. Y and Z axis compensation does not take into account errors caused by the
X axis. In other words, current compensation methods do
not take into account errors caused by axis interaction. You
can try to build a perfectly precise and aligned machine to
eliminate these problems but again, even minute variations
can cause significant errors especially as machine size increases. It is virtually impossible to make a large machine
accurate through mechanics alone.
hermwood has developed new technology that addresses this problem and this new technology is part of
every CNC router it manufactures. The approach is called
“Volumetric Compensation”.
Before
After
The idea is actually quite simple, but requires new technology which has only recently become available. The idea
is to compensate the machine as you normally would and
then measure the exact X,Y and Z position of the cutting
head within the working envelope and compensate all three
axes at each position for any remaining error.
Before
Before
After
After
These charts represent the current state-of-the-art in machine accuracy but portray an image that is not really correct. When viewing these charts you assume the positioning
accuracy of the machine is at or near what the charts show,
but that is seldom, if ever true. In fact, the actual accuracy
could be five or ten times worse than the charts show.
Obviously this increases the overall accuracy of the machine the same way that traditional compensation improves
accuracy along an individual axis, and it does this without
dramatic increases in the cost of the machine. Making this
simple idea work in the real world, however, requires two
dramatic new technologies.
The first is a 3D laser interferometer that can measure the
X,Y and Z position of the head anywhere in the working
envelope of the machine. This technology, although expensive, is now available and is finding its way into the
machine tool world.
Note that the “before” readings are after normal axis by axis compensation and represent what we believe are typical results you can expect
from anyone who offers a careful laser compensation but does not use
volumetric compensation. Volumetric compensation creates a fundamentally better machine and it is only available on CNC routers from
Thermwood.