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Performance
of 50 Completed ATP Projects
Status
Report - Number 2
NIST SP 950-2
Chapter
6 - Manufacturing
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Saginaw
Machine Systems, Inc.
Better Precision for Machine
Tools Through Thermal-Error Correction
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| Machine
tools are used in hundreds of thousands of plants and shops to cut
and shape metal parts and pieces. The interface between the cutting
or shaping tool and the material being worked almost always gets hot.
In most cases, a coolant is directed onto the interface area to take
away enough heat to allow the job to be performed. |
COMPOSITE
PERFORMANCE SCORE
(Based on a four star rating.)
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| A new high-precision
vertical lathe which incorporates the new thermal-error compensation
technology, first delivered to customers in 1998. |
High Heat Degrades
Machining Quality
Even with the coolant, the machine tool itself often becomes warm enough
to change shape slightly, and the accuracy of the machining operation
degrades. The result can be a finished part that fails to meet specifications.
What would have become a salable part becomes scrap metal, and some high-precision
parts cannot be made at all.
Thermal-Error Compensation
With ATP funding, Saginaw Machine Tools — a small, privately held
company founded in 1983 to build precision computer-controlled machine
tools for high-volume manufacturing — together with researchers at
the University of Michigan, developed a solution to the heat problem.
Their technology monitors the temperature gradients in computer numerically
controlled (CNC) machine tools and alters the control process dynamically
(while the machine is working) to compensate for heat-related changes
in the machine tool as the part is being worked. When the new technology
is incorporated into machine tools, the result is higher-quality parts.
The technology uses
a laser system to measure machine geometric and thermal errors and heat
sensors to monitor temperatures near the interface between the cutting
tool and the metal being worked. A computer program, using a thermal volumetric
error model, processes the laser and sensor data and sends corrective
instructions to the machine tool in real time, as it shapes
the metal. Use of this thermal-error compensation technology enhances
the accuracy of CNC machine-tooled products by fourfold to fivefold as
measured by spindle drift (shifting of the shaft, in a lathe or other
machine tool, that holds the piece being formed), at a commercially viable
cost.
First Products to
Market
At the end of the ATP funding period, additional devel-opment work not
originally foreseen by the company remained to be done. Saginaw continued
to advance the technology and has invested as much of its own funds since
the close of the project as the ATP put in at the beginning.
Since completing the
development work, the company has begun to move its first product, which
uses the Accu-System incorporating the ATP technology, into commercialization.
By early 1998, Saginaw had developed prototype tools. One prototype was
tested by an independent laboratory and pronounced ready for market. Another
tool from Saginaw was subjected to a competitive evaluation process by
a large tool buyer, in which the Saginaw tool was pitted against tools
from seven other suppliers. The results showed that the Saginaw machine
with the Accu-System was the most accurate. All in all, 30 characteristics
of machine performance were measured, and the Saginaw machine had a weighted
average score that was 50 percent higher than the next best machine. On
the critical characteristic of spindle drift, the Saginaw machine achieved
a two-thirds reduction in drift compared with the next best machine.
By March 1998, Saginaw
had received orders from other companies for eight machines priced at
more than $200,000 each. Orders for several dozen additional machines
of the same type were expected over the next several months.
Productivity Improvements
Users of the technology are able to take advantage, at reasonable cost,
of a substantial increase in the accuracy of their machine tools, improving
the precision of the workpieces the machines produce. Customers manufacturing
high-precision parts realize productivity improvements of 10 percent to
30 percent because of reduced requirements for part testing and rework.
The number of potential
applications is large. Because the Saginaw equipment is now in use, other
manufacturers may imitate the technology. The company has concluded that
none of the technology is patentable, and it is likely that competitors
will be able to imitate its methods. Consequently, most machine tools
that make high-precision parts are likely to be improved in the long run.
If Saginaw had not
received the ATP award, company officials say, it would not have done
the project. Being primarily a manufacturing company, it did not have
a substantial research and development capability. While working on the
ATP project, Saginaw collaborated with the University of Michigan on a
subcontractor basis to extend the company’s research capabilities.
In addition, officials say, having the ATP award helped Saginaw win a
subsequent $1 million award from the Defense Advanced Research Projects
Agency for a related project.
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Project
Highlights
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PROJECT:
To develop an easily adaptable thermal-error correction technology
for enhancing the accuracy of computer numerically controlled machine
tools.
Duration: 4/15/1991 — 11/16/1993
ATP Number: 90-01-0232
FUNDING (in
thousands):
| ATP |
$540
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84%
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| Company |
100
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16%
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| Total |
$640
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ACCOMPLISHMENTS:
Saginaw, working closely with researchers at the University of Michigan,
accomplished the project’s technical goals by developing a
generic mathematical model of thermal errors, as well as the sensor
and computer-control systems for a thermal-error correction technology.
The company also:
- developed
several prototype tools incorporating the new technology;
- submitted
a prototype, as did seven other manufacturers, for testing by
an independent laboratory, which found that the Saginaw machine
was the most accurate of the eight machines, with an overall score
50% higher than the next best machine; and
- developed
the Accu-System, which incorporates the ATP-funded technology,
offered commercially for the first time in a machine tool
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COMMERCIALIZATION
STATUS:
Commercial products were introduced to the market in early 1998.
OUTLOOK:
The outlook for this technology is very promising. Saginaw started
receiving orders in early 1998 for machine tools that incorporate
the new technology. Machine tools that could benefit from the improved
accuracy are used in plants and shops throughout the nation. Other
tool producers are likely to imitate the technology, which is not
expected to receive patent protection. Users of the tools that incorporate
the new technology will benefit from a substantial improvement in
machine tool accuracy, increasing the overall precision of the pieces
produced by the machines.
Composite
Performance Score:
COMPANIES:
Saginaw Machine Systems, Inc.
301 Park St.
Troy, MI 48083
Contact:
Gerald J. Romito
Phone: (248) 583-7200
Number of employees: 120 at project start, 120 at the end
of 1997
Subcontractor: University of Michigan
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Return to Table
of Contents or go to next section.
Date created: April
2002
Last updated:
April 12, 2005
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