Development and changes in NC created by a machine tool
manufacturer

Celebrating 50 years of the development of"OSP" control systems
Adachi Mitsuaki, FA Systems Headquarters, Okuma Corporation

Fusion of PC
Technologies

Figure 1

Figure 1

NC device "OSP" product model changes“OSP” control model developments

Our company was founded in 1898 as a machine tool

Our company also maintains an "absolute value

manufacturer and advanced ahead of other companies

philosophy" according to which we allow nothereafter to begin developing NC technologies, then incompromises. We do not allow for relative assessments,

1963 released the "OSP series" NC controls. We would

believing measures must be absolute, and continually

like to express our wholehearted gratitude to the many

work to create NC controls that improve upon current

people who have supported us over the years, allowing

controls and cannot be found from any other company.

us to celebrate this 50thanniversary this year.

Looking back on the past 50 years we see theOur company maintains a corporate philosophy ofdevelopments detailed below, also shown in Figure 1.

"total responsibility" as a machine tool manufacturer

In 1963, we succeeded in developing NC controls,

which has expanded its business domain to include NC

which at the time were mainly hardwired circuit,controls. We take our responsibility seriously, and work

positioning NC controls.

as a "manufacturing service", carrying out development

Starting from around 1980, the progress of computerof NC controls based on our passion to provide atechnologies began to make possible more advanced andsuperior service not available anywhere else in thecomplex control. Our company has intensified itsworld.

development of technologies which integrate machinerydesign and electrical control, and has created a wide

information and intelligence technologies evolved withvariety of machinery and electrical fusion technologies

time, and technologies which fused these individual

including high precision digital servo motor systems,

technologies were created. Among all of this, ourhigh speed NC control technologies that allow for die

company was proud to introduce several our own "onlymachining at high speed and high accuracy and thermal

one" technologies.

displacement compensation technologies on higher
rigidity machinery.
Starting from around 1990, networking throughintranets became more prevalent. Our company
intensified the development of technologies which
combined information with machinery and electricalfusion technologies, establishing machinery, electricaland information fusion technologies which manage
information throughout an entire plant such as
downloading programs through a network, linking withproduction management systems and monitoring thestatus of various machinery.
Photo 2

"OSP5000" NC control with "IGF" interactive
programming function<Introduction of "only one" technologies>① Absolute position feedback (1963-)
At the time of the development of the original "OSP"
unit, the "incremental method" which was used by theindustry was a method where a specific position is set
as the "home position", and a pulse signal is provided
from this home position to the motor while
simultaneously counting the pulses to detect thepositions of moving parts. Of course there were issues
Photo 1

"OSP2000" minicomputer utilizing NC control

such as when the NC power is turned off, the pulse
count is lost, so when the power is turned on again, a

From 2000 onwards, handling of PC based CNC"return to home position" operation is necessary where

allowed for use of applications which operate on

the moving parts are moved back to the specified

Windows, greatly increasing the scalability of users.

position, and if the pulse count is mistaken, control will

Further, intelligent technologies were added to thebe carried out with the incorrect detection position.

machinery, electrical, information fusion technologies,

Meanwhile, the "absolute position detection method"functions to prevent mechanical collisions, functions todeveloped scrupulously from the first of our company'sdetermine optimal processing conditions, and other"OSP" units, can identify and detect any position withinfunctions were developed, and the 4 existing

the entire moving part range immediately after power isintelligence technologies were commercialized.

turned on by detecting the gear train mechanical

Each of the machinery design, electrical control,condition. As such, no "return to home position" isnecessary when turning on power, and absolute position
detection means that control won't be carried out while
the position is incorrect, making this a highly reliable
control method.

② Software variation (1972-)
Machine tools are used for 10 or more years afterbeing installed. Because NC at the time were all"hardwired NC" where numerical control logic was all
carried out by hardware, it was not possible to update
the features from the time of installation.

Photo 3"Advanced One-Touch IGF” interactive programming

Based on a concept of "software variation", ourcompany made a practically usable "softwired NC",
which has numerical control software loaded in a NC
specialized high speed minicomputer, ahead of othercompanies (Photo 1). Shifting numerical control logic
to software made possible arc interpolation, tool
diameter/nose R compensation, various automatic cycles
and other advanced control, progressing advanced
functionality, leading to the full-scale introduction of
NC machine tools to plants and greatly contributing toincreased productivity.

Our company developed the "IGF" interactive
programming function that allows for easy creation of
NC programs by simply sequentially inputting
machining methods, shape, tools, and cutting conditions
while looking at machining diagrams without using G/Mcode to create NC programs (Photo 2).
Thereafter, these functions could all be easily carriedout using the "Advanced One-Touch IGF" function
which allowed for all machining processes to be
automatically determined just by inputting themachining shape, and even machining of complex③ Interactive programming function (1981-)
Entering the 1980's, as the introduction of NC
machine tools progressed, the number of NC operators

shapes in keeping with the increasing complexity ofmachine tools and the evolution of machining methods(Photo 3).

became insufficient, or the operators did not keep pacewith the advanced functions, leading to demand for an
NC where those advanced functions could be moreeasily utilized.

④ High precision digital servos (1982-)
The direct current servo motors that were mainstream
at the time, were controlled by an analog speed signal
output by a tachogenerator, which resulted in issues
such as temperature drift caused positioning errors andvibration caused by tachogenerator ripple voltage.
This prompted our company to develop a high precision
digital servo system that uses a microprocessor. Thissystem uses 160,000 division high resolution position
detectors to carry out servo control through software
processing based on digitally detected absolute positions,which allows for stable, high precision control. Inaddition, shifting control to software served as the basis

for the subsequent construction of a variety of highquickly reading mass quantities of the enormous

precision servo technologies.

amounts of micro straight line commands that make up
NC programs for machining free form surfaces andinternally generating the machining curves, thencontrolling acceleration and deceleration automatically
based on curvature. In recent years, progress has been
made in high speed contour machining control of asimultaneous 5 axes consisting of the basic 3 XYZ axes
with 2 additional axes of rotation (Photo 4 and Figure3).

Figure 2

Brushless servo motor

In addition, direct current servo motors were limited
in terms of what degree that could be sped up due toflashovers caused by sparks from the brushes, and also
suffered from design constraints in the mechanicalstructure in order to allow for brushes to be replaced.

Photo 4

Machining using "Super-NURBS" high speed contouring

Our company then developed the world's first brushless
servo motor as a part of a high precision digital servo.
The motor is a simple structure with no brushes,allowing for high speed rotation (Figure 2). A major
feature of our company's brushless motors is a small
cogging torque ripple (motor torque ripple) of 0.5% orless, realizing fine machined surfaces through smooth
feed.

⑤High speed contour machining control function"Super-NURBS" (1987-)
At the end of the 1980's, multiple high performancemicroprocessors were used, taking advantage of thedigital servo technologies noted earlier, to develop highspeed contour machining control which allows for highspeed and high precision machining of the free form
surfaces that are characteristic of shapes in automotive
press dies and plastic dies.
This control is a machining technology which allows
for continued compensation for machining accuracy
while machining curved surface shapes at high speed by

Figure 3"Sup e r-NU R BS" h i gh sp ee dspe ed c o nt ro l

⑥ "AbsoScale" absolute positioning linear encoder⑧ "PREX" Motor (1997-)
In general, the turret (cutting tool holder) for lathes is(1988-)
In general, ball screws suffer from thermal expansion

equipped with 2 motors, a servo motor which rotates theduring operation, decreasing machining accuracy. Direct

turret and carries out positioning, and an induction

detection of the positions of moving parts is carried out

motor which drives the rotating tool at high rotation

by linear position detectors as a countermeasure against

speeds. Our company developed a synchronous

this. In general, induction and linear encoders were used,reluctance motor which allows for both servo functions

however the former involved complex and difficultfor positioning and high speed rotation, allowing for aassembly and signal adjustment work, and the latterstructure with only one motor installed on the turretused the incremental method, and so had reliability(Figure 5). This motor does not use a permanent magnet,

issues due to noise and other factors.

instead using an excitation current to control a fieldmagnet, which allows for unrestricted control even up toLens

high rotation speeds.

Glass Scale

LED⑨ High precision servo technologies (2000-)
Index Scale
External View

Figure 4

Light Sensitive Elements

Internal Structure"AbsoScale" absolute positioning linear encoder・ Projection Flatten Control
In curved surface convex peaks and other quadrant
reverse rotation sections, servo motor follow error
creates projections, and in die machining these

Our company thus developed "AbsoScale" (Figure 4)

projections become projections that appear on theto overcome these shortcomings of induction and linear

machined surface (Figure 6). Previously, these wereencoders. Specifically, this is an optical encoder whichcorrected in a manual process called polishing, howevercombines 2 tracks consisting of a high resolution trackin recent years there has been a desire to make polishingthat detects accurate positions and an absolute position

unnecessary, leading to the development of reversetrack. This 2 track detection method later evolved into

torque compensation which suppresses quadrant reversal

an absolute value irregular cycle code, and is today usedprojections based on acceleration.

in products by all encoder manufacturers as absolute
position linear encoders.

⑦ Machining management (1993-)
In order to improve the productivity of machining, itis necessary to reduce job change time and increase thepercentage of time actually spent on machining. In 1993,
our "MacMan function" was developed to automaticallycollected machined processing results (what type ofparts were processed when and in what quantity),
operation results (amount of time powered on, cutting
time, job change time, etc.), and displayed theinformation in graphs and also reported the information
to a management computer in real-time via a network.

Figure 5

Conversion of turret to single motor structure using"PREX" synchronous reluctance motor

Figure 7

Projection flatten control block diagram

The cause of follow error during reverse rotation is
nonlinear friction, and precision compensation control

Figure 6

Quadrant reverse projection example

Photo 5Die machining surface projections

is carried out for motor torque during reverse rotation
based on thorough analysis of friction models. Figure 7
shows a block diagram of reverse torque compensation
based on acceleration.

・ Ball screw bending compensation
In large machines which machine automobile chassis
dies, ball screw bending due to acceleration andAs a countermeasure against these projections, thedeceleration is approximately 50 μm, and inball screw bending amount is predictively calculatedbi-directional die machining bending error appears as

based on the command acceleration, and the position,projections as shown in Photo 5.

speed and torque are compensated. A block diagram ofthis ball screw bending compensation is shown in
Figure 8.

⑩ "IT plaza" (2000-)
As a result of the IT revolution of the late 1990's,
primarily represented by the internet, in order to build
new production processes in the manufacturing industry,a variety of IT tools were introduced, and in 2000, ourcompany proposed the "IT plaza" production system
which was a fusion of machinery, machining and control
technologies. The "IT plaza" concept model shown in
Figure 9 shows the process innovation aimed for in theFigure 8

Ball screw bending compensation block diagram

production processes for "quickly and inexpensively
creating high value added products" from the 3 basic
axes of design/production technology
processes, production management processes andknowledge management, as well as the orientation foreach thereafter.

thermal deformation compensation control, whichallows for stable, machining of precise dimensions
without the need to worry about thermal deformation instandard plant environments.

・ Collision prevention "Collision Avoidance System"
This function uses 3 dimensional data of machinery,materials and tools to simulate actual operations
slightly ahead of time, allowing it to stop the machine
just before a collision actually occurs, allowing for safe
operation even in complex multitasking/5 axis
machining.

・ Machining condition search function "Machining
Figure 9"IT plaza" concept model

Navi""Machining Navi" visualizes the cutting conditions,allowing for even non-expert users to utilize machineryand tools to their full potential. For example, whenchatter occurs in milling, the function analyzes it anddisplays the optimum spindle speed so that the operatorcan follow the on-screen guidance to change therotation speed and verify the results.

Photo 6The latest "OSP-P300" control<Introduction of the latest technologies>
Here we would like to introduce our latest

Figure 10 Comparison of number of operations with previous NC controls"OSP-P300" control (Photo 6) which fuses the latest PC
technologies, our companies control technologies and"intelligent technologies" which can take the place ofskilled operators, to allow for "easy operation" so thatcomplex machinery can be operated by anyone fromveteran operators to beginners.

◆ Intelligent functions
・ Thermal deformation compensation "thermo friendlyconcept"
This function realizes an original concept of (1)making thermal deformation manageable, (2) creating amachine structure which evenly distributes temperatureand behaves predictably and (3) adds highly precise

Photo 7

"Single mode operation" for tool registration

◆ Easy operation function of the latest"OSP-P300" NC device
The "easy operation" function analyzes operator work
procedures and helps to realize smooth operation inaccordance with operator intent.
For example, for complex machines which use a widevariety of tools, the preparation of the tools is a majorburden. Specifically, (1) the various tools have to beequipped and offset, (2) the reference tools have to beregistered using the interactive programming function"Advanced One-Touch IGF" and (3) the tools being
used have to be registered in the "Collision Avoidance
System" collision prevention function.
This function has realized "single mode operation"
which allows for smooth processing without having toswitch between the operation screens in a complicatedmanner (Photo 7). Figure 10 shows a comparison of thenumber of key operations between a previous type of
our company's NC mounted on a multitasking machine
and the "OSP-P300" which provides a smoothness ofoperation that cannot be expressed by statistics alone,
as well as a significant reduction in the number of key
operations.

<Conclusion>
Innovation is "new combinations" and "newdirections".

The "OSP" series has created a newtechnology trend based on concepts of being "YourSingle Source for Machine & Control" and "the fusionof mechanics, electronics and information" since 1963
and we will continue to strive to create new innovationsin the "fusion of mechanics, electronics and informationand knowledge" in the future in order to provide better
added value to customers and contribute to improving
customer productivity.