“Paperless,” as in “paperless factory,” doesn’t only mean that product
designers, manufacturing engineers and CNC programmers share product
manufacturing information strictly by computer rather than paper drawings.
“Paperless” also implies that data formats requiring human interpretation will
be obsolete. That means moving away from the electronic equivalent of an
engineering drawing.
Manufacturing personnel have been interpreting information conveyed by
engineering drawings for centuries. Making manufacturing far less reliant on the
human interpretation of this information (whether delivered on paper or by
computer) is the real promise of the paperless factory. It’s not only the sheets
of pressed wood fiber that must become unnecessary. What must also be eliminated
are the numerous steps wherein a person must intellectually analyze and assign
meaning to information before further computer processing can proceed.
In a paperless factory where “paperless” applies in its fullest sense, part
production would be seamless and highly automated. Some have envisioned part
production as streamlined and as instant as printing a copy of something you see
on your laptop or personal computer. Producing “hard copies” of 3D shapes
created on a computer would be as smooth as printing a document or a digital
image. Of course, removing material from stock to create a part is far more
complex than putting lines of letters or arrays of colored dots on a page.
Nevertheless, the comparison does make a sharp point.
Fortunately, for the printing task, it doesn’t matter what brand of computer
you are using, what word processing software or Web browser you’re in, or what
brand of printer is at the other end of the cable. The necessary connectivity,
interoperability and compatibility have been adequately addressed.
That’s certainly not the case in manufacturing, at least not for most
companies. Almost every step between the designer and the shop floor includes
vexing difficulties with data exchange, incompatible formatting, lack of
interoperability and—perhaps most damaging—unavoidable human intervention
involving uncertain interpretation. Efforts to get manufacturing computer
systems to work together seamlessly and achieve higher levels of automation have
been going on for years.
We are, in fact, moving closer to fulfilling the dream of the paperless
factory as defined in the opening paragraphs. Progress, however, has been slow
and frustrating. Yet some recent steps forward may help bring some momentum back
to this grand quest.
In one encouraging development, a CAD/CAM software provider has completed an
interface that allows its CAM offerings to read product data in a standardized
file format that includes both machinable features and critical specifications
necessary for machining. The CAD/CAM provider,
Gibbs and Associates
(Moorpark, California), has been working with South Carolina Research Authority
(SCRA) to develop this interface. The format for the product data is defined by
STEP Application Protocol 224 (AP224). STEP (Standard for the Exchange of
Product model data) is the international standardization effort to alleviate
obstacles to the exchange of product data among different and otherwise
incompatible hardware and software. STEP is the much-expanded outgrowth of the
effort that created IGES, the Initial Graphics Exchange Specification, in the
1980s.
STEP includes the development of a “manufacturing suite” of standardized data
codes and file formats (protocols) for the data requirements that arise among
the major phases (applications) of designing and manufacturing products. One of
those application protocols is AP224.
AP224 specifically supports the transfer of manufacturing product information
between design engineering and manufacturing engineering groups. It focuses on
mechanical parts and covers all the information necessary to machine these
parts. AP224 captures part features, geometric dimensions and tolerances,
material, surface finish and other part data that are needed in machining.
Like all STEP application protocols, AP224 encodes the information so that it
can be interpreted directly by a computer system. The encoding is neutral—that
is, not dependent on any particular computer system.
GibbsCAM’s AP224 interface reads this formatted information and then creates
machinable part features that correspond to the features in the AP224 file.
Neither the NC programmer nor the programming software has to “featurize” the
part geometry as part of the process leading up to the creation of machine
commands and toolpath data. This is a significant step toward the paperless
factory, although many more such steps have yet to be made.
STEP In Active Duty
To improve overall operational efficiency and reduce deployment and
maintenance costs, various branches of the U.S. Department of Defense have
invested in STEP-based technologies. Currently, a number of STEP formats are
in use in various military depots around the United States. One of these is
the Anniston Army Depot (ANAD) in Anniston, Alabama (about 60 miles east of
Birmingham). ANAD’s primary mission is to maintain, repair and refurbish
combat vehicles such as the Army’s M1 Abrams tank, the Armored Personnel
Carrier and the Stryker all-wheel-drive armored vehicle.
ANAD’s manufacturing facilities have been using STEP application
protocols such as AP224 since the mid 1990s. According to SCRA’s Bill
Freeman, the depot has reduced the typical time from part order to part
delivery by 30 percent or more compared to conventional procedures, thanks
to benefits of the STEP standards. For some especially complex parts, the
time savings may be as high as 50 percent. The key, he says, is having a
complete, feature-based product model that can be shared among design
engineers, process planners, manufacturing engineers, CNC programmers and
part inspectors.
Dr. Freeman, the director of research and development at SCRA’s Institute
for Solutions Generation (ISG), knows these results well. He not only holds
management responsibility for ISG’s Readiness and Sustainment Business Unit,
which led the development of AP224 and its ISO registration, but he has also
worked closely with the management team at ANAD in its implementation of
STEP-based technologies. In his words, this depot is an excellent example of
the ideal of “STEP in, STEP out, STEP throughout.”
A quick look at how STEP standards helps this depot return a
battle-damaged or service-worn tank to combat readiness shows the value of
this technology.
 |
| The first step in refurbishing an M1 Abrams tank
at Anniston Army Depot is disassembly. |
After delivery to the depot by railcar, each tank is completely
disassembled. Machined parts that can be repaired in one of the depot’s
machine shops first pass through Part Design, where a CAD model defining
each part is created. The department uses STEPTrans, a software utility
developed by SCRA ISG to process the completed CAD file and capture
machinable features amenable to AP224. In its AP224 format, the resulting
product model has all material callouts, GD&T specifications and other
manufacturing information encoded within the definitions of each feature.
This AP224 file is electronically transmitted to the Process Planning
department to develop a “macro plan” for the part’s repair process by using
STEPPlan, a computer-aided process planning system. STEPPlan, another SCRA
ISG-developed software utility, formats the plan in compliance with STEP
AP240. This AP covers process plans for machined parts. In this format, the
resulting plan not only retains all of the AP224 machining features, but
also defines all processing steps as STEP data, including machining
operations in sequence, tooling and even intervening processes such as
welding.
The AP240/AP224 file is electronically transmitted to Micro Planning, the
department that processes this data to generate CNC programs using a
proprietary CAM system from yet another vendor. Although programmers do not
have to reference additional engineering drawings to proceed, the CAM system
currently in use does not have an interface to interpret the AP224 machining
features directly. This gap in the otherwise seamless data exchange process
highlights the value of SCRA’s recent work with CAM developers to create the
necessary interfaces. As Dr. Freeman points out, GibbsCAM users would be at
an advantage in these circumstances.
As it is, shopfloor-ready CNC programs are available in days, not weeks.
Companies in the commercial sector that are interested in implementing
STEP-based technology have access to the STEP application protocols as well
as to SCRA’s related suite of software utilities. The utilities are
available under fee-based licensing agreements. For more information about
SCRA and its ISG products, visit www.isg-scra.org. |
More About AP224
AP224 is one of a set of application protocols created under STEP for the
manufacturing community. This “manufacturing suite” represents a number of
interrelated standards that address the specific needs that manufacturing
companies have for product model data. Because discrete, machined parts are
critical to many products, including military aircraft and fighting vehicles,
the product model data that covers machining have received a lot of attention.
AP224’s official title is “Mechanical Product Definition For Process Planning
Using Machining Features.”
AP224 might be considered one of the foundational formats within the
manufacturing suite because the information it encodes is essential to
downstream manufacturing tasks such as process planning, machine setup, CNC
operations and inspection. Protocols for these further applications are
completed and software to implement them is soon to follow. The approach to
standardization embodied in STEP pays attention to ensuring that these APs are
“harmonized,” that is, that the formats are compatible with one another so that
data prepared by one AP can be reused by another. Because the processes and
stages in manufacturing products flow together, there are overlaps in what the
APs cover.
SCRA has played a key role in the development of AP224. SCRA is an
organization devoted to applied research and commercialization on a contract
basis. It has offices in Anderson, Charleston and Columbia, South Carolina, as
well as other locations. SCRA’s Readiness and Sustainment Business Unit within
the Institute for Solution Generation provided leadership for the team
responsible for developing AP224. It was originally issued in 1991.
AP224 and other STEP formats are in use at various military repair and
overhaul depots throughout the United States. These facilities have the
challenge of providing repair parts and spares, many of which are needed for
military equipment with useful lives that stretch for decades. Encoding
information about these parts as product model data interpretable by computer
systems helps these facilities meet their manufacturing challenges with greater
efficiency and economy. See the box on page 100.
The AP224 interface for GibbsCAM was implemented under funding from the
Army’s Tank Automotive Research, Development and Engineering Center. Working
with a CAD/CAM provider from the private business community meets two goals at
once: First, it brings AP224 into the realm of consumer and general business
product manufacturing, where efficiency and economy are also highly valued.
Likewise, it gives companies in the military supply chain a commercially
available CAD/CAM system to help meet their needs and leverage their investment
in STEP data.
Of course, SCRA is eager to see other CAD/CAM providers follow Gibbs and
Associates’ lead in developing interfaces. The CAD/CAM provider has not been the
only one to work with SCRA on STEP-related projects.
As a “foundation format,” AP224 has two very important aspects that all CNC
machine tool users should understand—it deals with machining features, and the
data codes are for computer interpretation, not just display on a computer. As
hinted at earlier, much of the activity associated with NC programming involves
recognizing and evaluating features for machining. Without any additional
notation or indications, part geometry simply describes a shape, using its
surfaces or its volumes as a solid entity. It is necessary to interpret this
shape to identify the various portions of this geometry as representations of
particular part features such as pockets, bosses, holes, fillets and so on.
Likewise, these features must be analyzed according to their tolerances because
the tightest and/or most difficult of these will usually determine which
machining processes are the most appropriate and which sequence is the most
advantageous. Finally, the machining steps and tool paths for producing these
features in a blank workpiece have to be organized by the NC programmer and
processed by the CAM software.
 |
| The GibbsCAM AP224 interface makes a connection
between the features in the AP224 file and the software’s own Features
Manager utility. |
Along with other manufacturing data, AP224 captures information about the
machining features embodied in the geometric model of a part. The standard
covers 16 different categories of features, and many features are further
classified into numerous subcategories. This means that designers can use AP224
to “package” de scri ptions and specs of part features into a complete,
computer-interpretable data model to send for manufacturing. Nothing remains to
be conveyed with supplemental engineering drawings. With AP224, all tolerance
information, material specifications, machining feature information and other
special requirements are completely defined as STEP data. These definitions are
designed to be complete, unambiguous and reusable.
This brings up the other important aspect of this protocol. Data in an AP224
file is in a computer-interpretable format. This is an important point that John
Callen, Gibbs’ VP of marketing, stresses in his discussions of AP224. “The
information in these files is not simply displayable, it is consumable,” he
says. This is a critical distinction, according to Mr. Callen.
As he explains, displaying this information so that NC programmers, for
example, have it handy when they need to make decisions when interacting with
CAM software is one thing. Consuming this information, however, means being able
to invoke software routines that import and act on this data directly—a
different proposition, he says. This capability opens the door for automated NC
programming functions, which create a payoff in terms of reducing programming
time and improving programming effectiveness.
What The Interface Accomplishes
According to Mr. Callen, greater CAM automation and streamlining are precisely
what the GibbsCAM AP224 interface accomplishes. As a start, the interface makes
a connection between the features in the AP224 file and the features that this
CAM software knows how to handle, so to speak. For example, the features
extracted from an AP224 file can be organized and manipulated as feature
entities in GibbsCAM.
GibbsCAM's Feature Manager utility will automatically isolate the geometric
faces within that feature so that they can be passed as a coherent group to
various operations used for machining within the software. For example, hole
features can be selected as a group and then passed to the software’s Hole
Manager for processing.
Likewise, specific pocket features and boss features can be selected and
grouped together for processing based on the various proprietary GibbsCAM
strategies for optimization when milling pockets with islands. Interfacing with
AP224 gives the NC programmer an alternative to the software’s automatic and
interactive feature recognition functions. With AP224, part features arrive “prerecognized.”
To be clear, the features defined in an AP224 file are geometrically oriented
features. In other words, the definitions are independent of possible machining
operations that might be used to produce them on a machine tool. Thus, the
definitions do not constrain how a downstream application such as NC programming
might use them. This is noteworthy as multitasking machines gain in popularity.
This class of machines allows some very novel techniques for feature machining
that defy traditional concepts.
The other product manufacturing information contained in the AP224 file is
also read into GibbsCAM by virtue of the interface. This makes this information
readily available for referencing by the user while creating a CNC program.
“AP224 is one-stop shopping for the manufacturing engineering staff. NC
programmers and process planners have all the information they need in one
file,” Mr. Callen says. In short, AP224 streamlines the flow of product
manufacturing information and avoids delays created by missing, illegible or
ambiguous product information.
The GibbsCAM AP224 interface will undergo further enhancements and expansions
as the company and SCRA pursue further phases of its development. One
encouraging outcome of these efforts is the implementation of interfaces with
other STEP application protocols, particularly those pertaining to upstream and
downstream manufacturing operations. AP 219 and AP 240, for example, address
dimensional inspection and process planning, respectively. One of the most
promising of these is AP238, the STEP NC application protocol.
STEP NC defines a machine-independent, data-input standard for CNC systems.
This AP revolves around the concept of using this file format as direct input to
the CNC unit, thus bypassing the creation of traditional M and G codes and the
use of postprocessors that these traditional formats entail. This vision for
machining comes close to the seamless experience given in the laptop-to-printer
scenario cited earlier.
Currently, implementations of AP238 STEP NC have largely been stalled. One
reason is that commercial design systems are not structured to provide the high
level of product manufacturing information required by AP238. Also,
manufacturers of machine tool control units have not been eager to adopt this
technology.
Mr. Callen believes that support for foundational formats in the STEP
manufacturing suite will create a groundswell of end-user interest in full
implementations of STEP-enabled innovations. The strong business case for
implementing STEP will become more apparent. “Shops will see a clear bottom-line
advantage that STEP promises,” he says.
Adding urgency to this movement to STEP implementation is the imminent
evaporation of the manufacturing industry’s engineering know-how. “The expertise
that companies rely on for effective manufacturing and machining will be lost as
it is carried away for good by retiring engineers, programmers and machinists,”
he points out.
STEP application protocols create a discipline and a means for encoding
product manufacturing information so that it will be available for computerized
reading and interpretation by advanced CAM software functions. Building on the
groundwork laid by these data-communications standards, such CAM functions will
capture the analytical skills and machining expertise of those currently active
in manufacturing groups. Thus, their wisdom and knowledge will be retained and
deployed as new product models enter development and soon become the next
generation of aircraft, scientific instruments and medical appliances.
Showing Us The Path
Given the extraordinary complexity and diversity involved in machining,
producing machined parts may never be a click-click-click affair, even in the
ultimate realization of the paperless factory concept. But neither should it
remain the often bumpy, strenuous affair it is for many manufacturing companies
today. Looking for steps that move in the right direction—and this article
highlights one of them—will show us the path.
MMS Online is a trademark of Gardner
Publications, Inc, copyright 1997-2008.
MMS Online and all contents are
properties of Gardner Publications,
Inc.
All Rights Reserved
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