CAD CAM & controls
Simulation and verification tools have become critical in complex manufacturing environments,
where multiple axes are in motion simultaneously and hundreds of thousands of pounds of
investment are at stake. CGTech has been at the forefront of research for two decades now
and is ever expanding its areas of expertise. By Martin Oakham
Laying down the future
CGTech has seen a growth of
simulation for non-traditional
cutting operations such as
machining with a parallelkinematics
machine eg the
Ecospeed Z3 Sprint
tripod spindle head from
DST.
CGTECH’S expertise in NC/CNC program simulation
and analysis software began in 1988 in Irvine, California,
when founder and President Jon Prun responded to a
growing need to verify NC tool path programs without
wasting machining time cutting ‘prove-outs’. The software -
Vericut - ran on UNIX workstations and used a 3D solid
model to graphically show how material would be
removed; PC versions followed in 1993. Any potentially
damaging errors such as axis over-travel, collision between
tooling and work-holding devices, rapid moves in material,
and tool change collisions would be detected and written to
an error log where they can be addressed.
The software was quickly adopted by companies running
complex CNC cycles, most notably the aerospace,
automotive and power generation sectors. Once established,
CGTech was able to extend Vericut by offering toolpath
optimisation, which could reduce machining times by up to
50% by adaptively adjusting feeds and speeds based on
material removal rate. This in turn improved surface
finishes and extended tool/machine life. CGTech then
focused on simulating the kinematics of multi-axis and
multi-spindle machine tools, so that the entire cutting
process including any jigs and clamps could be ‘proved-out’
virtually. CGTech then included an additional AUTO-DIFF
module for model analysis, allowing a
cut model to be compared with a
design model from a CAD system.
The Model Export option also allows
the cut model to be exported to a CAD
system as a solid model.
The latest release added more NC
70 MWP november 2008
program-checking tools, with a user-configurable syntax
checker in addition to the program’s already supplied
control emulation. ‘We’ve found that syntax checking not
only has to do with checking what’s valid for a specific
brand or model CNC control’s logic, but also what meets a
specific company’s standards and preferences,’ says CGTech’s
John Reed.
Other new functions include simulation of tapping
operations, reading the machine’s tap cycle commands, and
applying a parametric tap tool to create a tapped-hole
feature in Vericut’s simulated cut part. This also allows
several error checks for common tapping problems such as
wrong spindle direction, wrong feed rate for the tap’s lead,
missing or undersize drilled holes, and improper motion.
CGTech has successfully modelled machine tools and
palletising systems from many companies, including
‘Technology Partner Program’ members - Cincinnati,
Mazak, Mori Seiki, Chiron, Makino, Hermle, Okuma,
Matsuura, DMG and DIXI - who freely help with details of
critical design criteria, for modelling purposes. The
company enjoys a worldwide presence, with wholly-owned
subsidiaries in France, Germany, Italy, Japan, China and the
UK. Approximately 40% of revenue comes from Europe,
30-35% from the USA, the remainder from growing
establishment in Asia Pacific, primarily in Japan and China.
UK users go back to around 1990 in the aerospace business.
CGTech’s success has been born from its independence;
simulation is based on the actual NC-code generated by the
post processor output, ie the machine-specific data actually
used to cut the part. Most verification products associated
with CAD/CAM products derive their simulation data
from the APT/CL-File, or system’s internal toolpath. This is
effectively like ‘marking their own homework’, and, while
useful as part of the CAM process, does not provide the
necessary confidence to allow users to eliminate prove-out
on the machine tool.
A comprehensive machine tool and controller definition
is essential for precise simulation, taking into account
factors such as tool length compensation (multiple driven
points, 5-axis ‘RTCP’ etc), Subroutines (both part program
and controller resident), Cutter Radius Compensation, XC
Interpolation (typical on mill/turns) etc. Furthermore,
Vericut’s ease of configuration, allow easy support for
steadies, sub-spindles and tailstocks - without which it
would be impossible to detect machine tool collisions.
In fact, so strong is CGTech’s argument for total NCverification,
that CAM developers are forming partnerships
with CGTech and developing interfaces to Vericut within
their product. CAD/CAM Software Partnerships include
leading developers such as: PTC, Siemens, Dassault Systems,
Mastercam, GibbsCAM (Cimatron) and Edgecam
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