software & controls
read more about
software & control
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Case Studies
■ EdgeCAM instrumental
in satellite project
Edgecam
http://tinyurl.com/24e694
■ Radan software
recommended to punch
press users Radan
http://tinyurl.com/yrybeh
Streamlining CAD and CAM communication has long been the dream
of engineering organisations that face handoff issues every day. Many
manufacturers would love to put an end to the cumbersome
interpretation process. By Martin Oakham
Say it how it is
ALMOST from the onset of Computer Aided
Design (CAD), software engineers were expected to
create expert systems that would at the very least,
dramatically aid in the processes behind good designs,
and ultimately remove humans from the CAD-CAM
loop. What designers wanted was a system where, after
finishing a design, they could press a button on the
computer and fabrication could automatically begin -
the idea being that they should be able to go from CAD
to CAM with all the decisions about starting
production made automatically. The CAM program
generated would automatically be tailored to the most
appropriate machine to create the part based on its
physical size, the machine’s kinematics and tooling
available.
With hindsight, you might say this was somewhat
ambitious, but it’s clear from looking at the systems
available today that CAD is evolving along this track.
Most new CAD systems have reliable tools to test the
integrity of a design and make sure that it is capable of
doing the job that it was intended for. These also usually
include manufacturing expertise to point out obvious
problems, such as unsuitable section thicknesses, or
interference issues, where two components or parts of a
component are trying to occupy the same space. CAM
systems on the other hand, do communicate with CAD
systems and accurately extract key information about
the geometry, so that toolpaths can be assigned to
features automatically. These usually entail simple
holes, pockets and islands, but the list is growing very
fast. This is not straightforward though, determining
which side of the line to cut on is anything but simple,
and human intervention may be required to
distinguish a pocket from an island, for example.
Mastercam’s new Feature-Based Machining will
automatically evaluate the part and program pockets,
contours, bosses, and drilling routines with minimal
user input, dramatically reducing programming time.
Mastercam has also developed its software to fully
integrate within SolidWorks CAD platform, allowing
SolidWorks users to program their parts directly within
SolidWorks using Mastercam’s toolpaths and
machining strategies.
Most laser cutting setups are interesting in that they
take input directly from a CAD drawing to produce
complex nested 2D forms in flat sheet. Many can now
cut parts that have been pre-formed - adding a third
dimension into the equation. Also, consider rapid
prototyping. When it first appeared some 20 years ago,
98 MWP march 2008
the ability to create a digital design in three dimensions
seemed like a technology straight from Star Trek. You
could hold that design in your hand - often that same
day. It’s only when the problems get more subtle, that
manufacturing feedback becomes problematic. Having
said that, the complexity involved in programming
multi axis machines is driving this entire scenario to
reality. Already most of the details of 5-axis movement
are out of the hands of the CAM programmer. The
software determines the details of which axes need to be
moved, and when they need to be moved in order to
avoid collisions. The CAM programmer is only
concerned with the most suitable strategy on offer to
give the best overall finish/time ratio.
FeatureCAM 2008 for example, offers a variety of
methods for controlling the tool axis in 5-axis
simultaneous machining. The user can set a specific
lead and/or lean angle. This can be done either to
access areas unable to be reached with 3-axis machining
or to give better cutting conditions. Alternatively, the
tool angle can be set in an orientation either to or from
a point or to or from a line.
Many three-axis toolpaths generated in FeatureCAM
can be converted to 5-axis toolpaths by using automatic
collision avoidance to change the tool axis when
collisions might occur. The software automatically tilts
the cutter away from the obstacle by the specified
tolerance and then returns the cutting angle to the
value set for the overall toolpath once the obstacle has
been cleared. 5-axis drilling is also supported. This new
functionality, coupled with the advanced featurerecognition
in FeatureCAM, makes it possible to create
drilling programs in seconds for multiple hole types
and sizes.
At present, it’s often simple problems that are
working against efficient ‘art to part’ production. For
example, there is a good chance that your company’s
CAM system will not speak the customer’s CAD
system’s native language, meaning that the design files
have to be translated into an open format like STEP or
IGES before they can be read at all. Once translated, the
CAD information must then be interpreted by the
shopfloor engineers who move information from CAM
to the numerically controlled machines. Interpreting
this CAM information requires a good deal of
knowledge about the machine, tooling available and
machining process generally.
Interestingly by removing the human link between
CAD and CAM, USA based Injection moulding
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