Port Machining No Problem - Mastercam

Port Mqchining No Problem
n racinS, you can't have too much horsepower, and one of
I
the
I ways to increase it is to "let the engine breathe,, by enlarging
the intake and exhaust ports of the engine. Karlo Apro, product
manager-multiaxis, CNC Software lnc. (Tolland, CT) explains
how the porting process has changed: "Before the computer
age, the traditional method of opening these ports was by hand.
Very skilled craftsmen, called Master Head porters, would use
a die grinder, which is stmilar to a dentist's tool but larger, to in-
crease the size of the ports. The shape of these tunneled porls
is highly complex. And, there are at least eight intake and eight
exhaust ports on an eight-cylinder engine. Making all of them
exactly the same, by hand, was nearly impossible.
"When five-axis CNC machines entered the racing engine
shop, the repeatability aspect of port cutting improved dramati-
:ally. However, there was still the challenge of getting these
:omplex shapes jnto a CAD/CAM programming system that
,vould generate the five-axis toolpath
automatically to cut these features. The
answer came in the form of digitizing
cr probing. A lVaster Head Porter cuts
cne master port, and then that port gets
5igitized. The way the process works is
-o touch the probe to as many points on
:he master port as possible. These points
are then imported into a CAD system as
: point cloud. The point cloud is then
:onverted into a surface model. Once
:rere is a suface model of the port, the
^ext step is to create a smooth, efficient,
've-axis toolpath to drive the machine
.c cut the part. The problem is, these
.rolpaths are often choppy, inaccurate,
refficient, and require many tweaks and
-erations to perfect," Apro explains.
Enter a new add-on to Mastercam.
:s called Port Expert, which creates a
: ean, continuous, highly accurate tool-
:ath on pre-existing port surface or solid
:ata, while simultaneously minimizing
-achine motion and avoiding collisions.
"Port Expert has been created for
-achining cylinder head ports, but it can
:e applied to any tube-type application,"
A Moster Head Pofiet culs one moster port, and then that
poil gets digitized.
says Apro. "The new utility uses a tapered lollipop tool, and has
collision checks for the entire tool, including shank, arbor, and
holder. There are multiple cutting options available: you can cut
the top only, the bottom only, and specify how much stock to
August2011 | www.sme.org/manufacturingengineering 41

s.MIS MOTION WITH MINIMUM TiLT
TAPERED OVERLAP
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SMOOTH, SPIRAL PATH
Mqstercom's Port Expert odd-on creoles highly occurole five-
oxis loolpoth on prc-existing poi surtoce or solid doto, simul-
loneously minimizing mochine motion ond ovoiding collisions.
leave on the entire port. The toolpaths use three-axis machinlng
as far into the port as possible, and then convert automatically
to five-axis motion with minimum tilt. This leaves no fishtails or
inefficient reverse moves, and smoothly transitions where the
toolpaths meet at the middle of the port. The add-on provides
both roughing and finishing toolpaths to make ports from cast-
ings or billets. Further, because Port Exped can support unlim-
ited sudaces, the geometry can be made of multiple surfaces
that are stitched together.
"After programming the toolpaths, a programmer can
simulate the cutting process without leaving his or her desk.
Mastercam creates five-axis code that can run any CNC
machine. The simulation proceeds step-by-step through the
toolpath, even conveying the motion used in transition at the
middle of the port. Simulation is a safe and cost-effective way of
proving out the toolpath, and it can also aid in designing better
fixtures. With Port Expert, not only are engines breathing easier,
so are the machine programmers and Master Head Porters,"
Apro concludes.
For more information from CNC Software email karlo.
apro@mastercam.com "
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