The end mill then plunges downward to machine a square pocket. After
that comes the chamfering tool to create the 45-degree angle, which will
help secure the bolt in place. The plasma then cuts a square hole through
This isn’t a simple operation. The mill plunges down a certain amount,
removing only so much material; then comes the chamfering, then the
plasma. How much material remains at the bottom of that hole? Based
on that, what consumables would be best, and what speeds and feed
rates would work best to achieve a truly square hole?
A novice operator probably shouldn’t attempt such an application.
Most fabricators find long-term success in combo plate cutting when
they ramp up application complexity gradually.
The example also illustrates that plasma cutting and milling and drilling both have their complexities. One isn’t fundamentally easier than the
other, especially in the context of a combination plate cutting machine.
Ultimately, a fabricator’s product mix drives the process complexity
more than anything else.
Many fabricators tend to choose someone with machining experience
to operate a combo plate cutting machine. This can make sense, especially if the product mix involves complex machining geometry. But if the
product mix calls for simple holes but profile cutting with complex bevel
geometries, a plasma cutting veteran could have valuable insights.
Beveling with a plasma can be very complicated procedurally. Every
degree the plasma pivots from vertical, the material thickness changes
and, with it, the plasma settings. Modern systems have the information
they need to create an effective bevel, but the operator needs to follow
the right procedure.
The torch itself has to start perfectly vertical; if it’s a little off, the bevel
angle will be off, and so will the expected cut thickness and plasma settings. If, say, an operator cuts a beveled circle and yet the torch is at the
wrong angle, that circle will turn into an egg shape.
Regardless, when a fabricator is deciding who should run a combo
plate cutting machine, the ultimate decision depends on the company
culture, available talent, and training regimen.
An eager and engaged fabrication novice could operate a combo system, given the right training and enough time before ramping up to more
A Creative Combination
Combination systems work well for a variety of plate plasma cutting and
machining applications—but not all plate machining applications. It goes
back to the system’s clamping capability and the nature of plate material.
Due to the nature of the rolling process, plates tend to be ever-so-slightly
thicker in the middle. Because of this, a combo system really isn’t suited
for surface milling. The machines perform well when milling pockets, relief
holes, slots, and other shapes. But because of how the plate is held, along
with the thickness variation, the combo machine’s end milling capability
cannot create a surface tolerance that’s within umpteen places to the right
of the decimal point.
That said, some fabricators have integrated a T-slot machining center
right onto one end of a combo machine’s cutting table—essentially, a
true machining center with its own tools, controller, and the clamping capabilities required. After the combo machine finishes the initial cutting,
the critical parts are moved over to the machining table, where they can
be clamped down flat for a true surface milling application.
Material on the Move
Combination cutting really is about looking at the big picture, and this
includes material handling. Say a combo machine finishes a nest of complex
parts, milling, drilling, and plasma cutting the part profiles. Each part
weighs about 600 pounds, so now operators need to wait for an overhead
crane. And wait. And then wait some more.
Today certain combination systems come with heavy-duty pick-and-place automation. As a nest is complete, a robot with a magnetic end
effector lifts each piece and stacks it on an adjacent pallet. The automation
knows which parts it’s picking, so it can place them in a configuration that
best suits part flow. For instance, if parts flow in kits, the robot stacks the
cut blanks in kits. After parts are offloaded, the skeleton can be removed,
usually via manual torch cutting.
This kind of automation shows what combination plate cutting is all
about: reducing the number of times a part must be moved or handled.
Ultimately, it’s about ensuring that the downstream constraint of the
shop—be it in welding, forming, or anywhere else—is never starved for
work. If a plate cutting process has a problem, and it causes a downstream
constraint to operate at a lower capacity level, then a fabricator isn’t
being as productive as it could be.
Jeff Lee is U.S. operations manager of Kinetic Cutting Systems, P.O. Box 652, West Burlington, IA
52655, 319-754-5040, www.kineticusa.com.
» A robotized magnetic lifter picks a heavy workpiece for sorting on an adjacent pallet.