Developing Bevel Compensation Values
There are more than a few factors to consider for cutting di;erent bevel types.
For example, V cuts have a smooth cut edge and a sharp bottom edge. The cut
part becomes trapped beneath the skeleton and cannot be removed until the
skeleton is taken o; the table. The torch follows a path on the top of the plate.
However, the part’s larger bottom-surface dimension, called the major size, varies with the material thickness and bevel angle. If the bevel angle or material
thickness changes ever so slightly, so does the part’s major size.
When an A bevel is made with plasma cutting, high-temperature gases blown
into the kerf result in a rough edge with a rounded top. The dropped part rests
on top of the skeleton. The minor size (in this case, the part’s bottom surface)
varies with the material thickness and angle. In addition, the top-edge rounding
makes the major size (top surface) slightly smaller than it would be a;er plasma
cutting a V bevel.
Performing A bevels can present di;iculties when a fabricator is trying to
achieve 45-degree cut angles on thin materials, because the high angle compensation values require a bevel head capable of tilting more than 55 degrees
(see Figure 6). In this case, a torch with a small included shield angle is less
likely to a;ect the clearance, the e;ective cut height, or both.
Y-top bevel cuts have a straight land dimension, a parameter that V and A
bevels lack. In this case, the specific multipass cut sequence used a;ects the
results. Operators should first cut the land and then make the bevel.
The key to plasma beveling is to gather the right process data for every conceivable bevel situation. Because the number of di;erent bevel types combined
with di;erent material
types, thicknesses, bevel
angles, kerf, cut height,
cut speed, and arc voltages is so great, there are
thousands of possible
Fabricators can use two
approaches to determine
the right bevel angle and
part size. The first is to
use trial and error to uncover process compensation values for every individual job. The second
approach focuses on the
most commonly cut bevel
types (V, A, and Y-top),
material thicknesses (;;;
to 2 in.), and angles ( 15 to
45 degrees) to iteratively
derive the relationship
between the desired angle and size and the process compensation data.
The first approach might seem
less tedious initially, but trial and
error for each new bevel job—as
is o;en done now—leads to a lot
of wasted time and material. The
second approach, though more
complicated, can save time and
material in the long run.
Some of the latest plasma cutting systems have so;ware technology that takes this second
approach. In addition to plasma
variability, process variables include table motion, bevel head motion, precision of transformation equations,
li;er performance, and arc voltage control accuracy. Though not exact, the values in the process parameter tables should result in a part that is very close to
the desired dimensions, though some fine-tuning may be necessary.
Still, fabricators using the embedded parameters are pleased by what they
are seeing. Some using the latest technology report setting up new bevel jobs in
minutes on the plasma table, with no postbeveling cleanup required—a far cry
from making bevels with an oxyfuel torch, hand grinder, or other methods. The
time and money this saves means more competitive pricing for customers and
extra profit for the company.
Madhura Mitra is a design engineer at Hypertherm Inc., 800-643-0030,
There are two types of plasma cutting heads for beveling: AC and ABXYZ. AC types tilt about the X axis and rotate about the Z axis. ABXYZ heads tilt about the X and Y axes
and have XYZ linear axes.
The bevel pivot point, or rotation point, is the point in
space that the bevel head tilts around.
Process shi; occurs when the plasma arc moves
across the top of the plate when the head tilts. The latest plasma cutting systems minimize this.
Higher torch angles require smaller shield
diameters and angles to maintain the desired
clearance and e;ective cut height.