Such tooling is time-efficient relative to setup
with general-purpose tooling, but the hemming die
set is limited to a specific hem size.
Here’s a CAD tip: Avoid unnecessary tooling expense.
Check with the fab shop to learn the sizes and features
of hem tooling that is already on hand.
Jogging in Place
A jog bend is simply a pair of equal and opposite
bends closely spaced to create a lazy Z offset, which
is often equal to the material thickness. This makes
for a nice fit and finish with a mating cover, perhaps.
The jog bend also does a nice job of stiffening an
edge without adding much bulk or thickness.
As with the hem bend, a jog bend is easier to
model than it is to fabricate. A jog bend requires
specific tooling, setup, and machine operation that
are distinctly different from that used for creating
Here’s a DFM tip: Jog bends carry their own nonrecurring engineering costs and setup requirements into the
overall production costs. Yep. It’s the same as hems.
As shown in Figure 3a, the jog bend is set up
in 3-D CAD by sketching a line to locate the bend,
setting the surface offset distance, picking a bend
radius, and choosing an angle for the pair of bends.
Here’s another DFM tip: To match the actual behavior
of jog tooling, override the bend radius on the Jog
feature and set it to a small value, 0.004 in., for
example. Also override the bend angle and set it to
a value less than 90 degrees. A jog’s internal angle
at 80 degrees is generally a good starting point. The
model with jog bends is shown in Figure 3b.
In the fab shop, the jog bend is created with a die
set that presses both bends into the workpiece simultaneously (see Figure 3c). Not surprisingly, a
jog bend takes about twice as much pressure to create as a single bend does.
The jog bend is typically completed as a bottom-bending operation. That is to say, the tooling does
not coin, but it does fully contact the workpiece. If
the jog tooling is being bottomed, then set the internal jog angle closer to 90 degrees instead of the
recommended 80 degrees (see Figure 3d).
Jog bending results in slightly different stretching
of the workpiece than two simple 90-degree bends.
Consult with the fab shop for its experience with calculating flat layouts around hems and jogs. Adjust
the jog radius and angle to match actual tooling.
Making the Miter Flange
In the CAD shop, a miter flange is a time-saving
miracle. A simple sketch can create one (see
Figure 4a) or more bends (see Figure 4b) on one or
more edges in a single modeling step. When more
than one edge is selected for routing the sketch for
the flange, the resulting corner is mitered at 45 degrees to create the needed flat layout.
Here’s a DFM tip: When setting up a miter flange,
remember that bends will be overbent to allow for
springback; include at least a 0.015-in. gap in mitered
Presenting the Sketched Bend
The Sketched Bend feature is very similar to the Jog
feature except that only one bend is created (see
Figure 5a). As with the Jog feature, a single line
sketch locates the bend.
The result of this example sketch is shown in
Unfold/Fold Versus Bend Processing
It is sometimes advantageous to model features in
the flat workpiece rather than in the formed prod-
uct. The CAD tools Unfold and Fold provide a pa-
rameter-driven design feature to unfold any or all
bends in the model.
Figure 6a shows work-in-progress for adding
bend relief cuts in the corners of the flat part. The
CAD work flow is:
1. Add an Unfold feature to flatten the part.
2. Add some feature, such as Cut-Extrude.
3. Add a Fold feature to return the part to normal.
A jog bend is located using a sketched line. The size of
the jog is set with parameters. Jog tooling typically has
a small radius, and the bend angle is usually less than
90 degrees. Check with the fab shop for exact features
of available tooling.
In this example, two jog bends are completed. For an
imaginary reason, the jog bends were used to move
the hem bends outboard.
Jog tooling is mounted in a press brake. The first step
in creating a jog bend is to position the workpiece between the upper and lower dies.
As the dies are pressed together, a pair of bends is
formed in the workpiece. The angle of the jog and the
depth of the jog are controlled with the stroke length of
the press brake. In general, dedicated tooling is required
for each size of jog and for each material thickness.
This simple sketch creates the flange shown using the
Miter Flange tool. A more complex sketch is shown in
Unlike the straight line in Figure 4a, this edit to the miter flange creates multiple bends.
The work flow for a Sketched Bend feature strongly
resembles a Jog Bend. A sketch is used to locate the
The Sketched Bend tool is one of several ways to make
internal flanges like this one. This method allows for
easy editing of kerf width, flange length, and bend