finished stars and stripes pen we will create in this article.
Laser engraving specialists are sometimes faced with the often daunting
job of engraving on a curved or cylindrical surface. One example of this
is engraving a two line message on a pen where, for example, its
necessary to engrave one line of text parallel to the pens axis
and then rotate the pen to bring the next portion of the pens circumference
into position to receive the second line.
most laser owners are aware, one way to laser engrave cylindrical surfaces
is to use a cylindrical attachment, a device which is available with most
lasers, which rotates the item as you engrave. Cylindrical attachments
are great, especially if you want to engrave a line of text or a design
reading around the circumference rather than parallel with the center
line. However some of the cylindrical attachments are better suited for
holding wine bottles and other large items than they are for pens and
the like.They are also an expensive extra that is rarely needed in the
any event, I have found that a number of lasering jobs involving limited-coverage
engraving on cylindrical surfaces can be done with excellent accuracy
and repeatability using an inexpensive home-made indexing fixture I created
myself. The principle used in my fixture is that you hold the cylindrical
item between centers so that it can rotate on its axis. You
set up a line of text or other graphical element (not extending too far
out from the top of the curve) and then engrave the item as if it were
a flat engraving job. To engrave a second line of text, you rotate the
item on its axis to provide the desired spacing between lines and engrave
that set up, again treating it as a flat layout.
triggered my invention was my experience as a woodworker for over 20 years.
I immediately thought of an indexing pin on a wood lathe as a good starting
point for my fixture. This utilizes a disc with holes equally spaced around
it and a pin that creates a stop when its inserted in the hole.
Because my fixture would be fabricated from acrylic and vector cut on
the laser, I was able to easily make several interchangeable indexing
wheels to accommodate virtually any number of steps around a cylinder.
For example, Figure 1 shows three separate indexing wheels which contain
10, 14 and 8 indexing notches, respectively. Using a wheel containing
a greater number of notches provides a greater number of rotary indexing
steps having a smaller angle and reduced line-to-line spacing between
indexing wheels can then be mounted to the fixture, allowing the pen or
other item to be rotated between notches (Fig. 2). Instead of using a
pin, I mounted a knife which slips into the notches I cut
around the indexing wheels.
more easily understand how to set up the computer files to work with this
fixture, well use the U.S. Flag pen shown in the opening photo as
an example. This set up is much more complicated than a couple lines of
text but it really demonstrates the operation of the fixture. Lets
start with the lower barrel of the pen (stripes).
first thing we do is measure the diameter of the cylinder. I use dial
calipers for this. Note: The more accurate this dimension is, the more
uniform the widths of the alternating red and white stripes will be.
know that the U.S. flag has 7 red stripes so lets divide the cylinder
into 14 equally spaced parts. Well use the 14 step indexing wheel
for this since 7 can be divided equally into 14.
diameter of this particular pen barrel when finished is .613". Draw
a circle of that diameter and then divide it into 14 equal segments. Then
measure the width of the segment. The length of the pen barrel is 2.375".
Figure 3 shows how we transfer these dimensions into a framework suitable
for drawing wavy stripes.
clarity, I drew only two stripes in the grid. Normally we would only need
to draw one because its a repeat pattern. If the pattern around
the pen were totally different or non-uniform, wed have to use the
next step is to set up the laser. Position the indexing jig in the engraver
with the wooden barrel mounted to it, and align the first segment of the
grid exactly on top of the barrel in the laser engraver. In CorelDRAW
create a box that represents the engravable area on the pen barrel (.25"
high x length of segment). With the red dot pointer activated on the laser
engraver, vector trace the outline of the box (with the engraver lid open
of course). Adjust the location of the engraving box until it traces accurately
onto the pen barrel. Now position the grid with all segments so that your
first segment is centered within the engraving box. Once were aligned,
set up your layers. This is essential with complex patterns but not really
necessary if the pattern doesnt change from one segment to the next.
our Corel layout, the first stripe in the pattern will be assigned to
a layer we will call PRINT. All of the layers in the file
will have the print function disabled except for this one. Also set up
a layer called STRIPES. This layer will accommodate the stripes
or segments of the pattern that arent being printed (engraved).
When we get to the upper barrel of the pen (stars), the reason for this
will become clearer.
you begin cutting, make sure that the indexing knife on the jig is engaged
in the 14 step indexing wheel. With the pen barrel mounted to the indexing
jig and accurately aligned inside the engraver, you can now engrave your
PRINT layer should be the only active (printable) layer and
the 1st segment of your pattern should be the only design element on that
layer. I find that toggling the visible icon in the layers
palette off and on is a quick way to see what you have on any given layer.
youre sure that the top stripe is the only element on the PRINT
layer, you can engrave into the pen barrel. Once the item is engraved
to the desired depth, slide the indexing knife out of the wheel and advance
the barrel and wheel by two notches in preparation for the second cut.
Re-insert the knife and engrave the second stripe. Repeat this seven times
to complete the cylinder.
characteristic of the indexing jig as opposed to rotary attachments is
that when you engrave around a cylinder using the indexing jig, you will
always end up exactly where you started. With the rotary attachment, if
the diameter that you enter is slightly off when you make your way around
the cylinder, your alignment will also be slightly off.
engraving the stars on the upper barrel of the U.S. flag pen, we will
be using two different pattern segments instead of just one as we did
with the stripes (Fig. 4).
arrive at a total of 50 stars, I used a grid with 11 segments and alternated
between five stars and four stars per segment. The first and last segments
each have five stars, which isnt really a problem because, when
assembling the pen, I positioned the clip in between the two rows of five
the upper barrel of the pen mounted on the indexing jig and the 11 step
indexing wheel installed, were ready to set up our layers. Lets
create a new layer called STARS. Make sure the printable
icon is turned off. We also want to move the stripe that was on the PRINT
layer to the STRIPE layer. When you start engraving the stars,
youll want to do all of the segments with five stars in them first.
As before with the stripe segments, align the first star segment with
the upper pen barrel which is mounted on the indexing jig in the laser
engraver. Again use the red dot pointer to make sure the stars are perfectly
centered on the barrel. Put the row of five stars on the PRINT
layer. They should be the only design element on that layer and that should
be the only active layer.
6: Engraving box: Grid in starting position for engraving 5-star segments.
Engraving box: Grid nudged into 2nd position
for engraving the 4-star segments.
you are ready to engrave the pen barrel. Once the engraving is at the
desired depth, slide the indexing knife out of the wheel and advance the
barrel and wheel by two notches. Re-insert the knife and engrave the next
row of five stars. When youve completed the 6th row of stars switch
the layout to the row of 4 stars. To do this, enter the height of the
segment (in this case .188") into the nudge offset box
in CorelDRAW (Fig. 5). This is an excellent way to toggle up and down
(using the arrow keys on your keyboard) through the segments of your pattern
and still be perfectly aligned with the pen barrel on the indexing jig.
the grid including all segments and stars. Use the up arrow
to nudge the second segment of the pattern (four stars) into the engraving
box (Fig. 6).
switching from the five star segment to the four star segment, the five
stars which were on the PRINT layer must be moved to the STAR
layer and the four stars in the second segment must be moved to the PRINT
indexing wheel has to be advanced two more notches after the last five
star segment is engraved. This sets you up to start engraving the first
four star segment. Continue advancing the indexing wheel by two notches
after each four star segment is engraved until youve completed all
five segments and are back at the beginning. That completes the indexing
jigs involvement in this project.
you can see, a complex pattern with completely different shapes throughout
the entire design would have you moving segments on and off the print
layer after each segment was engraved. However, if you follow that approach,
your chances for success are all but guaranteed.
7: When using the indexing jig your inlayed pieces match and you get
a nice tight fit. When using the rotary attachment the fit is not
identical and not as clean.
8: The pen kit costs are kept reasonable because the stars are cut
from a flat piece of veneer.
technique is especially wellsuited for doing inlays, i.e. when you laser
cut a cavity and then vector cut an inlay to fit precisely within it.
One important factor to note regarding the indexing jig versus the rotary
attachment for this type of inlay work is that unless all of your inlayed
pieces are vector cut from a cylinder with the same diameter as the engraved
cylinder, you will not get tight, clean-fitting pieces (Fig. 7).
walls that are engraved on a cylinder using the indexing jig are straight
sided or parallel to each other, whereas the walls created using a rotary
attachment are all tapered toward the center of the cylinder. For the
U.S. flag pen, being able to vector cut several hundred stars from a flat
piece of veneer in a couple of minutes is extremely convenient as opposed
to turning wooden cylinders to cut the stars. This also makes it possible
for me to sell these pens in kit form (Fig. 8) and keep the costs reasonable.
if your lasering needs are not as complicated as this stars and stripes
inlaying job, you can take full advantage of using an indexing fixture
like mine. Its an excellent technique when you need to mass produce
multiple jobs involving simple additions of two or three lines of copy.
Try it. Youll like it.