CAUTION: Head strikes are bad—they damage print heads and budgets. To
reduce the risk of having a head strike, you should always pass your custom substrates
through a slot ruler before printing on the surface. Since we’ll build a slot
ruler that is no thicker than your platen gap, you should have a margin of safety.
Refer to Chapter 3 for information on printer platen gaps and media tolerance
for various printers.
CAUTION: Check that the tubes you use for your slot ruler are straight and even,
since you’ll rely on them to test substrates. Place them on a flat table and check all
four sides. If you can see light between the tube and the table, they’re bent.
FIGURE 17.5 Some of the materials for making a slot ruler.
MATERIALS NEEDED
Two 1" x 1" square, aluminum tubes
Double-sided tape
New U.S. coins
Masking tape
TOOLS NEEDED
Caliper
To make your own slot ruler:
1. Cut your tubes to be two inches wider than your
printer’s width. If your printer is wider than 24",
use tubing with a larger cross-sectional area to
ensure that the tubes are rigid.
2. You need to insert a spacer between the tubes that
is no thicker than your platen gap. You can use
either coins (see the “English and Metric Units”
sidebar in Chapter 2) or washers to do this. In
either case, check the thickness of your spacer
with your caliper.
3. Use very thin double-sided tape to tape the
spacers between the two tubes (Figure 17.5).
4. Apply masking tape around the tubes and spacers
to keep the stack together. This tape is just used to
keep it from shifting—the double-sided tape holds
the spacers in place.