The signage, awards and personalization industries have seen many new marking technologies
emerge in recent years. One could argue that the kingpin of these marking technologies is laser
engraving. True enough, laser technology is widely popular and rightfully so, considering all of
its many features and benefits it brings to the table. However, mechanical/rotary engraving is
one of the foundational technologies that revolutionized the industry. Though it may not be
monopolizing the spotlight these days, rotary/mechanical engraving remains one of the most
versatile and effective marking methods available and is still highly relevant to today’s
industries. Markets ranging from the weekend DIY hobbyist to the most advanced sign shops
all can benefit and profit from mechanical/rotary engraving technology.
There are two main forms of mechanical/rotary engraving. The rotary engraving method uses a
rotating bit or tool to carve away material. A similar engraving method commonly known as
diamond drag engraving utilizes a non-rotating diamond-tipped tool that drags across the
material, scribing lines and shapes into the surface to create the design. For the scope of this
article, we will focus primarily on rotary engraving.
Simply put, rotary engraving is the removal of a substrate’s surface using a rotating carving bit,
typically referred to as a “tool”. The tool is installed into the spindle of a computer-controlled
router. A nose cone is attached to the bottom of the router’s spindle, which normally pushes
against the material’s surface during engraving. Engraving depth is controlled using an
adjustable dial known as a “micrometer” on the spindle. Most micrometers adjust in very small
increments of thousandths of an inch to allow the tip of the engraving tool to protrude out the
bottom of the nose cone. The distance the tip of the the tool protrudes past the nose cone
surface is the depth the engraving will be.
Many substrates that are designed for rotary engraving do not require deep engraving. Most
engravable sheet products are designed to be engraved at depths ranging from .001” to .015”.
There are also thicker gauge substrates that allow for deeper engraving if heavy embossed
effects or bevels are desired. More on this later.
There are a number of engraving tool styles available for rotary engraving. Some are meant for
hard substrates such as brass, aluminum and stainless steel while others are meant for softer
substrates like plastics, acrylics, phenolics and more. We will look at tools for softer materials
in this article. When choosing a tool to use for an engraving substrate, it is important to use the
correct bit for the type of engraving intended.
It is common to see terms such as “flute” and “spiral” when selecting a tool. A flute is a groove
milled into the side of the tool that creates space for engraved chips to be removed from the
tool tip during engraving. Single fluted bits have one opening for chip removal and also only
have one cutting edge. Most often single fluted tools are also “straight fluted” in that the
groove or opening does not spiral up the tool. It is simply an opening on the side of the tool tip
that allows chips to escape while the tool rotates. There are some variations, but generally
single fluted tool tips appear like the tip has been cut in half. The missing “half” is the flute.
Single fluted straight tools are great choices for plastics, woods and generally all types of
materials because they produce a smooth finish in the engraved areas. They are designed for
higher feed rates which help reduce production time. However the single fluted straight
geometry does not lift away chips, therefore a vacuum system attached to the nose cone is
highly recommended. If in doubt on which tool to choose or if all others have failed, a single-fluted
straight tool is a great one to try.
Other types of tools include double fluted straight and double fluted spiral tools. These tools
tend to have a longer lifespan and are better balanced due to the double cutting edges. The
spiral fluted version helps in chip removal and is a good general-use tool for many kinds of
substrates including plastics, wood and aluminum. There are three and even four fluted tools
as well. These types of multi-fluted tools can achieve extremely smooth edges and can be a
good solution to very abrasive materials. The drawback to these tools is the feed rate must be
greatly reduced due to the multiple cutting edges.
Diverting attention back to single flute straight tools, these style tools meant for soft materials
may also be referred to as FLX bits, meaning they are meant to be used on soft, flexible
materials. FLX bits are among the most common types of bits used on plastics. The width of
the tool tip determines how wide a line or path the tool will engrave. Common tip sizes range
from .005” to .125” widths. The most common shank (shaft) sizes are 1/8”, 11/64”, and 1/4”
diameters. The rotary engraver user manual will specify which shank size fits the spindle.
Choosing the best tip width to use for the engraving job depends on the artwork design. Wider
tip widths will cut wider paths which is useful for large, bold lettering where precise corners on
seriffed fonts may not be required. The larger cut paths also help to reduce production time by
removing more material per tool pass. Conversely, smaller tip widths will produce much more
precise detailed engraved lettering and graphics where small sharp edges and corners are
important to produce accurately.
There are two components that are extremely important to rotary engraving success. The ﬁrst component is a vacuum system. The vacuum system is imperative for high quality engraving and must adequately remove all of the chips produced during engraving. The system must be purpose-built for rotary engraving or CNC routers and must be properly attached to the nose cone of the engraver. The vacuum system should be cleaned, emptied and checked regularly to ensure optimum performance. General purpose vacuums or shop-vacs are not recommended. The second important component is a solid holding system for the engraving substrate. High quality engraving results are impossible to achieve if the substrate is not held down straight, level and strong to the engraver bed. There are numerous options for this task, including purpose-built jigs, double-sided tapes, and tacky mats. Tacky mats are one of the most popular methods for securing engraving substrates because they hold a strong grip on the substrate, they last a very long time if taken care of, and can easily be cleaned and reused over and over again. Some mats are double-sided, so they can adhere straight onto the engraving bed, and the substrate then adheres directly to the top surface of the mat.
To round out our introductory journey into rotary engraving, we will walk through a basic engraving job. The ﬁrst step requires setting up the engraver for the engraving job. Select the proper tool and install it into the spindle. Once the tool is installed, a process known as “zeroing” the tool must be done. Zeroing is matching the depth of the engraving tool to the surface of the nose cone. Before zeroing the tool, make sure the micrometer is set to “0” to ensure the depth settings will read accurately when adjusted.
Next, set up the artwork for engraving. In most engraving software, the graphics import as vector line art. The line art is then ﬁlled with tool paths that the engraver follows to complete the job. Tool path spacing is generated automatically based on the engraving tool parameters set in the software. A handy feature in the software (if available) is the ability to simulate the engraving on screen prior to physically engraving the job. The simulation allows the operator to check the details of the engraving to ensure the proper tool size and spacing is used to create the engraving as precisely as needed.
Once the artwork is ready and all other settings are in place, it is time to send the job to the engraver. When engraving plastic, the protective masking can be left on the surface to help prevent ghosting and minor surface scratching.
In some cases however, leaving the masking on is not always practical. When cutting out a shape such as a sign blank, leaving the masking on during cutting will help protect the rest of the substrate for future use.
After cutting out the blank from the substrate, the masking can be removed from the blank and the process of engraving the graphics can begin. Depending on the complexity of the shapes, diﬀerent sized bits may be needed, requiring tool changes throughout the job.
Once the engraving is complete, the new sign is ready to be removed from engraver.
The new sign can now have any ﬁnishing touches added, such as ﬁxtures or frame options.
In conclusion, rotary engraving is the “tried and true” seasoned veteran of professional marking. In today’s high-tech world, rotary engraving continues to oﬀer great value to clients, customers and hobbyists alike. The technology adds great ﬂexibility, versatility and proﬁt to those who have already discovered the “latest and greatest” but still seek that one last tool to complete their arsenal of fabrication potential.