Awards & Engraving

January '20

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A&E JANUARY 2020 • 61 BACK TO BASICS 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 thousandths of an inch increments to allow the tip of the engraving tool to pro- trude out the bottom of the nose cone. The distance the tip of 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 prod- ucts are designed to be engraved at depths ranging from .001 to .015 of an inch. There are also thicker gauge substrates that allow for deeper engraving if heavy embossed effects or bevels are desired. More on this later. TOOLS OF THE TRADE 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 plas- tics, acrylics, phenolics, and more. When choosing a tool to use for an engraving sub- strate, it is important to use the correct bit for the type of engraving intended. We look at tools for softer materials in this article. 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; there- fore, 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 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 Simply put, rotary engraving is the removal of a substrate's surface using a rotating carving bit, typically referred to as a "tool." IMAGE COURTESY GRAVOTECH

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