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Question and Answer

A Closer Look at CNC Engraving Technology

by Staff

February-March, 2006
Although CNC engraving technology is not new, advancements in technology, software, and machinery continue to increase - making it a more viable, user-friendly, and efficient option for producing high-quality flat stamping and multi-level engravings. In an effort to gain a comprehensive understanding of where CNC engraving technology is today, InsideFinishing spoke with several companies from various spectrums of the CNC process, from engravers and software designers to machinery manufacturers, to get a closer look.

What are the advantages of CNC engravings?
As CNC engraving technology continues to advance, so too do the many advantages it offers. Artwork can be immediately transferred to the engraver digitally; therefore, neither cost nor time is lost with film output and transferal. Digital artwork also facilitates a precise translation to the CNC engraving program. In addition, CNC engraving allows one machining program to be executed repeatedly, producing multiple quantities in exact replication, which can result in quicker, more precise set-up on press. Finally, because the CNC machining program is stored digitally by the diemaker, customers can reorder dies without again supplying artwork. Additional advantages to the CNC engraving process include the following:

  • Allows the flexibility to vary depth and bevel of embossing.
  • Allows the flexibility for individual relief designing by computer, which can provide various design possibilities.
  • Computerized-custom designing of textured and diffraction dies goes far beyond the possibilities of photoengraving, particularly in combination with CNC laser engraving.
  • Perfect computerized calculation of heat reduction and paper clearance ensures a perfect fit between die and counter, which translates into reduced set-up and makeready time.
  • Pre-cast counter die molds can be precisely calculated and produced to ensure a perfect fit between die and counter. Extra relief can be put into the mold as opposed to the labor-intensive efforts of grinding around the image by hand.
  • CNC engraved dies are made from brass, which allows for a longer lifespan over other metals.
  • Mounting holes, adjustment holes, and counter die line-up holes can be calculated precisely and engraved with ease.
  • Fast delivery times – comparable to delivery times of etchings / photoengravings.
  • Corners are always perfect, as opposed to imperfect hand-tooled corners.
  • CNC operations operate 24/7 at no overtime rate; therefore, production stays in progress even through the night.
  • CNC dies are very easy and simple to hand-finish all marks away, creating much smoother surfaces.
  • Customers have the option to order counter masters for additional counters to be made while the original job is simultaneously running on a press.
  • Because the CNC engraving process is machine-intensive as opposed to labor-intensive, lower costs are incurred.

What are the disadvantages of the process?
CNC engravers continue to push the boundaries for efficiency and craftsman-style results on sculptured dies. Depending on the skill level of the engraver operating the CNC machinery, CNC programming can take more or less time than a conventional hand engraving. Some CNC engravers offer viable solutions, particularly in cases of multiple-ups, such as producing one master engraving from which duplicate dies can be produced or utilizing a machining program to produce CNC-engraved repeats. Modifying a CNC program during operation can be very difficult, so you have to be careful to check your work before starting the process.

Cost is another issue, as capital equipment, software, and tooling will run approximately $75K - $100K to get the operation up and running. In addition, designers need to learn an ‘artistic’ CAD/CAM program and develop some knowledge of machining and engraving tooling and techniques.

And like any machine process, users run the risk of a machine unplanned outage or spindle breakage. If a tool were to break during operation, the engraver may be forced to start the engraving process from the beginning – thereby having to write-off the time and expense of that first, partially completed die.

What has developed in the way of software to streamline the production process of CNC engravings?
Over the last few years, a gradual transition from traditional methods of engraving to computerized design and manufacturing has taken place. This has allowed companies to cut lead times into at least half because they can quickly create intricate designs in engravings, which then automatically calculate and produce toolpaths for machining. These programs provide design methods that are more in tune with how an artist or sculptor would create a die manually. The programs are faster and easier to learn and operate than mechanical CAD/CAM programs, while still providing those same tools for designers that prefer them.

Mathematics of the programming software continues to improve, which has a direct correlation to the quality of the engravings. Functions have been combined in the programming of combination, embossing, and sculpturing dies through simplified macros; and referencing techniques on previous jobs have improved, thereby allowing greater consistency from job to job. Not only does this allow for identical execution, but also prevents varying results when different programmers or designers run the same job.

The programs also provide shading and rendering methods that create photo-realistic images showing what the finished dies will look like. This enables an engraver to ‘see’ the finished product before cutting the die itself. These programs also provide methods to import designs from other design programs and from scanned artwork. Some CNC systems operate with ‘intuitive’ software, which questions the logic programmed by the operator before engraving begins. This reduces error and enhances machine accuracy during the engraving process.

Cutting-edge software programs such as ArtCAM Pro 8 from Delcam have advanced vector and picture editing functionality, which allows quick and easy designs to be created or imported from standard file formats. Modifications then can be made using the simple editing tools. Advances in modeling tools include the ability to mirror and merge the 3D relief, thereby allowing the quick and efficient building of symmetrical designs. A fade relief tool allows the designer to create the illusion of perspective in a shallow relief by fading out the whole or part of a model; and an enhanced sculpting brush diameter (increased to 200 pixels) achieves faster results when sculpting large areas. Production tools such as Smart engraving provides strategies for engraving intricate text and shapes giving the designer the ability to utilize progressively smaller tools for maximum speed and quality of finish.

What types of advances have taken place in CNC machinery to specifically aid in the engraving process?
Advances in high-speed machining, high-speed spindles, machine controls, and cutting processes have resulted in very efficient CNC engraving. Producing precision, fine detail dies requires very small cutters, with some as small as .002” in diameter. Advances in high-speed cutting spindles now provide speeds in excess of 60,000 rpm to efficiently use such small tools. Complex die designs will result in machine tool cutting files that are composed of very small moves and that get to be very large in size. Advances in controllers enable those files to be processed rapidly, creating smooth curves and surfaces at high travel speeds from those short moves.

Network-compatible controls now exist with larger storage capacity and fast transmission rates, and digitally operated motors for the tracking of engraving equates to improved accuracy. Finally, improved control over the life span and exchange of cutting tools allows replacement tools to be automatically exchanged – an important advantage for broken or worn cutting tools during overnight and weekend running. This advancement allows the continual operation of the engraving machine.

CNC engraving provides a way to produce complex dies much faster and at much lower costs than manual methods. While the CNC engraving process still may not be for everyone, companies that have adapted these methods have quickly confirmed their value, and most have completely moved away from older, manual methods.

References:
CNC Engravings
h+m USA, David Bohne, (888) 387-4226, www.hmusadies.com

Metal Magic Engravers, Ted Geisler, (800) 851-4120, www.metalmagic.com

CNC Machinery
MHO Corporation, Frank Block, (925) 405-0361

CNC Software
Delcam International, Mary Shaw, (800) 664-3506, www.delcam.com