Adding Creativity to Engineering.
By Tom Imerito
Since that day long ago when one of our early ancestors knapped a chunk of flint into a projectile point, manufacturing has largely entailed removing unwanted material from a larger mass until the desired item emerged amidst a pile of scrap. Through the millennia, as flint-nappers evolved into stone cutters, wood workers, iron masters and manufacturing engineers, their tools became increasingly capable of producing complex shapes.
The trend to complexity culminated in the twentieth century’s CNC machines which took the handiwork out of the manufacturing equation and replaced it with the pure knowledge of Cartesian coordinates executed by numerical machine controls. Although each of the incremental improvements in tool design enabled increasing creativity of engineering design, the craft of making things was limited to sculpting the exterior surfaces of big pieces of stuff into smaller pieces of stuff. To make matters more oppressive, no tool existed that could build a complex, unitary part from the bottom up or from the inside out.
Then in 1983, the world of engineering design changed dramatically when an inventor named Chuck Hull broke the top-down, subtractive manufacturing barrier by fashioning a method for solidifying sequential layers of a liquid polymer with ultraviolet light, thereby bringing to life a new technology called additive manufacturing. In the thirty-odd years since Hull’s invention, advancements in digital imaging, scanning and processing have coalesced with parallel advancements in laser optics and machine controls to turn additive manufacturing into a revolutionary creative force in engineering design and manufacturing.
As its name suggests, additive manufacturing makes things by adding materials in precisely configured layers as opposed to removing materials by cutting, grinding, shearing, turning, bending, stamping, drilling and milling the way conventional machining processes do.
In principle, all additive processes apply a layer of material to a substrate and fix, cure or otherwise solidify select areas in accordance with a set of horizontal coordinates. Subsequent layers, having different coordinates, serve to shape the accruing body in three dimensions as it rises through the vertical axis.
Additive materials can be polymers, composites, metals or ceramics in the form of liquid, powder, film or wire. The methods of deposition can be by bed, jet, nozzle or orifice. Fixing methods include curing, fusing, melting or sintering by UV, laser, electron beam, or plasma arc.
At first glance, the appeal of additive manufacturing resides in its fast-turnaround times for molds and prototypes as well as its ability to produce one-off customized products, such as jewelry and dental implants, at an affordable price.
But the overarching advantage of additive manufacturing inheres in the creative freedom its component technologies offer engineers who can think beyond the bounds of traditional, subtractive manufacturing conventions. Over the past several decades, concurrent advancements in materials science, computer processing, digital imaging, laser optics and machine controls have added to the innovation toolbox a new set of capabilities that demands a creative and cognitive revolution in engineering and design.
For all the speed and customization that additive manufacturing has to offer, its most compelling benefit is the ability to manufacture things that simply could not be made before. All the same, additive manufacturing’s newfound freedom of design comes with significant burdens, not the least of which is thinking about product design outside the limitations of conventional machines.
As Dr. Timothy W. Simpson, Co-Director of Penn State’s Center for Innovative Manufacturing Materials Processing 3D (CIMP-3D) puts it, many in the field are excited because “Additive manufacturing turns the conventional Design for Manufacturing paradigm on its head by enabling Manufacturing for Design. In other words, rather than allowing their thinking to be governed by how a machine will produce an item, engineers will be free – indeed required – to consider a first-principles approach to how an item will function best, without regard to the limitations of the machines that will produce it.”
At this juncture, The American Society for Testing and Materials (ASTM) has classified additive manufacturing technologies into seven categories based upon the mechanisms used to apply, bind or cure the respective materials, all of which are applied in sequential layers.
Acknowledging that the field is in its formative stages, and recognizing that new definitions cannot emerge as quickly as the innovations they define, I recently made two trips to Penn State to set the principles of additive manufacturing solidly in my mind. At both Materials Day, sponsored by PSU’s Materials Research Institute and a three-day CIMP-3D forum put on by the Advanced Research Laboratory, I found early adopters and pre-adopters from all over the United States seeking the same information I was: Introductory knowledge, machine demonstrations, technical definitions, disciplinary boundaries and practical limitations for the burgeoning field.
Given the intensity of the discussions and the attendees’ credentials and experience, it was clear the field is on the cusp of a massive expansion. At the same time, it was equally clear that the idea of building things in sequential layers is much bigger than the current array of process technologies can possibly accommodate.
Thanks to a series of highly informative presentations, thought provoking discussions with industry thought-leaders and an eye-opening tour of the highly secured CIMP-3D laboratory, by the end of my quest, I had found the answers I was looking for, and then some.
In addition to technologies formally classified as additive manufacturing, I found more than a few companies offering manufacturing services that obviously employ additive techniques, but which break the bounds of the current ASTM classification scheme.
For instance, in a natural exploitation of existing CAD data and recent advances in laser optics and robotics, John Haake, President of Titanova, Inc. in St. Charles, Missouri has developed a process called laser puddle steering to rebuild worn, high-cost machine parts. Haake’s process begins by adding a large amount of molten material to a worn part via a large laser, then steering the molten pool with a more tightly focused laser. The in-situ laser process effectively reduces the surface tension of the molten pool in strategic locations to provide the layer-by-layer precision necessary for a super-smooth surface edge when the metal solidifies. Naturally, Haake’s process is robotically controlled to ensure accurate replication of the part’s original dimensions by means of its original CAD data.
In yet another example of the creativity that additive manufacturing is bringing to innovation, Barry Fell of Thermoplastic Products Corporation in Hummelstown, PA, has leveraged the advantages of digital imaging and computer processing to yield a new set of pre-operative procedures for orthopedic surgeons. Fell employs computer software to convert the digital output of CT and MRI scans into digital control data for the CAD and STL files used to drive 3D printers. The scan-derived models and prostheses conform precisely to a patient’s pre-surgical physiognomy.
As a practical matter, Fell’s method allows surgeons to see, touch and practice on a 3-dimensional model of a patient’s internal condition in advance of an actual surgical procedure. In cases anticipating prosthesis implantation, a precise replacement bone structure is manufactured additively from titanium alloy using the patient’s converted digital scan data as control data for a 3D printer.
Fell is currently working with an advanced form of additive manufacturing called point-in-space printing which, as the name suggests, deposits material in three degrees of freedom, directly onto a bone, without the use of a disposable substrate. Fell’s arthroscopic bone augmentation technology employs a multi-lumen applicator to deposit a layer of a biocompatible polymer with one lumen which is laser cured in-vivo, with a second lumen, before the next layer is applied.
At the farthest reaches of additive manufacturing, tissue engineer Antonio D’Amore of The McGowan Institute for Regenerative Medicine, in Pittsburgh, PA, views additive manufacturing as a potential solution to stubborn problems facing the field of cardiovascular tissue engineering such as angiogenesis (blood vessel regeneration) and scaffold seeding with stem cells. D’Amore cites the possibility of employing additive methods to incorporate synthetic blood vessels into synthetic tissue scaffolds which he fabricates by means of a process known as electrospinning.
Electrospinning employs an electrically charged polymeric fluid which is drawn through a computer controlled nozzle toward an oppositely charged spinning mandrel to produce a micro-scale fiber. By controlling the angle of the nozzle as the mandrel turns, D’Amore is able to emulate the complex micro-geometry of natural tissue scaffolds to create a biodegradable fabric suitable for seeding with stem cells and implanting in an organ. Similar to the way Barry Fell derives additive manufacturing control data from CT scans, D’Amore quantifies the geometry of natural scaffolds by means of digital imaging data.
Although electrospinning employs some of the principles of additive manufacturing, due to variations in the micro-geometry of tissue scaffolds, it is not conventionally accepted as a branch of the discipline. Nonetheless, D’Amore and others consider the hybridization of the technologies to be a promising area of investigation.
In an extreme example of creativity in additive manufacturing that breaks the conventionally defined boundaries of the emerging field, Advantech U.S., also of Pittsburgh, employs chemical vapor deposition in its proprietary additive manufacturing technology for the production of thin film transistors (TFTs) and passive thin film electronic components. The company’s semiconductor devices are fabricated in a sequential layering process using vaporized bulk materials selectively deposited on thin films by means of a precisely positioned exclusionary barrier called a shadow mask. The shadow mask alignment system enables production of electronic devices with feature sizes between 5 and 100 microns with layer-to-layer alignment accuracy of 1 micron.
Serving to improve both cost efficiency and environmental responsibility, the Advantech U.S. process reduces the number of production steps entailed in conventional photolithography and circuit board manufacturing processes at the same time it avoids the use of environmentally hazardous inks and cleaning solvents.
In an effort to leverage the company’s technology to its fullest potential, CEO Whit Little has set a course for the development of custom, quick-turn transistors, conductors, resistors, capacitors, insulators, and light emitting components deposited in-situ on rigid or flexible substrates made of metal, polymer or composite materials as thin as a sheet of paper.
While chances are just about non-existent that additive manufacturing will replace conventional manufacturing processes, it’s a pretty good bet that over the next few years additive machines, instruments, devices and processes will become integral parts of industrial engineering, design and production for just about anybody who makes anything.
And given the freedom of design additive manufacturing has to offer, the term “anything” will, in all probability, add up to “everything.”
Even the stuff we couldn’t make before.