Like it or not, since the mid-1980s, the STL file format has been the de facto industry standard for transferring information between CAD programs and additive manufacturing equipment. However, the STL format only contains information about a surface mesh, and cannot represent color, texture, material, substructure, and other properties of a fabricated object.
As additive manufacturing technology has evolved from producing primarily single-material, homogenous shapes to producing multi-material geometries in full color with functionally graded materials and microstructures, there has been a growing need for a standard interchange file format that could support these features. A second factor that prompted the development of a new standard was the improving resolution of additive manufacturing machines. As the fidelity of printing processes approached micron scale resolution, the number of triangles required to describe smooth curved surfaces resulted in unacceptably large file sizes.
The Additive Manufacturing File Format (AMF) was introduced as an alternative to the STL file format to address many of the shortcomings of the popular file format. STL files introduce errors such as leaks and inconsistences, and also does not support color, material The choice, or orientation. STL files also rely on triangle subdivision to account for curvature. As the STL file scales in size, retaining resolution means introducing significantly more triangles. For example, a 10cm sphere at 10 micrometer resolution requires 20,000 triangles. Scaling up the 10cm sphere at the same resolution would significantly increase the amount of triangles, resulting in a much larger file. AMF seeks to address these issues by redesigning the way a 3D object is digitally stored.
Since the dawn of 3D printing, a little over three decades ago, there has been one file format that has dominated communicating with 3D printers — STL. Love it or hate it, and even with its limitations and shortcomings, STL has remained the de facto standard for the 3D printing industry. That may finally be changing, though, with the advent of more contemporary and robust file formats for 3D printing, such as AMF and 3MF. Over the next couple weeks we’ll be discussing the evolution, advantages, and disadvantages of 3D printing file formats, starting this week with STL.
So What Exactly Is An STL File?
Essentially, an STL file stores information about 3D models, but this format describes only the surface geometry of a 3D object without any representation of color, texture, or other common model attributes.
As it has been for three plus decades, the STL file format is still by far the most commonly used file format for communicating with 3D printers.
The true meaning of the file extension .STL has always been somewhat of a mystery. I’ve always considered it be an abbreviation of the word STereoLithography, although sometimes I have also heard it referred to as Standard Triangle Language or Standard Tessellation Language. Which is correct? Probably all of them.
Introduction To The STL File Format
The main purpose of the STL file format is to encode the surface geometry of a 3D object using tessellation. Tessellation is the process of tiling a surface with one or more geometric shapes with no overlaps or gaps. Having no gaps is especially important, as an object must be watertight to be printed. A good real life example of tessellation is a tiled floor.
These are the dog days of summer, the hottest part of the season in the Northern Hemisphere. It’s also one of the slowest times of the year for noteworthy “hot” news; MCAD included, politics excluded.
However, this week marked a very noteworthy bit of news: Desktop Metal announced it has completed a $115 million Series D investment round to further accelerate the company’s rapid business growth and adoption of its end-to-end metal 3D printing systems. Since its inception in October 2015, Desktop Metal has raised a total of $212 million in financing, with the Series D marking the largest individual private round for a metal additive manufacturing company.
Desktop Metal Studio System
The Series D round included significant new investment from New Enterprise Associates (NEA), GV (formerly Google Ventures), GE Ventures, Future Fund and Techtronic Industries (TTI), a leader in quality consumer, professional and industrial products, including Milwaukee Tool, AEG, Ryobi, Hoover, Oreck, VAX and Dirt Devil. Additional investors included Lowe’s, Lux Capital, Vertex Ventures, Moonrise Venture Partners, DCVC Opportunity, Tyche, Kleiner Perkins Caufield & Byers, Shenzhen Capital Group (SCGC), and Saudi Aramco.
With the Studio System, engineers can print complex, functional parts in a variety of materials, including copper. With its high electrical and thermal conductivity, copper is an ideal material for heat exchanger applications, like this copper heat sink for an LED light bulb. (Photo: Desktop Metal)
According to Ric Fulop, CEO and co-founder of Desktop Metal, the funding will help fuel the company’s speed to market, expand its sales programs, as well as progress the development of advanced R&D. The company is also exploring international expansion as early as 2018.
An impossible object is a type of optical illusion. It consists of a two-dimensional figure that is instantly and subconsciously interpreted by the visual system as representing a projection of a three-dimensional object.
In most cases the impossibility becomes apparent after viewing the figure for a few seconds. However, the initial impression of a 3D object remains even after it has been contradicted. There are also more subtle examples of impossible objects where the impossibility does not become apparent spontaneously and it is necessary to consciously examine the geometry of the implied object to determine that it is impossible.
The unsettling nature of impossible objects occurs because of our natural tendency to interpret 2D drawings as 3D objects. With an impossible object, looking at different parts of the object makes one reassess the 3D nature of the object, which confuses the mind.
Although possible to represent in two dimensions, it is not geometrically possible for such an object to exist in the physical world. However, some models of impossible objects have been constructed, such that when they are viewed from a very specific point, the illusion is maintained. Rotating the object or changing the viewpoint breaks the illusion, and therefore many of these models rely on forced perspective or having parts of the model appearing to be further or closer than they actually are.
Below is the Penrose triangle (an impossible object) that was first created by the Swedish artist Oscar Reutersvärd in 1934. The mathematician Roger Penrose independently devised and popularized it in the 1950s, describing it as “impossibility in its purest form.”
A 3D-printed version of the Reutersvärd Triangle illusion, its appearance created by a forced perspective.
So what does all this have to do with MCADCafe? (more…)
Last month at the RAPID + TCT event, many new things were presented and among those was GE Additive’s setting a target of growing its new additive manufacturing business to $1 billion by 2020, and selling 10,000 metal 3D printing machines in 10 years, building upon acquisitions it announced last year.
“It’s a big number,” said Tim Warden, senior sales director of GE Additive. “That’s why they’re investing heavily,” he said, referring to GE.
GE controls Concept after agreeing last October to buy an initial 75% stake in the German company, with plans to acquire the rest over an undisclosed number of years. The GE Additive turned to Concept Laser after a previously announced deal with SLM Solutions fell through.
The company estimates that it ultimately can expand additive manufacturing into a $10 billion business. GE owns more than 70% of Arcam but doesn’t have full control of the Swedish company.
The following video shows GE Power’s advanced manufacturing facility in Greenville, SC to learn about GE Additive’s metal 3D printing process for creating a gas turbine component that is used to power homes.
GE Additive and the Power of Additive Manufacturing
For now, “We’re concentrating on Concept where we can do what we want to do,” Warden said. “We’re going to support Concept in every way possible.”
The spring season seems to be the time of year when many companies and professional organizations hold their annual conferences, and this spring was no exception. I’ve attended several events in the past few weeks and noted striking differences of two of them — divergence at RAPID + TCT 2017 and convergence at LiveWorx 17 — and that’s how I want to wrap up our spring 2017 trade event tour (although I have one more next week).
Divergence at RAPID + TCT 2017
Diverge (dih-vurj, dahy-): Tomove,lie,orextendindifferentdirections fromacommonpoint;branchoff. To turn aside or deviate, as from a path, practice,or plan.
3D printing/additive manufacturing (AM) are about making something digital into something analog. Although the technologies are 30+ years old, many things are still being done as they were in the beginning, such as building 3D models, exporting STL data, etc. However, several aspects of AM are diverging from its historical roots.
For example, the first AM materials were polymers, and they still account for ~85% of all materials used, but metals are coming on strong and now account for about 14% of the materials used. The range of materials being used, though, is constantly increasing — everything from ceramics to composites to food to living tissue.
Panel Discussion at RAPID + TCT 2017
Volume quantities are also diverging from one-offs or small quantities for rapid prototyping to real production quantities where the costs can be justified when costs go down and production speed goes up.
It’s not often (thankfully) that I cover two major conference events in the same week, but this week was exceptional (in a good way) — Siemens PLM Connection and RAPID + TCT 3D Printing & Manufacturing.
Siemens PLM Connection
The Siemens PLM Connection event in Indianapolis was a first timer for me and I got a lot out of it.
The major theme I came away with was Siemens’ push for what it calls the digital enterprise hub based on a digital twin.
There are many definitions of the digital twin, but for Siemens, a digital twin is a set of computer models that provide the means to design, validate and optimize a part, a product, a manufacturing process or a production facility in the virtual world. It does these things fast, accurately and as close as possible to the real thing – the physical counterpart. These digital twins use data from sensors that are installed on physical objects to represent their near real time status, working condition or position.
Siemens supports digital twins for product design, manufacturing process planning, and production through the Smart Factory loop and via the Smart Product.
A deployment of a digital twin includes three pillars: in product design, in manufacturing process planning and in feedback loops.
1. In product design. A digital twin includes all design elements of a product, namely: (more…)
Clean up after anything is not usually an especially enjoyable endeavor, even where subtractive or additive manufacturing processes are concerned. This is where post processing comes in.
The Problem with CAD In Subtractive Manufacturing
To cut parts using a CNC cutting machine, it has to be programmed with the path of the desired shape or nest of shapes. Most parts are designed with a CAD program where they are saved in a CAD drawing format, such as DWG, STEP, or several others.
But you can’t just take the CAD file and send it to a cutting machine. It has to be interpreted first, so the CNC on the cutting machine can understand it. The problem with CAD file formats is that:
They usually contain a lot of information that the CNC cutting machine doesn’t need or would find confusing, such as title blocks, Bills Of Material, dimension lines, borders, welding symbols, etc.
They usually have multiple layers, some of which are useful to the CNC and some of which the CNC needs to ignore.
They sometimes have many parts in one file, some of which might need to be cut on the CNC cutter, and some might need to be machined, cast, or sent to an EDM.
They don’t have all of the information needed by a CNC machine. Machines need to be told when to turn a process on and off, how to lead-in and lead-out from a part, etc. All of this information is referred to as the process technology.
Last month at IMTS 2016 we checked out a lot of new and improved manufacturing technologies, including several innovative developments in 3D printing/additive manufacturing. A couple of the most unique technology introductions were from Stratasys.
The company demonstrated its next-generation manufacturing technologies as part of its Shaping What’s Next vision for manufacturing that builds on its industrial FDM 3D printing expertise in response to the needs of customers’ most challenging applications, addressing manufacturers’ needs to rapidly produce strong parts ranging in size from an automobile armrest to an entire aircraft interior panel.
Stratasys developed two new prototype machines that they called demonstrators to prove their practicality – the Infinite Build 3D Demonstrator and the Robotic Composite 3D Demonstrator.
Stratasys CMO, Tim Bohling, Leads Tour of Company’s 3D Printing at IMTS 2016
The Infinite-Build 3D Demonstrator
The Stratasys Infinite-Build 3D Demonstrator was designed to address the requirements of aerospace, automotive and other industries for large, lightweight, thermoplastic parts with predictable mechanical properties. The 3D Demonstrator featured a new approach to FDM extrusion that increases throughput and repeatability. The system also employed a unique “infinite-build” approach, that prints on a vertical plane for parts that are virtually unlimited size in the build direction, such as entire airplane panels.
The Infinite-Build demonstrator is called that because, by flipping the vertical FDM process on its side, “We’re able to print parts in that vertical plane direction essentially as large as we want,” said Rich Garrity, president of Stratasys Americas.
With all the fanfare that took place a couple years ago with the launch of cloud-based Onshape, we thought we’d weigh in with partner Geometric’s announcement of its STL Workshop.
Onshape is by no means the first cloud-based/mobile CAD application. It was and still is, however, a unique true cloud-based technology and not a desktop/cloud hybrid.
Onshape began with what was one of the best and worst kept secrets in the engineering software arena. Worst, because even early on, it was evident that the technology would be cloud based, even if virtually no details were disclosed. Best, because virtually no details were disclosed, and that just added to the anticipation for the official launch of Onshape.
One of the inherent advantages that Onshape has always had is the fact that it was created from scratch by a team used to creating things from scratch with no legacy baggage to overcome and work around. Of course, the development team has not done everything themselves, because Onshape includes software components from Siemens PLM (Parasolid; ironically the same modeling kernel used by SolidWorks) and D-Cubed. This component licensing has let the Onshape team focus its efforts on what it does best.