3D printing without post-processing

| Manufacturing

3D printed component using augmented polymer material

Andy Pye finds out about the possibilities for volume 3D additive manufacturing without post processing using augmented polymer deposition.

Wohlers Associates reports that the commercial 3D printing market grew five-fold from 2009 to 2015 and forecasts more than four times growth from $6 billion in 2016 to $26 billion by 2021. Plastics represent 80% of that market. But current technologies have limitations which are holding back progress.

Augmented Polymer Deposition (APD) was invented by Eugene Giller, Founder of Rize, who had previously developed inkjet technology-based approaches for rapid manufacturing and rapid prototyping at Z Corporation (later acquired by 3D Systems). Giller recruited Tom Davidson, Rize VP of Engineering who had also previously worked at Z Corporation.

Despite the continued evolution of 3D printing, Giller saw that the technology’s promise was far greater than its real-world use for those who depend on prototyping or see the potential for on-the-go production parts. Users have to make sacrifices throughout the process, from file to usable part. For many, 3D printing hasn’t been viable because it wasn’t robust enough for the application, it wasn’t safe enough to use on the desktop in an office, or because the time and hassles of pre- and post-processing severely limited its use and effectiveness.

Today’s parts made by 3D printers all require post-processing. Gary Rabinovitz, Reebok’s Additive Manufacturing Lab Manager says he spends about 50% of his time post-processing parts, including support removal, sanding, painting, coating and curing, delaying when he can deliver usable parts to his internal clients.

So Giller and Davidson set out to develop a 3D printing platform that would set a new standard for turnaround speed and ease of use in industrial machines that could exist as comfortably and safely on desktops as they could in additive manufacturing lab environments and deliver on-demand 3D printing of injection moulded-quality parts,

Augmented Polymer Deposition (APD) involves simultaneous extrusion of a proprietary compound of thermoplastic and jetting of functional inks through industrial print heads to change the material properties of the thermoplastic. This eliminates post-processing. Gone are the messy and toxic post-processing materials, the special hookups and space required for post-processing devices and, most importantly, the hours of expensive labour required to deal with all of it.

After the thermoplastic support is extruded using APD, a print head jets a layer of Release One ink between the support and the first layer of the part. The release ink provides just enough bond to prevent the part from slipping during printing, but enables the user to simply release the part from its support after printing, in seconds with their bare hands in a typical office environment, without mess, chemicals, special facility and storage requirements or filing.

Rize will also provide other functional materials, such as conductive, thermo-insulating and thermo-conducting inks. This might be a way to create smart sensors from a 3D-printed part with active materials in it, or a battery within a 3D printed structure. Another capability is the ability to 3D print high-definition text and images onto the part. In this case, Marking Ink is jetted by the print head when called for in the file to print directly onto parts.

The Rize software automatically prepares the imported CAD file for 3D printing, including imperfect files. Making CAD (computer aided design) files 3D printable, including overcoming hurdles like incomplete surfaces or mismatching surface boundaries, can be a tedious, time consuming and complex process. In fact, many users purchase additional file-fixing software on top of their CAD program to help with this activity. Still, even file-fixing software involves additional time, considerable expertise and cost in order to generate a file that can be successfully 3D printed,

Intelligence and sophistication built into the Rize software automatically identifies and handles problems in the imported 3D file. Because the slicer tolerates imperfect 3D files, the file can be printed quickly and easily, without the need for additional software tools, enabling users to 3D print files in the software programs they use the most,

Any given part is only as strong as its weakest point. Z-directional strength is impacted by the strength of the internal bond between the layers of a part. Most 3D printing technologies are unable to create parts that are as strong in the Z-axis as they are in the X- and Y-axes due to weak bonds that form between each layer of material. Those bonds are referred to as anisotropic – their physical properties have different values when measured in different directions.

Rizium One is Rize’s proprietary compound of engineering- and medical-grade thermoplastic. It has properties similar to polycarbonate (PC), such as strength, but it has high strength in the Z-axis, due to the way that the material bonds during the process. Parts made this way only experience a 10% loss in isotropic properties, compared to stock material – not even all injection-moulded parts have 100% isotropy, due to the way that moulds are created. In comparison, typical traditional FDM parts lose around 40% of their Z-strength and, therefore, are not nearly as strong as Rize parts.

In a Reebok comparison between Rize APD and Stratasys FDM using the same part, the Rize support was removed in 25 seconds at the user’s desk, while the Stratasys method took three hours in a chemical solvent bath that could only be used in a lab. “We run our 3D printers 24/7 to create the parts, and, unfortunately, post-processing has been a necessary but laborious and time-consuming process.” says Rabinovitz. “Since our intent was to make the entire 3D printing process hassle-free, we also focused on the front end of the process. An easy-to-use, zero post-processing 3D printer like Rize would dramatically improve workflow, enabling us to deliver parts as much as 50% faster than similar technologies while reducing the cost of labour, materials and equipment.”

The industrial-class Rize One has a build volume of 300 x 200 x 150mm that will accommodate 80% of industrial parts, it was designed to 3D print multiple parts simultaneously, on demand, 24 x 7 x 365. Watertight, isotropic thermoplastic parts built with Rize’s APD process have a resolution of 0.25mm and high-definition 300dpi text and images.

One specific application Rize is working on is the ability to change the mechanical properties of the plastic by coating it with a flexible additive in order to produce comfortable, yet effective hearing aids. Many of the world’s hearing aids today are 3D printed with stereolithography. Rize will be able to 3D print them in such a way that the interior channel of the hearing aid is rigid so that sound can bounce through the hearing canal, while the exterior is coated in soft, flexible material so that it fits comfortably in a wearer’s ear. BOX ITEM –

Post-processing after 3D printing

All other 3D printers, including desktop 3D printers, require post-processing following 3D printing in order to produce a usable part. For example:

* Fused Deposition Modelling (FDM): The 3D printed part spends around 4-8 hours in a heated, agitated sodium hydroxide bath
* Stereolithography (SLA): The part is rinsed in alcohol, supports are cut or sanded and the part is light cured
* Photopolymer Jetting: Supports are removed from the part using a water jet system or wax oven
* Selective Laser Sintering (SLS): The part must be excavated from a bed of powder and then fully de-powdered
* Digital Light Projection (DLP): The part is rinsed in alcohol, supports are cut or sanded and the part is light cured
* Powder Bed Binding: The part must be excavated from a bed of powder and then fully de-powdered, sanded (if smoothness is desired) and coated with a material such as cyanoacrylate (CA)

These and other processes are not only time consuming, expensive and messy, in many cases, they are also toxic. To be sure, none of them are suitable to use inside a standard office. In fact, many require special venting, storage or disposal facilities and equipment. The Illinois Institute of Technology recently conducted an emissions study involving several desktop 3D printers and the results were sobering. They discovered that numerous toxic particles, such as styrene, lactide and acetic acid are emitted from these machines,

Latest posts by Andy Pye (see all)

About Andy Pye

Andy Pye is a graduate of Cambridge University and has had a high profile career in the technical press as well as being a pioneer in web publishing.

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