Additive manufacturing (AM) refers to processes used to make a three-dimension object layer-by-layer. The shape of each layer can be dynamically controlled by computer-aided design (CAD). The advantages of AM, compared with traditional material removal manufacturing technologies, include: material waste reduction, energy savings, simplified manufacturing processes accomplished by eliminating steps in the production process, and potentially unlimited geometrical complexity.
The stereolithography (SL) process—the first commercialized AM technology—is a widely used AM technology. In that process, the liquid photosensitive polymer is solidified by a pattern controllable irradiation light source, such as a digital light processing (DLP) projector or a laser beam. Two kinds of layouts of DLP/laser are used in the SL processes with different resin-filling mechanisms: free surface method and constrained surface method.
The constrained-surface process has several advantages over the free-surface method, including: higher vertical dimensional accuracy, higher material filling rate and speed.
But there are challenges. The biggest is separation of the newly cured layer from the constrained surface.
This difficulty results from an adhesive bonding that is developed between the newly cured layer and the constrained surface. Thus, a solution is needed to separate the built part from the constrained surface. The separation force significantly affects printing speed, reliability of printing process, printable size area and life cycle of the constrained surface.
Current existing methods to address this problem include tilting the vat, sliding the vat and adopting the oxygen permeable membrane. However, the construction complexity and cost of the SL systems increases significantly with the increase of the maximum area that the system can build based on the current methods. Thus, known separation methods essentially impeded large-scale 3D printed builds using SL technology.
In “A vibration-assisted method to reduce separation force for stereolithography,” which was chosen as one of three best papers at SME’s North American Manufacturing Research Conference (NAMRC) in June.
Yong Chen and his team from USC presented a novel approach aiming to use the vibration in a certain frequency to separate the newly cured surface from the constrained surface with a minimum incremental construction complexity as the building area increases.
Chen’s team significantly reduced the separation force and improved reliability when it comes to large-area 3D printing for SL technology using the constrained surface method, he said. Chen presented his experimental hardware system and the results from the vibration-assisted printing process at NAMRC.
Chen said more work is needed to adapt the methodology to address the reliability of printing small parts.
NC State researchers exploring blockchain tech
Blockchain is a distributed and decentralized ledger system through which data is protected from tampering due to hashed linking of data blocks and the presence of these data blocks on every node of a decentralized system. Blockchain technology also enables “smart code” through smart contracts to be run on the decentralized system.
Just as in regular legal contracts, a code-based contract can be initiated between two or more parties and when deployed its terms and conditions cannot be changed.
Binil Starly and his team at North Carolina State University demonstrated how small and medium-scale manufacturers can deploy individual smart contracts using blockchain technology to enable accessibility and transparency of data.
Manufacturing service providers who share data via blockchain are enabling transparency of an organizations’ capability, as well as paperless contracts between manufacturers called “smart contracts,” Starly said in a paper paper titled “A case study for blockchain in manufacturing: “FabRec:” A prototype for peer-to-peer network of manufacturing nodes,” which he and his team presented at NAMRC. This lets supply chain or procurement professionals find and access trusted data of a service provider.
Traditional methods of searching for clients and manufacturers depended on trust enabled through human networks and/or historic performance. An engineer working with his purchasing department awarded a contract to a small job provider either because of past business or through known contacts.
In a digitally connected world, establishing supply chains need not depend solely on human networks or prior relationships. This increases competition among job shops and service providers to let organizations focus more on their core expertise.
Perhaps the most important result from this work is the ability for machines to directly write “events” to the public blockchain called Ethereum. These events included basic machine status information, such as “on,” “off,” “busy.”
Starly’s team demonstrated how a decentralized system like Ethereum can autonomously execute code to consume information from a physical CNC machine and initiate a command to another physical machine based on “smart contract” code running on the Ethereum chain.
Starly’s research demonstrates the ability to design and build a decentralized manufacturing marketplace built on verified and trusted manufacturing data without a central party controlling the flow of this information.
In a decentralized system, clients and sellers can interact with each without layers of intermediaries in place. Decentralized systems have been proposed. But they have not always been practical in manufacturing due to key missing information technology elements that would make it economically and practically feasible.
Data veracity has been a central issue. How does a company digitally verify the claims of a manufacturer’s capabilities? Was the part manufactured by the service provider or sub-contracted to another, unauthorized provider? How does one trust the source of raw materials and the firms that provide them? How can one speed up due diligence work in supplier assessment and verification? Answering these questions today is extremely time-consuming and prevents supply chains from being agile and dynamic.
Starly’s team created a proof of concept, demonstrating a decentralized network of manufacturing information through which suppliers of manufacturing services or parts are assessed, verified and selected for a contract. Databases maintained by the top-tier-system integrators can have real-time status updates on basic information about their suppliers.
“We foresee pertinent metadata from machine assets of service providers providing an even bigger role in terms of a service provider projects its own capabilities and available capacity to win future orders and may incentivize manufacturers to upgrade machines to be digitally connected while providing a secure framework through which data is shared and publicly or privately consumed,” he said.
The central premise of the work Starly’s team is doing is that a job shop manufacturer’s service data is shared in a distributed and decentralized system. While the data is secured and relatively hard to tamper with when using blockchain technology, authentication of the original source of the data cannot be determined.
For example, if a job shop reports 40% available capacity based on a machine data stream tied to blockchain technology, how does a third party know a machine even exists? The data could have been spoofed by a server agent reporting spurious availability data. Therefore, future work includes developing new protocols to authenticate the original data stream right from the source—before the data payload becomes involved in a blockchain scenario.