The Digital Thread Impact on Design for CNC Machining

cnc machining milling tools

To succeed in a post-COVID world, digital manufacturers need to stay on top of current trends and streamline their production processes.

However, this is easier said than done, since many digital manufacturers are still struggling with the process of product creation. Despite the recent developments in digital manufacturing, many manufacturers still use 3D computer-aided (CAD) software that is incompatible with their customers and suppliers. They may still also be converting 2D CAD drawings to 3D models, which is an inefficient and error-prone way of navigating from design to finished product.

To cut down on costs and boost efficiency, manufacturers should adopt digital thread. An all-encompassing concept that seeks to unite different aspects of the manufacturing process, digital thread involves digitizing every step and aspect of a product’s development from design to production. This includes product concept creation, 3D modeling, libraries, simulation, testing and verification, and computer-controlled manufacturing and inspection.

Digital thread can be applied to 3D printing as well as computer numerical control (CNC) machining. Read on to learn more about digital thread and test beds for implementing digital thread.

What Is Digital Thread?

Digital thread refers to how manufacturers use standard 3D models to create, observe, test, verify, and inspect every step of the product life cycle from start to finish. These steps are:

  • Product creation
  • Tracking
  • Quality assurance
  • Testing or troubleshooting
  • Maintenance

In many ways, digital thread functions as a product’s “birth certificate.” Since it contains so much information about a product, digital thread can help engineers and manufacturers trace the origin of various problems when they pop up. For instance, if a product was made with the wrong finish or material, manufacturers can look at the product’s digital thread to discover who or what was responsible for the error and when (i.e., which step of the product life cycle) it happened.

Although digital thread has become a popular concept, it has yet to gain widespread implementation. Research has shown that most small and medium enterprise (SME) suppliers still rely on 2D printed or CAD drawings to create 3D models, despite the clear disadvantages. The same report reveals that by shifting to digital thread, manufacturers can:

  • Produce higher quality parts
  • Reduce costs
  • Reduce cycle time
  • Reduce the risks of errors

Digital thread can be applied to any manufacturing process, including but not limited to:

Test Beds for Implementing Digital Thread

To encourage manufacturers to shift to digital thread, several institutions have created test beds. These include:

NIST’s Smart Manufacturing Systems (SMS) Test Bed

The National Institute of Standards and Technology (NIST) has launched the Smart Manufacturing Systems (SMS) Test Bed. A model factory with resources for helping manufacturers implement digital thread, the SMS can be used to evaluate the effectiveness of standards for distributing and collecting production data.

According to the co-coordinator of this project, NIST mechanical engineer Thomas Hedberg, the SMS test bed aims to be a shared resource that facilitates smart manufacturing development and research. 

That is why NIST is actively looking for manufacturers and collaborators who want to link their data sets, product data systems, and fabrication processes with their test bed. That way, NIST can help these manufacturers adopt digital thread and let other participating members learn from their knowledge and experience.

The SMS Test Bed consists of:

  • A Computer-aided Technologies (CAx) lab with software tools for controlling every step of the production process, including design, creation, inspection, data management, verification, and validation testing.‌ The CAx Lab is intended to help manufacturers develop test cases and standards, craft CAD models for experiments, and test cyber-physical connections throughout the product lifecycle.
  • A manufacturing lab located at NIST’s headquarters in Gaithersburg, Maryland. This location features myriads of CNC machining design, fabrication, and inspection tools (such as CNC turning and CNC milling) and works like a contract manufacturing shop. This lab is partnered with the NIST Fabrication Technology Office (FTO).
  • Online data collection, streaming, storage, and publication services that manufacturers can use to test the digital manufacturing process. These also include: 
    • A searchable hub of all SMS test bed data that has been generated.
    • Pre-made data packages for products that had been made before using digital thread. Manufacturers can download these packages and use them in their own facilities..

NIST’s Design to Manufacturing and Inspection Project

To encourage manufacturers to adopt digital thread, the NIST has also created the Design to Manufacturing and Inspection Project to demonstrate the feasibility and strengths of implementing digital thread.‌ The system contains 3D designs of parts that can be converted into a standardized STEP AP 242 model that can be used by manufacturing software to create CNC instructions for machines. The STEP AP 242 model can also drive the machines to inspect parts to ensure that they were created according to the original specifications. 

The Importance of Standardization in Implementing Digital Thread

Like NIST, the International Organization for Standardization (ISO) has also been developing manufacturing standards that work across the board to increase productivity and integrate all phases of the product creation process. 

Although the ISO does not have the specific mandate of promoting digital thread, the ISO’s most recent standard, ISO 10303-242 or STEP AP 242, will serve as a useful model for companies implementing digital thread. Complementary to many visualization formats and capable of supporting advanced data content, STEP AP 242 is of particular interest to automotive, aerospace, and other industries that use CNC machining. 

STEP AP 242 also includes many modules, models, and capabilities for kinematics and other functionalities. It allows manufacturers to add computer-readable product and manufacturing information (PMI) to 3D models, such as:

  • Finishing requirements
  • Dimensions
  • Materials
  • Surface texture
  • Process information

Like NIST’s SMS Test Bed and Design to Manufacturing and Inspection Project, STEP AP 242 is flexible and can be applied to:

  • Products, which include aerospace, automotive, and other mechanical products, including parts, tools, assemblies of tools and parts, and raw materials.
  • Product Data Management, which includes: 
    • Properties of parts or tools
    • Identification of standard parts
    • Breakdown data showing parent-child structures
    • Data describing the changes that occur during each step of the process
  • Mechanical Design, which includes different types of geometric models, such as 2D and 3D-wireframe models, boundary models, 2D-sketch models, and more.
  • Kinematics, which refers to simulation data for describing kinematic motion and structures.
  • Composite Design, which includes: 
  • Identification of material specifications from external and internal sources
  • Depiction of composite laminate tables that describes the stacking sequence, material, and ply orientation
  • Parts of the composite or a part of the composite with a defined shape

The Impact of Digital Thread in Manufacturing

Digital thread — a concept that involves digitizing all of the steps and processes for developing products — is slated to play a major role in manufacturing in the near future. 

As we move towards an increasingly digitized manufacturing process, many companies will find implementing digital thread a boon to their business. Digitizing every step of the manufacturing process will simplify the product creation process and help manufacturers spot and avoid errors, saving them a lot of time, money, and energy. 

Although many manufacturers are still relying on 2D drawings to create 3D models, we can expect an increasing number of companies to adopt digital thread as the concept gets more exposure through the NIST’s SMS Test Bed and Design to Manufacturing and Inspection Project. The ISO’s newest manufacturing standard, STEP AP 242, will also encourage manufacturers to adopt digital thread so they can streamline the product creation process.