Linear Motion in the Third Industrial Revolution

According to The Economist magazine, a third revolution is coming for the manufacturing industry, ushered in by 3D printing, new materials, and collaborative manufacturing services. Anyone who has watched the 3D printing industry develop over the past decade, or even the past five years, will likely agree. Gartner forecasts that worldwide shipments of 3D printers will reach over 217,000 units in 2015 and will more than double each year between 2015 and 2018.

This is good news for manufacturers and distributors of linear motion components and systems, because while the processes may vary – from stereolithography to laser sintering to thermoplastic extruding – the backbone of virtually every 3D printer is a linear motion system. (For a primer on 3D printing technologies, see the 3D Printing Industry’s Beginner’s Guide.) And the 3D printing industry provides opportunities for a wide range of motion technologies, based on the diversity of its users and the printer’s intended purpose.

Desktop 3D Printers

Desktop 3D printers can be loosely defined as those with a print area less than 10 in. x 10 in. x 10 in. These models range from kits costing a few hundred dollars to pre-assembled printers costing a few thousand dollars, making them within reach of home users, hobbyists, and small manufacturers. Nearly all desktop 3D printers use Freeform Fabrication (FFF, also called Fused Filament Fabrication) technology, which involves heating, extruding and depositing layers of thermoplastic material to build a 3D model.

With relatively low dynamic requirements and ease of assembly being key considerations, these printers often use round shafts and belt-pulley systems to move the extrusion head. While these components offer the lowest-cost linear motion systems and positioning that meets the printer’s specifications, they are difficult to install and align, which can lead to binding and torque spikes. Over time, round shafts and belt systems will also develop backlash, which can lead to degraded print quality. Linear guides with self-aligning and ease-of-assembly features help alleviate these problems and improve both printer performance and customer satisfaction, by reducing maintenance and providing consistent build quality.

Prosumer 3D Printers

Falling between desktop and professional versions, prosumer 3D printers can have a print area up to 18 in. x 18 in. x 18 in., and may be based on either FFF or Selective Laser Sintering (SLS) technology, which uses a laser to melt and fuse powered metal, ceramic, or plastic. With the ability to print larger models and a wider variety of print materials, prosumer 3D printers can be found in commercial and industrial applications, including part modeling and rapid prototyping.

In the prosumer range of 3D printers, requirements for larger print areas and smaller layer thicknesses lead manufacturers to use components such as linear rails and leadscrews, or even preassembled systems. As Mark Heubner, Market Development Manager at PBC Linear, explains, “Linear rails can provide pre-engineered alignment, which significantly reduces manufacturing and assembly time and service costs versus round shafts. And anti-backlash leadscrews provide better positioning and less positional degradation than belt driven systems. Leadscrews are also self-lubricating, which reduces maintenance and eliminates issues with oil or grease in the printer’s work area. All of these features contribute to lower manufacturing costs for the OEM and lower cost of ownership for the user.”

 

Professional 3D Printers

For models of high-precision parts, functional prototypes, tooling, or even finished parts, users turn to professional or industrial-grade 3D printers. These units can have a print area up to 1 meter (39 in.) with layer thickness – often referred to as resolution – of 10 microns. Professional 3D printers employ FFF, SLS, stereolithography (SLA), or, in some cases, technology which is proprietary to the printer manufacturer.

To achieve smaller layers, better surface finish, and faster build times, manufacturers of professional 3D printers use higher precision and more robust linear motion systems, such as ball screws and profiled rail linear guides. At the highest end of the technology spectrum, linear motion is achieved not with mechanical drives, but with linear motors. As RJ Hardt, Applications Engineer at Aerotech explains, “The level of precision needed from the linear motion system is dependent on the feature size of the part being produced.”

Aerotech has significant experience with high-precision 3D printing applications, and one area that the company sees moving rapidly toward these smaller feature sizes is printed electronics, where he predicts that traditional mechanical drives, such as ball screws, won’t be able to keep up with the precision required by the application. Decreasing feature sizes and increasing precision also place higher demands on the motion control system, and this can become a sticking point for 3D printer manufacturers. According to Hardt, “Essentially, many manufacturers don’t allocate enough of their time and budget to this area. And no matter how precise the mechanical system, an inadequate control system will prevent the printer from producing the desired resolution.”

 

As material technologies advance and printing processes are refined, the use of 3D printing will increase among a wide range of products, from relatively basic consumer items to high-tech aerospace and medical components. But with so many technologies, end uses and manufacturers, it will be quite some time before the performance requirements of 3D printers exceed the capabilities of linear motion systems and controls – whether screws and profiled rail guides or linear motors and air bearings. The challenge for manufacturers of linear motion components and systems will be to educate designers and OEMs on the capabilities of each technology and help them as they lead the Third Industrial Revolution.