3D Printers Lack Closed Loop Control

One of the main technical hurdle the current 3D printing technologies need to take is to go from open loop to closed loop control systems. Closed loop control will enable higher resolution and faster printing.

So what is closed versus open loop control? In an open loop control system machines get their instructions and start working. Components of the machine work within a set of parameters. There is no check if the components actually function as expected. It is assumed that they do. Regular calibration of these components insures that the machine keeps on functioning properly. Every mechanical component has variances during operation due to wear-and-tear or environmental conditions. During the design phase, components are selected which can keep on operating inside a specific range of operating parameters. Calibration during installation and maintenance cycles make sure they keep within that range.

Closed loop systems check themselves during operation to see if they are working correctly. If not, the machine calibrates itself while operating. In case the machine cannot correct the problem, it goes into error mode. Due to closed loop control machines are more reliable, and it allows machine manufacturers to push the components to their limits where variances in operation are greater but are self-corrected. In practice, this means better performance – both in speed, reliability and accuracy.

For a more in-depth explanation, please read the article Open And Closed Loop Control in CNC systems.

The current generation of 3D printers does not have or only extremely limited closed loop control systems. Wipers, laser mirror systems, print heads, material feeders and build platforms are operating nowhere near their capabilities. The only significant closed loop control system I am aware of is temperature control in the build chamber in various machines.

An excellent visible example where closed loop control systems made a significant impact are car engines. Up until 1980s car engines where mostly open loop systems and they tended to break down often. At the end of the 1980s, car manufacturers started to introduce closed loop systems in cars. The result was far more reliable engines while increasing performance and fuel efficiency.

Another reason to closed loop control systems to 3D printers is the option to extend the current material portfolio. 3D printing processes are very much married to their specifically designed materials because of this. For any new material, it is looking for a needle in the haystack to get the material properties perfectly aligned with the machine capabilities. It takes a considerable effort to make sure the material properties are kept stable during production of that material.

Closed loop control systems will make a significant impact on 3D printing technology in terms of speed, reliability and accuracy.