# High-Precision Roller Supported by Active Magnetic Bearings
## 6 Conclusions  
In this study, the automatic alignment of the precision roller for printing was implemented using the ability of magnetic bearings to move the position of the roller within the air-gap range. A precision roller for printing capable of \(\pm\)0.2 mm movement and magnetic bearings were designed and fabricated. When the precision roller contacted the alignment reference surface, the contact forces at both ends of the roller could be measured using load cells. An automatic alignment produce was developed by using the forces measured by the load cells as feedback. The improved alignment was implemented by applying two-step displacements, and the difference in the contact forces between each end was within 0.3 N. Vibrations of less than approximately 2 \(\upmu\)m peak-to-peak was confirmed under the no-load condition and of less than approximately 5 \(\upmu\)m peak-to-peak was observed under a rotation speed of 30 rev/min and a load of 300 N. This vibration is very small compared to the vibration of 10-100 \(\upmu\)m peak-to-peak of conventional printing rollers supported by ball bearings [13].  
The proposed system is the first magnetic bearing system designed to produce a controllable lateral load onto an external object, making it superior in terms of energy, time and quality to existing systems. If the proposed magnetic bearing roller system is used, it is expected that the disassembly-assembly process for the realignment of the assembled roller will not be necessary. In addition, the proposed system will also provide significant benefits in terms of the cost and volume because additional  
Figure 17: (**a**) Experimental setup and test results of force distribution (**b**) before and (**c**), (**d**) after roller alignment.  
actuators required for uniform printing force control on both ends of the roller will not be necessary. The lower friction of the bearings will also make the system more energy efficient and prevent printing failures, which makes the system greener. In the future, the vibration performance of the roller will be further improved by applying additional control algorithms against loads and disturbances that may occur in printing equipment, such as printed electronics equipment. In addition, improved control algorithms will be used to automate the fine adjustments near the setpoint.  
The following are available online at [[http://www.mdpi.com/2076-3417/9/20/4389/s1](http://www.mdpi.com/2076-3417/9/20/4389/s1)]([http://www.mdpi.com/2076-3417/9/20/4389/s1](http://www.mdpi.com/2076-3417/9/20/4389/s1)), Video S1: Vibration Performance of Roller under Radial Loads.wmv.  
Conceptualization, C.H.P.; methodology, D.K.; software, C.H.P. and T.G.Y.; validation, D.K.; writing--original draft preparation, C.H.P., T.G.Y., and H.R.; writing--review and editing, C.H.P. and H.R.; supervision, C.H.P.; and funding acquisition, C.H.P.  
This research was funded by the R&D Program (No. R0005638) of the Ministry of Trade, Industry & Energy (MOTIE), Korea Institute for Advancement of Technology (KIAT) through the Encouragement Program for The Industries of Economic Cooperation Region.  
The authors declare no conflict of interest.