# Operational Temperature Effect on Positioning Accuracy of a Single-Axial Moving Carrier
## 3 Results and Discussions  
### Positioning Accuracies under Different Operational Temperature Conditions  
In our experiments, the moving speed and movement stroke of the single axial carrier are 8.5 mm/s and 400 mm, respectively. An air velocity of 1.18 m/s was employed. The air inlet and outlet were located on the same side of the chamber. During the measurements, one stroke of 400 mm was divided into six individual measuring points. The distance between each point was 80 mm, and the positioning accuracy of the carrier can be obtained by averaging the measured positioning accuracies of the six points. Different environmental temperatures can be created within the designed environmental chamber to investigate the ambient temperature effect on the positioning accuracy of the moving carrier. Figure 5 illustrates the distribution of the temperature rise and drop within the chamber over a period of 150 min, respectively, in which the brown line indicates the temperature distribution in the chamber without an environmental control. In Taiwan, the lowest indoor temperature in wintertime is about 15 \({}^{\circ}\)C, and the highest indoor temperature in summertime is about 33 \({}^{\circ}\)C. Thus, the two temperatures are chosen to be the limit values in the cases of temperature rise and temperature decline. In this case, the initial temperature was maintained at approximately 23 \({}^{\circ}\)C while the carrier was halted. When the time reached 30 min, the carrier started to move, and heat was generated from the driving linear motor and the frictional force between the carrier and the linear guideway. Thus, the temperature inside the chamber gradually increased with time and attained a value of 27 \({}^{\circ}\)C after 60 min. The dotted line indicates the temperature distribution in the case in which the environmental temperature was controlled to approach a value of 23 \({}^{\circ}\)C with a 0.5 \({}^{\circ}\)C variation, while the carrier periodically moved at a speed of 400 mm/s. An ambient temperature setting of 23 \({}^{\circ}\)C was used in a stable ambient operational condition considering the thermal expansion characteristics of the materials. In addition, the average moving speed of the carrier in real applications of machines is about 400 mm/s. To investigate the effect of a rising ambient temperature on the positioning accuracy of the moving carrier, an air conditioning system was applied to create the operational conditions of the rising temperature, as shown by the yellow dotted line in Figure 5. As the time elapsed to 70 min, the operational temperature attained a value of 33 \({}^{\circ}\)C and then was controlled at approximately 32 \({}^{\circ}\)C with a variation of 0.5 \({}^{\circ}\)C. Similarly, an air conditioning system was designed to create a temperature decline in the ambient operational conditions for the moving machine to investigate the effect of an ambient temperature drop on the positioning accuracy of the moving carrier, as shown by the deep green dotted line in Figure 5. The operational temperature declined from 23 to 14.5 \({}^{\circ}\)C in 66 min and then, was controlled at about 15 \({}^{\circ}\)C with a variation of 0.5 \({}^{\circ}\)C.  
Table 1 indicates the corresponding positioning accuracy of the periodically-moving carrier under different operational temperature conditions. As shown in the table, the positioning accuracy of the moving carrier is approximately 18.3 \(\upmu\)m in the case without an ambient temperature control, initially at time = 0 min (without temp. control 0). However, when the carrier started to move, the operational temperature gradually increased with time. At the time of 60 min (without temp.