机械机床外文翻译---利用三坐标测量仪确定聚苯乙烯材料表面形态(编辑修改稿)

机械机床外文翻译---利用三坐标测量仪确定聚苯乙烯材料表面形态(编辑修改稿)内容摘要：

from warm to cold areas at a rate proportional to the temperature gradient and the thermal conductivity of the wire it is owing through. A thermocouple is connected to the hot wire to give a reading of the wire temperature. Manipulating the current and voltage of the wire can control the temperature. The temperatures considered in this experiment are 100, 200 and 300 8C The objective of this experiment is to reveal the surface form of polystyrene through the use of a CMM with different types of wires, temperatures and cutting feedrates. The surface form is affected by the federate and temperature of the hotwire cutter. The test material was polystyrene with width of 300mm, length of 300mm and thickness of 50mm. These sizes were selected because they can be easily handled when performing the test. The wires used as the cutting tool were nickel–chromium alloy (Nichrome), Inconel and nickel–chromium–iron (NiCrC) spring wire [5]. The reasons for selecting Inconel and NiCrC spring wires are due to their ability to maintain their shape after being applied to the operating cutting temperatures [6, 7]. Nichrome wire was chosen as it is the most monly used wire for cutting polystyrene polystyrene was cut using different types of wires at different temperatures and feedrates. The feedrate ranged from 100 to 500mm/min. After each cut, the surface of the polystyrene was measured using the CMM with 20 touch points. A test was done prior to this experiment on the number of touch points. Touch points from 10 to 200 touches were investigated using the CMM. The higher the number of touches, the longer the time required in order to perform the test. Results show that the surface form from 20 and 200 touches were very similar. Therefore, in this experiment 20 touch points were chosen. 6 RESULTS The surface form of the polystyrene was calculated and recorded directly from the CMM. Using different types of wires, temperatures and cutting feedrates, the polystyrenes were cut into small pieces of 10mm thickness. Then, the CMM ran the 20 touch points D AITCHISON AND R SULAIMA842 N test on the cut pieces of polystyrene. Figure 3 shows that a Nichrome wire at a temperature of 100℃ and a feedrate of 100mm/min produces a surface form of units. The best surface form should be the one nearest to 3 also shows that the most suitable cutting temperature and feedrate for Nichrome wire were 200℃ and 200mm/min respectively. Cutting can only be done up to a feedrate of 300mm/min. At a feedrate higher than this, the wire tends to slip and bend. This affects Fig. 3 Surface form against feedrate for Nichrome wire of diameter Fig. 4 Surface form against feedrate at a temperature of 100℃ the cutting quality and, hence, the surface form of the polystyrene. Figure 4 illustrates the parison of all three types of wire used in this experiment at a cutting temperature of 100 8C. The best surface form was made by Inconel wire at a temperature of 100 8C and a feedrate of 200mm/min. The surface form was units. Notice also that Inconel was able to perform the cutting at feedrates up to 500mm/min. However, at this cutting speed the surface form was poor. Figure 5 shows the cutting performance of all three wires at a temperature of 200 8C. At this temperature, two wires were able to cut up to a feedrate of 500mm/min, namely Inconel and NiCrC spring wires. The best surface form was made from Inconel at a feedrate of 300mm/min. However, NiCrC produces a consistent surface form of below unit at different feedrates. 7 DISCUSSION As mentioned earlier, the reason for selecting Inconel and NiCrC spring wires was due to their ability to maintain their shape after being applied at temperatures of 100, 200 and 300 8C. Nichrome wire was chosen as it is the most monly used wire for cutting polystyrene materials. Maintaining their shape was a main concern because a bent wire will affect the quality of the cut polystyrene. Figure 6 shows the parison of the three types of wire selected in this experiment against their spring rate. Assuming that the wires are shaped into a loop, similar to a spring, the spring rate was calculated as Gd4 R= —— —— 8nd3 where R =spring rate G = shear modulus d =wire diameter n =number of coils D =mean coil diameter Its unit is force per unit of deflection (or force per millimetre). The spring rate actuall。