數(shù)控機(jī)床相關(guān)畢業(yè)設(shè)計(jì)翻譯---通過熱量誤差補(bǔ)償來改善數(shù)控機(jī)床的精確度-數(shù)控設(shè)計(jì)-預(yù)覽頁
【正文】 ortion of the spindle housing , the expansion of three axes and the distortion of the column. Due to the dimensional elongation of leadscrew and bending of the column , the thermal errors are not only timevariant in the time span but also spatialvariant over the entire machine working space. In order to measure the thermal errors quickly , a simple protable gauge , i. e. , 1D ball array , is utilized. 1D ball array is a rigid bar with a series of balls fixed on it with equal space. The balls have the same diameter and small sphericity errors. The ball array is used as a reference for thermal error measurement . A lot of preexperiment s show that the thermal errors in zaxis are far larger than those in xaxis and yaxis , therefore major attention is drawn on the thermal errors in zaxis. Thermal errors in the other two axes can be obtained in the same way. The measuring process is shown in . A probe is mounted on the spindle housing and 1D ball array is mounted on the working table. Initially , the coordinates of the balls are measured under cold condition. Then the spindle is run at a testing condition over a period of time to change the machine thermal status. The coordinates of the balls are measured periodically. The thermal drift s of the tool are obtained by subt racting the ball coordinates under the new thermal status f rom the reference coordinates under initial condition. Because it takes only about 1 min to finish one measurement , the thermal drifts of the machine under different z coordinates can be evaluated quickly and easily. According to the rate of change , the thermal errors and the rotation speed are sampled by every 10 min. Since only the drift s of coordinates deviated from the cold condition but not the absolute dimensions of the gauge are concerned , accuracy and precise inst rument such as a laser interferometer is not required. There are only four measurement point s z 1 ,z 2 , z 3 , z 4 to cover the zaxis working range whose coordinates are 50 , 150 , 250 , 350 respectively. Thermal errors at other coordinates can be obtained by an interpolating function. Previous experiment s show that the thermally induced displacement between the spindle housing and the working table is the same with that between the spindle and table. So the thermal errorsΔ z measured reflect those in real cutting condition with negligible error. In order to obtain a thorough impression of the thermal behavior of the machine tool and identify the error model accurately , a measurement strategy is developed. Various loads of the spindle speed are applied. They are divided into three categories as the following : (1) The constant speed 。熱量誤差的獲得是通過 1D滾珠排列和建立在錠子轉(zhuǎn)速基礎(chǔ)上的自動(dòng)退刀的表征。熱量誤差已經(jīng)被作為機(jī)器精確度失衡的最大誘因，而且可能也是機(jī)器獲取更高精確度的最大障礙。在過去的幾年里，對此技術(shù)的研究已經(jīng)獲得重大 成果。但是，目前只有很少被報(bào)道的實(shí)際過程補(bǔ)償案例適用于商業(yè)機(jī)床。 為了改善數(shù)控機(jī)床生產(chǎn)的精確度，有個(gè)方法是值得嘗試的。利用這個(gè)模型，熱量誤差能夠在機(jī)械加工程序制造的時(shí)候被預(yù)測出來。在調(diào)查的線性機(jī)械加工中心中，熱量誤差是由錠子膨脹、錠子固件變形和三個(gè)軸空間的變形一起引起的。由于滾珠的直徑相等，球狀的誤差比較小，因此，滾珠排列被用于熱量誤差測量的一個(gè)參考。測量的過程如圖 1 所示：剛開始，滾珠的坐標(biāo)是處在低溫狀態(tài)的，然后錠子在試驗(yàn)狀態(tài)下改變機(jī)器的熱量。根據(jù)轉(zhuǎn)動(dòng)速率的變化，熱量誤差和轉(zhuǎn)速是每十分鐘就是一個(gè)循環(huán)。在其他的坐標(biāo)中熱量誤差可以通過一個(gè)插值函數(shù)來獲得。錠子轉(zhuǎn)速的多種加載方式是可用的。在這種機(jī)床中，最大的熱源來自于 z軸。在 z1， z2， z3， z4 點(diǎn)上的熱量轉(zhuǎn)移剛開始是一樣的，然后隨著時(shí)間的流逝和溫度的增加而逐漸分離。但是，不同坐標(biāo)中的熱量轉(zhuǎn)移是隨 z坐標(biāo)不斷改變的。熱量誤差是由多種熱源引起的，而只有錠子引起的熱量被認(rèn)為是最重要的熱源影響因素。這樣，就形成了如下的熱量誤差表現(xiàn)模型。 為了能確定模型預(yù)測的精確度，使用了許多新的操作條件。例如，每隔十分鐘， Δz 的熱量誤差就會(huì)被模型計(jì)算一次。一些表面是由低于冷啟動(dòng)和一個(gè)小時(shí)不同轉(zhuǎn)速的旋轉(zhuǎn)磨碎的。研究的核心是一個(gè)以錠子轉(zhuǎn)速為基礎(chǔ)的誤差模型，而不是以溫度為基礎(chǔ)的傳統(tǒng)方法
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