磁力輔助研磨拋光為一種藉由施加磁場改變磁性磨料特性以達增強加工效果的技術。本研究針對現有相關技術尚未開發的潛能，建構一通用之實驗平台並研擬其操作手法，來開發及驗證一新方法技術。此平台可針對不同條件設定對加工效果的影響進行試驗，並評估將其應用於通用加工機具之可行性。

此機台由刀具本體、線性運動平台、以及磨漿供應泵所組成。為了簡化設計縮減體積重量，採用無須供電及冷卻、單位體積可提供更高場強的永久磁鐵為磁場來源。刀具本體為低碳鋼所構成的磁迴路結構，將其內一對磁極反向置放的磁鐵產生之磁通導引至刀尖，並在該處形成水平橫越模式之磁場，而其場強可由一內置之滑塊連續調整。相較一般垂直穿透模式設計，水平橫越模式可在刀尖產生較高場強、工件厚度不受限制、毋須鐵磁性材質夾治具為輔助磁極。運動平台承載試片使其位於刀尖下方，可依需求設定速度、行程，並以升降來調整刀尖與試片之間距。磨漿供應泵以注射筒為本體，可裝填任意種類的磨漿，少量調配即可使用，並提供足夠之高壓以克服磨漿受刀尖高場強作用而劇增的流阻。磁性磨漿以商用磁流變液混入#1000號綠色碳化矽磨粒並添加調整流動性的矽油調配而成，依設定之供給量將其推送至加工區而達成連續供應。

磨漿由供料泵推送擠出刀尖出料口時，將受該處高場強作用而形成半固態之磁刷，平台往復運動時磁刷將刮擦試片而達成研磨加工作用。經驗證可將初始表面粗糙度Ra~0.5 µm之鋁合金試片加工至Ra~0.06 µm，隨磁場強度增加材料的移除效率將隨之增加，加工後之表面亦略為細緻。而初始形成之磁刷在經約200~300趟的往復運動後將硬化而使加工效能大為提升，使原本需時5~6min之加工縮短至2~3 min。此磁刷固化的程度可以蕭氏硬度計配合特製治具來評估，其硬化前固化程度與場強呈正相關，而硬化後則無明顯相關。

本研究所開發之機具及方法，經以上驗證具備應用於一般加工機具之可行性。而後續可望以全新之概念來設計刀具以充分開發此磁刷硬化現象之潛能，而達突破現有技術之性能表現。

Magnetic assisting finishing is a machining process that the effect can be enhanced by applying a magnetic field to change the property of magnetic abrasives. This study aimed at the untapped potential of the present technology of magnetic abrasive finishing, where a novel technology and methodology was developed and verified by means of an innovative experimental platform for general purpose and the subsequent operating methods. The experiments for evaluating the processing effects influenced by different conditions therefore could be conducted by the platform developed. The feasibility of its application on general purpose tools was also evaluated.

The platform is composed of a tool as the main part, a linear moving table, and a slurry supplying pump. For design simplification as well as for volume and weight reduction purpose, permanent magnets are adopted as the magnetic field source for it providing higher magnetic field strength per unit volume and requiring no power supply and cooling system.

The tool per se is a magnetic circuit structure made of low carbon steel, in which the magnetic flux generated by a pair of reversely placed magnets is directed to the tool tip, where a the magnetic field of horizontal transverse mode is formed and its strength can be adjusted continuously by a movable slider acting as a mechanical magnetic switch. Comparing with the normal vertical through mode, the horizontal traverse mode allows for a higher magnetic field strength, unrestricted workpiece thickness, and requires no ferromagnetic fixtures as an auxiliary magnetic pole.

The moving table carriering a specimen is located under the tool tip and provides a linear motion relative to the tool. The speed, displacement and grinding times can be set according to the experiment requirement, and the clearance between the tool tip and specimen, an important machining parameter, can be adjusted by lifting the table.

The slurry supplying pump consists of a syringe where any type of slurry with small amount can be loaded after blending, as well as provides sufficient high pressure to overcome the dramatically increasing flow resistance of magnetized slurry caused by the high magnetic field strength near the tool tip.

The magnetic abrasive slurry is composed of commercial magnetorheological fluid, the green silicon carbide #1000 as abrasive particles, and silicon oil as the diluent for adjusting the flow property. The slurry then is pushed to the working zone between the tool tip and workpiece continuously according to the set quantity.

A semi-solid magnetic brush forms when the magnetic slurry is propelled by the supplying pump to the tool tip and magnetized there. When the table moves relative to the tool the magnetic brush scrubs a specimen on it to carry out a grinding process. It was verified that a aluminum alloy specimen with initial surface roughness of Ra~0.5 µm can turn to be Ra~0.06 µm after the process. The material removal efficiency could be increased, and the surface would be slightly finer with the increase of magnetic field strength. It was observed that the processing efficiency improves greatly as the magnetic brush gets hardened gradually during the 200-300 times of reciprocating motions. Consequently, a process that originally took 5~6 minutes can be finished in 2~3 minutes. The degree of hardening of the magnetic brush can be evaluated by a Shore durometer coupled with a special made fixture. The experiments verified that the degree of hardening at initial stage is positively correlated with the magnetic field strength, whereas no obvious correlation after saturation.

In this study it has been verified that the facilities and methodologies developed are feasible and applicable on general purpose machining tool. Its capability for fully exploiting the potential of the magnetic brush hardening phenomenon would enable innovative concepts for tools design, and possible breakthroughs in performance current technologies could achieve therfore could be expected.

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