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Estudo comparativo de grafites para ferramentas de EDM para produção de cavidades moldantes
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| 5.5 MB | Adobe PDF |
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Abstract(s)
O presente trabalho estuda o comportamento do processo de maquinagem por eletroerosão (EDM), analisando diversos índices de performance no uso de ferramentas de grafite de três granulometrias diferentes. Os índices de performance que são alvo de estudo são a Taxa de Remoção de Material (MRR – para a 1ªEletroerosão, 2ªEletroerosão e Global), Rugosidade Superficial (SR – Rugosidade Ra e Rz, e Classificação SR), Desvio Dimensional (DD – Planeza, Classificação Planeza, Dimensão e Centro Geométrico), Custo Total do Processo (CPtot), Custo Específico do Processo (CEP) e o Índice de Performance Global (IPG). Este estudo é de elevado interesse para a indústria dos moldes, que recorre ao uso da tecnologia de EDM para maquinar (erodir no caso da tecnologia de EDM) cavidades moldantes em aço de elevada dureza.
O processo de EDM comporta também a erosão da própria ferramenta (elétrodo), sendo necessário o uso de múltiplos elétrodos para o sucesso da operação. Este estudo tenta aferir a possibilidade de, para atingir a geometria pretendida com a melhor qualidade superficial possível e de forma economicamente mais viável, usar um menor número de elétrodos, usando para isso uma grafite de menor granulometria. De igual modo, é analisado o comportamento global do processo de eletroerosão no uso de grafites de diferentes granulometrias.
Neste estudo são utilizados 3 tipos de grafites, de granulometrias diferentes, com tamanho médio de partículas de 8 (grafite de referência), 5 e 4 μm respetivamente. Duas geometrias foram projetadas neste estudo, o Rib e a Caixa (CX), geometrias habituais na indústria dos moldes, sendo o Rib normalmente usado como reforço estrutural e a CX para montagem de postiços de moldação. Ambas as geometrias foram erodidas em três profundidades distintas, 3, 6 e 12 mm, usando as três grafites em estudo.
The present work studies the behaviour of the Electrical Discharge Machining (EDM) process, analysing several performance indices in the use of graphite tools of three different grain sizes. The performance indices that are the target of study are the Material Removal Rate (MRR – for 1st EDM, 2nd EDM and Global), Surface Roughness (SR – Roughness Ra and Rz, and SR Rating), Dimensional Deviation (DD – Flatness, Flatness Rating, Dimension and Geometric Centre), Total Process Cost (CPtot), Process Specific Cost (CEP) and the Global Performance Index (IPG). This study is of great interest to the mold industry, which uses EDM technology to machine (erode in the case of EDM technology) moulding cavities in high hardness steel. The EDM process also involves the erosion of the tool itself (electrode), requiring the use of multiple electrodes for the success of the operation. This study tries to assess the possibility of using a smaller number of electrodes to achieve the intended geometry with the best possible surface quality and in a more economically viable way, using a graphite with a smaller particle size. Likewise, the global behaviour of the EDM process in the use of graphites of different grain sizes is analysed. In this study, 3 types of graphites are used, of different particle sizes, with an average particle size of 8 (reference graphite), 5 and 4 μm respectively. Two geometries were designed in this study, the Rib and the Box (CX), common geometries in the mold industry, with the Rib usually used as structural reinforcement and the CX for the assembly of moulding inserts. Both geometries were eroded at three distinct depths, 3, 6 and 12 mm, using the three graphites under study.
The present work studies the behaviour of the Electrical Discharge Machining (EDM) process, analysing several performance indices in the use of graphite tools of three different grain sizes. The performance indices that are the target of study are the Material Removal Rate (MRR – for 1st EDM, 2nd EDM and Global), Surface Roughness (SR – Roughness Ra and Rz, and SR Rating), Dimensional Deviation (DD – Flatness, Flatness Rating, Dimension and Geometric Centre), Total Process Cost (CPtot), Process Specific Cost (CEP) and the Global Performance Index (IPG). This study is of great interest to the mold industry, which uses EDM technology to machine (erode in the case of EDM technology) moulding cavities in high hardness steel. The EDM process also involves the erosion of the tool itself (electrode), requiring the use of multiple electrodes for the success of the operation. This study tries to assess the possibility of using a smaller number of electrodes to achieve the intended geometry with the best possible surface quality and in a more economically viable way, using a graphite with a smaller particle size. Likewise, the global behaviour of the EDM process in the use of graphites of different grain sizes is analysed. In this study, 3 types of graphites are used, of different particle sizes, with an average particle size of 8 (reference graphite), 5 and 4 μm respectively. Two geometries were designed in this study, the Rib and the Box (CX), common geometries in the mold industry, with the Rib usually used as structural reinforcement and the CX for the assembly of moulding inserts. Both geometries were eroded at three distinct depths, 3, 6 and 12 mm, using the three graphites under study.
Description
Keywords
Eletroerosão (EDM) Grafite Granulometria Taxa de remoção de material Rugosidade superficial Desvio dimensional
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CC License
Without CC licence