Abstract
This work evaluates the hole quality on AISI H13 hardened steel using high-speed drilling. Specimens were machined with new and worn out drills with 8.6 mm diameter and (TiAl)N coating. Two levels of cutting speed and three levels of cooling/lubrication systems (flooded, minimum lubrication quantity, and dry) were used. The hole quality is evaluated on surface roughness (Ra) parameter, diameter error, circularity, and cylindricity error. A statistical analysis of the results shows that the cooling/lubrication system significantly affects the hole quality for all measured variables. This analysis indicates that dry machining produces the worst results. Higher cutting speeds not only prove beneficial to diameter error and circularity errors, but also show no significant difference on surface roughness and cylindricity errors. The effects of the interaction between the cooling/lubrication systems, tool wear, and cutting speed indicate that only cylindricity error is influenced. Thus, the conclusion is that the best hole quality is produced with a higher cutting speed using flooded or minimum lubrication quantity independent of drill wear.
Highlights
Nowadays, the molds and dies industries are very important in the supply chain to obtain a new product at low costs
The goal of this work is to evaluate the interaction between cutting speed and tool wear on hole quality and to describe its quality with a statistical methodology obtained by a complete randomized factorial design
The minimum quantity of lubricant is more effective only with the new drill running at 25 m/min because when high cutting speed and worn out drill are applied, the spray generated during the process loses its effectiveness, not cooling the cutting region
Summary
The molds and dies industries are very important in the supply chain to obtain a new product at low costs. Considering industrial competitiveness and short product life, the requirements on production times and lower costs of machining processes are of significant importance. When the production of molds and dies is considered, the machining process corresponds to 65% of the costs and drilling is the most utilized process. Cooling fluids are very important in high-speed cutting where the temperature can approach annealing point. Heat generation and friction between the tool and chip generally limit drilling performance, coolants and lubricants are used in high quantities to reduce the temperature and friction in the cutting region [2]
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