Accuracy estimation in drilling small holes on engineering plastics by a mathematical approach

Abstract

Engineering plastics have wide applications in different fields of industry due to their light weight and easy shaping. In manufacturing multi-component products, assembly is an inevitable stage and drilling is one of the necessary processes before joining of the components of these products. In this study, two of the most common types of engineering plastics, polyacetal (POM) and cast polyamide (castamide), were drilled with twist drills of 0.5 mm and 1 mm diameters, under different cutting speeds and feeds. In determining the accuracy of the drilled small holes, a mathematical approach was used in which least square circle method was applied and radial error of the each drilled hole was obtained. Thus, the hole accuracy could be determined without measuring equipment such as coordinate measurement machine. It has been seen that POM gave better hole accuracy than cast polyamide due its thermal and tribological properties. The effects of feed and cutting speed on the radial error were also investigated. POM did not show apparent difference in radial error according to the cutting parameters while cast polyamide showed lower radial error in higher feeds with 0.5 mm of drill tool and lower radial error with 1 mm of drill tool. Additionally, the radial error could be reduced with decrease of spindle speed at higher feed.

Cutting force, Vibration, and Temperature in Drilling on a Thermoplastic Material of PEEK

“…Engineering plastics have wide applications in industries as substitutions for traditional metallic materials due to their light weight, moderate strength, easy shaping, and environmental resistance. 1,2 In many cases, engineering plastics are used in making various machine parts because their superior specific strength compared with carbon steels. 3 High-performance engineering plastics commonly used include the crystal ones of polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyimide (PI), polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polyacetal (POM), polyarylate (PAR) and the non-crystal of polyethersulfone (PSF), polyethersulfone (PES), polyetherimide (PEI), polyamide-imide (PAI).…”

“…In addition to the better mechanical and/or thermal properties, their prices are competitive, very suitable for structural parts in different fields such as automobile, medical appliances, electronics, aerospace, construction machinery, and biomechanical applications. 1,4…”

“…Especially, the viscoelastic behavior of the plastics makes it difficult to realize the correlations between the cutting conditions and the materials. 1,6 Thermoset polymers generally have brittle behavior and are very sensitive to water, while thermoplastic polymers are generally ductile. 7 The heat cannot be quickly conducted to the cutting tool due to their low thermal conductivity, which results in localized heating at the machined surface.…”

“…In addition to the better mechanical and/or thermal properties, their prices are competitive, very suitable for structural parts in different fields such as automobile, medical appliances, electronics, aerospace, construction machinery, and biomechanical applications. 1,4 Machinability is usually defined by the surface finish and integrity of the machined part, tool life, force and power required, and chip control. 5 However, the machinability of plastics depends on its mechanical, thermal, and rheological properties.…”