Precision Lathe Pd 250 E

[Ezilda Newnam]

Thenew generation lathe with system accessories available. Made in Proxxon's Austria factory, PD 250/E allows face, longitudinal and taper turning - thread cutting - toolpost grinding and more. designed for turning steel, brass, aluminium and plastics. Includes mounting flange for the mill/drill head option PF 230.

Machine bed: Cast iron, wide-legged shape, prismatic and rectangular slideways. High damping factor for vibration-free work, even at high loads. Rear mounting flange for the optional PF 230 mill/drill column and head. Covered leadscrew for thread cutting and automatic longitudinal feed.

Headstock: CNC-machined diecast aluminium with main spindle mounted in precision bearings (runout without chuck does not exceed 10 microns). Hollow spindle 10.5mm through permits bar feeding. New 70mm standard hollow chuck 14mm through. Female MK2 (Morse Taper 2) spindle nose. Auto feed selectable 0.05mm or 0.1mm per revolution.

Spindle drive: Quiet DC special motor with triple-range multi-vee belt drive and additional full-wave electronic speed control. Low range 100 to 400/min - mid range 400 to 1000/min - high range 750 to 3000/min. Switchable clockwise/anticlockwise rotation. Main contactor includes high-mount emergency stop with re-start protection (zero volt release).

Chuck: High quality 3-jaw scroll chuck is included, meeting DIN 8386 Class 1 (concentricity tolerance 0.04mm) and covers 2mm thru 75mm gripping diameter range via reversible jaws. Transparent chuck guard is safety interlocked. Optional 4-jaw independent chuck available.

Machining is one of the most important manufacturing processes used worldwide in the mechanical industry, and in order to optimize productivity, cutting fluids can be used in the process. Vegetable based fluids present low toxicity as well as good biodegradability and environmental sustainability; however, they also have low oxidative stability. Esters which are obtained from different vegetable oils, maintain the qualities mentioned and provide the required stability. This study presents a production and characterization of the raw materials, methyl esters and epoxidized methyl esters, as well as mainly the comparative evaluation of the cutting fluid formed by these esters with commercial fluids derived from minerals. The emulsions were evaluated regarding the mechanical properties resulting from their use in the process, registration of the temperature obtained during machining, the rough surface the dimensional deviation of the final product and also the evaluation of surface oxidation occurred on the pieces in the medium term. Emulsions containing 5% of esters (methyl and epoxidized methyl) seemed to be the best option, presenting less oxidation of machined pieces, lower working temperature during the process and better surface completion, demonstrating the best performance over the tested fluids.

Machining is one of the most important manufacturing processes used worldwide in the mechanical industry (Mukherjee and Ray, 2006MUKHERJEE, I., RAY, P. K. A review of optimization techniques in metal cutting processes. Computers & Industrial Engineering, v. 50, n. 1-2, p. 15-34, 2006.). Industrial evolution, technological advances and rising global consumption have contributed towards the expansion of the machining processes, increasingly used, and a part of everyday life.

Based on this, the objective of this paper was to assess the use of methyl esters and epoxidized methyl esters in the formulation of cutting fluids in machining processes, more specifically in turning operations. Thus, utilizing cleaner technology for the production of machined pieces.

For the production and evaluation of the lubricants, the first step consisted in the production and characterization of methyl esters and epoxidized methyl esters utilized in the formulations. The formulations for the lubricating emulsions were assessed.

The transesterification reaction was carried out according to Schneider, Zanon Baldissarelli et al. (2004)SCHNEIDER, R. D. C. D. S., ZANON BALDISSARELLI, V., TROMBETTA, F., MARTINELLI, M., BASTOS CARAMO, E. Optimization of gas chromatographic-mass spectrometric analysis for fatty acids in hydrogenated castor oil obtained by catalytic transfer hydrogenation. Analytica Chimica Acta, v. 505, n. 2, p. 223-226, 2004.. In a 500 mL trial balloon the following were added: 100g of soybean oil and 100 mL methanolic solution of NaOH at 2% previously prepared. The temperature of the mixture was raised to 70C in an oil bath, and remained for 20 minutes under vigorous shaking and reflux, until the solubilization of the soybean oil was achieved. Afterwards, 22 mL of BF3/CH3OH (40%) were slowly added to the reactional medium and then left in reflux for over 10 minutes. After this, 100 mL of heptano were added and left in reflux for an additional 10 minutes. The organic phase was separated and the solvent was removed through rota-evaporation. Part of the methyl ester was utilized for the production of cutting fluids and part was used at the epoxidation reaction.

The equipment was adjusted according to the parameters suggested by the insert manufacturer, with maximum cutting speed of 475 m min-1, cutting depth from 0.23 to 2.7 mm and advance between 0.05 and 0.2 mm rev-1. Initially a cutting depth of ap = 0.5 mm was defined. This value was used with the main objective of preventing the cutting force to achieve very high values, which could cause premature wear to the tool and interfere with the experiment. Furthermore, it made it possible to use the same rotation in two consecutive passes, without any significant change to the cutting speed, adjustment interval f = 0.061 mm and at low depth (Diniz and Jos de Oliveira, 2004DINIZ, A. E., JOS DE OLIVEIRA, A. Optimizing the use of dry cutting in rough turning steel operations. International Journal of Machine Tools and Manufacture, v. 44, n. 10, p. 1061-1067, 2004.).

Two passes were conducted: the first comprised the external diameter of 50 mm, advancing 0.5 mm in the piece to the internal diameter of 49 mm; the median diameter (Md), to be utilized in the formula reached 49.5 mm. The second pass reached a diameter from 49 mm to 48 mm, with a median diameter of 48.5 mm.

For the adjustment of the lathe, an intermediate rotation of 1600 rpm was used. The cutting speed (Cs) during the turning operation was given by team 1(Ferraresi, 1995FERRARESI, D. Fundamentos da usinagem dos metais. So Paulo: Editora Blcher, 1995.).

For each experiment the cutting fluid reservoir was cleaned and dried and the fluid circulation hoses were drained. An ethanol solution at 70% was circulated for the purpose of cleaning. The reservoir was filled with 15.4 L of cutting fluid. The circulation pump was turned on for moving and homogenizing the fluid. The fluid outflow was controlled by a valve adjusted prior to the test, keeping a constant outflow of 450 mL min-1, while a uniform fluid flow was maintained during the experiment.

Three temperature measurements were conducted in each pass of the turning operation, and the highest value was used after starting the operation. Each turning pass was only started after the multimeter displayed the initial temperature of the cold end of the thermocouple, and was ended after stable temperature was achieved.

The dimensional accuracy, determined with a caliper (Absolute, Mitutoyo brand), which was also chosen for checking the efficiency and the cost saving factor at machining (Khan and Dhar, 2006KHAN, M. M. A., DHAR, N. R. Performance evaluation of minimum quantity lubrication by vegetable oil in terms of cutting force, cutting zone temperature, tool wear, job dimension and surface finish in turning AISI-1060 steel. Journal of Zhejiang University SCIENCE A, v. 7, n. 11, p. 1790-1799, 2006.).

It was observed that after transesterification there were 3 vibrational modes of C-O axial deformation in the regions of 1.241 cm-1, 1.195 cm-1 and 1.171 cm-1, typical to long chain fatty acids methyl esters, where the last one presents higher intensity than the others.

It was also observed that there were modes in the region of 3.006 cm-1 (axial deformation of C-H) and 1.649 cm-1 (axial deformation of C=C) which characterize the presence of unsaturation in the structure of the molecule. These unsaturation modes were also observed at the analysis of the starting oil. After epoxidation, the characteristic unsaturation modes (3,006.27 cm-1, axial deformation of C-H, and 1,649.31cm-1, axial deformation of C=C) are not visualized in the epoxidized methyl ester, which confirms the consumption of molecule unsaturation for forming the oxirane ring. The oxirane ring that was formed was evidenced by three characteristic modes. The presence of the mode in the region of 1,268.76 cm-1 which shows the modes of the symmetric axial deformation or oxirane ring pulse frequency, where it became evident that all the connections of the ring expand and contract in phase. The characteristic mode of epoxidized oils, present in the region of 838.95cm-1 was also present on the spectrum, which shows the vibrations of the asymmetric axial deformation of the oxirane ring where connection C-C increases and connection C -O diminishes. The latter, was slightly overlaying the so-called 12 microns close to the region o 820 cm-1.

Through gaseous chromatography, it was possible to confirm that there was the conversion of unsaturates (oleic and linoleic) into epoxidized esters by comparing the mass spectrum with the spectrums of the Wiley online library.

Machining carried out without the use of cutting fluid (dry machining) served as a control to the use of alternative cutting fluids. The reduction of the temperature was considered regarding dry machining (Table 2). According to Trent and Wright (2000)TRENT, E., WRIGHT, P. Metal Cutting. Butterworth-Heinemann, 2000. 464p., the energy consumed at machining was converted, for the most part, in heat, close to the tool-chip interface. This temperature (and its measure) characterized the machining process. The reduction detected between dry machining and machining with cutting fluids was in accordance with what was expected, emphasizing the importance of the fluid for reducing the temperature.

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