Issue 22

D. Gentile et alii, Frattura ed Integrità Strutturale, 22 (2012) 85-92; DOI: 10.3221/IGF-ESIS.22.09 88 COMPONENT UNIT. COST ( €) TOTAL NUMBER TOTAL AMOUNT (€, NO TAX) TOTAL AMOUNT (€, 21% VAT) carriage 4 linear recirculating ball bearing units 31.56 20 631.20 763.75 Linear guidance systems with recirculating ball bearing units 24.48 10 244.80 296.21 self-lubricating kit 27.91 20 558.24 675.47 cover 15 0.16 50 8.00 9.68 ring nut 14.69 10 146.88 177.72 belt 340 4.80 1 4.80 5.81 belt 525 5.70 1 5.70 6.90 belt 400 5.10 4 20.40 24.68 pulley 30 3.90 10 39,00 47.19 timing-belt pulley 4.80 2 9.60 11.62 bearing 3.30 2 6.60 7.99 choke ring 1.50 20 30.00 36.30 bearing 3203 17.79 20 355.80 430.52 bearing 22206 39.81 20 796.20 963.40 choke ring A25 1.20 5 6.00 7.26 encoder+fan 1050.00 1 1050.00 1270.50 LSMV 80 222.30 1 222.30 268.98 sub-total 4135.52 5003.98 MIN (€) MAX (€) MIN + tax (€) MAX + tax (€) machinery 10000.00 € 10000.00 € 12000.00 € 12100.00 software 3000.00 € 5000.00 € 3600.00 € 6050.00 € 15600.00 € 18876.00 total amount € 20603.98 € 23879.98 Table 2 : Example of the work sheet implemented for cost analysis. This procedure allowed to have a clear process of realization: clear components, clear machinery work, clear costs, clear assembling and verification. Components that were not possible or convenient to have commercially, have been designed and realized very accurately in order to ensure constant bending at high fatigue cycles. One of these parts is the spindle body with the related shafts and supports. Part of spindle is reported on Fig. 3. Also shafts have been realized in house. Following classical mechanical formulae in order to verify strength and stiffness the shaft reported in Fig. 4 has been defined. Other fundamental components are the bearings. Among the solutions available bearings by SKF have been used. From SKF catalogue have been selected the following: spherical roller bearings SKF 22206 E (CCW33), angular contact ball bearings, double row SKF 3203 ATN9 in order to support spindle’s shaft, and deep groove ball bearings, single row SKF 6004-2 RSH as support of connectors between engine and pulleys. In order to have a very useful machine in different conditions, as for example fatigue tests at high temperature, a system with a single engine has been preferred to realize, five different load cells have been used, one for each sample. This allowed to realize a modular machine able to work for one or “n” samples depending of the mounted spindles. Concerning the fatigue tests a different temperatures, this machine is able to test each specimen at different temperature in a single test.