重庆大学 机自实验班 计算机辅助设计与制造习题

1、ME3261/ME3261E NATIONAL UNIVERSITY OF SINGAPOREME3261/ME3261E COMPUTER-AIDED DESIGN AND MANUFACTURING(Semester I : AY2010/2011Time Allowed : 2 HoursINSTRUCTIONS TO CANDIDATES:1. This examination paper contains FOUR (4 questions and comprises SIX (6 printedpages.2. Answer ALL FOUR (4 questions.3.All

2、questions carry equal marks.4.This is an OPEN-BOOK EXAMINATION.5.Programmable calculators are NOT allowed for this examination.QUESTION 1For the cast part shown in Figure 1, write a NC program to conduct the following machining operations:(aProfile mill (i.e. mill the contour or the profile of the t

3、runcated circular island ofradius 20mm in two passes: one rough pass (leaving 0.4mm of material followed by a finish pass (to remove the remaining 0.4mm of material using offsets stored in D01 and D02 respectively. The maximum allowable Z-direction depth of cut at each pass is 10 mm.(14 marks(bDrill

4、 a through hole of diameter 8mm at the center of the truncated circular island.(5 marks(cDrill the five holes of diameter 10mm and depth 6mm located below the truncatedcircular island.(6 marksThe origin of the work reference (using G55 is at the center of the circular island, as shown in Figure 1. T

5、o avoid any potential clashing with the fixtures, approach the circular island from the right of the work piece and start profile milling close to Point A indicated in Figure 1. Z=0 plane is set to the top surface of the island. Use the tools and machining conditions given in Table 1 below. Assume t

6、hat T01 is already in the spindle at the beginning of the program. Use subprogram whenever it is deemed suitable.Table 1. Tool details and their corresponding machining conditions Figure 1QUESTION 2For the following chess part shown in Figure 2, write a NC program to machine it. The program origin (

7、G50 is set to the farthest right side as indicated in Figure 2. The part is basically symmetric to the central line. You can assume that the tool nose radius is equal to zero and you can program a finish cut for the machining. Due to the machine constraint, you should always prepare your NC code und

8、er diameter mode. Use the tool and machining condition given in Table 2 below. Assume that T01 is not the current tool and the turning cut is finished when the tool reaches Point C.(20 marks Since the surface speed remains constant, calculate the rpm for Point A and B and comment on their difference

9、.(5 marksTable 2. Tool detail and its corresponding machining condition Figure 2QUESTION 3(a A cubic Bezier curve segment has the following control points: V0(0, 0, 0, V1(1, 2,1, V2(3, 2, 3, V3(1, 4, 1. The cubic Ferguson model of this curve segment has thefollowing end conditions: P0, P1, t0, t1. O

10、btain the angle between t0 and t1.(6 marks(b A composite curve is formed by 3 curve segments. The first one is a line segmentfrom A(0, 0, 0 to B(2, 2, 2. The third one is also a line segment from C to D(6, 6, 6.The composite curve is C0 and C1 continuous at B and C. If a quadratic Bezier curve segme

11、nt is used as the second segment, obtain its control points.(6 marks(c When the cubic B-spline curve model is used to fit (n+1 data points, P i, i = 0, 1, ,n, into a composite curve with C2-condition, a total number of (n+3 control points, V j, j = 0, 1, , n+2, are obtained. It is observed that when

12、 V11 and V12 are changed, only 4 curve segments are affected. Determine n and list all the affected segments using their end points.(7 marks(d A bi-cubic Bezier surface patch has a 4×4 array of control points V ij with i = 0, 1, 2,3 and j = 0, 1, 2, 3. It has4 boundary curve segments. Obtain th

13、e Ferguson model ofthe boundary curve segment along V00, V10, V20, and V30.(6 marksPAGE 6 ME3261/ME3261E QUESTION 4 (a A plane is defined by x + 2y + 2z - 9 = 0. A quadratic Bezier curve segment has 3 control points V0(x, y, 2, V1(1.5, 2, 3, and V2. It is known that the tangent vector of the Bezier

14、curve segment at V0 is perpendicular to the plane. Obtain the distance from V0 to the plane. (7 marks (b Refer to the half-circle shown in Figure 3. Obtain the parametric equations of the following planar patches by the ruled surface construction method: (i (ii The hatched portion on the left side of the half-circle. The triangular portion (ABC. (8 marks y A (5, 7, 0 Figure 3 B(2, 4, 0 (5, 4, 0 C(8, 4, 0 x Figure 3