Interference detection and optimal tool selection in 3- axis NC machining of free-form surfaces

D.C.H. Yang*, Z. Han

CAD/CAM Laboratory, Department of Mechanical and Aerospace Engineering, University of California, Los Angeles,

Introduction:

Step 2

Step 1

Step 3

New tool-path generation scheme

Step 2

Step 1

Step 3

Step 4

Tool interference types :

1.Global interference

2.Local interference

Global interference checking

Protrusion Interference( PI)

Overlapping Interference )OI(

Boundary Collision Interference( BCI)

Phase I: protrusion interference checking

Step 1. Sorting critical iso-inclination curves

iso-phote

P)u,v(

n)u,v(

V = )0, 0, 1(,

Global interference checking

critical iso-inclination curve

Step 2. Identifying the visible part of the critical iso-inclination curve

Global interference checking

Step 3. Determining the PI boundary

Phase I: protrusion interference checking

Global interference checking

Phase I: protrusion interference checking

Phase II: overlapping interference checking

Global interference checking

Phase III: boundary collision interference checking

Global interference checking

Local interference checking

total interference area )TIA(

original interference area )OIA(

Phase I: original interference area determination

Local interference checking

maximum and minimum normal curvatures k1,2,H represents the mean curvature;

K, Gaussian curvature

Local interference checking

Phase I: original interference area determination

Phase II: total interference area determination

Local interference checking

Optimal tool selection

number of tool change is Ntc ,time required for each tool change is tc,

radii of cutters are Ri )i . 1,…,Ntc(. ,corresponding machining times are ti,length of tool path is Li

feed-rate is fiarea of machining Ai,cutter radius Ri ,scallop height h ,

size of path interval gi,Sio and Sii be the lengths of the outer and inner boundaries of Ai,

Optimization procedure

B-Spline surface with 6 x11 control points, mold surfaces of an automobile panel.

conclusions