Question

Suppose that surface finish is very important for the profile milling job described in Problem 4. Thus down milling is going to be used. Rewrite the NC program points to accommodate this requirement. Show the new path on a sketch such as Figure 40-B. (Up versus down milling is discussed in Chapter 24.) | Pt. 4 Pt. 3 I y-axisI Pt.5 Origin Pt. 2 l Pt. 1 End milling cutter 1" diameter X-axis FIGURE 40-B

Answer 1

The tool is to be kept at an offset of half inch from the surface to be machined so as to account for the cutter diameter.

We have been provided wwit an origin point, takes its coordinates as (x=0, y=0).

From figure it is clear that at point one the cutter is directly below the origin and moves along the x axis to reach point 2. Thus for starting point 1 x=0. Also to keep distance of half an inch y=-1/2.

Assuming the object to be milled has length l and breadth b

We can program the remaining points as

1. (0,-0.5)

2. (L+0.5, -0.5). Since from 1 to 2 tool moves in x direction, y remains constant.

3. (L+0.5, B+0.5). From 2 to 3 tool moves in y direction. Also we move 0.5 inch above B to account for clearance distance mentioned before.

4. (-0.5, B+0.5)

5. (-0.5,-0.5)