w y(q)=Lc=h+L2sinq=(L1+L2)sinq+2(cosq—1)

2。4。 Determination of the stroke of the input   link

w L1sinq+2(cosq1)tanq2

(7)

It is important to establish the relationship between the stroke of the input link, which is the linear output from the motor control, and the tool inclination angle so that the magnitude of the stroke can be determined for a required tool inclination angle。 According to Fig。 4, the equation for the stroke can be expressed as   follows:

Ls=x1+x2=r+tanq =2sinq+L1(1—cosq)+(

)(L sinq 2(cosq—1))=(tanq

2tanq2

If we let atanq — 2  and b2tanq —L1, Eq。 (8) can be further simplified  as,

2 2

Fig。 4。   Formulation of the stroke Ls from the motor output in terms of the inclination angle。

Fig。 5。   Photo of the actual prototype of the new CNC tooling mechanism。

Ls=]a2+b2sin(q+tan1b)—b (9)

a2+b2)—tan

1   。

a

3。 Performance of the new CNC tooling prototype   developed

Fig。 5 shows the photo of the actual prototype of the new tooling mechanism for CNC lathes。

There are seven major mechanical units that construct the prototype, described as follows。

1。 Input link:

It consists of Curved Slots 1 and 2 and is also used to clamp the toolholder in place。

2。 Cover plate:

It contains Curved Slot 3 and is also used to clamp the input link in place。

3。 Motor mounting plate:

It is used to mount the linear stepper motor that is used to drive the input link。

4。 Two shafts:

They are used to support the holes at points A and B and hold the three slots in place。

5。 A standard tool holder with a standard tool   insert:

The toolholder will rotate within the space limit inside the tool shank。

6。 A standard tool  shank:

The tool shank is a standard attachment of CNC machines and designed to hold the toolholder on the CNC turret。 In this work, the tool shank is also used to hold the whole new CNC tooling mechanism。From~优Y尔R论^文W网wWw.YoUeRw.com 加QQ7520.18766

7。 A stepping motor with linear  output:

The linear output will drive the input link to produce the required stroke corresponding to a tool inclination angle。 The three movements, i。e。 linkages 1–3 as shown in Fig。 1, will move simultaneously according to the linear stroke which is controlled by the stepping motor。

Fig。 6 shows the computer simulated positions of the new tooling mechanism at three different tool inclination angles。  Fig。 7 gives  another computer simulation showing  that the tooltip  stays at the same point, that is, its working point, when the tool inclination angle changes。

The new CNC tooling mechanism can be used to study patterns of cutting forces with   continu-

Fig。 6。   Simulation of the positions of the new CNC tooling mechanism at three different inclination angles。

Fig。 7。    Simulation of the tooltip locations at three different inclination   angles。

ous change of the tool inclination angle, as shown in Fig。 8 for a typical set of results from experimentation where the cutting forces decrease as the tool inclination angle increases。  Two case studies using six different tool chip-breakers at the different cutting conditions also confirmed that increasing tool inclination angle decreases the cutting forces, as shown in Fig。 9。 The experi- mental outcomes with different tool chip-breakers also indicate that a controllable tool inclination angle, combined with varying chip-breaker designations, may contribute to on-line optimization of tool geometry in achieving best chip control with reduced cutting forces。 Thus, it can be seen clearly that the tool inclination angle has a significant effect on cutting forces, thus an on-line controllable tool inclination angle may play an important role in real-time optimization of machin- ing performance in automated machining systems or in CNC machines equipped with open archi- tecture controllers。