Rockwell-automation 8520-GUM 9/Series CNC Grinder Operation and Progra Instrukcja Użytkownika Pobierz pdf (Strona 629)

100

101

Turning Operations

Chapter 18

18-13

Axis feedrates - When threading, the speed of the grinding axis is

determined by the spindle speed and the thread lead through the

following equation:

axis feedrate = (S) / (F threads per inch)

= (S) / (E threads per inch)

= (S)(E inches per thread)

Where: Is :

S theactual speedofthe spindle(programmedspindle speed timesthespindle

speedoverride switch settinginpercent).

F threadsper inch ormillimeter depending on thecurrentactive mode

E threadsper inch orinchesper revolutionas determinedin AMPbyyour

system installer.

The programmer should use this equation to verify that the feedrate

resulting from the thread parameters does not exceed the maximum

allowable feedrate for the grinding axis. Otherwise an error results and

axis motion is stopped. This equation can also be applied to face

threads and tapered threads.

Pullout angles - During threading passes, the control synchronizes the

moves and speeds of the X, Z, and spindle axes. This occasionally

forces the X-axis to move quite rapidly in order to produce the desired

thread taper or pullout angles at the rates dictated by the active spindle

speed. Compounded with the fact that many machines have X-axis

feedrate limits lower than those for the Z-axis, velocity limitations can

result. This is best prevented by first executing a Feed Check prior to

actually grinding the threads and then reducing spindle speed or

changing the pullout angle where necessary.

Tapered Thread Lead - When grinding a tapered thread, the thread

lead (E or F word) is applied to the axis that travels the greatest distance

from the start to the end of the threading pass.

Infeed - Plunge infeed relies on a grinding wheel dressed at the exact

thread angle so that two sides of the grinding wheel are grinding as it is

fed perpendicular to the work on successive passes. On larger threads,

this type of infeed can cause vibration. In that case, angular infeed can

be preferred. This results in the grinding wheel being fed along the

thread flank with each successive pass, meaning only one side of the

grinding wheel grinds. Figure 18. 11 illustrates plunge and angular

infeed.

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