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M138 Spindle Speed Variation On / M139 Spindle Speed Variat...

M138 / M139 Spindle Speed Variation On/Off

Spindle Speed Variation (SSV) lets you specify a range within which the spindle speed continuously varies. This is helpful in suppressing tool chatter, which can lead to an undesirable part finish and/or damage to the cutting tool. The control varies the spindle speed based on Settings 165 and 166. For example, to vary spindle speed +/- 100 RPM from its current commanded speed with a duty cycle of 1 seconds, set Setting 165 to 100 and Setting 166 to 1. The variation you use depends on the material, tooling, and the characteristics of you application, but 100 RPM over 1 second is a good starting point.You can override the values of settings 165 and 166 using P and E address codes when used with M138. Where P is SSV Variation (RPM) and E is the SSV Cycle (Sec). See example below:
M138 P500 E1.5 (Turn SSV On, vary the speed by 500 RPM, cycle every 1.5 seconds);
M138 P500(Turn SSV on, vary the speed by 500, cycle based on setting 166);
M138 E1.5 (Turn SSV on, vary the speed by setting 165, cycle every 1.5 seconds);

NOTE: If you have an M138 Enn on one line and a G187 Enn on another line, the E codes would be unique to the line they are on. The Enn Code for the G187 would apply to G187 only and not affect the active SSV behavior.
M138 is independent of spindle commands; once commanded, it is active even when the spindle is not turning. Also, M138 remains active until canceled with M139, or at M30, Reset, or Emergency Stop.