Typical Rigid Tapping Parameters for SERVO

[martyscncgarage]

I have setup several knee mill type machines for rigid tapping. Pretty much used the parameter settings states in TB123 "Rigid Tapping Setup" and they've worked:
34=(Spindle Encoder Counts per rev) (8000 in my case)
35=(Spindle Encoder input) (5 in my case)
36=(Bitwise Value to enable Rigid tapping) (I have used 1)
37(Spindle Deceleration Time) (I use 3.0, and set the VFD Decel to 3.0 seconds)
68=(Minimum Rigid Tapping Speed) (I use the default of 400)
69=(Duration for Minimum Spindle Speed Mode in Seconds) (I use the default of 1.25)
74=(Spindle M function to be run at the bottom of the hole for G84/top of hole for G74 counter tapping) (I use the default 4 for M4)
78=(Bitwise Value SPEED) (I use 1=Displayed speed is actual speed from the spindle encoder)
84= (Spindle M fuction to be runat bottom of hole for G74 tapping/top of hole for G84 counter tapping) (I use the default of 3 for M3)
82= (Spindle Drift Adjustment) (I use the default of 720)

So, it always has seemed to work, but I would like to hear from those more knowledgeable, if they pretty much use the default settings or if there are better settings for a typical knee mill with 3hp spindle with VFD/Braking resistor. I am particularly interested in hearing more about Parameter 36 and 78 and the bitwise choices. Trying to learn a little more here.

Thanks
Marty

[cncsnw]

Those should work fine.

I typically set a lower speed in Parameter 68, and a shorter time in Parameter 69: for example, slow down to 120 RPM for 0.5 seconds. That, in turn, calls for a much shorter drift distance is Parameter 82 (usually less than one turn).

I have gotten in the habit of setting up the spindle and spindle encoder as axis #6 instead of axis #5, so that I can use the same setups and PLC code on five-axis machines as I use on 2-axis, 3-axis and 4-axis machines.

[tblough]

P36 = 5
rigid tapping enabled and allow spindle override while tapping

P37 = 0.5
on a mill, I set this as quick as my brake resistor can stop the spindle. Some lathes need to be slower to not unscrew the chuck on stopping.

P68 = 200
with a 2HP motor driven 3:2 I have enough torque to tap 1/2-13 at 200 rpm in stainless

P69 = 0.1
mill spindles have fairly low inertia and with a brake resistor, they don't take long to slow down

P78 = 7
display actual speed, adjust feedrates based on actual speed, wait for spindle to reach speed (in my case 90%)

P82 = 250.0
this is determined empirically. do a test run on a series of holes and watch the DRO for the actual depth reached. take the average difference in depth and divide that by the pitch of the thread and then multiply by 360. Add (or subtract if undershoot) this number from the existing value in P82.

One other thing I do with a brake resistor is program 0 dwell time at the bottom of the hole in Intercon since you really don't need to wait for the spindle to coast to a stop. As both you and Marc noted, the Centroid recommended numbers work just fine. I tuned my setup with a brake resistor to get a "smoother" and faster rigid tapping cycle.

[martyscncgarage]

Thank you both for your comments. I may play with the settings a bit and see how they go. I have a block of machineable wax to test on.
Marty

[aamir]

My experience with mitsubishi and Delta vfd VE or C2000 of rigid tapping is so so .
I really enjoy rigid tapping with fanuc analog type Spindle drive and Mitsubishi FR spindle drive .
Those drive are really low declaration and acceleration time, also torque is good .
Never face problem of synchronization of z speed with the spindle .
Also on Delta drive I did rigid tapping maximum till 800RPM
But with fanuc and Mitsubishi I try till 1500RPM on M8 .

Plz share your experiences of tapping at what speed and what size u tried

I think rigid tapping is more related to drive quality

Now a days one chines company name CTB has special Rigid tapping mode that provide accurate synchronization .

I didn't try it on mill yet but try one lathe threading .Result is good no speed variation very stable even on high depth of cuts

Thanks

Aamir