[ichudov]

I added an encoder on the spindle. The rest of the job of implementing rigid tapping, was setting up EMC config correctly.

Here are some details, pics and videos.

Spindle Encoder and Rigid Tapping with EMC/EMC2

All comments are welcomed.

i

[machintek]

True rigid tapping uses software to mathematically couple the spindle RPM to the Z axis position. Does your setup do this or just hold the spindle speed more precisely? Curious.

George

[ichudov]

George, I use software to precisely couple the downfeed speed (or the up speed after the tap is reversed) to the actual, sensed angular position of the spindle.

So, say, if the control computer detects a 1 angular degree rotation of the spindle, it would lower the Z axis by 1/360/TPI of an inch.

The speed of the spindle rotation is controlled by the VFD and is not precisely regulated, however, it is precisely sensed.

i

[samco]

Nice work! I hope to have mine rigid tapping soon

I would say emc2 electronically gears the z axis to the spindle. It works very well. (the spindle just has an encoder mounted on it)

sam

[lloydsp]

Ig, the video doesn't show the spindle stopping and starting. Did you use a reversing tapping attachment, or did you stop the spindle and reverse-tap out of the holes?

L

[ichudov]

Lloyd,

1) It is a very poor quality video, taken by my cell phone
2) The tap is held in a regular Jacobs drill chuck
3) The spindle reverses very quickly
4) You can actually see it reverse, it is hard to see but you can see it.

I can try to shoot a better video if you want. I have a video camera that upsets me to NO end, because it only produces enormous AVCHD files. So I often use my cell phone.

Igor

[lloydsp]

Yeah, Ig. I kind of figured that, because I didn't see no "stinkin'" big, honking reverser in the chuck. But I had to ask.

Tell me about your spindle motor. Did you keep the same Interact/R2E3/4 reverser and vari-drive? Did you lock it to a certain speed, and use the VFD to vary it?

(you may have answered these questions elsewhere, but I just did an 8x10 engraving of ALL curves on my R2E4, and now I'm "hot" to get the remaining features the way I'll like them for a while)

LS

[ichudov]

Yeah, Ig. I kind of figured that, because I didn't see no "stinkin'" big, honking reverser in the chuck. But I had to ask.

Tell me about your spindle motor. Did you keep the same Interact/R2E3/4 reverser and vari-drive? Did you lock it to a certain speed, and use the VFD to vary it?

(you may have answered these questions elsewhere, but I just did an 8x10 engraving of ALL curves on my R2E4, and now I'm "hot" to get the remaining features the way I'll like them for a while)

LS

Lloyd, I have a Bridgeport Series II Interact 2 mill.

I kept, pretty much, all mechanical and electric hardware in my mill. So, I still have the V belt varidrive, spindle brake, lube pump, servos, spindle motor, etc.

The spindle motor is driven by a 3 HP, single phase rated VFD with a big brake resistor. It can stop in 0.6 second. Thus the reversal is rather quick.

[tranhaitrung]

Please post another better video for us to see

[ichudov]

Please post another better video for us to see

I will try.

[Tooljunkie]

Probably a dumb question, but is a VFD required for this operation, or could I use my existing Rotary Phase Converter?

[ichudov]

Probably a dumb question, but is a VFD required for this operation, or could I use my existing Rotary Phase Converter?

VFD is not required.

What is required is an encoder reporting spindle's exact angular position, and software that "electronically gears" the Z axis to that position.

i

[samco]

Here is EMC2 rigid tapping on a large HMC. this shows the z axis tracking as the rather large spindle slows down and reverses.

1"-8 tap

[nomedia="http://www.youtube.com/watch?v=2E3PMooch1k"]YouTube - kearney and trecker rigid tapping at 400rpm[/nomedia]

(slower)
[nomedia="http://www.youtube.com/watch?v=LLcztAbgEcU"]YouTube - kearney and trecker rigid tapping 1 inch hole.[/nomedia]

sam