Rigid Tapping

[NinerSevenTango]

I want very badly to add rigid tapping to the Tormach that I am buying. I've been looking it over a little, and I see it mentioned that the feature is not supported in Mach, although it frequently gets requested.

I can obtain a servo motor and controller that will do the job, if I feed it the step and direction signals. Since the G-code isn't supported, is there a way to fix gearing between axes to correspond with the proper pitch, and use an unused axis as output to the servo? A macro could drive a relay to switch the signal between the spare axis and the standard spindle output. I couldn't find anything explicit in the manual about setting gearing between axes, but it must be possible, considering what can be done with rotary axes for other machining purposes.

I can program, and I can wire, and I can fabricate. What I'm hoping is that I can roll my own rigid tapping canned routine using the VB macro language to set the pitch and switch the signal source to the servo.

Anyone with some experience here have any thoughts on this?

--97T--

[ajl6549]

Both axis and spindle servos are controlled together with respect to accelleration and decelleration on moderen production cnc machines as opposed to fixed gearing. I'd look into what it would take to sycronize your axis with your spindle via the drives and controller etc.

[ger21]

I haven't heard of anyone doing rigid tapping with Mach3. Everyone I've read about uses a tapping head.

[NinerSevenTango]

I'm thinking that I can make the spindle control rigid enough to just follow the pulse train rate from the z axis, so I can let the existing accel and decel of the z drive push the whole process. (I'll spend the $$ to do it.) *If* I can do that, all I should need for the actual tapping portion of the cycle would be a multiplier to set the pitch. It looks like maybe I can write a vb macro in Mach2 to do this.

--97T--

[NinerSevenTango]

Originally Posted by ger21 I haven't heard of anyone doing rigid tapping with Mach3. Everyone I've read about uses a tapping head.

Yes, that's what I found, too. But I want to find a way to get it done. It might cost a few thou for the spindle servo, but it would be worth it to me.

--97T--

[ajl6549]

I'd have to assume that it can be done, it'll just take $$$ like anything else. I know that it (software/ drives etc.) is fairly complex. The spindle would have to have some kind of setup to feed back to the control...like an axis...with an encoder to feed back velocity and position etc. Then I'd guess it's not much different than controling two axis simultainiously.

[DSL PWR]

Try this

http://www.newfangledsolutions.com/i...ill_addons.htm

[NinerSevenTango]

I've been looking at a servo system, it has the features I will need to get this done. The Addons product is very nice but it does not appear to have a rigid tapping cycle. I guess I will have to write my own macro since it isn't implemented in the software.

--97T--

[HillBilly]

Before machining centers had rigid tapping, tapping was done with a floating tap holder. The tap is able to float up and down in the tool holder and the spindle speed and feed were calculated as close as possible. The main criterior would be a spindle drive with velocity feedback (tach) to maintain the commanded speed or fault out.

The main thing this lacks over rigid tapping is the ability to re-enter a tapped hole.

Darek

[Willyb]

Hi NinerSevenTango

What would you do about the Spindle Belt Drive on the Tormach? Direct drive the Spindle with the replacement motor? I guess if you get this new Spindle Motor doing Rigid Tapping than there would certianly be no problem using this same motor for general machining operations.

Willy

[JFettig]

I've been wanting to do this for a long time and have tested my theory briefly.

All you have to do is set your spindle up as a servo(with your servo of course) using step/dir. and ALSO set it up as a C-axis using the same pins. If you type M3 S1000 command, it will run 1000rpm, M5 and its off. Now, if you type G1 C1200 F1000, it will spin 1200 degrees at 1000deg/m.

So now you just do this:
G1 Z0
G1 Z-1 C10000 F1000 (or whatever the values may be
G1 Z0 C0 F1000
and you've gone in and out and tapped your hole.
With doing it like that, I don't see why that cannot be integrated into mach3, instead just tell it that when you put in your G84 parameters it needs to do this or that.

I have a 1kw sanyo P5 servo that I want to add onto my mill and do this, but I have not gotten around to doing so yet.

Jon

[RogerN]

I'm not sure how this would be done in Mach, but...
If your spindle were set up as another axis, then you should be able to do a G01 linear move with your Z axis and Spindle. You could scale your spindle to the number of steps per revolution. To tap a hole 1/2" deep at 20 TPI, use (in absolute mode) G01 z-.5 (spindle axis)10, then G01 Z0 (spindle axis)0.

You need a way to use the spindle in velocity mode for normal operation and in position mode for rigid tapping. Perhaps a control output could switch a servo drive from velocity mode to step & direction mode. I don't know what Mach has built in for spindle control, but an output may be able to be used to switch to rigid tapping mode.

Good Luck!

RogerN