[ghack]

Hi all. i have a 3hp freq drive motor on my mill and i paid the 750 for rigid tap. but it flat out does not work. you can set it up to work for a specific depth, speed, and size after several broken taps but change anything and your scraping parts. So i am thinking a bout a servo spindle motor. question is what would work right and what would i need.

Thanks
Todd

[cnckeith]

Todd,
Hello. Please provide more detailed info on the system such as.

Machine make, model. spindle motor make model, spindle encoder make model and specs, control system model and serial number (cnc10?cnc11?windows or linux? what version are you running? etc)
and provide a "report" from the control so we can see what the rigid tapping related parameters are set to. and i can give you some direction.

Ac spindle motors powered by and inverter (freq drive) with an encoder mounted to the spindle 1:1 ratio work very well for rigid tapping. most all troubles with it are all setup related.

-cnckeith

[ghack]

the mill is milltronics rigid head knee mill bridgeport type head that i gutted and installed a 1:1 drive micro v its a 3 hp marathon inverter rated motor with a dura pulse gs 2 freq drive from automation direct.dynapar encoder from you guys on the motor cnc10 v2.36, linux. I have not tried it in a long time because of this. i think there might inverter setting also that would help but not quite sure what at this point.

[cnckeith]

thanks for the info. yes, both inverter settings and control settings have to be set up correctly for rigid tapping to work on any machine. I'll ask the guys in tech support to look at the parameter setting you sent included and maybe we can shed some light on it.

just to be clear when you say you gutted the head, i assume there is now no HI and Low range correct?

also a good technique for debugging any tapping is to use machinable wax to test tap with.. if there is any setting off it will not make good threads in wax. this way you will know there is a problem before breaking taps.

[ghack]

Kieth, the head still has hi and low but i never use low if i remember it had to stay for functionality of the spindle so i set it up to work but don't use it. with inverter is not necessary. Machinable wax never had any. I'm pretty rural and these days i cant order anything my self, unless i can buy it local it's not happening. maybe some hard wood. And now my old wire feed welder just died. i spend more fixing stuff lately. oh well, that's what happens when your poor....

[diycncscott]

Hi ghack,

As you have already determined, you must change the control parameters to reflect the specific material, depth, speed, and size of the hole you are tapping.
Your induction motor/vfd combo simply does not have the low end torque and is not responsive enough to tap all holes in all materials using the same settings.

Using a compression tapping holder will give you a little room for variation in your motor/vfd response.

Some of your parameters settings may be causing you some trouble as well:

I noticed that you have your minimum spindle speed for rigid tapping set to 125rpm (parm 68) , that's a pretty low RPM for a 3hp motor in high range. Depending on hole size and material you're tapping, your spindle motor may stall. The manual recommends an initial setting of 640rpm.

You also have the spindle override enabled during rigid tapping and you have chosen to have the control ignore the index pulse during rigid tapping. Ignoring the index pulse makes it impossible to tap the same hole twice and enabling the spindle override during rigid tapping can further exacerbate problems caused by having your minimum spindle speed being set too low. Set parameter 36 to "1" to disable the spindle override and enable the wait for index pulse when rigid tapping.

[ghack]

I havent "chosen" anything at this point this mill has 4 different computer in it in the last 2 weeks.I think some how somethings may have changed? I setup this up under the guidance of Drew back in the day, 10 years ago. it has only run a few times in the last five years so all of this is kind of "new" again. i will take corrective action. Also i did find last night that the vfd was set to sensorless vector w/o encoder feedback so i changed that? I havent had a chance to try it. also what about dynamic braking what should that be set to i dont like the spindle coasting down from rpm. I dont have a compression tapping setup. may have to get one i guess I dont like tapmatic type heads. ill have to see what i can find.

Thanks
Todd

[ghack]

so just checking my manual says recommended starting point is a 100 rpm. so thats why it was set their. Of course i never tapped that slow usually about 750. other params changed.

Thanks
Todd

[ghack]

Kieth,Scott, Well i just tapped some 1/4 -20 in some maple @ 750 .750 deep. so i bumped it up to 1500 rpm and when the tool reached the clearance point the spindle slowed down and it tapped the hole. so i switched the dynamic braking off on the inverter( which is the GS3 not a GS 2) it seemed to slow down still but drove the tap in a lot farther full depth of the tap. So what is happening that the spindle slowing down to tap? it did pickup threads ok re-tapping the same hole btw.. What else can i do. What do you recommend for the inverter setting? Wish i had a servo spindle.

[ghack]

No further comment? maybe some advise on vfd settings?