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Thread Milling hardware requirements?
« on: March 13, 2008, 07:31:56 PM »
So I'm setting up my first cnc mill.....
and I want it to be able to do thread milling...
What are the hardware requirements?

I'm assuming I need good spindle location feedback like an indexed encoder, correct?  What about spindle speed control?  I don't know; that's why I'm asking.

Thanks in advance

Offline Hood

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Re: Thread Milling hardware requirements?
« Reply #1 on: March 13, 2008, 07:35:11 PM »
Nope all you need are the three axis.
 Thread milling usually cuts the full depth of thread in one pass so you dont need to have any spindle index at all like in a lathe because you dont need to sync for the next pass.
Hood
« Last Edit: March 14, 2008, 07:21:20 AM by Hood »

Offline Hood

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Re: Thread Milling hardware requirements?
« Reply #2 on: March 13, 2008, 07:46:33 PM »
Quote
Sweet, so there are no special hardware requirements unless you are getting really fancy and want to start the thread at the same place in each hole so that things screw in to the exact same height?  Speeking of which...If I put an indexed encoder on the spindle can I pull that off easily in mach?

Starting the thread at the same place in each hole is easy enough, just use the same code but with your new x and y positions
If you think about it all that is happening is your x and y are going in a circle the dia of the thread and the Z moves down at the pitch of the thread. You can start at the same X Y and Z position for each thread. Even if you do multi passes you still dont need to sync the spindle as the tool is moving round the work and not like the work moving round the tool in a lathe.
Hood
« Last Edit: March 13, 2008, 07:48:52 PM by Hood »
Re: Thread Milling hardware requirements?
« Reply #3 on: March 14, 2008, 07:00:14 AM »
Maybe worth clarifying a few differences here, I thought we were talking of rigid tapping which is a different ball game altogether. That would require a very well controlled spindle.

Offline Hood

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Re: Thread Milling hardware requirements?
« Reply #4 on: March 14, 2008, 07:18:09 AM »
Yes rigid tapping and thread milling are two totally different things. Thread milling is relatively easy to do but tapping needs good control of spindle speed and also spindle reversal. Thread milling only needs to move all three axis in unison and spindle control is not needed.
Hood
Re: Thread Milling hardware requirements?
« Reply #5 on: March 14, 2008, 02:54:49 PM »
I did originally mean thread milling but as long as we are on the subject of rigid tapping.....

Is there any benefit to rigid tapping over using a tapping head?
Will anything less than a servo motor driving the spindle give you good enough control?

The mill I am setting up has a 2 hp 3 phase spindle motor.  I got a WEG CFW10 to drive it because it takes single phase input and outputs "sinusoidal pwm (square vector modulation)" (whatever that is) to drive drive and control a 3 phase motor.  It has 1 programmable differential analog input and 4 programmable digital inputs.  If it was in the same location as me I'd open the owners manual and see just what I can program those inputs to do but it's in one place and I'm in another so all I know is what I verified before purchasing it and that is that it will accept a pwm input.  Anyone familiar with these and think it will or won't offer enough control for rigid tapping?  http://www.weglibrary.com/pdf/cfw10.01.07.pdf



Yes rigid tapping and thread milling are two totally different things. Thread milling is relatively easy to do but tapping needs good control of spindle speed and also spindle reversal. Thread milling only needs to move all three axis in unison and spindle control is not needed.
Hood
« Last Edit: March 14, 2008, 02:58:29 PM by usfwalden »

vmax549

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Re: Thread Milling hardware requirements?
« Reply #6 on: March 20, 2008, 01:50:33 PM »
Rigid tapping NO, Semi rigid tapping(SRT) YES if you can dynamically brake the spindle motr with the VFD. You have to be able to stop and reverse the spindle quickly

The advantage of SRT over the tapping head is the tapping head takes up a huge amount of Z travel and tool length offsetting on a knee type mill where you may only have 5-6" of travel.

If you have plenty of Z travel then the tapping head works well too.

(;-) TP