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Offline Graham Waterworth

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Spindle orientation
« on: September 18, 2006, 05:30:16 PM »
Hi all,

can any body give me any idea how to orientate a lathe spindle and lock it in position, a bit like a tool changer on a mill dose.  The motor is DC and has a index pulse for surface speed.  I have worked out how to lock the spindle but how do I get it to stop in the same place every time.  On industrial mills you can call M19 to orientate the spindle and then it is locked magnetically I think.

All ideas welcome, but the simpler the better.

Graham.
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Offline chad

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Re: Spindle orientation
« Reply #1 on: September 18, 2006, 05:42:10 PM »
Not an expert here but.. I don't think you can.
I had my head in the control cabinet of a Haas tl1 recently and it has 3 ac servo drives with encoder feedback. one for x, one for z , and one for spindle.  So what this is telling me is the spindle is treated just like an axis drive. Just a BIG ac servo motor with an encoder. With an index pulse you won't have the resolution to to be able to reliably position the spindle.. 

?

Chad
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Offline Graham Waterworth

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Re: Spindle orientation
« Reply #2 on: September 18, 2006, 05:51:12 PM »
Hi Chad,

are you sure it was for the spindle,  some of the more modern lathes use servos for the turret.

anyway thanks for your input, I hope your wrong.

Graham.
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Offline chad

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Re: Spindle orientation
« Reply #3 on: September 18, 2006, 05:56:59 PM »
I am sure, this is a lathe without a turret. Just has a quick change post.

Chad

Pretty cool machine..

http://haasportal.net/Portals/57ad7180-c5e7-49f5-b282-c6475cdb7ee7/DS_TLseries_US.pdf
« Last Edit: September 18, 2006, 06:29:28 PM by chad »
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Offline Graham Waterworth

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Re: Spindle orientation
« Reply #4 on: September 18, 2006, 06:01:58 PM »
I see, can't argue with that.  It was not a criticism just a thought.

Graham.
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Offline Graham Waterworth

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Re: Spindle orientation
« Reply #5 on: September 18, 2006, 06:15:55 PM »
The spindle is driven by a mach3 controlled vari drive,  the spindle is locked by a small disc brake operated by a solenoid, if I had one or more proxy sensors set could I look for them with a macro and when found fire the solenoid and kill the spindle.  The spindle would be running at its minimum speed 25 rpm.

Any thoughts.

Graham.
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Offline chad

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Re: Spindle orientation
« Reply #6 on: September 18, 2006, 06:27:17 PM »
Sorry, no offence taken. I ment no animosity. guess I should have worded that differently.

Chad

 ;D
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Offline chad

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Re: Spindle orientation
« Reply #7 on: September 18, 2006, 06:43:34 PM »
HHm that would be some pretty tricky timing. I am not a code guy at all.

Thinking about it I see a couple of possible problems. First you have the delay between energizing the solenoid and  when the spindle stops. probably on the order of 40ms.
Then you would have a problem with different mass in the chuck. Something small will stop faster than a big hunk of steel. So you would have to adjust your macro timing to deal with that. 25 rpm sounds slow but when you are looking at a timing pulse then a prox pulse then trigger a action with a variable inertia -- makes my head spin at about 25 rpm ;)

I don't know might be a fun thing to try.

Just another thought. could you rig up some quick connect / disconnect to the spindle motor?
You could shut down the spindle motor and engage a stepper and just treat it like a c axis ?

I dunno

Chad


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Hood

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Re: Spindle orientation
« Reply #8 on: September 19, 2006, 12:39:30 AM »
Its early morning here so this may be a crazy suggestion but do as you say above with the low speed and sensors but have a disk with a vee cut out on the peripheral and a solenoid firing a piston/rod with a vee on the end. That way it would not have to be spot on position when firing the solenoid but would then align itself as the piston pushes into the vee.
Hood
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Offline pabeader

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Re: Spindle orientation
« Reply #9 on: September 21, 2006, 11:49:46 PM »
As a matter of fact I can...
We do this on almost all the machines we have in our shop.  The BIG question is are you setup for multipass treadcutting?  If you are then use a z offset to control the number/length of revolutions.  Think of it this way.  To correctly treadcut you need to know the position of the spindle and start the threadcut at the same place each time.  If you set the z offset to let's say .5 then you will get a certain amount of spindle rotation for that amount of z travel.  If the spindle isn't in the desired position all you have to do is change the offest to change the final spindle position.
It will help if can get the spindle to a very slow speed of course.

So what you do is write a macro/sub program that does a very short threadcut based on the z offset.  Then just call that when you want to orient the spindle.


Hope this was helpful
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