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Polygon Turning
« on: June 07, 2010, 03:37:41 PM »
Can Polygon Turning be done using mach 3?  i.e. running two spindles at the same time accurately.  Im currently designing a benchtop machining centre and would love it to be able to do this :)  it already has live tooling for small tools (5/16" dia max), a 16c large bore spindle with auto collet closer and is about 40cm x 800cm c 40cm in size.   
My headstock spindle is servo driven with a mitsubishi 400w melservo (still wondering if this is big enough) and I am wondering if i could design the tool rack to hold a flywheeled servo driven tool maybe with a 200w servo and a hefty flywheel to dampen the cutting action.  Any ideas????

Its pretty awesome stuff...

ref videos:

http://www.youtube.com/watch?v=-9jMN9Bgg6g
http://www.youtube.com/watch?v=KMdBIBzGtKI
http://www.youtube.com/watch?v=yDNogxSWa-w

Rob :)
Re: Polygon Turning
« Reply #1 on: June 07, 2010, 10:16:06 PM »
Can Polygon Turning be done using mach 3?  i.e. running two spindles at the same time accurately.  Im currently designing a benchtop machining centre and would love it to be able to do this :)  it already has live tooling for small tools (5/16" dia max), a 16c large bore spindle with auto collet closer and is about 40cm x 800cm c 40cm in size.   
My headstock spindle is servo driven with a mitsubishi 400w melservo (still wondering if this is big enough) and I am wondering if i could design the tool rack to hold a flywheeled servo driven tool maybe with a 200w servo and a hefty flywheel to dampen the cutting action.  Any ideas????

Its pretty awesome stuff...

ref videos:

http://www.youtube.com/watch?v=-9jMN9Bgg6g
http://www.youtube.com/watch?v=KMdBIBzGtKI
http://www.youtube.com/watch?v=yDNogxSWa-w

Rob :)

You can actually do that pretty easily in hardware, by linking the two spindle drives with a digital phase-locked loop, then let Mach3 program the multiply/divide ratios to give the factor you need for the polygon.  There are digital PLL chips that will do this nicely.  Here's a pretty good introduction to the DPLL concept.

Regards,
Ray L.
Regards,
Ray L.

Offline kf2qd

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Re: Polygon Turning
« Reply #2 on: June 08, 2010, 05:09:23 PM »
If you are running the servos in stepper mode you may be able to adjust the counts per revolution settings and synchonize them that way. They come setup for either 2000 or 4000 steps per rev and you cn play with the ratio for each drive to come up with what ever ratio you might want. All it would require is a pulse source.

Offline Hood

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Re: Polygon Turning
« Reply #3 on: June 08, 2010, 05:17:32 PM »
The  servo drives I use have a follower mode and you can have up to 8 different ratios selectable from inputs so if I were to do that I would just use the spindle drives encoder  output and input it to the tools drive. Maybe one day I will do something like that but have to many other things to do first :(
Hood
Re: Polygon Turning
« Reply #4 on: June 08, 2010, 06:22:19 PM »
Hmm, that sounds good.  I haven't got the servo drivers yet but they are mitsubishi MR-C40A drivers.  
Im still trying to find a place to locate the polygon tool as I doubt having it on the atc would be rigid enough plus I wouldn't have the space for a flywheel - if its necessary as I wouldn't be taking mega cuts.  

It will be a fair while before i get really into this - late summer probably but it sounds like it would work aslong as I can get the rigidity needed.  
Ill keep posted as things progress.  

What servo's and drivers are you running hood?

  Rob  ;D

Offline Hood

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Re: Polygon Turning
« Reply #5 on: June 08, 2010, 06:37:58 PM »
What servo's and drivers are you running hood?

  Rob  ;D

Allen Bradley DSD drives

Hood

Offline Hood

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Re: Polygon Turning
« Reply #6 on: June 13, 2010, 05:47:13 PM »
Have just done a wee bit of reading on this and looks like driving the cutter twice the speed of the spindle is what you want for best results The amount of inserts/cutters determine the number of flats and not the gearing. Example 2 Inserts will give you 4 flats, 3 Inserts will give 6 flats.
Would be an easy enough thing for me to do but would require me to make a removable  attachment up to fit the cross slide as it would get in the way of normal turning due to my lathe having both front and back turret/toolpost, seriously considering doing this though :) just need to find the time :(

Hood

Offline Hood

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Re: Polygon Turning
« Reply #7 on: June 13, 2010, 07:16:05 PM »
Page 18 onwards in this pdf gives some good info.  http://www.hornusa.com/fileadmin/user_upload/usa/PDF/groove_milling/ChapterJ.pdf
Hood
Re: Polygon Turning
« Reply #8 on: June 14, 2010, 02:56:14 AM »
seriously considering doing this though :) just need to find the time :(

You said it! no going back now ;-) - it would be fantastic to see Mach doing this.

Last page was interesting too - "thread whirling! !!!!! what the heck is that !!!!!!!

ATB
Derek.
You can "chop it off" but can't "chop it on"
Re: Polygon Turning
« Reply #9 on: June 14, 2010, 07:32:46 AM »
It does look good fun doesn't it  ;D

I wonder if there is an optimal cutter diameter for say a max of 3/4" AF hex?  In our case the smaller the cutter dia the better and I see they do one 40mm dia!  Accoring to the pdf example you want the cutter to be (very) approx 3.5 times the af BUT could a 'hobby' type machine cope with the high speed intermittant cut? 

There is only one way to find out - HOOD GET ONTO IT!  (I know you want to)

 Rob  ;)