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Author Topic: Spindle servo on lathe is 10% fast  (Read 1207 times)

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Re: Spindle servo on lathe is 10% fast
« Reply #10 on: April 13, 2018, 03:07:22 AM »
Hi,
that story rather puts CNCing as a hobby or a job into perspective. I hope your recovery progresses, it sounds that while you have come a long way it is still a long road.

I play Bridge recreationally and its a competetive game and I have a phrase, 'Bridge, its only a game...its not life or death....its more important than that!' While the humour is fun
its not in fact 'life or death'.

Using a modern AC servo as a spindle  puts you at the leading edge performance. You will, once you get it sorted and provided you remain within the torque limits of the servo
have a spindle with speed/position stability the envy of many.

Craig
My wife left with my best friend...
     and I miss him!

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Re: Spindle servo on lathe is 10% fast
« Reply #11 on: April 14, 2018, 08:56:01 PM »
Yes, it is only a hobby, but at times one gets caught up in the moment and it seems more important in the grand scheme of things than it really is. I am interested however when you say:

"Using a modern AC servo as a spindle  puts you at the leading edge performance. You will, once you get it sorted and provided you remain within the torque limits of the servo have a spindle with speed/position stability the envy of many."

This implies that once you do have a accurate, controllable, spindle that more can be done with it than previously. I have seen a YouTube video of someone using parametric G Code to turn a hexagonal shape on a lathe, do you have any idea of this?
Cheers

David

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Re: Spindle servo on lathe is 10% fast
« Reply #12 on: April 14, 2018, 09:06:10 PM »
Here is an example of what I was talking about:
https://www.youtube.com/watch?v=DajrTlI8IWA
Cheers

David
Re: Spindle servo on lathe is 10% fast
« Reply #13 on: April 14, 2018, 09:27:15 PM »
Hi,
yes I have seen it, very impressive.  More of a party trick than a production technique.

Your spindle should do that.  Writing the Gcode for it would be a challenge.
Do you use Mach3 or Mach4?

I think the way to go about it is to call your spindle an A axis so that you can have coordinated rotation and cutting depth with the X axis. Success will depend heavily on the acceleration
of the X axis, if it can't accelerate quickly the hexagon will get rounded.

Craig
My wife left with my best friend...
     and I miss him!

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Re: Spindle servo on lathe is 10% fast
« Reply #14 on: April 14, 2018, 09:40:30 PM »
Yes, a combination of both the acceleration of the "A" axis and the X axis, may not have to be extremely fast acceleration though, just V well coordinated.

I am using M3, but I have an M4 license. I was initially V keen at converting to M4, but I use an ESS, which for a long time did not support threading on the lathe. The impetus to change to M4 has became a bit cooler over the intervening years.

I am still happy to M4 a try, but I need a reason to. :)
Cheers

David
Re: Spindle servo on lathe is 10% fast
« Reply #15 on: April 14, 2018, 09:52:59 PM »
Hi,
the Mach4 ESS plugin still does not support lathe threading but it is still progressing. Warp9 have decided that they wish to have multi-pulse per rev encoder capability and that has put them back
a bit. It may be a case of one step forwards but two backwards. It is happening though.

This hexagonal machining problem does not require Mach4.

The reason I ask is because if I have to write code I will not be writing VB, I will be writing Lua.

I will come back with some ideas about the Gcode necessary for the hexagonal machining trick.

Craig
My wife left with my best friend...
     and I miss him!
Re: Spindle servo on lathe is 10% fast
« Reply #16 on: April 14, 2018, 10:53:41 PM »
Hi Dave,
got some ideas....

The attached pi shows a segment of the required hexagon, the longest dimension R. As it rotates about the center by angle theta the resulting triangle has longest side of R still but a somewhat shorter side Rprime.
The sine rule allows us to define a relation between the angle theta and Rprime, and of course Pprime is the X coordinate of your lathe.


A table of results might make it clearer:

theta         Rprime
0               R
5               0.955 X R
10             0.927 X R
15             0.896 X R
20             0.879 X R
25             0.869 X R
30             0.866 X R
35             0.869 X R
40             0.879 X R
45             0.896 X R
50             0.927 X R
55             0.955 X R
60             R

Clearly this works only for theta on the range 0 to 60 degrees, but all the rest of the hexagonal sectors are identical.

We could just write Gcode as a series of moves between the A axis and X axis, much like in the table or could do the calculation in a macro. The macro would be more fun but I'm
writing in Lua which is not going to make much sense to you.

You know you bloody Aussies ought to try to keep up!

What do you think?

Craig
My wife left with my best friend...
     and I miss him!
Re: Spindle servo on lathe is 10% fast
« Reply #17 on: April 21, 2018, 07:37:41 PM »
Hi Dave,
I have a little bit of code here, its just a table of moves between A and X axes over a 60 degree segment of the A axis.
Its R dimension is 25mm, so your hexagon would be 50mm across the points.

Code: [Select]
G1 A0.0  X24.9975
G1 A0.5  X24.875
G1 A1.0  X24.7525
G1 A1.5  X24.635
G1 A2.0  X24.52
G1 A2.5  X24.4075
G1 A3.0  X24.2975
G1 A3.5  X24.19
G1 A4.0  X24.0875
G1 A4.5  X23.985
G1 A5.0  X23.8875
G1 A5.5  X23.7925
G1 A6.0  X23.6975
G1 A6.5  X23.6075
G1 A7.0  X23.52
G1 A7.5  X23.4325
G1 A8.0  X23.35
G1 A8.5  X23.2675
G1 A9.0  X23.19
G1 A9.5  X23.1125
G1 A10.0 X23.04
G1 A10.5 X22.9675
G1 A11.0 X22.8975
G1 A11.5 X22.83
G1 A12.0 X22.7625
G1 A12.5 X22.7
G1 A13.0 X22.64
G1 A13.5 X22.58
G1 A14.0 X22.5225
G1 A14.5 X22.4675
G1 A15.0 X22.4125
G1 A15.5 X22.3625
G1 A16.0 X22.3125
G1 A16.5 X22.265
G1 A17.0 X22.22
G1 A17.5 X22.175
G1 A18.0 X22.1325
G1 A18.5 X22.0925
G1 A19.0 X22.055
G1 A19.5 X22.0175
G1 A20.0 X21.985
G1 A20.5 X21.95
G1 A21.0 X21.92
G1 A21.5 X21.89
G1 A22.0 X21.8625
G1 A22.5 X21.8375
G1 A23.0 X21.8125
G1 A23.5 X21.79
G1 A24.0 X21.77
G1 A24.5 X21.75
G1 A25.0 X21.7325
G1 A25.5 X21.7175
G1 A26.0 X21.7025
G1 A26.5 X21.69
G1 A27.0 X21.68
G1 A27.5 X21.67
G1 A28.0 X21.6625
G1 A28.5 X21.6575
G1 A29.0 X21.6525
G1 A29.5 X21.65
G1 A30.0 X21.65
G1 A30.5 X21.65
G1 A31.0 X21.6525
G1 A31.5 X21.6575
G1 A32.0 X21.6625
G1 A32.5 X21.67
G1 A33.0 X21.68
G1 A33.5 X21.69
G1 A34.0 X21.7025
G1 A34.5 X21.7175
G1 A35.0 X21.7325
G1 A35.5 X21.75
G1 A36.0 X21.77
G1 A36.5 X21.79
G1 A37.0 X21.8125
G1 A37.5 X21.8375
G1 A38.0 X21.8625
G1 A38.5 X21.89
G1 A39.0 X21.92
G1 A39.5 X21.95
G1 A40.0 X21.985
G1 A40.5 X22.02
G1 A41.0 X22.055
G1 A41.5 X22.0925
G1 A42.0 X22.135
G1 A42.5 X22.175
G1 A43.0 X22.22
G1 A43.5 X22.265
G1 A44.0 X22.3125
G1 A44.5 X22.3625
G1 A45.0 X22.415
G1 A45.5 X22.4675
G1 A46.0 X22.5225
G1 A46.5 X22.58
G1 A47.0 X22.64
G1 A47.5 X22.7
G1 A48.0 X22.765
G1 A48.5 X22.83
G1 A49.0 X22.8975
G1 A49.5 X22.9675
G1 A50.0 X23.04
G1 A50.5 X23.115
G1 A51.0 X23.19
G1 A51.5 X23.27
G1 A52.0 X23.35
G1 A52.5 X23.435
G1 A53.0 X23.52
G1 A53.5 X23.6075
G1 A54.0 X23.7
G1 A54.5 X23.7925
G1 A55.0 X23.8875
G1 A55.5 X23.9875
G1 A56.0 X24.0875
G1 A56.5 X24.1925
G1 A57.0 X24.3
G1 A57.5 X24.4075
G1 A58.0 X24.52
G1 A58.5 X24.635
G1 A59.0 X24.755
G1 A59.5 X24.875
G1 A60.0 X25

It doesn't have any Feed word or any Z moves. Study it at see what you think.

Craig
My wife left with my best friend...
     and I miss him!

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Re: Spindle servo on lathe is 10% fast
« Reply #18 on: April 30, 2019, 05:05:26 AM »
Craig I'm very sorry, but your posts somehow slipped through tho the keeper. I had stopped thinking about the hexagon turning and moved onto my 3d printer, but I can always come back :). I'll have a read tomorrow and reply.
Cheers
Dave


Hi Dave,
I have a little bit of code here, its just a table of moves between A and X axes over a 60 degree segment of the A axis.
Its R dimension is 25mm, so your hexagon would be 50mm across the points.

Code: [Select]
G1 A0.0  X24.9975
G1 A0.5  X24.875
G1 A1.0  X24.7525
G1 A1.5  X24.635
G1 A2.0  X24.52
G1 A2.5  X24.4075
G1 A3.0  X24.2975
G1 A3.5  X24.19
G1 A4.0  X24.0875
G1 A4.5  X23.985
G1 A5.0  X23.8875
G1 A5.5  X23.7925
G1 A6.0  X23.6975
G1 A6.5  X23.6075
G1 A7.0  X23.52
G1 A7.5  X23.4325
G1 A8.0  X23.35
G1 A8.5  X23.2675
G1 A9.0  X23.19
G1 A9.5  X23.1125
G1 A10.0 X23.04
G1 A10.5 X22.9675
G1 A11.0 X22.8975
G1 A11.5 X22.83
G1 A12.0 X22.7625
G1 A12.5 X22.7
G1 A13.0 X22.64
G1 A13.5 X22.58
G1 A14.0 X22.5225
G1 A14.5 X22.4675
G1 A15.0 X22.4125
G1 A15.5 X22.3625
G1 A16.0 X22.3125
G1 A16.5 X22.265
G1 A17.0 X22.22
G1 A17.5 X22.175
G1 A18.0 X22.1325
G1 A18.5 X22.0925
G1 A19.0 X22.055
G1 A19.5 X22.0175
G1 A20.0 X21.985
G1 A20.5 X21.95
G1 A21.0 X21.92
G1 A21.5 X21.89
G1 A22.0 X21.8625
G1 A22.5 X21.8375
G1 A23.0 X21.8125
G1 A23.5 X21.79
G1 A24.0 X21.77
G1 A24.5 X21.75
G1 A25.0 X21.7325
G1 A25.5 X21.7175
G1 A26.0 X21.7025
G1 A26.5 X21.69
G1 A27.0 X21.68
G1 A27.5 X21.67
G1 A28.0 X21.6625
G1 A28.5 X21.6575
G1 A29.0 X21.6525
G1 A29.5 X21.65
G1 A30.0 X21.65
G1 A30.5 X21.65
G1 A31.0 X21.6525
G1 A31.5 X21.6575
G1 A32.0 X21.6625
G1 A32.5 X21.67
G1 A33.0 X21.68
G1 A33.5 X21.69
G1 A34.0 X21.7025
G1 A34.5 X21.7175
G1 A35.0 X21.7325
G1 A35.5 X21.75
G1 A36.0 X21.77
G1 A36.5 X21.79
G1 A37.0 X21.8125
G1 A37.5 X21.8375
G1 A38.0 X21.8625
G1 A38.5 X21.89
G1 A39.0 X21.92
G1 A39.5 X21.95
G1 A40.0 X21.985
G1 A40.5 X22.02
G1 A41.0 X22.055
G1 A41.5 X22.0925
G1 A42.0 X22.135
G1 A42.5 X22.175
G1 A43.0 X22.22
G1 A43.5 X22.265
G1 A44.0 X22.3125
G1 A44.5 X22.3625
G1 A45.0 X22.415
G1 A45.5 X22.4675
G1 A46.0 X22.5225
G1 A46.5 X22.58
G1 A47.0 X22.64
G1 A47.5 X22.7
G1 A48.0 X22.765
G1 A48.5 X22.83
G1 A49.0 X22.8975
G1 A49.5 X22.9675
G1 A50.0 X23.04
G1 A50.5 X23.115
G1 A51.0 X23.19
G1 A51.5 X23.27
G1 A52.0 X23.35
G1 A52.5 X23.435
G1 A53.0 X23.52
G1 A53.5 X23.6075
G1 A54.0 X23.7
G1 A54.5 X23.7925
G1 A55.0 X23.8875
G1 A55.5 X23.9875
G1 A56.0 X24.0875
G1 A56.5 X24.1925
G1 A57.0 X24.3
G1 A57.5 X24.4075
G1 A58.0 X24.52
G1 A58.5 X24.635
G1 A59.0 X24.755
G1 A59.5 X24.875
G1 A60.0 X25

It doesn't have any Feed word or any Z moves. Study it at see what you think.

Craig
Cheers

David

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Re: Spindle servo on lathe is 10% fast
« Reply #19 on: May 02, 2019, 03:41:57 AM »
Spindle pulleys in Mach is where you set the max velocity and any gear ratio.