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Author Topic: Spindle orientation on a Bridgeport...  (Read 3004 times)

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Re: Spindle orientation on a Bridgeport...
« Reply #10 on: February 21, 2018, 04:57:56 PM »
The way my BTC-1 does it is to inch the spindle and drop a shot pin into a ramped slot and when the shot pin reaches the bottom of the ramp/can't rotate anymore it sends a signal to stop inching and the spindle is orientated properly.


Mike

that is also a way i was thinking about. any photos ?
Sorry I do not have any photos.
If yiou really need them I could take some this weekend.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.
Re: Spindle orientation on a Bridgeport...
« Reply #11 on: February 21, 2018, 05:11:52 PM »
I don’t think this problem is a big as you think with sensorless vector VFD, I once built a pump with that kind of VFD and it ran reliably down to 18 rpm with a load, or 1/100 of base speed. My machines also had to stop and line up with rails that plugged in. Taper your drive dogs as much as you can too, so you don’t need to be perfect. Run the motor at the lowest possible speed and tell it to stop on the sensor. Worse that will happen is that it will overshoot a bit. As long as the overshoot is reliably consistent you can adjust sensor position to accomodate.
Re: Spindle orientation on a Bridgeport...
« Reply #12 on: February 21, 2018, 08:52:17 PM »
Another thought about this issue. Things like this work much better when they are designed to be extremely tolerant of misalignment rather than being very accurately made.  So I htink a better approach here is to have the tool gripper mounted to be spring loaded upward.  You press it against the spindle and if the dogs are not lined up the compressing of the spring triggers a limit switch that causes the spindle to rotate until the dogs drop into the slot and the limit switch then indicates that the alignment has been achieved, fasten the tool and  retract the gripper.  No spindle switch needed.

Offline TPS

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Re: Spindle orientation on a Bridgeport...
« Reply #13 on: February 22, 2018, 01:36:29 AM »
The way my BTC-1 does it is to inch the spindle and drop a shot pin into a ramped slot and when the shot pin reaches the bottom of the ramp/can't rotate anymore it sends a signal to stop inching and the spindle is orientated properly.


Mike

that is also a way i was thinking about. any photos ?
Sorry I do not have any photos.
If yiou really need them I could take some this weekend.

Mike

Mike i would realy appreciate, to get maybe new ideas.
Thank You Thomas
anything is possible, just try to do it.
if you find some mistakes, in my bad bavarian english,they are yours.

Offline Davek0974

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Re: Spindle orientation on a Bridgeport...
« Reply #14 on: February 22, 2018, 02:17:27 AM »
All sounding good, lots of options - pictures are always good :)

I gather that as nobody is tackling the AC synchronous -> AC servo swap question, it really is as difficult as i thought ??

:)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.
Re: Spindle orientation on a Bridgeport...
« Reply #15 on: February 22, 2018, 02:35:58 AM »
Hi Dave,
I recently bought a second hand 1.8kW Allen Bradley AC servo and drive for a spindle. I needed a spindle motor with some decent torque at slower speeds for steel.
This servo has turned out great. The main reason I went with a servo is that they are the most powerful/torque-y motor for the size.

Its the first time I've really ever played with a modern AC servo and I am impressed, very, very impressed! They are extremely capable and while it was not even
on the radar, stopping the spindle to line up the drive dogs is trivial with a decent servo. My 'zero window' is 4 counts of an 8000 count encoder ie 10.8 arc min!
Easily good enough to line up surely!

I had always been put off by the cost of servos but after playing with one I wont be looking for any other solution anytime.

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

Offline TPS

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Re: Spindle orientation on a Bridgeport...
« Reply #16 on: February 22, 2018, 03:06:14 AM »
Hi Dave,

for the Moment i am 'flirting' with two Solutions:

1st chinese spindle Controller (Manual attached)
i have servo Motors and Controller from this compnay on all my machines,
they are working without any Problems. still waiting for a offer for this Controller.

pro
-gives me all posibilities
-modern,standard equipment
contra
-maybe cost
-Need's to be rewired
-will take some time to get


2nd i call it dogcatcher
-will be a sloted plate (5mm makronlon, because i am getting scared to drive metal against metal)
-driven by a 20mm pneumatic cylinder
-8mm proximity will give the Trigger for drive in
-8mm proximity detect dog

pro
-have all the material laying around
-cheap

contra
-part's to make will also take time
-not sure i will work


i am just brainstormin, all comments wellcome.

Thomas



I don’t think this problem is a big as you think with sensorless vector VFD, I once built a pump with that kind of VFD and it ran reliably down to 18 rpm with a load, or 1/100 of base speed. My machines also had to stop and line up with rails that plugged in. Taper your drive dogs as much as you can too, so you don’t need to be perfect. Run the motor at the lowest possible speed and tell it to stop on the sensor. Worse that will happen is that it will overshoot a bit. As long as the overshoot is reliably consistent you can adjust sensor position to accomodate.

i have tryed this solution, but was not able to get the stopping Point good enough.


Another thought about this issue. Things like this work much better when they are designed to be extremely tolerant of misalignment rather than being very accurately made.  So I htink a better approach here is to have the tool gripper mounted to be spring loaded upward.  You press it against the spindle and if the dogs are not lined up the compressing of the spring triggers a limit switch that causes the spindle to rotate until the dogs drop into the slot and the limit switch then indicates that the alignment has been achieved, fasten the tool and  retract the gripper.  No spindle switch needed.

i have a 'umbrella' toolchanger witch drives in/out, and uses zhe Z-axis for tool Change, so no way.

anything is possible, just try to do it.
if you find some mistakes, in my bad bavarian english,they are yours.

Offline Davek0974

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Re: Spindle orientation on a Bridgeport...
« Reply #17 on: February 22, 2018, 03:08:36 AM »
Hi Dave,
I recently bought a second hand 1.8kW Allen Bradley AC servo and drive for a spindle. I needed a spindle motor with some decent torque at slower speeds for steel.
This servo has turned out great. The main reason I went with a servo is that they are the most powerful/torque-y motor for the size.

Its the first time I've really ever played with a modern AC servo and I am impressed, very, very impressed! They are extremely capable and while it was not even
on the radar, stopping the spindle to line up the drive dogs is trivial with a decent servo. My 'zero window' is 4 counts of an 8000 count encoder ie 10.8 arc min!
Easily good enough to line up surely!

I had always been put off by the cost of servos but after playing with one I wont be looking for any other solution anytime.

Craig

How big was the machine, what sort of cuts have you taken with it?

I was thinking to just throw on a 2.6kw servo and see what happens, my experience of servos on the axis drives has shown that they are extremely powerful for the size. I can get a 2.6kw 10Nm cont motor and drive delivered for £500

I would need to gear it up to get 4000 rpm by 1:1.6 as they only do 2500rpm but at top speed it would not be using max power anyway.
« Last Edit: February 22, 2018, 03:10:52 AM by Davek0974 »
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.
Re: Spindle orientation on a Bridgeport...
« Reply #18 on: February 22, 2018, 03:28:37 AM »
Hi Dave,
its 6Nm and 3500 rpm in a baby (X,Y,Z = 200,200,200) bed mill. I have taken 6mm deep cuts with a 16mm endmill in steel with cooling but my machine is flexing
and dancing but throwing chips like its going out of fashion, really impressive.

Prior to getting this Allen Bradley unit I bought a 2.6kW 12Nm 3000rpm Vickers unit, again second hand. When it turned up I would say it was new or maybe
re-manufactured. The date on it suggests 1994. Only downside is it has a 4 pole resolver which severely limits my choices of drive. My interest is electronics so I
decided to make a Field Oriented Control drive for it. Still working on it, been a long learning curve!

As it turns out this is a big servo, too big for my machine, I think it would topple over and my machine can't really handle it all anyway. My plan is to use it as a lathe
spindle motor.

If a hobby is measured by what you learn in the pursuit of it then this servo and drive is a very VERY good hobby, I've had to learn all sorts to stay on track!

Craig
My wife left with my best friend...
     and I miss him!
Re: Spindle orientation on a Bridgeport...
« Reply #19 on: February 22, 2018, 03:36:12 AM »
Hi Dave,
could you not try it direct rather than all the expense and shagging around to gear it?

Of course there is nothing so permanent as a temporary thing.....

May also be possible to push the 2500 rpm. You may have read about 'field weakening', an extremely clever means of manipulating the back EMF constant to
achieve higher rotational speeds for a given input voltage.

I have not seen it mentioned in any servo drive manuals that I've read but you can be sure that my Vickers servo (3000rpm rated, 4000rpm max) drive will have it!

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