Dynomotion

Group: DynoMotion Message: 12083 From: moray_cuthill Date: 8/8/2015
Subject: Thoughts wanted on controlling a varispeed mill spindle

Hi,


one of my long term retrofit projects is to get an old Matchmaker/Shizouka ST-N mill going.

The head on this is a varispeed, and also has a VFD on the spindle motor. The varispeed was originally controlled via the Summit (one arm bandit) tool changer and a stepper motor. There is an encoder fitted to the spindle, and just to a little extra to the mix, the spindle also has a high/low speed controlled via a pneumatic cylinder.


Nobody knows if the varispeed was ever used after the previous retrofit (which added the VFD, servos and Heidenhain control - the previous owner only bought it for servos and controller), but I'm thinking it would be good to be able to control it to maximise spindle power, as this mill will mostly be dealing with lumps of steel once running.


Which brings me to what I'd like input on.

I'm going to be fitting a KFlop plus Kanalog (plus a Konnect, but that doesn't really matter for this bit), and am wondering how others would go about controlling this lot.

Run the VFD at full speed, and rely on the varispeed, and switch between Hi/Lo when required?

Use some form of dual loop control between the VFD and varispeed?

Also, how do you actually program to use the HiLo? Extra code in the G-code, or program the KFlop to decide if a range change is needed?


Obviously speed control doesn't have to be absolutely precise, but I'm not wanting to end up with it continually hunting, and I'll need to somehow interface the varispeed stepper to the KFlop (I'm thinking of getting one of the analogue stepper drivers so I can control it via an analogue output rather than have to connect to the remaining header on the KFlop and add an individual stepper driver)


I'm open to everybody's thoughts/opinions on how they'd implement this.


Thanks,

Moray
Group: DynoMotion Message: 12084 From: Tom Kerekes Date: 8/8/2015
Subject: Re: Thoughts wanted on controlling a varispeed mill spindle
Hi Moray

Here are some questions/thoughts:

Can the desired gear be determined solely from the speed setting (S) ?

Does the spindle need to stop to switch gears?

Do you need CW and CCW control?  If so how it it handled?

If the speed is gradually increased (ie SSO) should the gears be switched?  One approach might be to only select gears when first commanded from a stop.

What is the issue with using another connector for Step/Dir?

Dual Loop sounds reasonable to me.  The inner loop might control the Varispeed position.  The Outer loop would work like a traditional servo with encoder feedback and the output adjusting the speed. 

HTH
Regards
TK

Group: DynoMotion Message: 12085 From: Moray Cuthill Date: 8/8/2015
Subject: Re: Thoughts wanted on controlling a varispeed mill spindle
Hi Tom,

thanks for the reply.
I just had to go and check, but yes, the gear can be decided by speed. Low range covers 80-480, and High 600-3600 according to the gauge on the dial. Obviously those speeds are for the rated motor speed of 1450rpm.

Yes the spindle does have to stop to change gears. The gear change is a simple sliding coupling affair, although a very low speed may be needed to ensure engagement, but that's a detail that can be dealt with later.

CW and CCW would be good, and would have to be controlled via the VFD.

If a gradual speed increase was commanded (or at least an increase/decrease that would involve switching speed ranges), I was thinking the KFlop could be programmed to halt the spindle, carry out the required change, then restart things.
However I'm not sure how things like gear changes are normally handled in G-code?

I've got no great issue with using a step/dir output, it was just I'd seen some stepper drivers that take analogue inputs, and I thought it may give a neater solution, but I'm open to using a conventional stepper driver.

The dual loop/control sounds like what I was thinking. I was thinking use the varispeed as a rough speed control, with the VFD fine tuning things. Something along the lines of the VFD having an upper/lower output limits, and if those limits get exceeded adjust the varispeed to bring the VFD back within the limits. Obviously some code would need to be added to ensure the varispeed only gets adjusted with the spindle running, and starting/stopping should take care of itself (VFD reaches limit, then varispeed is adjusted to reach correct speed). Although I suspect two sets of tuning parameters may be needed for Hi/Lo ranges given the different accelerations/ratios involved.

Moray

On Sat, Aug 8, 2015 at 9:16 PM, Tom Kerekes tk@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:
 

Hi Moray

Here are some questions/thoughts:

Can the desired gear be determined solely from the speed setting (S) ?

Does the spindle need to stop to switch gears?

Do you need CW and CCW control?  If so how it it handled?

If the speed is gradually increased (ie SSO) should the gears be switched?  One approach might be to only select gears when first commanded from a stop.

What is the issue with using another connector for Step/Dir?

Dual Loop sounds reasonable to me.  The inner loop might control the Varispeed position.  The Outer loop would work like a traditional servo with encoder feedback and the output adjusting the speed. 

HTH
Regards
TK

Group: DynoMotion Message: 12088 From: Tom Kerekes Date: 8/9/2015
Subject: Re: Thoughts wanted on controlling a varispeed mill spindle
Hi Moray,

See below:

Group: DynoMotion Message: 12093 From: Moray Cuthill Date: 8/10/2015
Subject: Re: Thoughts wanted on controlling a varispeed mill spindle
Hi Tom,

yes, there is a gap in the speed range between high and low ranges.

I've done a bit searching, and it appears M40-46 are usually reserved for gears, with M40 being automatic selection, and M41-46 selecting/forcing gears 1 to 6 respectively, with the actual implementation varying between manufacturers.

What you've said about using both the VFD and Varispeed to control speed is what I was thinking. It should be reasonably easy to implement by monitoring the VFD channel output, and adjusting the Varispeed output channel. 

So based on that, I'm thinking mostly rely on auto-selection, with the option to force gears, and prevent SSO from moving between ranges with the spindle running.
I'm also thinking it may be useful at times to run the high range slower relying on the VFD to do so, but that would involve detecting when the Varispeed has hit it's lower limit, to avoid the stepper from being continually driven trying to compensate for the slow VFD speed. There's currently no limit switches, but I'm sure a couple can be fitted.

Thanks for your input. I've now got a bit clearer plan in my head on how the spindle will work, so I can move onto the other details needed to get this machine running.

Thanks,
Moray


On Sun, Aug 9, 2015 at 6:35 PM, Tom Kerekes tk@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:
 

Hi Moray,

See below:

Group: DynoMotion Message: 12094 From: Eon de Koker Date: 8/10/2015
Subject: Re: Thoughts wanted on controlling a varispeed mill spindle

Hi

Just a comment. We also have an old mill with Continiously Variable Transmission belt drive and manual gear change. We fitted a Variable Speed Drive to drive the 3 phase AC spindle motor. We now only use the highest gear and fixed belt setting because we can set any slower Spindle speed by electronically adjusting the frequency of the Variable Speed Drive using a 0-10V analog voltage. The spindle speed is directly proportional to the motor frequency.

Because the full torque of the spindle motor is avaliable at any speed setting using the Variable Speed Drive, we have not yet found it necessary to use mechanical gearing or belt gearing.

Regards

Eon

 

From: DynoMotion@yahoogroups.com [mailto:DynoMotion@yahoogroups.com]
Sent: Monday, 10 August 2015 19:27
To: DynoMotion@yahoogroups.com
Subject: Re: [DynoMotion] Thoughts wanted on controlling a varispeed mill spindle

 

 

Hi Tom,

 

yes, there is a gap in the speed range between high and low ranges.

 

I've done a bit searching, and it appears M40-46 are usually reserved for gears, with M40 being automatic selection, and M41-46 selecting/forcing gears 1 to 6 respectively, with the actual implementation varying between manufacturers.

 

What you've said about using both the VFD and Varispeed to control speed is what I was thinking. It should be reasonably easy to implement by monitoring the VFD channel output, and adjusting the Varispeed output channel. 

 

So based on that, I'm thinking mostly rely on auto-selection, with the option to force gears, and prevent SSO from moving between ranges with the spindle running.

I'm also thinking it may be useful at times to run the high range slower relying on the VFD to do so, but that would involve detecting when the Varispeed has hit it's lower limit, to avoid the stepper from being continually driven trying to compensate for the slow VFD speed. There's currently no limit switches, but I'm sure a couple can be fitted.

 

Thanks for your input. I've now got a bit clearer plan in my head on how the spindle will work, so I can move onto the other details needed to get this machine running.

 

Thanks,

Moray

 

 

On Sun, Aug 9, 2015 at 6:35 PM, Tom Kerekes tk@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:

 

Hi Moray,

 

See below:

 

From: "Moray Cuthill moray.cuthill@... [DynoMotion]" <DynoMotion@yahoogroups.com>
To: DynoMotion@yahoogroups.com
Sent: Saturday, August 8, 2015 3:41 PM
Subject: Re: [DynoMotion] Thoughts wanted on controlling a varispeed mill spindle

 

 

Hi Tom,

 

thanks for the reply.

I just had to go and check, but yes, the gear can be decided by speed. Low range covers 80-480, and High 600-3600 according to the gauge on the dial. Obviously those speeds are for the rated motor speed of 1450rpm.

>> what about 480-600?

Yes the spindle does have to stop to change gears. The gear change is a simple sliding coupling affair, although a very low speed may be needed to ensure engagement, but that's a detail that can be dealt with later.

 

CW and CCW would be good, and would have to be controlled via the VFD.

 

If a gradual speed increase was commanded (or at least an increase/decrease that would involve switching speed ranges), I was thinking the KFlop could be programmed to halt the spindle, carry out the required change, then restart things.

>>> It could certainly be handled automatically, but I worry if you are cutting metal and the Operator nudges the SSO slightly and Spindle is automatically halted to change gears that bad things will happen.

However I'm not sure how things like gear changes are normally handled in G-code??

>>> Me either.  It is up to you.  The simplest thing would be to change gears explicitly with an M Code or User Button.  That way you would have full control how/when things happen.  But the disadvantage would be you would have to remember to do things properly.

 

I've got no great issue with using a step/dir output, it was just I'd seen some stepper drivers that take analogue inputs, and I thought it may give a neater solution, but I'm open to using a conventional stepper driver.

 

The dual loop/control sounds like what I was thinking. I was thinking use the varispeed as a rough speed control, with the VFD fine tuning things. Something along the lines of the VFD having an upper/lower output limits, and if those limits get exceeded adjust the varispeed to bring the VFD back within the limits. Obviously some code would need to be added to ensure the varispeed only gets adjusted with the spindle running, and starting/stopping should take care of itself (VFD reaches limit, then varispeed is adjusted to reach correct speed). Although I suspect two sets of tuning parameters may be needed for Hi/Lo ranges given the different accelerations/ratios involved.

>>> I assumed the VFD setting would be fixed and control would be made with the Varispeed.  But it sounds like you are thinking to adjust both.  One approach might be to have the servo output simply control the VFD.  But then have a background loop (or servo axis) control the Varispeed.  This loop's goal would be to keep the VFD output at say 95%.  So say if the VFD Output is less than 93% then gradually decrease the varispeed.  If more that 97% then gradually increase the Varispeed.

Regards

TK

 

 

 

Moray

 

 

On Sat, Aug 8, 2015 at 9:16 PM, Tom Kerekes tk@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:

 

Hi Moray

 

Here are some questions/thoughts:

 

Can the desired gear be determined solely from the speed setting (S) ?

 

Does the spindle need to stop to switch gears?

 

Do you need CW and CCW control?  If so how it it handled?

 

If the speed is gradually increased (ie SSO) should the gears be switched?  One approach might be to only select gears when first commanded from a stop.

 

What is the issue with using another connector for Step/Dir?

 

Dual Loop sounds reasonable to me.  The inner loop might control the Varispeed position.  The Outer loop would work like a traditional servo with encoder feedback and the output adjusting the speed. 

 

HTH

Regards

TK

 

From: "moray.cuthill@... [DynoMotion]" <DynoMotion@yahoogroups.com>
To: DynoMotion@yahoogroups.com
Sent: Saturday, August 8, 2015 10:37 AM
Subject: [DynoMotion] Thoughts wanted on controlling a varispeed mill spindle

 

 

Hi,

 

one of my long term retrofit projects is to get an old Matchmaker/Shizouka ST-N mill going.

The head on this is a varispeed, and also has a VFD on the spindle motor. The varispeed was originally controlled via the Summit (one arm bandit) tool changer and a stepper motor. There is an encoder fitted to the spindle, and just to a little extra to the mix, the spindle also has a high/low speed controlled via a pneumatic cylinder.

 

Nobody knows if the varispeed was ever used after the previous retrofit (which added the VFD, servos and Heidenhain control - the previous owner only bought it for servos and controller), but I'm thinking it would be good to be able to control it to maximise spindle power, as this mill will mostly be dealing with lumps of steel once running.

 

Which brings me to what I'd like input on.

I'm going to be fitting a KFlop plus Kanalog (plus a Konnect, but that doesn't really matter for this bit), and am wondering how others would go about controlling this lot.

Run the VFD at full speed, and rely on the varispeed, and switch between Hi/Lo when required?

Use some form of dual loop control between the VFD and varispeed?

Also, how do you actually program to use the HiLo? Extra code in the G-code, or program the KFlop to decide if a range change is needed?

 

Obviously speed control doesn't have to be absolutely precise, but I'm not wanting to end up with it continually hunting, and I'll need to somehow interface the varispeed stepper to the KFlop (I'm thinking of getting one of the analogue stepper drivers so I can control it via an analogue output rather than have to connect to the remaining header on the KFlop and add an individual stepper driver)

 

I'm open to everybody's thoughts/opinions on how they'd implement this.

 

Thanks,

Moray