Need help brainstorming a solution for this mill turn spindle

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Originally Posted by mactec54

No Resolution is lost if it was, your servo drive would go into a fault mode

Again you are fixated on resolution, there are many ways to solve this buy buying the right servo and Encoder to start with, or a lower count encoder and use mechanical gearing, machines have had this capability for years nothing new in what you are trying to do, mill turn machines are every where

The snip I posted was to show you that you can get this step resolution quite easy, which you keep saying you can't

You have no concept at all of what you are trying to do, I have done it so know how it works

Yaskawa
Mitsubishi
Delta
And others
All have a servo system where you could use there servo and servo motor direct drive and have an even much higher accuracy for indexing than what you are looking for, plus 3000RPM for turning all capable of being run by Mach3

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No man, you're still not getting it and I feel like you're not even reading my posts. I never once said you can't get that step resolution, you just can't get that step resolution AND high rpm. I've repeated it literally like 10 times and you just turn it into something else. Yes, you can get the resolution back with mechanic gearing. What happens then? YOU LOSE THE MAX RPM. I'm going to repeat it again. It's very easy to get as fine of resolution as you want, but not at the same time as getting high rpm along with it. Yes, many mill turns out there. They either use drives and servos worth thousands of dollars with higher frequency capability, or they use dual drive with magnetic clutches to engage one or the other. I understand what the limitations are and that i have to find a happy medium between speed and resolution, but your claim of not losing resolution when increasing electric gearing for higher rpm capability is just flat out wrong. Somehow you are going around in a circle and not realizing what the final result is. Yes you can have higher electronic gearing and get your resolution back by gearing it down mechanically, but you've just gone in a circle and brought your max rpm back down with mechanical gearing.

As for the brands you mentioned that can hit 3000 rpm with .005 degree resolution, they either have 3mhz plus frequency drives, which I doubt unless they are thousands of dollars, or you're once again flat out wrong.

Quinn,

There's a bit of useful advice buried above...

One way around the speed/resolution compromise is to find a different servo & drive combo. The DMM was suggested as it's a superb cost to feature package, but with the 500khz input limitation.

As an example of drives with higher input frequency limits, I have an older Parker Gemini I'm setting up for a spindle motor. A quick check shows it has a 2MHz step input limit - 4x the DMM. I suspect it's due to better optos, but I could be wrong.

Checking Parker's latest drives, it looks like the newer Compax series supports up to 5MHz inputs. With a drive input like that coupled with a 32bit encoder on the motor, you could have seriously fine resolution and still support high-speed spindle operation.

Trolling ebay for a gently-used creampuff servo & drive combo might get you where you want, although I think the DMM with a dual gear ratio drive would still work like a champ.

-R

EDIT - you obviously get it. Just sayin... I found my drive & motor for $hundreds, not $thousands.

Yep, another drive with higher frequency capability would be the only option for higher rpm with same resolution, but in my price range I'm sure that means buying used. Not that I'm against buying used, but the dmm is going to work fine for me and I've already come up with a happy medium configuration that will work for me. I'm just trying to clear up misinformation. The conversation was about the dmm drive to begin with and the idea that increasing electronic gearing doesn't decrease resolution, which it does.

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Originally Posted by QuinnSjoblom

Yep, another drive with higher frequency capability would be the only option for higher rpm with same resolution, but in my price range I'm sure that means buying used. Not that I'm against buying used, but the dmm is going to work fine for me and I've already come up with a happy medium configuration that will work for me. I'm just trying to clear up misinformation. The conversation was about the dmm drive to begin with and the idea that increasing electronic gearing doesn't decrease resolution, which it does.

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And is that not what I have been telling you check my posts

And again the electronic Gearing does not change the Resolution at the shaft of the servo motor the Encoder you can not change it's Resolution only the way you drive it

Well if you are still talking Dmm then you need to look at there 32Bit Encoder and job is done, this was developed for Robot precise positioning, so would work perfect for what you are trying to do, which I said from the start

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Originally Posted by spumco

I think the DMM with a dual gear ratio drive would still work like a champ.

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That is what I have been telling them

DMM has a 32 Bit encoder which I already suggested that as well too

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Originally Posted by mactec54

And is that not what I have been telling you check my posts

And again the electronic Gearing does not change the Resolution at the shaft of the servo motor the Encoder you can not change it's Resolution only the way you drive it

Well if you are still talking Dmm then you need to look at there 32Bit Encoder and job is done, this was developed for Robot precise positioning, so would work perfect for what you are trying to do, which I said from the start

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No, the encoder is not the limit in this case, the drive is. That's the part you're not getting. The dyn4 drive maxes out at 500khz. You can not get 3000rpm AND full resolution of encoder. With electronic gearing added to stay within 500khz, each step received by mach3 is going to turn the servo multiple encoder counts, therefore reducing resolution. I can get a quote directly from the manufacturer if that's what it's gonna take. If you drove the servo with full encoder resolution at 3k rpm, you would would be hitting the drive with over 3 mhz which it can't handle

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Originally Posted by QuinnSjoblom

No man, you're still not getting it and I feel like you're not even reading my posts. I never once said you can't get that step resolution, you just can't get that step resolution AND high rpm. I've repeated it literally like 10 times and you just turn it into something else. Yes, you can get the resolution back with mechanic gearing. What happens then? YOU LOSE THE MAX RPM. I'm going to repeat it again. It's very easy to get as fine of resolution as you want, but not at the same time as getting high rpm along with it. Yes, many mill turns out there. They either use drives and servos worth thousands of dollars with higher frequency capability, or they use dual drive with magnetic clutches to engage one or the other. I understand what the limitations are and that i have to find a happy medium between speed and resolution, but your claim of not losing resolution when increasing electric gearing for higher rpm capability is just flat out wrong. Somehow you are going around in a circle and not realizing what the final result is. Yes you can have higher electronic gearing and get your resolution back by gearing it down mechanically, but you've just gone in a circle and brought your max rpm back down with mechanical gearing.

As for the brands you mentioned that can hit 3000 rpm with .005 degree resolution, they either have 3mhz plus frequency drives, which I doubt unless they are thousands of dollars, or you're once again flat out wrong.

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This is doing a linear motion move but can be done from 0-3000RPM some models will do 6000RPM and any degree increment you want to choose

They show changing the electronic gear and the Degree's that it can move at

https://www.youtube.com/watch?v=LbVFEgC9DWo

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Originally Posted by QuinnSjoblom

No, the encoder is not the limit in this case, the drive is. That's the part you're not getting. The dyn4 drive maxes out at 500khz. You can not get 3000rpm AND full resolution of encoder. With electronic gearing added to stay within 500khz, each step received by mach3 is going to turn the servo multiple encoder counts, therefore reducing resolution. I can get a quote directly from the manufacturer if that's what it's gonna take. If you drove the servo with full encoder resolution at 3k rpm, you would would be hitting the drive with over 3 mhz which it can't handle

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Do it everyday

Every body that buys a DMM use there Electronic Gearing to set up there step ratio they all get the max RPM 3000 or 5000RPM is possible up to the 750W motors the larger servo motors for most manufactures top out at 3000RPM

You could set it up like my mill 4th axis, 3600 steps per degree. But on the other hand, my 4th axis maxes out at about 10 RPM :D

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Originally Posted by mactec54

Do it everyday

Every body that buys a DMM use there Electronic Gearing to set up there step ratio they all get the max RPM 3000 or 5000RPM is possible up to the 750W motors the larger servo motors for most manufactures top out at 3000RPM

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And like I keep saying, yes you can get the 3000 to 5000rpm, but not at full resolution. It's a really simple concept. If steps per rev are set for 2000 for example, the rotation is split into 2000 equal steps and a single step is the smallest move. Really feel like a broken record. It's getting kind of pointless. Doesn't matter how I put it, doesn't seem to get through. Only way to get full resolution and max rpm is with higher frequency capable drive. Do you understand how the frequency limit comes into play? It can only handle so many pulses per second. Do the math, it's simple. If you were sending 16 bit worth of pulses every rev at 3k rpm, you would be over 6 times the limit of the drive. There's no way around this.

Unless you changed the digital gearing on the fly - you don't care about positioning so much when you're using it as a spindle, and you don't care about speed so much when you're doing fiddly precision. How you get Mach3 to spit that out is another question altogether...

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Originally Posted by dharmic

Unless you changed the digital gearing on the fly - you don't care about positioning so much when you're using it as a spindle, and you don't care about speed so much when you're doing fiddly precision. How you get Mach3 to spit that out is another question altogether...

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Yep, and that's kind of how I'm gonna handle it. Don't think there's a way to do it on the fly, but basically for one group of smaller diameter parts, I need full rpm and not as much resolution. Other parts, mostly just the large gears I'll be hobbing, need higher resolution and no need for speed. I've decided a single mechanical gear ratio will work for both, but electrical gearing/ steps per rev will be changed back and forth for one vs the other. With hobbing the big gears, I need the resolution but doesn't require much torque so 2 to 1 mechanical is still fine. The hob itself actually pulls the gear along at the specific rate of 4th axis rotation, so the 4th needs hardly any torque behind it at all. I'm thinking most likely I'll get the dmm 1kw. More than enough power for what I need to do. I'll gear it down mechanically 2 to 1 for 1500rpm max and about 4000oz/in torque which is gonna be plenty for most of what I do. When geared down electrically far enough to allow full rpm, it will give me .015 degree step which will also be good enough for most work. When hobbing gears, i will take out electrical gearing which will give me .0025 degree resolution and limit rpm. All this is with leaving mechanic gearing at 2 to 1. I'll have different pulley options for turning faster at lower res or slower at higher res, but I think the 2 to 1 ratio is gonna be a good general purpose setup that allows turning and milling in same program. Keep in mind, these are aluminum parts, under 2 inches in diameter, most of them closer to 1 inch, So i think 4000oz/in torque should hold plenty well enough during index milling. On a 1 inch diameter part, it will handle 500lb of tool pressure on the outside edge. 2 inch part will handle 250lb of tool pressure. I think it's gonna work just fine. For turning operations, 1kw goes a long way in aluminum. Easily a few cubic inch per minute mrr.