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731

General Mach Discussion / Re: Switched out my PC and now Mach3 is unhappy

« on: August 23, 2010, 07:31:28 AM »

No, if tuned correctly they have very little noise and if you monitor the encoder in the software it does not vary at all.

Thx. I have the mistu software, but have not used it yet, however the J2S series drive has a 4 digit DRO that can be set to display just about any data in real time, including encoder feedback, so I can monitor that without the software. The J2S is the first servo drive I have used that I can say I am completely satisfied with . . . so far  . I would describe the J2S similarly to how you rate the Allan Bradley; 'very little noise'.

I will be needing more AC servos so I am just collecting info on the options.  The Mistubishi J3 is a freak! Too new though, and not readily avaialble from the junkyards yet.

732

General Mach Discussion / Re: Switched out my PC and now Mach3 is unhappy

« on: August 23, 2010, 07:04:03 AM »

. . .  are what they call intelligent encoders and you can have, if I recall correctly,  the drive interpolate up to 2 million counts per rev(8million pulses per revolution  ), thats even beyond SmoothStepper territory I was happy just at the base 1024 x 4 for a spindle.

I had 1800x4 on the 4th axis (good for division by 360) with the DC brush servo. With both the Dugong drive and the Granite drive, it makes no noise when holding still.

Currently I am working with two different series Mitsubishi AC servo drives now, the larger of which I *think* is similar to the Alan Bradley 3000 series . . maybe. The little Mitsu MR-C has only 4000 pulses per rev and 'sings' (to quote Gecko) when holding, presumably due to bouncing back and forth between adjacent pulses. This is very noticeable on the MR-C, but with the J2S drive, while it still sings, it is almost inaudible perhaps due to a much higher frequency and much smaller step (131,000 steps). That servo motor is also brand new so that may also have some contribution to the far lower noise level.

So, my question is; does the Allan Bradly drive/motor behave similarly, i.e. do they 'sing' or make any noise when holding still?

733

General Mach Discussion / Re: Switched out my PC and now Mach3 is unhappy

« on: August 21, 2010, 03:40:49 PM »

Glad you added the "(so far)" bit
It is like you say that 2 yrs is a long time but I also thought mine was fine,  occasionally however it would get wee glitches and dropping the kernel down to 45KHz cured these problems. Worth noting was that 65 and 75k ran like crap for some reason and was apparent from the start that things were not right on these kernels.

My last computer was as you describe. I could only run about 45 with the 2.6ghz processor. I switched only the processor to a 3.2ghz with hyperthreading and then I could run 75k. If I set it to 100k, it would only actually kick out 89k which I found odd. I would have though it would either work or not, but it was running as a reduced speed which made me nervous so I backed it off to 75, but it ran fine there . . . uh  . .  well , until the RPM readout went psyco on it. The new computer I just put in has a dual processor @ 2.93 (or there about) and dual channel memory so it is far more powerfull than the old one and SO FAR it is running at 100k no problem. I will leave it there for all of my testing, but probably drop it back to 75 if I cut anything expensive . .  

As for electronic gearing, some like it others dont, I am in the latter camp. Real world it may not make a big difference buit I just didnt like the jerky motion on a clock (DTI) when I commanded a very slow move with an electronic gearing of 6 or so, put it to none and it was silky smooth

There may be other factors, but one for certain is the way the drive handles the process. The Mistubishi MR-C series also is not very happy with multipliers. However, I would put a $100 bill on the bench and give it to you if you could tell the difference between a 6x an 0x multiplier on a Granite drive running a DC brush motor. Likewise the Mistubishi J2S series is smooth as silk running a HUGE multiplier . . .  the thing has outrageous resolution. "An up to 500kpps high-speed pulse train is used to control the speed and direction of a motor and execute precision positioning of 131072 pulses/rev resolution."The only time I have ever actually recommended the Smoothstepper was to use with Dugongs since that drive runs pretty badly with multipliers, especially at low speeds as you pointed out.  Curiously, the little brother Whale drive is fine with multipliers active. I still run those on my X and Y axis at 5x or 6x.  Mind you that when set at 1:1 the Dugong is a killer. Smooth and very powerfull with the ability to stop on a dime.

734

General Mach Discussion / Re: Switched out my PC and now Mach3 is unhappy

« on: August 21, 2010, 11:45:42 AM »

Thanks docltf

If they correct my rather significant boo-boo in the math (what's an order of magnitude between friends, eh?) then they are certainly free to use it.

The correct number of pulses per second for the servo example is 533,000 . . . slightly above Mach's maximum kernel speed.  

Even if one can run Mach at 100k, a 6x multiplier would still be needed in that example to get max RPM. This is  doable with many, if not most, servo drives . .  and also explains why I have to use multipliers . . .  

Another example for a realistic servo setup at the hobby level would be:

3,000 RPM x 2000 steps per rev (500 line encoder in quadrature) = 6,000,000 steps per minute which coincidentally is 100,000 per second . .  if I got it right this time  

735

General Mach Discussion / Re: High speed spindle recommendations

« on: August 21, 2010, 11:23:03 AM »

Seems we are on the same page, albeit in different scales and with some symantics. I recall you are in the middle east and I am in the USofA.

Big multiple V-belts as one would find on a machine tool are called 'banded' or 'ganged' in my world. Also big V-belts can be had in 'matched sets' (matched for exact length, but separate belts.)

The little brother is called 'grooved' or 'ribbed' and in automotive speak is a 'serpentine' belt, although that desribes the arrangment and not the belt structure. A difference, (other than the obvious  . . . size) is that the grooved belt has traction material on the smooth side which is intended as a drive surface in a serpentine arrangement.

I'm not clear on which belt type 'poly v' refers to, but it seems that you used the term for both a big machine tool and Hood's little engraving spindle, so it seems the term is somewhat universal. And yes, your are right about suppliers also. A 'grooved' belt purchased from an industrial supply house might be $10. But the identical 'Serpentine' belt from an automotive store is $38.      Go figure.

736

General Mach Discussion / Re: Switched out my PC and now Mach3 is unhappy

« on: August 21, 2010, 09:17:04 AM »

It is all in the numbers.

Figure out the RPM you want to run the motors and the numbers of steps required to achive that , for example (using round numbers);

Steppers  1,000 RPM x 200 steps per rev = 200,000 pulses (per minute) which is only about 3,300 pulses per second, so 25,000 kernel speed would be plenty, however, if you have 10 micro step drive, suddenly you need 33,000 pulses.

Servo     4,000 RPM x 8000 steps per rev = 32,000,000 pulses per minute which is 53,300 steps per second, so you yound need to run 60k kernel speed to get full rpm.

Alternatives to full kernel speed in Mach are pulse mulripliers in the drives or a pulse gerenator independent to Mach3 such as Smoothstepper or Kflop.

A few years ago is a long time in computer history. I just put together what I would call a 'budget' build using 2 gerations out-of-date technology (socket 775) and it is running Mach at 100k (so far). A good test of headroom is to open the task manager and set it on performance and then drag it rapidly around the screen as Mach is running a program.

737

General Mach Discussion / Re: High speed spindle recommendations

« on: August 21, 2010, 08:51:15 AM »

Timing belts produce noise (and heat) as the speed increases - this is a fact!

I agree with you on this point, although it also applies to belts of all types.

Since we cannot agree on v-belt vs timing belt, perhaps we should compromise on a grooved belt . . . a.k.a.  'serpentine' as it is commonly called in automotive applications.

This would avoid the single disadvantage of timing belts . . they cost several times more than v-belts.

In this way, I can be satisfied with it's 'flatness' and you can find joy in it's  . .  'V' ness. 

Seriously, a groove belt is an alternative worth considering because it fall in price between the 'timing' belt and the 'V'-belt and the pulleys are stupid easy to make and since the grooves are shallow, the pulley can be small in dia . . . . so long as it stays within the flex radius spec so we can be scientific. 

738

General Mach Discussion / Re: RPM readout showing negative numbers . . suddenly . . . WTF??

« on: August 21, 2010, 03:34:00 AM »

I got the tuning done and it was really sweet but was fully expecting having to detune again so I had exported the previous drive profile, ready to import it again,  but to my amazement that setting has been good and its still used for all work.

What has worked well for me is to tune the drives to be as stupidly sharp and tight as possible and then control the resulting 'bang' (with a light load) using Mach's acceleration settings. I find it easier to tweak with the acceleration than to retune the drives. And changing the acceleration in Mach has almost no effect on overshoot, so it is 'safer' to play with.

Incidentally,  are you running the Allen-Bradley drives using pulse step and direction out of Mach3?

739

General Mach Discussion / Re: RPM readout showing negative numbers . . suddenly . . . WTF??

« on: August 20, 2010, 05:53:26 PM »

Final update. New computer went in today and all is good . . . .  better than good, actually.

I wanted to re-use as much of my existing stuff as possible so I did a budget build using an ASUS motherboard P5G41-M LX2 with an Intel E6500 dual core processor. I re-used the memory, PCI parallel port card, hard drives, case, etc. from the old computer. The new computer is getting along fine so far with Mach3 and is running stable at the full 100k pulse speed.

Typically I use Intel motherboards for business and Gigabyte for everything else, but I have always heard good things about ASUS. This is my first ASUS and it's a quality board and everything went together perfectly.

740

General Mach Discussion / Re: Switched out my PC and now Mach3 is unhappy

« on: August 20, 2010, 05:48:48 PM »

FWIW, I just today installed a new computer on my CNC mill that happens to have an ASUS mother board also. The old computer got a gremlin in it and was doing very bizarre things.

The new computer is a budget build using an ASUS motherboard P5G41-M LX2 with an Intel E6500 dual core processor. I re-used the memory, PCI parallel port card, hard drives, case, etc. from the old computer. The new computer is getting along fine so far with Mach3 and is running stable at the full 100k pulse speed.