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Re: Hybrid Stepper Setup in M4
« Reply #10 on: December 01, 2018, 08:09:16 PM »
I know right but it was so much more rewarding being that much of a jerk isn't it...I mean if you can then...lol

The real magic of course is indeed the Ethernet bus and the interface you can then access and manipulate...even store, execute and run apps....it drives me right to my ever persistent frustration with control logic in general...I don't have the time to mess with them but don't even Arduino or Raspberry Pi's have IO speeds above 1mhz

One really nice thing is I could dial indicate the table and then give an absolute rotation number to the counter and measure my exact travel and very exactly 4000 counts and then -4000 back to an absolute zero and repeat which was really helpful...I then ran a program like I said to try to accumulate drift or backlash and damn was it true...like I said very neat tech....I was also very impressed with the screws.

I am a piss poor artist and always wanted to do scrimshaw...my tech my one day work...lol


Thanks Craig and you're a great well intentioned jerk...keep at it...;)
Re: Hybrid Stepper Setup in M4
« Reply #11 on: December 01, 2018, 08:47:45 PM »
Hi,

Quote
I don't have the time to mess with them but don't even Arduino or Raspberry Pi's have IO speeds above 1mhz

Yes that is correct and the CPU/CPU's inside a PC are very much more powerful again. The problem is that its not the PC's
fault. Mach4 is a Windows program that has a GUI, a Gcode interpreter and a trajectory planner.

What a PC can't do is generate highly accurate very fast pulse streams. There is just too much going on inside a PC's CPU for
it to concentrate on that one job. Consequently the critical job of timing and generating high speed pulse streams is farmed out
to an external motion controller. You can see the size of the FPGA IC on your 57CNC, its not that big and yet it does the business.
It receives numerical trajectory commands from the PC, be it Mach4 or Mach3 or even UCCNC, and converts those numbers into
pulse streams, so in a real sense its the FPGA which is driving your machine, not your PC at all. As it turns out there are a number
of devices which can generate pulse streams, FPGAs are popular but so are a number of microcontrollers optimized for motor control
loaded with highly sophisticated pulse stream modules and various D(igital)S(ignal)P(rocessing) ICs.

Various controllers use different ICs to do the business, some are faster than others, the ESS and HiCon stand out in that regard.
Thus you could use them to signal at full speed and max resolution.....but why? For reasons that I have already posted all the
extra expense and difficulty in doing so will gain you nothing in terms of accuracy, finish or throughput of your machine.

That time and expense is best devoted elsewhere, maybe a better quality spindle with better bearings......or ground C3 grade ballscrews
rather than C7's.....or cast iron beds rather than aluminum.....etc.

The 57CNC controller is very good and has any number of satisfied customers. Once you realize the trade off/balance that you have to make
then it will have your machine singing at top speed. Get your machine up and running and THEN ask yourself 'would uprating to a faster
controller like the ESS of HiCon make any real difference?'.

Craig
My wife left with my best friend...
     and I miss him!
Re: Hybrid Stepper Setup in M4
« Reply #12 on: December 02, 2018, 05:56:12 PM »
OK...point taken and as promised I did some far lower MS...I also started using the tuning app wizard a bit toward the end...I got it to travel out quite well at 16X but it's still behaving rather odd...it sort of self set the Velocity at 226 and Accel 19.95 so I let that ride for the bit of testing I did...Math states 10445.456 Steps and with some tuning I last played with 10,446.6 as per the wizard' of Mach direction...funny thing is on Go To Work Zero I would always be off a thou and repeatedly the thou would accumulate...several back and forth jogs resulting in 3-4 thou off and counting...definitely better but not very good ???
Re: Hybrid Stepper Setup in M4
« Reply #13 on: December 02, 2018, 06:06:36 PM »
Hi,
do you have ballscrews? What pitch? Do you have any gear/belt reduction between the ballscrew and the stepper?

You should be able to calculate the steps per unit. You need to fill in the blanks so we can work it out.

Craig
My wife left with my best friend...
     and I miss him!
Re: Hybrid Stepper Setup in M4
« Reply #14 on: December 02, 2018, 09:03:30 PM »
Greetings Craig...(Drum Roll please)...I may have it...

For clarity...for you...(I am never that lucky)....I have no complications...other than those I live with every minute...not belts or gears to further complicate the mess anyway...PIC LEAD screws and Nuts/flanges(Nearby outfit I use on other stuff....Like I said I ran through the internal motor program for a while and .0002-/+ straight off dovetails  to and fro shocked the hell out of me...I thought there would be something...PIC-Design.com)

I kept after it after I swore I would just drink and got it going pretty well...about 10,414.********* steps in MS and I got it to 0-4998-0-4999 true counter steps...anything beyond that and it would bounce either way about 8 tics and I will mess with the .********* and see what I can do...or not...;)...again just awesome to be able to set the drive in stand-alone mode and then over to S/D and compare dial indicator to internal steps...odd thing is when you put it in S/D mode you can't get the counter but I think I know a trick...talk to my Schneider guy tomorrow...the thing is in S/D mode you lose direct access to the encoder

Like I said I got the Wizard of Mach counting for me and after I got it figured out I had to keep updating the "what's your counter now" part I got pretty good results and eventually ended up with 14,414.*********, 227V and 20.95A and it was almost humming around like the internal program...all in all very close now...
You were right on...16X and this setup can appear to really produce some exemplary results...I will clarify tomorrow I hope.

Thanks for all the co-horting...makes all the difference in the world to us jerks that have to have it beyond sanity...just because..;)
J
Re: Hybrid Stepper Setup in M4
« Reply #15 on: December 02, 2018, 09:30:12 PM »
Hi,

Quote
ended up with 14,414.*********, 227V and 20.95A

All I need to know is the pitch of the ballscrew. Then you can calculate it exactly. Do you have a spec on the screws?

Craig
My wife left with my best friend...
     and I miss him!
Re: Hybrid Stepper Setup in M4
« Reply #16 on: December 03, 2018, 08:25:52 AM »
2mm Pitch, 4 start = ~8mm...I ran it out with a dial indicator monitoring the counter and got 7.771mm in 0-4000 counts...just to be exact...but 8mm as factored...;)

Offline Stuart

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Re: Hybrid Stepper Setup in M4
« Reply #17 on: December 03, 2018, 08:42:18 AM »
Are those trapezoid screws

My books list that size as a trap.

But I cannot find any ref to 4 start ball screws


But of course I stand to be educated

If they are traps. Then that may be the cause of your errors

Stuart
Re: Hybrid Stepper Setup in M4
« Reply #18 on: December 03, 2018, 11:23:02 AM »
Stuart they are in fact an Acme thus a trap screw but I go back to my earlier comment about these particular drives and my verification process for travel....I wrote a standalone program I could use directly off the internal encoder counter and I downloaded that into the motor itself and executed...with all my current hardware and setup I ran the program making a ~100MM circle for about 5-10 minutes with a dial indicated go-to-stop position and repeated and repeated .0002-.0004 kind of numbers and at a speed the Pokeys can't even transmit...I was actually quite surprised to say the least...totally impractical for anything other than a precision tool snapper but as an exercise to determine things like drift, backlash and general limits of functional capabilities it was nothing short of amazing...for a jerk like me anyway...;)
Re: Hybrid Stepper Setup in M4
« Reply #19 on: December 03, 2018, 12:36:09 PM »
Hi,
that pitch specification sounds pretty weird....I would have expected 0.2 or 0.25 inch with an imperial screw and 4, 5 or 6 with
a metric screw. You have devised a means of measuring it ie rotate one turn by observing the encoder and measuring the travel
with a dial gauge. The repeated circles confirm your measurement. Trying to calculate the steps per unit in face of the
unusual pitch spec is questionable.....you have obviously found the right value by measurement.

The only other area that may benefit from tuning is your acceleration. You can of course increase the max velocity but as you
have pointed out it goes pretty damn quick anyway. To increase it beyond that is likely to cause stepper overload and have them
miss steps which with closed loop steppers means they fault 'following error'. What WILL help your cause when machining is having the
highest acceleration your steppers will tolerate. It will improve your CV accuracy and your cycle times dramatically, much more so than
increasing your max axis speed.

May I suggest doubling and redoubling your acceleration until you find a limit where steppers stall/fault 'following error' and then back off
until you get reliable acceleration with the machine loaded with the max weight workpiece.

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