Messages

3431

Mach4 General Discussion / Re: Hybrid Stepper Setup in M4

« 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

3432

Mach4 General Discussion / Re: Hybrid Stepper Setup in M4

« on: December 01, 2018, 08:47:45 PM »

Hi,

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

3433

Mach4 General Discussion / Re: Hybrid Stepper Setup in M4

« on: December 01, 2018, 07:40:27 PM »

Hi,
even I you had a controller that could deliver the pulses and the electronics to drive a signal over the cable so you could use
256 micro steps OR 8 micro steps I doubt you could tell the difference. The resolution at even 8 micro steps is likely to exceed the
rigidity and accuracy of a hobby machine so the finish and accuracy of the parts you make are going to be determined by the
mechanics of the machine....not the resolution of your steppers at all.

I see your comment about whizzing the machine around but from the internal program. The internal program is speed limited only by
the TCP/IP speed, ie very high indeed.

If you had Gcode to copy that program and run it in Mach4 through your 57CNC controller provided you kept within the pulse speed limitation of
the 57CNC it would perform perfectly. But that would mean slowing it down to approx. 10% of its current speed. Alternately you can, as I have
recommended, reduce the resolution and therefore can increase the speed. There is a tradeoff and balance that you can experiment with.

In my previous post I told you about me making my own line driver to drive my servo at 466kHz. I needed that frequency only because I wanted
full resolution, ie 8000 counts per rev or 2.7 arc min......for a spindle.....why? The reason is because I was being a jerk....I don't need anything like
that resolution on a spindle, 30 arc min would be entirely adequate for rigid tapping. That would have reduced the required pulse speed to 42kHz
which my single ended BoB could have done easily!

Craig

3434

Mach4 General Discussion / Re: Hybrid Stepper Setup in M4

« on: December 01, 2018, 06:45:23 PM »

Hi,
this is from the Schnieder website for your 23 size stepper:

Encoder (3) Line count 1000 lines / 4000 edges per rev

So what's the point in trying to achieve a micro step regime that has finer resolution than the encoder can support?
The encoder has 1000 lines or therefore 4000 counts per rev. Trying to exceed that is pointless.

Craig

3435

Mach4 General Discussion / Re: Hybrid Stepper Setup in M4

« on: December 01, 2018, 06:34:35 PM »

Hi,

Is there perhaps another controller to drive this level of motor more effectively...this is a toy for me in truth and it's the exercise itself that intrigues me the most

There is, the Ehternet SmoothStepper (ESS) by Warp9 TD is good to 4MHz and the Hicon by Vital Systems is goo to 8MHz.
You don't need either.....the only reason you are having difficulty is because you wish to retain totally impractical and unrealistic resolution.
Its good for bragging......but it has no substance in reality.

With your current setup:
51200 pulse per rev connected to a 5mm pitch ballscrew suggests a linear resolution of 0.1um....or 100nm. If your machine is that good that you
can expect 100nm accuracy then what are you doing pissing around with steppers (of any description), a 57CNC and Mach4?

With my recommendation of 8 micro steps per full step:
1600 pulse per rev connected to a 5mm pitch ballscrew is a linear resolution of 3.1um. That's impressive.....not just for a hobby machine but would
be respectable is heavy industrial machines worth hundreds of thousands of dollars. You will also be able to take full advantage of the speed of the
steppers.

Steppers, closed loop  or otherwise lose torque the faster you go. Even good (low inductance) steppers are likely to have less that 25% of their holding
torque at 1000rpm. If you believe the advertising material that suggests closed loop steppers avoid that problem then....YOU"VE BEEN HAD by slick
advertising. I would argue that expecting a stepper to go much faster than 1000rpm is not realistic.....that sort of speed it where servos come into
their own.

In truth (I have just read your comment about the ESS) is that you don't need a better controller but be realistic about what you expect from it.
I like the ESS, I have one and love it. I have a servo as a spindle motor and to drive it at full resolution (8000 counts per rev) at full speed (3500rpm)
requires a pulse stream of 466kHz. The servo drive can handle up to 500kHz with a differential drive. So I had to make one for my ESS as my BoB
couldn't manage that being single ended. If you think its a simple matter to drive a signal in the low MHz range you're dreaming.

Craig

3436

Mach4 General Discussion / Re: Hybrid Stepper Setup in M4

« on: December 01, 2018, 04:18:43 PM »

Hi,
I think your microstepping regime is wrong.

You have left it as default at 256 microsteps per full step or 51200 microstepps per revolution. If you want your stepper to do 1200rpm
or 20 revs per second then the pulse rate would be 20 X 51200 =1.024MHz. That's radio frequency stuff.

This is from the advertising material of the 57CNC:

•high performance 8-axis 125 kHz pulse engine with dedicated motor connectors

Thus you are demanding a pulse rate from the 57CNC ten times its capability.

Microstepping with steppers is not, contrary to the name about increasing resolution, microstepping beyond half steps seldom works,
although is closer to true representation with closed loop drives. The real purpose of microstepping is smoothness of motion.

In the early days astronomers used steppers to drive there telescope drives but suffered from vibration. They came up with the idea
of microstepping, no doubt hoping to achieve greater resolution but found that dream illusory but did end up with much smoother
motion.

May I suggest you drop the ridiculous 256 microstepps per full step......that's 25 arc sec resolution.....just pie in the sky stuff.
Try 8 microstepps per full step. That's resolution of 13.5 arc min, which is very acceptable AND take advantage of the smooth motion.
That would reduce the pulse per rev to 8 X 200 = 1600 per rev. At 20 revs per sec it would require a pulse rate of 32kHz, well
within the 57CNC ability.

Craig

3437

Mach4 General Discussion / Re: Torch Height Control

« on: December 01, 2018, 12:35:42 AM »

Hi Steve,

The Proma S/D model should work since it generates the step and direction signals for
torch motion itself.

I do recall you mentioning a model that would work. I imagine that would work well as a override axis. That would mean that
the primary Z axis would retain reference but the torch would be 'jiggled up and down' by a secondary axis. If you required accurate
Z reference you would have to centralize the secondary.....a bit of a pain but doable.

Any idea what the Proma SD is worth?

It might be a cost effective alternative to the HiCon.

Craig

3438

Mach4 General Discussion / Re: Torch Height Control

« on: November 30, 2018, 08:52:48 PM »

Hi,

Is HiCon really the only game in town?

To the best of my knowledge that is correct.

Followup question, does Mach4 even need to be aware of the THC?  Can't you just wire in a Proma THC and let it do all of the thinking?

This is sort of the point, Mach4 IS UNAWARE of THC. It is aware of two input signals ISIG_THCUP and ISIGTHC_DOWN but Mach does not
do anything with them but rather hands them to the motion controller and the motion controller issues the pulse streams necessary to rasie
or lower the Z axis. The controller must in addition keep a track of the THC corrections to report back to Mach otherwise Mach has lost
Z axis refence.

The normal Proma THC device cannot do that.....all it does is tell the motion controller 'go up' OR 'go down'. I understand there
is a device within the Proma range that can cause a DC motor to go up or down......at the expense of Mach no longer being referenced.

THC in Mach4 is about where THC with Mach3 was about 5-8 years ago......some manufacturers have cracked it and some have not. At this time
Vital Systems is it.

There may be some workarounds or cheats that allow some sort of THC response but each will have its shortcomings be it slow response
or loss of reference. Quite frankly any of the cheats or workarounds that I have seen proposed are deficient. To whit....I have recommended
to three customers to go with the HiCon, they have and their tables are running well. If you want decent THC pay up!

Craig

3439

Mach4 General Discussion / Re: Torch Height Control

« on: November 30, 2018, 03:12:04 AM »

Hi,

I did see the Vital Systems though. Seems a lil pricey

I agree however they are excellent devices and highly thought of by their customers.

Like no one has created any plugin or written code for this?

No, excepting Vital Systems. Given the price of the HiCon  it should not come as a surprise that Vital Systems have the budget to
invest in their device to insure that it is fully functional.

Warp9 TD have been rumbling about THC support for sometime. Regrettably their rumbles take a long time to come to fruition....but they
do eventually.

There was a suggestion that Mach could do it by using an override axis. Mach4's instruction loop time is pretty smart, of the order of a few ms, or about
ten times faster than Mach3's instruction loop. That would be pretty lethargic for highspeed (genuine realtime) THC (such as the HiCon) but would be adequate
for many users and be VERY much less demanding on controller manufacturers to implement. Have not had any confirmation from NFS.

I have seen Warp9 TD (ESS), PoKeys (57CNC) and CNCDrive (UC300) all claim that they 'couldn't possibly support THC until Mach does this that
or the other'. BULLS*********T! It would make their job easier to implement THC if for instance NFS added a THC screen to Mach but its not impossible
in its absence...as proven by Vital Systems.

This thread is a few weeks old and OP seemed sure that PoKeys had Mach4 THC support, you'll note that I'm skeptical, it may be worth a PM to OP
to find if indeed PoKeys have Mach4 THC support.
http://forum.machsupport.com/forum/index.php/topic,38744.0.html

In the mean time have the owner of the ESS hassle/badger/abuse Warp9 TD to get it together. I've been asking for two years.....and have promoted
the sale of three HiCons over that period of time because the ESS just can't do the business.

Craig

3440

Mach4 General Discussion / Re: Torch Height Control

« on: November 30, 2018, 12:51:03 AM »

Hi,
THC is a realtime function which is enacted by the motion controller.

At this time the only Mach4 ready external motion controller to offer THC is the HiCon by Vital Systems.

What motion controller do you have?

Craig