Messages

41

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 14, 2019, 07:37:39 PM »

Hi again Craig,

Attached is the easy servo(closed loop stepper) driver "in-position" parameter adjusting page, its factory setting is 0 which means "not enabled" i guess.

The double nut ballscrew has 10mm pitch, i am gonna adjust it to D  for a 5micron resolution, is this the correct approach?

Regards,

Hakan

42

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 14, 2019, 05:34:25 PM »

Hmmm..

u are right, i thought that those are detailed tweaking parameters and left them to the end, first i adjusted the main parameters of the drive and when i got these readings dived into mechanical and controller side, well it does not explain why an open loop stepper did the same positioning error in the X axis but i will do the adjustments as u say before i go on.

Regards,

Hakan

43

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 14, 2019, 03:53:09 PM »

Hi again Craig,

well i haven't got in to that much detail yet, most probably they left it like that to give the user space for starting up and tuning the motor/drive without causing any error.

I will adjust p11 to 4 and p12 to 20 as u suggest and check if it makes any difference in measurements or not. Then i am gonna make the test cut to see how machine actually cuts after i tuned the servo and increased the ball quantity within the ballscrew nut.

During the week i took apart the machine components i thought that maybe there is something wrong with the nuts(a broken ball, contaminants, etc) and contacted with the ballscrew manufacturer(gten), then i took all balls out of the nut and check(for the X axis) nothing was wrong but there were a space for 1 more ball in every complete set(there were 2 sets within) so i asked them why they left that empty space and if anything bad may happen when i add 1 more ball to each set, they said they done it for keeping the noise level down, for smoother operation and adding a ball wont harm anything.

I cant say i bought the "smooth operation" thing but of course it may also be true, as u know there are precision classes for these ballscrews, 3 class i think one is regular, one is more precise and one with a preload so it is the most precise one, actually i felt that the nut is more stiffer and has less pitch movement after adding that 2 balls but who knows? we will see if it is going to make any difference after the test cut.

Regards,

Hakan

44

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 14, 2019, 08:52:27 AM »

Hi Craig,

I think in this driver they call it "positioning deviation out of tolerance detection" but i am not sure, check the attached page, there is 2 settings related with this as far as i can see and 11 is related with an output signal if i understood correct, 12 must be the setting u are talking about but its factory default looks like 20000 which may show that its not the setting u are talking about 

Regards,

Hakan

45

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 14, 2019, 05:41:06 AM »

Hi guys,

the steel part that the indicator touching was the spindle head(a machined bulky steel cube which i mount the BT40 spindle) its outer face may or may not be perpendicular with the indicator, the indicator is parallel with the moving axis since the touching point is a sphere the surface will always stay tangent to it so the indicator will only show the moved distance. There is no that much machining error on that touching surface in reality its mostly the camera's optics doing the distortion.

For me,

to get this kind of readings in linear movements and machined squares and rectangles being 10-20micron accurate is weird,
machined squares and rectangles being 20micron accurate but circles being like an ellipse in 30-60 degrees to both X and Y +60microns is weird,
sometimes getting 1-2micron positioning accuracy and mostly get 30-50micron positioning error in every axis during the measurements is weird,
in full 1 turn reading the actual pitch and in small increments reading this error is weird,
getting this positioning error in small movements and seeing that every axis return to zero after moving 500mm within couple of microns is weird,


At first i also thought that this looks like an mechanical error thats why i took apart the moving components(motors, ballscrew supports, ballscrews, nuts, couplings, etc) and realigned/fixed them all over again. Linear rails in every axis are schneeberger and aligned/paralleled within 15microns, of course there is an error in every guideway when u move the axis but it does not result a total error more than 10-15microns(in high speed movements).

But there are things which proves that this is not mechanical error(other than being checked all of the mechanical aspects), mechanical error should always be there and should be repeating. If it was ballscrews it would add with the distance moved but its not adding, it reaches to 50-60micron error in 10mm and stops, it does not add more to it.

i was sure that this is because of the pulse signal loss and differential drive gonna fix it when Russ suggested that but seeing the actual pulse reaching the driver and drivers performing the commanded pulse without loosing even 1 digit in 10000 pulse per revolution made me more confused.

Regards,

Hakan

46

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 13, 2019, 01:52:03 PM »

i checked all mechanical aspects for a week everything is fixed as it should be, screws are new, couplings are german made R+W, every screw tightened with torque wrench to the specified torque values. End bearings are korean and they are also new.

I already tried different speeds, speed difference had no effect on readings, 6000mm/min and 50mm/min gives same results. Inertia was the first thing came to my mind because X axis is relatively heavy(400-500kg)and there were jitters on some side cuts in the test cut so i tuned the X axis servo and they are all gone now axis moves very smooth in all speeds also i am checking both encoder displays(commanded pulse and actual encoder feedback) they are identical in every command. While driving the heaviest axis motor only use 1-2Amp, there is no noise, no heat, no sign of overload.

Also, while dial indicator touching the axis i push the axis back and forth and can see the position value on servo driver display, it is very rigid and when i push hard it fixes the error immediately within 1-2microns. While doing that i am not even reading any backlash.

By the way thank u guys for helping out, if noone else getting this kind of odd readings clearly i am missing something thats for sure.

Regards,

Hakan

47

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 13, 2019, 11:17:04 AM »

well

none of us was right.

I sent the necessary pulse signal for 1 full turn of the ballscrew to every axis which has servo installed, checked the settings and made measurements with precision 1micron marcator and tesa indicators;

drivers received exactly 10000pulses(4x2500) for 1 full turn, received and actual encoder pulses are same(10000), so nothing wrong with the pulse signals or signal generators,

measured the 25mm(X axis), 10mm(Y axis) and 5mm(Zth axis) ballscrew pitches, they are exactly 25.001mm, 10mm and 5.001mm, i assume 1micron is the measuring error of the dial indicator, so nothing wrong with the ballscrews,

before measured backlash is still there and its not the problem,

i made many measurements again with +1mm, +2mm, +3mm, +4mm, +5mm, +10mm and +25mm command set, it is still repeating that odd positioning error in most of the time, but in couple times it made the exact positioning within 1-2microns for the whole 1 set in every axis.

without a hope i tried to adjust the count per unit value with the wizard and of course it didnt fix anything.

i still dont know why i am reading this positioning error in the dial indicators, when every axis commanded to go 500mm and return back to 0 all of them returns back the exact point within couple of microns.

before this error presented itself i was making a test cut which has couple of circles, tilted square and rectangles on it, weird thing is this; for the rectangle(35mmx25mm) machine made it within 20microns, it was 35.02 in the X and 25.01 in the Y direction. But according to the measurements i am reading it should have done that cut with 50-60 micron error. The rectangle and squares was ok but the circles were not true circles, they were reflecting the errors i am measuring and +60micron wrong.

I am gonna make the same test cut again, after tuning the servos and aligning the ballscrews within 10micron to guideways.

I wonder what u guys read on the dial indicator when u move one of the axis of your machines +1mm for example?

Regards,

Hakan

48

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 13, 2019, 04:20:49 AM »

Hi again,

Yes, i will perform the following test today;

gonna send 1 turn pulse from Mach4 to one of the servo drives and check the pulse reaches the driver, if it displays 10000(4x2500) it means there is something wrong with the lead of the balscrew(its not actually 25mm, its something like 24,89..), but if the pulse number is below 10000 then it means there is a loss in pulse signal.

Personally i dont think Mach4 or ESS causing this, since the error is persistent in every axis, its always short and its not adding up with the distance i am leaning more towards the differential thingy side. We will see..

Regards,

Hakan

49

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 12, 2019, 05:58:53 PM »

Hi Overloaded,

and thanks for the advice, i checked the manual of the servo drive it also suggests what your drive manual suggests i think, see the attached image.

The differential line driver u connected was something like this? and how did u connect it to pulse and direction signals? how is the wiring? i never used one, if all other fixing attempts fail i am definitely gonna try it, thanks.

https://www.amazon.com/Cnc4Pc-C72-Differential-Line-Driver/dp/B06Y3M2ZB2

50

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 12, 2019, 03:28:08 PM »

Hi again,

I understand what u are saying, its ok i am going to measure it, last couple of days i was thinking the error was mechanical so i took apart many things and saw that i was wrong and put them back together within a specific precision so it melted half of my brain down

While browsing the documents all over again, i found out that servo drive shows the commanded pulse and actual pulse in its display by using that i can make the shaft rotate one exact turn and measure the exact pitch.

And one other thing, i remember reading in the Mach4 user manual a warning for the user which strongly suggests not to tweak the count per unit value(because it is a calculated value), but if your suggestion is true that value should be tweaked according to the actual measurements, it may not be defined as tweaking because actually its still the same calculation what we are doing is measuring the pitch and putting it back to formula but it still sound like tweaking.

When u read that statement in the user manual u just dont touch that value 

Regards,

Hakan