Messages

31

Mach4 General Discussion / Re: Mach4 positioning error

« on: February 21, 2020, 11:52:27 AM »

Yes,

in current machines i use(with ballscrews) i am gonna tune them more accurately with it and fix the lead error as much as possible via Mach4, i fixed the backlash issue for now with backlash compensation but its not an healthy way to solve it as u know, i am gonna fix it by changing the ballscrews/support units with more precise(preloaded double nut, C3 precision) ones.

In the machines i am gonna manufacture from now on i am gonna use linear motors so there wont be any backlash problem at all. 

Regards,

Hakan

32

Mach4 General Discussion / Re: Mach4 positioning error

« on: February 21, 2020, 11:17:09 AM »

Hi Mike,

I think the same, it should work with cnc4pc diff. to single ended converter board, in some forums i read that people make these encoders work by just connecting the A and B phases to ESS(i am not sure that it works as it should be like that) but i will try it with cnc4pc board.

Again, that model would be better in my case, i will not pay the original amount to it i found it way more cheaper than that, and since i am going to use it as a ruler basically to check the positioning accuracy of each axis, i am not going to need the absolute option, incremental reading should be enough for me. I will write a lua script which will make the axis move to different positions, say 10-15 different locations in different speeds, check the commanded and actual movements(from the linear scale) and then calculate and output an average positional error value. I will also use this method to check/tune the positioning accuracy of the small machines i am going to manufacture and sell.

I will check with the Andy from Warp9 and CNC4PC guys before i order anything, i just wanted to get someone's opinion who knows more then me about the encoders and this technical stuff.

So thanks for your help and the document u attached.

Regards,

Hakan

33

Mach4 General Discussion / Re: Mach4 positioning error

« on: February 20, 2020, 11:10:16 AM »

Hi Mike,

Thanks for the info, that encoder is the one i can get with very suitable price so it would be better for me to go in that direction.

I think in its documents it says that the output method is "differential line driver" i do not have much knowledge in encoders but what i understand is it has output like A, A-, B, B- right? and as much as i know ESS accepts the encoder signals as A, B(i think they call it TTL) so i thought that if i get this;

https://www.cnc4pc.com/c46-differential-to-single-ended-converter.html#description

I could connect the encoder at one end and connect the other end(A, B output) to the ESS via BOB, so in my mind it should work but in real world nothing works like the way it works in my mind

So u are saying that i should get this;

http://pico-systems.com/osc2.5/catalog/product_info.php?products_id=27

and connect the encoder's A, A-, B, B- pins to input of it and connect the output of it to ESS via BOB and it will give the output as A, B right?

that encoder is worth 2700USD so buying the 150USD board to make it work with Mach4 is not a problem, i just want to make sure that its gonna work like that.

Regards,

Hakan

34

Mach4 General Discussion / Re: Mach4 positioning error

« on: February 19, 2020, 12:11:42 PM »

Hi Guys,

I wanted to close this thread by writing the real cause of the errors i was reading.

I was not the electronics, noise or Mach4, i changed the controller from mainboard to bob completely and it was repeating the same errors.

The error was there because of the mechanical problems, half of it was because of the angle errors in the support units i ordered from a manufacturer in China(they should be 0.01 accurate but manufacturer did them 0.1 accurate because of the misunderstanding) which i connected the ballscrew bearing units and motors. And the other half was because of the backlash and error in the real pitch values, when backlash compensation done and step per unit pulses tuned after scraping the support pieces and paralleling/squaring them to the each axis by hand within 5 microns, now, every axis has good positional repeatability with max 15microns error.

I think the best thing can be done in here is to replace the longest axis's ballscrew/support units with 40mm diameter, double nut, C3 precision, mid preloaded ballscrew and C3 heavy duty support units because the one i have in hand in the Y axis has the best backlash value of 5microns.

And for measuring the positioning error and tuning the every axis of this type of machines i think the best way is to get a precision linear scale from a good brand like mitutoyo and use it to take the measurements via Mach4.

The one i attached below should be more than enough for my purpose it has 5-6microns accuracy within 1000mm, any of u connected this kind of linear scale to Mach4 before? or know how to connect it to Mach4 via pmdx-124 and ess? any other breakout board needed?

My aim is just reading the encoder values with Mach4 and tune the axis manually.

Thanks to all of u for your help.
 
Regards,

Hakan

35

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 16, 2019, 02:28:43 PM »

Hi Craig,

I will adjust p12 later as u describe when i solve this huge problem.

I forgot to mention that i saw that flashing led 2 times in machine idle state and it didnt go away until i move an axis back and forth for some time.

I dont have an oscilloscope but if tomorrow Y axis moves as it should be with parallel port commands from another computer, i will take apart all the controller cabinet and build it from scratch electric/electronic wise, thanks.

Regards,

Hakan

36

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 16, 2019, 10:45:15 AM »

Hi Guys,

I adjusted p11 to 4 and p12 to 20 but the servo gave an alarm with that settings so i increased the p12 to 4000 with that setting it works without giving any alarm.

But these values has nothing to do with the error i am reading, today i checked X and Y axis, X axis works more noisy, there is noticeable backlash and it is almost 100micron short in 10mm movement. So i guess increasing the ball number within the ballscrew nut was not a good idea. I am gonna reverse it to its original ball number(105) tomorrow.

In Y axis before measured error still there but it is also increased by 10micron and its not a reading error. I didnt touch anything related with that axis but its error increased.

I am where i was at the beginning of this post, this does not look like a mechanical or servo/step motor based error to me, because nothing changes when i tweak the parameters or realign the ballscrews. Tweaking the step per unit value or electronic gear ratio value does not make it any better, it makes it worse and the error readings changes with days.
 
Today while taking the measurements i noticed something within the controller which i think should not be happening, there is "step" led on PMDX bob which flashes when u send pulse signal to the servo/step drives. While the machine was at rest and i wasnt touching anything that "step" led was flashing in high frequency intervals like it does when u send a pulse signal.

I believe that led should flash only when u move an axis. Anyone has an idea about this?

another thing; Delta spindle drive shows on its display 0.1-0.2 changing frequency input in idle state.

There is a 3phase EMC filter in main line input, but no EMC filter before the control cabinet.

I didnt have time to test one axis with a shorter cable directly connected to the pmdx bob, tomorrow i am gonna try it and if it does not work, i am gonna completely bypass the controller, hook up another motherboard and a parallel port bob from outside, connect it to the Y axis for example and send signal to it then we will see if this is related with the noise within the controller.

There is no HF source within the controller, its just the motherboard, PMDX+ESS+spindle board attached to pmdx and input boards, there is only a small PSU(with metal cover) which supply power to the motherboard. There is no noise source that i know of but that led should not be flashing in idle state.

Regards,

Hakan


 

37

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 15, 2019, 06:46:59 PM »

Hi again Russ,

Attached is the documentation of the servo driver i am using in this one, i played with the electronic gear ratio values(in every manual they describe it and the math different though) and it does the same thing with the step per unit value. At last i set p13 and p14 to 1 so it is 1:1.

Well i played with many parameters to see if there may be any effect on the motion and i am not sure about the "encoder output scaling factor" i dont recall something like that. Adjusting that parameter would be a better idea then adjusting the gear ratio, i am gonna check it for sure, thanks.

Regards,

Hakan

38

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 15, 2019, 03:57:43 PM »

Hi Russ,

That may also be the reason but the thing is there is 2 servo motor and 2 closed loop step motor installed in this machine, servos has 10000ppr, steppers has 30000ppr resolution encoders. If one is faulty what is the possibility of all being faulty? these are not cheap chinese motors, servos are Gservo aka golden age motor(one of the biggest servo and torque motor manufacturer in china) and steps are easyservo brand korean made. I didnt go for panasonic or delta since i used these motors before they work quite nice and precise in other machinery.

Also as i wrote before, to rule out the mistakes for parameters or any other problem within the servo motor/driver combo in X axis, i removed the servo motor, connected 16nm open loop(without any encoder) stepper motor and send the same set of commands to it, it repeated the exact same error.

After adjusting the settings that Craig suggested i am gonna connect the X axis drive directly to the pmdx bob with very short cables like 50-60cm and then send the commands to see if it is going to change anything.

Regards,

Hakan

39

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 15, 2019, 03:39:15 PM »

Dear Rich,

Thanks for the info but a human being who does not take all of that to consideration can not build a 4 ton milling machine and bring the accuracy within 15micron linearity and parallelism.

We are not talking about chasing 1-2 micron in here there is a 50-60micron positioning error in every axis of the machine in 10mm(20-30micron in 1mm), 50-60 micron is not a small value. With that error u can not do anything with a milling machine. And it is way out of the limits of any standard ballscrew tolerance, the ones i use has 10micron max. error in 500mm. and even both ends machined directly by the manufacturer with spinder precision CNCs not by a local shop or by me.

For your information couplings are german made R+W precision elastomer servo couplings which is backlash free, has excellent vibration damping capabilities and balanced to 12000rpm. One of those couplings price is 60euros.

Most of the mechanical and electronic parts used in this machine are high quality and some are the highest quality.

All linear rail beds, guideways and ballscrews scraped/aligned with a 000 granite straight edge + 00 granite table and 0.5-1 micron precision Mahr and Tesa indicators within 10microns. Ballscrew nuts fixed to steel blocks which are fixed to the axis of the machine with 4 M10 screws, every single screw used in the machine mounted with a torque wrench with specified torque values written in the spec. sheets of every single component.

I didnt buy these components from stores, i got most of them directly from the manufacturers, linear rails manufactured and sent to me by schneeberger in 3 months and they are high precision not regular precision. 4th axis has Kamo Cycloid installed which has 4micron runout. I got these components and bring them all together from the manufacturers around the globe, from Japan, Germany, Korea, China, USA etc..

After bringing all mechanical parts to some accuracy(which is below 1520microns in total) if u get an 50-60micron error reading in 10mm free forward move, it touches your nerve little bit.

So dont give me lessons about precision or measuring, measurements are not complicated measurements and we are not talking about 5-6micron in here its 50-60microns within 10mm u dont need a micron dial indicator or optics or laser interferometer to measure it, even a 10bucks worth chinese dial indicator can measure it.

Before everything u said, if u dont warm up the machine(linear guideways/blocks and ballscrews) prior to the measurements u get different measurements every time.

So if u have an idea which may cause this kinds of errors shoot it, if u dont then shut it.

Regards,

40

Mach4 General Discussion / Re: Mach4 positioning error

« on: December 15, 2019, 05:22:15 AM »

Hi Russ,

Yes i also thought the same thing when i read it first, it looks like they done it to turn on an output for a PLC/controller or any other equipment but internally within the driver circuit it is possible that they are using it also for positioning adjustment so i agree with Craig, it is better to be adjusted as smaller values to keep the tolerances tight. It may not have any effect in fixing the error i am reading but in normal cnc usage(especially for Mach4) those should be small values.

Regards,

Hakan